NO341425B1 - Wellbore probe device and a method of operation - Google Patents

Description

When drilling and completing oil and gas wells, it may sometimes be necessary to carry out auxiliary operations, such as monitoring the operation of the equipment used during drilling or an evaluation of the production capability of formations crossed by the wellbore. After a well or a well interval has been drilled, for example, interesting zones are often tested to determine the various formation properties, such as permeability, fluid type, fluid quality, formation pressure, formation temperature, bubble point and formation pressure gradient. These tests are carried out to determine whether the intersected formations are commercially exploitable and to what extent production can be optimised.

Wireline Formation Testers (WFT) and Drill String Testing (DST) are commonly used to carry out such tests. A basic DST test tool includes a gasket or gaskets, valves or ports that can be opened and closed from the surface, and two or more pressure sensing devices. The tool is lowered to the zone to be tested using a working string. The gasket or gaskets are placed, and drilling fluid is evacuated to thereby isolate the zone in relation to the drilling fluid column. The valves or ports are then opened so that a current can flow from the formation to the tool for testing, as the recording devices begin to map the static pressures. A sample chamber captures clean formation fluid at the conclusion of the test. WFT generally uses the same methodology, but a cable is used to lower the test tool into the wellbore, after the drill string has been taken up, although WFT technology can sometimes be carried out using a pipe string. The wireline tool typically also includes gaskets, but the gaskets are placed closer together compared to drill string testers, to achieve more efficient formation testing. In some cases, no gaskets are used. The test tool is then brought into contact with the formation and the testing takes place without zone isolation in the borehole.

The WFT may also include a probe device for interacting with the borehole wall and for obtaining formation fluid samples. The probe device can include an insulation pad that is placed against the borehole wall. The isolation pad seals against the formation and around a hollow probe, which puts an internal cavity in fluid communication with the formation. Thereby, a fluid stretch is formed which enables formation fluid to flow between the formation and the formation tester, isolated from the borehole fluid.

To obtain a usable sample, the probe must be insulated against the relatively high pressure in the borehole fluid. The integrity of the seal, as provided by the insulating pad, is therefore critical to the function of the tool. If the borehole fluid is allowed to leak into the collected formation fluids, a non-representative sample will be obtained and the test must then be repeated.

When WFT and DST are used, the drill string with the drill bit must be pulled out of the borehole. Then, a separate working string with the test equipment, or in the case of WFT, a wireline tool string, must be lowered into the well to carry out secondary operations. An interruption of drilling to carry out formation testing can add up to significant time loss for the drilling programme.

DST and WFT can also cause tool fixation or formation damage. It will also be difficult to run WFT in a strongly deviated and extended well. WFT also has no flow bores for drilling mud, nor are they designed to withstand drilling loads, such as torque and weight of the drill bit.

An accurate measurement of formation pressure during drill string tests and especially in connection with wireline formation tests, can be affected as a result of filtrate invasion and build-up of mud cakes, because a considerable time may have passed before a DST or a WFT is brought into contact with the formation. Mud filtrate intrusion occurs when drilling mud fluid displaces formation fluid. Because mud filtrate penetration into the formation begins at the borehole surface, such penetration will be strongly predominant there and will decrease further into the formation. When a filtrate intrusion occurs, it may be impossible to obtain a representative sample of formation fluids, and at the very least the sampling period must be increased so that one can first remove drilling fluid and then obtain a representative formation fluid sample. The mud cake consists of solid particles that have settled on the well wall when the filtrate penetrates during drilling. The presence of mud cakes on the borehole surface forms a "skin". A "skin effect" can thus occur because the formation testers can only draw fluid from relatively short distances into the formation, so that the filtrate will therefore distort a representative formation fluid sample. The mud cake also acts as an area of reduced permeability near the borehole. When mud cakes are formed, the accuracy of reservoir pressure measurements will therefore decrease, which will affect the calculations of the formation's permeability and production capacity.

Other testing equipment includes testing while drilling (MWD) or by logging underneath

drilling (LWD). Typical LWD/MWD formation testing equipment is suitable for integration into a drill string during drilling. Various devices or systems are used for isolating a formation from the rest of the wellbore, for drawing fluid from the formation, and for measuring physical properties in the fluid and in the formation. When using LWD/MWD

testers, the test equipment is exposed to demanding conditions in the wellbore during drilling, so that the formation test equipment can be damaged and degraded before and during the testing. These conditions include vibration and torque from the drill bit, exposure to drilling mud, cuttings and formation fluid, hydraulic forces from the circulating drilling mud, and scraping of the formation test equipment against the wellbore side. Sensitive electronics and sensitive sensors must be robust enough to withstand pressure and temperature, and especially the extreme vibration and shock conditions that occur in the drilling environment, while the electronics and sensors must be able to maintain the desired accuracy, repeatability and reliability.

The invention will now be described in more detail with reference to the drawing, where

Figure 1 purely schematically shows an embodiment of a formation test device arranged in an underground well, Figures 2A-2C are sections through parts of the bottom hole device and the formation test device in Figure 1, Figures 3A-3B are enlarged sections through the formation test tool part of the formation test device in Figures 2B -2C, Figure 4 is an elevation of the formation probe device shown in Figure 3B and the balancing valve requirement, Figure 5 is an enlarged section along the line 5-5 in Figure 4; Figure 6A is an enlarged section through the formation probe device and equalization valve shown in Figure 5, with the probe in a retracted position, Figure 6B is an enlarged section along line 6-6 in Figure 4 and shows the probe device in an executed state, Figures 7A-7F are section through another embodiment of the formation probe device, taken along the same section line as in Figure 6B, the probe devices being shown in different positions in Figures 7A-7F, Figure 8A is a section through the probe retraction switch of the formation probe device, Figure 8B is an enlarged section of the contact part of the retraction switch shown in Figure 8A, Figure 9 shows a schematic section of a hydraulic circuit that is used when activating the formation test device, Figure 1 OA is a top view of a hydraulic reservoir accumulator that is used in the formation test device,

Figure 10B is an end view of the reservoir accumulator of Figure 10A,

Figure 10C is a section along the line C-C in Figure 10B,

Figure 1 OD is a section along the line D-D in Figure 10B,

Figure 10E is a section along the line E-E in Figure 10D,

Figure 10F is a section along line F-F in Figure 10C,

Figure 1 AND is an enlarged section taken from Figure 10D,

Figures 10H-10I are perspective views of the reservoir accumulator and the probe collar, Figures 11-13 are sections through the draft piston and shut-off valve devices in the probe collar of the formation test device, and

Figure 14 is a flowchart illustrating the formation test sequence.

Certain words and expressions used in the following description and in the requirements refer to special system components. Here, it is not intended to distinguish between components that have different names, but not different functions.

Below and in the requirements, the expression "including" shall be intended to be comprehensive and shall therefore be interpreted as "including, but not limited to...". Also, the terms "coupling", "connections" and "coupled" used to describe electrical connections are intended to include both indirect and direct electrical connections. If, for example, a first device is "connected to" a second device, then the connection can either take place by means of an electrical conductor that directly connects the two devices, or by means of an indirect electrical connection via other devices, conductors and connections. The expressions "up" or "down" are intended to facilitate the description, as "up" shall denote a direction towards the surface in the borehole, while "down" shall mean in a direction towards the bottom in or the distal end of the borehole. In the description given below and in the patent claims, it can sometimes be said that certain components or elements have a fluid connection. This means that the components are designed and interrelated so that a fluid can be passed between them, for example through a passage, a pipe or a line. The terms "MWD" or LWD" are intended to include all generic measuring devices and systems used during drilling or logging while drilling.

To understand how formation testing takes place, it is essential to first understand how hydrocarbons are stored in underground formations. Hydrocarbons are not found in large underground spaces, but are instead found in very small holes or pore spaces in certain rock types. It is therefore important to know certain properties of the formation and the fluid there. Sometimes in the description given below, certain formation and formation fluid properties will be stated more generally. Such formation properties include, but are not limited to: pressure, permeability, viscosity, mobility, spherical mobility, porosity, saturation, coupled compressibility porosity, skin damage and anisotropy. Such formation fluid properties include, but are not limited to: viscosity, compressibility, fluid compressibility, density, resistivity, composition and bubble point.

Permeability is a property of a rock formation that enables hydrocarbons to move between the pores, and into a wellbore. Fluid viscosity is a measure of the hydrocarbons' flow properties and permeability divided by viscosity is called "mobility". Porosity is the ratio between voids and the volume of the rock formation in which the voids occur. Saturation is a proportion or percentage of the pore volume occupied by a specific fluid (eg oil, gas, water etc). Skin damage is an indication of how mud filtrate or mud cakes have changed the permeability near the wellbore. Anisotropy is the ratio between the formation's vertical and horizontal permeabilities.

The resistivity of a fluid is the ability of the fluid to resist an electric current. The bubble point occurs when a fluid's pressure drops so quickly and so low that the fluid, or parts of it, changes phase and becomes gaseous. The dissolved gases in the fluid leave the fluid, while gas in the fluid occurs in a non-dissolved state. Typically, such a phase change of the formation hydrocarbons being tested and measured will be undesirable, unless a bubble point test is carried out to determine the bubble point pressure.

In the drawing and in the following description, like parts are given the same reference numbers. The drawing figures are not necessarily to scale. Certain inventive features may be shown in exaggerated size and somewhat schematically, while other details relating to conventional elements are not necessarily shown, thereby facilitating the overview. The present invention includes various embodiments. Specific embodiments are described in detail and shown in the drawing, under the assumption that the description is to be seen as an illustration of the invention, so that the invention is limited to what is shown and described here. It should also be mentioned that the various details of the designs mentioned below can be used individually or in suitable combinations to provide the desired results. The various features mentioned above, and features and properties that will be described in more detail in what follows, will be able to be understood by professionals by studying the description and the associated drawings.

Figure 1 shows a formation test tool 10 as part of a bottom hole device 6 which includes an MWD stub 13 and a drill bit 7 at the lower end. The bottom hole device 6 is lowered from a drilling platform 2, for example a ship or another conventional platform, by means of the drill string 5. The drill string 5 passes through the riser 3 and the wellhead 4. Conventional drilling equipment (not shown) hangs in the tower 1 and can be used for rotation of the drill string 5 and the drill bit 7, so that the drill bit 7 will form a drill hole 8 through the formation material 9. The drill hole 8 penetrates underground zones or reservoirs, such as the reservoir 11, which are believed to contain hydrocarbons in a commercially exploitable amount. It should be mentioned that the formation tester 10 can be used in other downhole devices and with other drilling equipment in connection with land-based drilling, and thus not only in connection with the offshore drilling shown in Figure 1. In all cases, in addition to the formation tester 9, the borehole device 6 will include various types of conventional devices and systems, such as a borehole drilling motor, rotatable tool, mud pulse telemetry system, measurement-during-drilling sensors and systems, and other known equipment.

It should also be mentioned that although the formation tester 10 is shown here as part of the drill string 5, the below-described embodiments of the invention can be guided down into the drill hole 8 by means of wire technology, as partially described above, or by means of a rotating and controllable drill string , which will be well known to the professional world. Earlier mention and examples of methods using the embodiments described here can be found in US patent application "Methods for Using a Formation Tester", with US Express Mail Label Number EV 303483362 US and Attorney Docket Number 1391-54101, and in US patent the application "Methods for Measuring a Formation Supercharge Pressure", which has US patent application serial number 11/069,649. These documents are considered part of the present description.

Figures 2A-C show parts of the formation test tool 10. Figure 2A shows the electronic module 20, which may include battery packs, circuit boards, capacitors and other electrical components. Figure 2B shows the filling port device 22 with filling ports 24, 26 for supplying or removing hydraulic or other fluids to/from the tool 10. Under the filling port device 22, a hydraulic insert device 30 is arranged. Under the device 30, a hydraulic coupling ring device 32 is arranged, which acts as a hydraulic manifold. Figure 2C shows the part of the tool 10 that includes the equalization valve 60, the formation probe device 50 (or the probe device 200), the pull rod valve device 74, the pull piston devices 70, 72 and the stabilizer 36. The pressure instrument device 38 also includes pressure transducers used by the formation probe devices 50, 200 .

Figure 3 A-B shows enlarged parts of the tool 10 shown in Figures 2B-C. Here you can see the hydraulic input device 30, the probe retraction accumulator 424, the balancing valve 60, the formation probe device 50, the pull-shutoff valve 74 and the pull-piston devices 70, 72 more detailed. The balancing valve 60 can be one of many known balancing valves.

In Figure 4, the formation probe device 50 is arranged in a probe weight tube 12, and it is covered with a probe cover plate 51. In the probe weight tube 12, an equalization valve 60 with the corresponding valve cover plate 61 is also arranged. Near the formation probe device 50 and the equalization valve 60, a flat part 136 is designed in the probe weight tube 12 surface 17. The probe weight tube 12 includes a draw cover 76 which protects other devices which are assigned to the formation probe device 50 in the weight tube 12, such as draw pistons (not shown).

Figure 5 shows how the formation probe device 50 and the compensation valve 60 are placed in the probe weight pipe 12. The formation probe device 50 and the compensation valve 60

is mounted in the probe weight tube 12 just above the flow bore 14. The flow bore 14 can deviate from the center axis 12a of the probe vector 12, or from other parts 14b, 14c of the flow bore 14, to make room for at least the formation probe device 50. Figure 5 is an example of the flow bore part 4a displaced radially relative to the longitudinal axis 12a, and also relative to the flow drill part 14b, via the transitional flow drill part 14c. You can also see the pull-piston devices 70, 72 and the pull-shutoff valve 74.

Details regarding the first embodiment of the formation probe assembly 50 are best shown in Figures 6A-6B. As shown in Figure 6A, the formation probe device 50 is held in the probe weight tube 12 by being screwed into the neck tube, and is also held in place by the cover plate 51. The formation probe device 50 includes a stem 92, a generally cylindrical and threaded adapter sleeve 94, a piston 96 designed for reciprocation in the adapter sleeve 94, and a snorkel device 98 designed for reciprocating movement in the piston 96. The probe weight tube 12 has an opening 90 for receiving the formation probe device 50. The cover plate 51 fits over the top of the formation probe device 50 and holds and protects it when the device 50 is located itself in the probe weight tube 12. The formation probe device 50 can go out and in through the opening 52 in the cover plate 51.

The stem 92 includes a circular base part 105 with an outer flange 106 where a stem-holding screw 97 (shown in figure 6B) is arranged for holding the stem 92 in the opening 90. From the base 105 there is a tubular extension 107 which has a central passage 108. The end of the extension 107 has external threads 109. The central passage 108 has fluid connection with the fluid passage 91 (not shown, but shown schematically in Figure 9) which connects the fluid passage 93 (not shown, but shown schematically in Figure 9) which leads to other parts of the tool 10, including the balancing valve 60.

The adapter sleeve 94 has an inner end 111 that goes towards the flange 106 on the stem 92. The adapter sleeve 94 is fixed in the opening 90 as it is screwed into the neck tube 12 in the section 110. The outer end 112 of the adapter sleeve 94 can be essentially flush with the recess 55 in the neck tube 12 for the reception of the cover plate 51. The outer end 112 also has a flange 158 which enters a recess 162 in the cover plate 51. The adapter sleeve 94 has a cylindrical inner surface 113 with sections 114, 115 of reduced diameter. A gasket 116 has been inserted into the surface 114.

The piston 96 is slidably held in the adapter sleeve 94 and includes a cylindrical outer surface 151 with a base portion 118 of a larger diameter. A gasket 143 is provided at this base portion 118. Just below the base portion 118, the piston 96 may rest on the flange 106 of the stem base portion 105 when the formation probe assembly 50 is in the fully retracted position shown in Figure 6A. The piston 96 may also have a cylindrical inner surface 145 with a portion 147 having a reduced diameter. The piston 96 can further have a central bore 121 with a bore wall 120, which bore extends up through the upper part 119.

As shown in Figure 6B, a sealing pad 180 is arranged at the top of the protruding part 119 of the piston 96. The sealing pad 180 has a donut shape, with a curved outer sealing surface 183 and a central opening 186. The sealing pad 180 can, however, have other geometric designs of a known type, for example as shown in US Patent Application 10/440,835 "MWD Formation Tester". The base surface 185 of the gasket pad 180 can be connected to a skirt 182. The gasket pad 180 can be tied to the skirt 182, or connected in another way to the skirt 182, for example by the gasket pad 180 being molded onto the skirt 182 so that the gasket pad material will fill in grooves or holes in the skirt 182, as shown in US patent application 10/440,835. The skirt 182 is releasably connected to the projecting part 119 as a result of a threaded cooperation with the wall 120 in the central bore 121 (see Figure 6A), or by means of other means of cooperation, for example a press fit in the central bore. Because the packing pad/skirt combination can be detached from the projecting portion 119, the combination can be easily replaced in the field. Alternatively, the packing pad 180 may be connected directly to the part 119, without a skirt.

The packing pad 180 is preferably of an elastomeric material. The packing pad 180 provides a seal and prevents drilling fluid or other contaminants from entering the formation probe device 50 during formation testing. More specifically, the packing pad 180 can seal against the filter cake that can be found on a borehole wall. Typically, the pressure in the formation fluid will be less than the pressure in the drilling fluid that is injected into the borehole. A residual layer of drilling fluid will form a filter cake on the borehole wall and separate the two pressure chambers. In the extended state, the packing pad 180 can conform to the shape of the borehole wall and/or the mud cake and thereby form a seal through which formation fluid can be collected and/or formation properties can be measured.

In an alternative embodiment of the packing pad 180, it can have an internal cavity which can contain a fluid volume. A fluid can be pumped into the cavity of the packing pad to the desired extent, so that the pressure in the pad can be increased or decreased. Fluid used in the packing pad may include hydraulic fluid, salt solutions or silicone gel. For example, the packing pad can be emptied or pressure relieved when the probe is brought out to interact with the borehole wall. Depending on the contour of the borehole wall, the packing pad can then be pressurized by filling the packing pad with fluid, whereby the packing pad will conform to the shape of the borehole wall and provide a better seal.

In yet another embodiment of the packing pad, it can be filled with an electro-rheological fluid, either before or after the interaction with the borehole wall. An electro-rheological fluid can be an insulating oil that contains a dispersion of its solid particles, for example with a diameter of from 5 µm to 50 µm. Such an electro-rheological fluid is well known within this technical field. When exposed to an electric field, such fluids will develop an increased shear stress and an increased static tensile stress which makes the fluids more resistant with regard to flow. This change in the fluid properties becomes noticeable, for example, as an increased viscosity, especially of the plastic viscosity, when it is applied to an electric field. The fluid in the packing pad can change to a semi-solid form. This semi-solid form is reversed when the fluid is no longer exposed to the electric field. In the absence of the electric field, the electro-rheological fluid in the packing pad will become less viscous, so that the packing pad can adapt to the contour of the borehole wall. As soon as the packing pad has adapted to the borehole wall, an electric field can be applied to the electro-rheological fluid in the packing pad. Thereby, the fluid viscosity increases, the packing pad hardens, and a better seal is achieved.

As shown in Figure 6B, the snorkel assembly 98 includes a base portion 125, a snorkel extension 126, and a central passage 127 through the base 125 and the extension 126. The base portion 125 may have a cylindrical outer surface 122 and inner surface 124. The extension 126 may have a cylindrical outer surface 128 and inner surface 138.1 the top of the extension 126, a filter 100 is arranged. The filter 100 is an essentially tubular element with a central bore 132 between a fluid inlet end 131 and a fluid outlet end 135. The filter 100 has a flange 130 at the fluid inlet end 131 and an internally slotted segment 133 with slots 134. Between the slotted segment 133 and the outlet end 135, the filter 100 has a threaded portion 137 for threaded engagement with the snorkel extension 126.

At the bottom of the snorkel's 98 base part 125, a scraper tube holder 152 is screwed on, which includes a circular base part 154 with a flange 153, a tubular extension 156 with a central passage 155, and a central opening 157 for receiving the trunk extension 107. Just below the scraper tube holder 152 is arranged a retaining ring 159 which cooperates with the snorkel 98 so that the snorkel 98's movement will be limited in the direction of retraction. The scraper tube holder 152 holds a scraper tube 150 when the scraper tube 150 is in the retracted position shown in Figure 6B. The scraper pipe 150 has a central passage 151 up from the scraper pipe holder 152 and through the passage 127 in the snorkel 98. On the top of the scraper pipe 150 is attached a scraper or scraper 160. The scraper 160 is screwed together with the scraper pipe 150 in the threaded section 161. The scraper 160 is a essentially cylindrical element which includes a scraper plug part 163, a central bore 164 and openings 166 which have fluid connection with the central bore 164. The scraper 160 is arranged in the central bore 132 of the filter 100 and can be activated back and forth (or reciprocating) between the inlet end 131 of the filter and the outlet end 135 of the filter. When the scraper tube 150 and the scraper 160 are in the retracted positions, as shown in Figure 6B, the openings 166 will have a fluid connection with the fluid outlet end 135 of the filter 100, so that thereby fluid can pass from the filter 100, through the scraper bore 164 and into the the central passage 155 in the scraper tube 150. The scraper or scraper 160 is thus designed as a movable or free scraper.

In an alternative embodiment of the scraper 160 in the filter 100, the activation of the scraper 160 can take place with a rotational movement about the longitudinal axis of the scraper 160. This rotational movement can occur instead of the reciprocating movement, or in addition to it.

As shown in Figure 6B, a connector 176 is arranged in the opening 178 in the probe weighing tube 12, just below the inner end 111 of the sleeve 94. A contact line 175 provides an electrical connection between the connector 176, via a wire to a contact device (not shown) which is advantageously arranged in the flange 106 of the stem base part 105, so that the contact device can thereby have direct contact with the base part 108 of the piston 96. The figures

8A-8B show details regarding the connector 176 and the contact device 310, with the surrounding structure shown more generally so that the various parts of the formation probe device 50a will essentially correspond to similar parts of the formation probe device 50 in Figures 6A-6B.

In Figure 8A, the connector 176a is arranged in the opening 178a in the probe weight tube 12a. The contact wire 175a is connected to the wire wires 300, which go through a recess 301 in the weight tube 12a to an opening 305 in the base part 105a of the stem 92a. From the opening 305, the wire 300 passes through the base part 105a and to a cavity 3007, where the contact device 300 is placed.

As shown in Figure 8B, the wire 300 goes to the contact device 310. The contact device 310 includes a housing 316 with an opening 317, a conductive contact body 312 with a flange 314 and a central bore 319, a stripped end 318 of the wire 300 that enters and is soldered to the bore 319, a non-conductive spring support 322, and disc springs 324. The flange 314 of the body 312 is arranged between the upper part of the housing 316 and the lower part of the spring support 322. Disc springs 324 are arranged between the spring support 322 and the flange 314, between a lower plate 326 and an upper 328. The springs 324 exert an upward force against the flange 314 so that the top surface 313 of the body 312 will exit from the opening 317, so that the top plate 313 protrudes from the cavity 307. When the formation probe device 50a is withdrawn, the piston 96a will make contact with and press down on the surface 313 of the body 312. Thereby the springs 324 are compressed and the bottom surface 350 is moved down into the space 324. When the piston 96a makes contact with the surface 313 of the body 312, it will there is an electrical circuit which is grounded via the piston 96a, and a signal is provided to the tool electronics, not shown, that the formation probe device 50a is fully retracted. After the piston 96 has made contact with the surface 313 of the body 312, the piston 96a will continue to move until it makes contact with the base part 105a of the stem 92a. The wire 300 is heat-shrunk to a sheath 320 which will provide mechanical protection.

In Figures 6A and 6B, the formation probe device 50 is arranged so that the piston base 118 is allowed to reciprocate along the surface 113 of the adapter sleeve 94, and so that the outer surface 141 of the piston can reciprocate along the surface 114. The snorkel base 125 is arranged in the piston 96 and is designed for reciprocating movement along the surface 147, while the flange 153 of the scraper tube holder 152 reciprocates along the surface 145. The snorkel extension 126 is designed for reciprocating movement along the piston surface 120. The central passage 127 of the snorkel 98 is arranged in axial flush with the tubular extension 107 of the stem 92, the scraper tube holder 152, the scraper tube 150, the scraper 160 and the filter 100. The formation probe device 50 can move back and forth between a fully extended position, as shown in Figure 6A, and a fully retracted position, as shown in Figure 6B. The scraper tube 50 can also reciprocate between a fully retracted position, as shown in Figures 6A and 6B, and a fully extended position, as shown with a similar scraper tube 278 in Figures 7A-TE. When the scraper pipe 150 is fully retracted, fluid can flow in the central passage 108 of the extension 107, through the passage 155 in the scraper pipe holder 152, through the passage 151 in the scraper pipe 150, in the scraper bore 164, through the scraper openings 166, the filter 100 and the surrounding environment 15.

The operation of the formation probe device 50 will now be described with reference to figures 6A and 6B. The formation probe device 50 is normally in the retracted position. The device 50 remains retracted when not in use, for example when the drill string rotates during drilling if the formation probe device 50 is used for an MWD application, or when the wireline test tool is lowered into the borehole 8 when the formation probe device 50 is used with a wire. Figure 6A shows the formation probe device 50 in the fully retracted position, with the exception that the scraper pipe 150 is shown in the retracted position. The scraper pipe 150 is typically driven out when the formation probe device 50 is brought into place, see Figures 7A-7E. Figures 7A-7F also serve to describe the operation of the formation probe device 50, because the structure of the device 50 as described above is similar or equivalent to the parts of the probe device 200 that can be seen in Figures 7A-7F.

The formation probe device 50 thus starts from the retracted position shown in Figure 6A. After a corresponding order to the device 50, a force is applied to the base part 118 of the piston 96, preferably by means of hydraulic fluid. The piston 96 moves in relation to other parts of the formation probe device 50 until the retaining ring 159 will go against the flange 153 of the scraper tube holder 152. This position of the piston 96 in relation to the snorkel device 98 can be seen in Figure 7B. When hydraulic fluid is still pumped into the hydraulic fluid reservoir 54, the piston 96 and the snorkel device 98 will continue to move together upwards. The base part 118 slides along the surface 113 of the adapter sleeve all the way to the base part 118 for contact with the shoulder 170. After such contact, the device 50 will continue to pressurize the reservoir 54 until the reservoir 54 has obtained a certain pressure Pi. Alternatively, if the packing pad 180 makes contact with a borehole wall before the base part 118 has made contact with the shoulder 170, the formation probe device 50 will continue to exert pressure against the packing pad 180 and thereby pressurize the reservoir 54 up to the pressure Pi. The pressure Pi acting in the formation probe device 50 can be, for example, 57,456 Newton per m (1,200 psi).

The force from the hydraulic fluid in the reservoir 54 causes the snorkel device 98 to be driven out so that the outer end of the snorkel extension 126, the inner inlet end 131 of the filter (100) and the top of the scraper 160 will extend from the packing pad surface 183, through the opening 186 in the packing pad. The force acting on the snorkel must overcome the retraction force acting on the retraction side of the snorkel base 125 against the piston shoulder 172. This retraction force, provided by the retraction accumulator 424 and the retraction valves, is initially greater than the force acting outwards, so that the snorkel 98 thereby held in the retracted position. However, the push-out force will continue to increase until it becomes greater than the retraction force of, for example, 38,392 Newton per m<2> (900 psi). The snorkel device 98 stops its outward movement when the snorkel base part 125 contacts the shoulder 172 of the piston 96. The scraper tube 150 and the scraper 160 are in the extended position, as best shown in Figure 7E.

Alternatively, if the snorkel device 98 makes contact with a borehole wall before its base part 125 makes contact with the shoulder 172 of the piston 96, the hydraulic fluid in the reservoir 54 will still deliver a force up to the previously mentioned maximum pressure. The maximum pressure applied to the snorkel device 98 is, for example, 57,456 Newton per m2 (1,200 psi). Advantageously, the snorkel and packing pad will make contact with the borehole wall before the piston 96 or the snorkel 98 makes shoulder contact in the fully extended condition. The force acting on the packing pad is supported by the stabilizer 36, or a similar device which is arranged at or near the probe weight tube 12.

If, for example, the packing pad 180 has made contact with the borehole wall 16 before the pad is fully deployed and pressurized, the packing pad 180 will seal against the mud cake on the borehole wall 16 as a result of a combination of pressure and packing pad extrusion. The gasket will separate the snorkel device 98 from mud cakes, drilling fluid and other contaminants outside the gasket pad 180. When the snorkel device exits, the snorkel extension 126, the filter inlet end 131 and the top of the scraper 160 will penetrate the blocked mud cake, and advantageously pass through both the mud cake layer and into the formation 9.

When the filter 100 and the scraper 160 have been removed, the device including the piston 96 and the snorkel 98 will look as shown in figure 7E. When the snorkel extension 126 is introduced into a mud cake and into the formation, contaminants and residues will tend to collect on the filter 100, and this could affect the sampling of formation fluids. In order to remove the residues, which may be mud cakes or other contaminants from previous sampling, the scraper 160 can be withdrawn after the snorkel device 98 has been brought out. A downward retraction force is applied to the scraper tube 150, preferably by applying a hydraulic fluid force against the flange 177 of the scraper tube 150. The cavity formed by the scraper tube 150 and the snorkel surface 124 is filled with hydraulic fluid when the scraper tube 150 is moved downwards, until the scraper tube 150 bottoms out in the scraper tube holder 152. When the scraper 160 is pulled into the snorkel extension 126, the scraper 160 will pass through the filter 100 in frictional contact with it, whereby residues that may have collected on the filter 100 are agitated and removed. Alternatively, as mentioned above, agitation of residues can be achieved with a rotational movement of the scraper 160 about its longitudinal axis in the filter 100. When the scraper tube 150 is fully retracted, the openings 166 will align radially with the outlet end 135 of the filter 100, so that fluid connection between the bore 132 in the filter 100 and the passage 151 in the scraper tube 150. This action with the scraper 160, where residues are removed, is advantageously carried out as part of the withdrawal of the formation probe device 50, as described below.

In order to withdraw the formation probe device 50, forces or pressure differences can be applied to the snorkel 98 and the piston 96 in directions opposite to the forces acting for execution. At the same time, the output forces can be reduced or switched off in connection with a probe retraction. A hydraulic force is applied to the snorkel base part 125 at the shoulder 172 to thereby push the snorkel device 98 down until the flange 153 of the scraper tube holder 152 goes against the retaining ring 159, whereby the snorkel device 98 is fully retracted. At the same time, a hydraulic force is applied downwards on the piston base part 118 at the shoulder 170 until the base part 118 goes towards the stem base part 105, so that a full retraction of the formation probe device 50 is achieved. When the piston 96 makes contact with the stem base part 105, the probe retraction switch will 176 is triggered as described above. This is a signal that the formation probe device 50 has been withdrawn. The scraper 160 can be driven out to its original position at any time during a retraction. Scrapers 160 are deployed when the output pressure of the probe device, which pressure provides the retraction pressure for the scraper device because the probe device's executed parts are hydraulically coupled with the retraction parts of the scraper device, drops below the scraper device's output pressure.

Another embodiment of the invention is shown in Figures 7A-7F. The probe weight pipe 202 has a flow bore 14a where a telescoping formation probe device 200 is arranged. The probe device 200 can, compared to the probe device 50, be driven out towards a borehole wall that is further from the casing 202. Such borehole walls that are further from the casing 12 can occur in washed out parts of a well when the well has irregular shapes, when the well has been drilled with hole openers or reamers close to the drill bit, or when larger wells are drilled with bi-center drill bits. In such wells, the telescoping probe device 200 will be useful.

The telescoping probe device 200 includes a stem plate 210, a stem 212, a generally cylindrical and threaded adapter sleeve 220, an outer piston 230 designed to reciprocate in the adapter sleeve 220, a piston 240 designed to reciprocate in the outer piston 230, and a snorkel device 260 designed for reciprocating movement in the piston 240. The probe weight tube 202 has an opening 204 for receiving the telescoping formation probe device 200. A cover plate 206 covers the top of the probe device 200 and holds and protects the device 200 in the probe weight tube 202. The formation probe device 200 is designed to be able to exit through a opening 208 in the cover plate 206.

As shown in Figure 7A, the adapter sleeve 220 has an inner end 221 near the bottom 207 in the opening 204. The adapter sleeve 220 is held in the opening 204 as a result of a threaded cooperation with the neck tube 202 in the section 209. The outer end 223 of the adapter sleeve 220 is substantially flush with the opening 205 which is formed in the neck tube 202. The outer end 223 is formed with flanges 225 for cooperation with the cover plate 206. The adapter sleeve 220 has a cylindrical inner surface 227 with a part 226 of reduced diameter. A gasket 229 is arranged in the surface 226.

As shown in Figure 7B, the stem plate 210 has a circular base part 213 with an outer flange 214. From the base 213 there is a short extension 216. Through this extension 216 and the base 213 there is a central passage 218 intended for receiving the lower end 215 to the stem 212 with a central passage 203. The lower end 215 has threaded engagement with the stem plate passage 218. The central passage 218 has fluid connection with the fluid passage 91 (not shown, but shown schematically in Figure 9) which connects the fluid passage 93 (not shown, but shown schematically in figure 9) which leads to other parts of tool 10, including the equalization valve 60. The stem 212 extends up centrally in the probe device 200. An outer stem 219 is arranged around the stem 212. An outer stem-catch screw 222 with a central bore 224 has gang cooperation with the top of the outer stem 219.

As shown in Figure 7B, the outer piston 230 is slidably arranged in the adapter sleeve 220. This outer piston 230 has a cylindrical outer surface 232 with a base portion 234 of larger diameter. A gasket 235 is arranged in this part 234 with the larger diameter. The outer piston 230 also has a cylindrical inner surface 236 with parts 237, 238 of reduced diameter at the upper projecting part 233.1 surface 237, a seal 239 is arranged.

As shown in Figure 7C, the piston 240 is slidably disposed within the outer piston 230 and has a cylindrical outer surface 242 with a base portion 244 of a larger diameter. A gasket 245 is arranged in this part 244 with the larger diameter. Just below the base part 244, the piston 240 rests on a catch sleeve 254 which cooperates with the base part 234 in the outer piston 230. The retaining ring 256 cooperates with the bottom of the catch sleeve 254 and holds it in place. The piston 240 has a cylindrical inner surface 246 with a portion 248 of reduced diameter. The piston 240 further has a central bore 249 with a bore surface 241, which bore extends up through the extended part 250.

On top of the extended part 250 of the piston 240, a packing pad 280 is arranged. As shown in Figures 7A-7F, this packing pad 280 may have a donut shape, with a curved outer surface 283 and a central opening 286. However, the packing pad 280 may have other geometric shapes which will be known, for example as shown in US patent application 10/440,835 "MWD Formation Tester". The base surface 285 of the gasket pad 280 can be connected to a skirt 282. The gasket pad 280 can be tied to the skirt 282 or connected to the skirt 282 in another way, for example by the gasket pad 280 being molded onto the skirt 282 so that the material in the gasket pad will fill in grooves or holes in the skirt 282, as shown in US patent application 10/440,835. The skirt 282 is releasably connected to the protruding part 250 as a result of a threaded cooperation with the surface 241 in the central bore 249. Other fastening methods can be used here, for example a press fit in the central bore. Because the packing pad/skirt combination is detachable from part 250, the combination can be easily replaced on site. Alternatively, the packing pad 280 can be connected directly to the projecting part 250, without the use of a skirt. Other features of the gasket pad 280, such as the gasket pad material and how the gasket pad 280 works, are described above in connection with the gasket pad 180.

In Figure 7D, the snorkel 260 is shown to have a base portion 262, a snorkel extension 266, and a central passage 264 through the base 262 and the extension 266. The base portion 262 has a cylindrical outer surface 268 and inner surface 269. The extension 266 has a cylindrical outer surface 263 and inner surface 265.1 the top of the extension 266 a filter 290 is arranged, best shown in Figure 7F. The filter 290 is a mainly tubular element with a central bore 292 between a fluid inlet end 294 and a fluid outlet end 296. The filter 290 has a flange 298 at the fluid inlet end 294, and an internal slotted portion 293 with slots 295. Between the slotted portion 293 and the outlet end 296, the filter 290 has a threaded section 297 for threaded engagement with the snorkel extension 266.

A scraper tube holder 270 with a circular base part 272 and a holding edge 273, a tubular extension 274 with a central passage 275 and a central opening 271 for receiving the outer stem 219 is threadedly connected to the bottom of the snorkel 260 base part 262. The outer stem 219 has a central passage 243. A retaining ring 277 is arranged radially flush with and cooperates with a retaining edge 273, which limits the movement of the snorkel 260 in the retraction direction. After the snorkel 260 has been brought out, the retaining ring 277 will be under the scraper tube holder 270 in the piston surface 246, see figure 7E. The scraper tube holder 270 carries the scraper tube 278 when the scraper tube 278 is in the retracted position shown in Figure 7F, and isolates the hydraulic fluid reservoir formed by the tubular extension 274 and the snorkel surface 269. The scraper tube 278 with the central passage 279 is slidably held over the scraper tube holder 270 in the snorkel's passage 260 264. A scraper 288 is connected to the top of the scraper pipe 278. The scraper 288 has threaded connection with the scraper pipe 278 by means of the threaded section 281. The scraper 288 is a substantially cylindrical element with a scraper plug part 284, a central bore 287 and openings 289 which have fluid connection with the central bore 287. The scraper 288 is located in the central bore 292 of the filter 290 and can move back and forth between the filter inlet end 294 and the filter outlet end 296. Alternatively, as mentioned above, the scraper 288 can be rotatable in the filter 290. When the scraper tube 278 and the scraper 288 is in the retracted positions, as shown in Figure 7F, has an opening one 289 fluid connection with the fluid outlet end 296 of the filter 290, so that thereby fluid can go from the filter 290, through the scraper bore 287 and into the central passage 279 of the scraper tube 278.

As shown in Figure 7B, a probe retraction switch connector 276 is arranged in the opening 278 of the probe weight tube 202, just below the inner end 221 of the sleeve 220. The details regarding the switch connector 276 are as described above in connection with the switch 176, see Figures 8A-8B. Although not shown, the switch and connector 276 are electrically connected to a contact device provided in the stem base portion 213. The contact device makes contact with the plunger 240 when the plunger 240 moves toward the stem base portion 213, and indicates in the tool electronics that the probe device 200 now fully retracted.

The formation probe device 200 is designed so that the outer piston base 234 can reciprocate along the surface 227 of the adapter sleeve 220, while the outer piston surface 232 can reciprocate along the surface 226. Correspondingly, the piston base part 244 can reciprocate along the inner surface 236 while the piston surface 242 can reciprocate along the surface 237. The snorkel base part 262 is arranged in the piston 240 and can reciprocate along the surface 248, the holding edge 273 of the scraper tube holder 270 reciprocating between the holding ring 277 and the part 248 with the reduced diameter. The snorkel extension 266 is designed for reciprocating movement along the piston surface 241. The central passage 264 in the snorkel 260 is axially aligned relative to the stem 212, the outer stem 219, the scraper tube holder 270, the scraper tube 278, the scraper 288 and the filter 290. The formation probe assembly 200 is reciprocable between a fully retracted position, as shown in Figure 7A, and a fully extended position, as shown in Figure 7F. The scraper tube 278 is reciprocable between a fully deployed position, as shown in Figures 7A-7E, and a fully retracted position, as shown in Figure 7F. When the scraper tube 278 is fully retracted, fluid can flow in the central passage 203 of the stem 212, through the passage 243 in the outer stem 219, the passage 275 in the scraper tube holder 270, the passage 279 in the scraper tube 278, the bore 287 in the scraper 288, the scraper openings 289, the filter 290 and in the surrounding environment 15.

The operation of the formation probe device 200 will now be described with reference to figures 7A-7F. The formation probe device 200 initially has a retracted position, as shown in Figure 7A. The device 200 remains retracted when not in use, for example when the drill string rotates during drilling if the device 200 is used for an MWD application, or when a wireline test tool is lowered into the borehole 8 when the device 200 is used for a wireline test. Figure 7 A shows the device 200 in the fully retracted position, with the scraper tube 278 extended.

As a result of a suitable command to the probe device 200, a force is applied to the base part 234 of the outer piston 230, advantageously by means of hydraulic fluid. The outer piston 230 rises relative to the adapter sleeve 220, as the base part of the outer piston slides along the sleeve plate 227. The retaining ring 256 and the catch sleeve 254 force the piston 240 upwards together with the outer piston 230 by acting against the piston base part 244. As shown in 7B, the snorkel 260 remains in contact with the stem plate 210, while the outer piston 230 and the piston 240 begin to rise, until the head ring 277 contacts the retaining edge 273 of the scraper tube holder 270. At this point, the upward hydraulic force will still act on the device 200 reciprocating parts, and the fluid reservoir 334 expands and fills until the base part 234 abuts the adapter sleeve shoulder 332, as shown in Figure 7C. Now hydraulic fluid will be directed into the reservoir 336. Thereby the piston 240 and the snorkel 260 are caused to go out, as the piston base part 244 slides along the surface 236 of the outer piston. Finally, the piston base portion 244 will move toward the outer piston shoulder 342, as shown in Figure 7D. Usually here, too, the snorkel 260 and the packing pad 280 (figure 7C) will make contact with the borehole wall before these components are fully deployed. The tool stabilizer, or another similar device, will provide resistance to the force that causes the probe to travel. Before it reaches the position shown in Figure 7D, the packing pad 280 will preferably make contact with the borehole wall (not shown). To provide a seal by means of the packing pad 280, the device 280 will continue to pressurize the reservoirs 334, 336, until the reservoirs have reached a maximum pressure. Alternatively, if the packing pad 180 makes contact with the borehole wall before the probe device 200 has been fully extended, the probe device 200 will continue to exert pressure on the packing pad 280, up to the aforementioned maximum pressure. The maximum pressure exerted with the probe device 200 can be, for example, 57,456 Newton per m (1,200 psi).

Hydraulic fluid continues to be pumped through the reservoirs 334, 336, and the snorkel 260 will slide along the surfaces 248, 241 as hydraulic fluid enters the reservoir 338 and the force acting on the snorkel in the outward direction increases. This snorkel extension force must overcome the retraction force acting on the retraction side of the snorkel base 262 facing the piston shoulder 352. The retraction force provided by the retraction accumulator 424 and the retraction valves was early greater than the output force, thereby retaining the snorkel 260 in the retracted position. However, the pull-out force continues to increase until it becomes greater than the pull-back force, for example 38,392 Newton per m (900 psi). Finally, the snorkel base 262 will move toward the piston shoulder 352, as shown in Figure 7E. The snorkel 260 is now extended so that the outer end of the snorkel extension 266, the inlet end 294 of the filter 290 and the top of the scraper 288 will extend past the gasket pad surface 283, through the gasket pad opening 286. The scraper tube 278 and the scraper 288 are still in the executed position, as shown in figure 7E. If the packing pad 280 cooperates with the borehole wall, the snorkel extension 266, the filter inlet end 294 and the top of the scraper 288 will penetrate the sealed mud cake and advantageously through the mud cake layer and into the formation 9.

As previously described, introducing the snorkel extension 266 into the mud cake and into the formation will cause contaminants and residues to accumulate on the filter 290, which could affect the sampling of formation fluids. The scraper 288 is used to remove such residues in the same way as described above in connection with the formation probe device 50. A downward force acts on the scraper pipe 278, advantageously by applying a hydraulic fluid force against the flange 372 of the scraper pipe 278. The cavity formed by the scraper pipe 278 and the inner snorkel surface 269 will be filled with hydraulic fluid when the scraper tube 278 is moved downwards, until the pipe flange 372 goes towards the scraper tube holder 270. When the scraper 288 is drawn into the snorkel extension 266 in this way, the scraper 288 will pass through the filter 290 and agitate and remove residues that have collected on the filter 290. The scraping effect is due to the frictional interaction between the scraper 288 and the filter 290, as described earlier. It is also described above that you can alternatively have a rotating filter, and this also applies to the filter 290. When the scraper tube 278 is fully retracted, the openings 289 will align radially with the filter outlet end 296, so that a fluid connection between the filter bore 292 is made possible and the passage 279 in the scraper tube 278. The scraper 288 action for removing residues is advantageously carried out as part of the retraction sequence for the formation probe device 200, as described above.

For retraction of the probe device 200, a force or a pressure differential can be applied to it in a direction opposite to the output forces. At the same time, the execution forces can be reduced or removed completely, thereby facilitating the retraction of the probe. Advantageously, a pressure difference is applied to the flange 372 of the scraper pipe 278 by increasing the hydraulic fluid pressure against the bottom of the flange 372. Then the scraper pipe 278 will go out until the scraper 288 is fully finished again, whereby the filter 290 is scraped clean when the scraper 288 passes. A hydraulic force is then applied to the snorkel base part 262 at the shoulder 252 to push the snorkel device 260 down until the holding edge 273 of the scraper tube holder 270 goes against the retaining ring 277, whereby the snorkel device 260 is fully retracted. Then a hydraulic force is applied down against the piston base part 244 at the shoulder 342, until the base part 244 goes against the catch sleeve 254 and the retaining ring 256 at the outer piston base part 234. Hydraulic fluid is now introduced at the adapter sleeve shoulder 332 and against the base part 234 of the outer piston , thereby pushing the outer piston 230 downwards. The outer piston 230 will go towards the bottom 207 in the opening 204, and the piston 240/snorkel 260 device will go towards the stem plate 210, whereby the probe device 200 is fully retracted. When the piston 240 makes contact with the stem plate 210, the probe retraction switch 276 is triggered, as described above, signaling that the device 200 has been retracted.

It should be mentioned that in the formation probe device 50, the outer end of the piston-extending part 119 can only be brought out over the outer end of the sleeve 94 over a distance which is less than the length of the piston 96. The length of the piston 96 is defined as the distance between the upper end of the projecting part 119 and the lower end of the base part 118. For comparison, in the probe device 200, the outer end of the upper piston part 250 can be brought out past the outer end of the sleeve 200 over a distance that is greater than the length of the piston 240. The telescoping design of the probe device 200, i.e. the concentric pistons 230, 240, thus enables the packing pad 280 to cooperate with a borehole wall which is located significantly further from the collar tube 202 than the corresponding length of the piston 240.

An example of how the probe devices can be used in connection with testing a formation will now be described in more detail with reference to Figure 14. The test sequence 200 can begin (box 702) in response to an order to the tool 10 from the surface, or for example from a built-in tool - software. In a first embodiment, the piston 96 and the packing pad 180 can be moved out (box 704). In another embodiment, the piston 230 can be extended (box 703) to provide the aforementioned telescoping action. The borehole wall makes contact with the packing pad 180 (706). A volume around the snorkel 98 is sealed (box 708). In another embodiment, the packing pad 180 can be filled with a fluid (box 707), as described above. In the continuing sequence 700, the snorkel 98 can be extended (box 710), and the borehole wall makes contact with the snorkel 98 (box 712). The scraper 160 can now be retracted (box 714), with associated agitation and removal of contaminants from the snorkel 98. Now a formation property can be measured (box 716). In another embodiment, contaminants may be filtered (box 715), such as with the filter 100. After the measurement of a formation characteristic, the snorkel 98 is retracted (box 718), and also the piston 96 and packing pad 180 are retracted (box 720), while the scraper 160 is exported (box 722). The execution of the scraper 160 may also serve to remove contaminants from the snorkel 98. The sequence 700 ends (box 724) with a formation property being measured for further use, which will be described in more detail below.

In an alternative embodiment of tool 10, the formation probe devices 50, 200 can be located at other places in the tool. In Figure 3B, the formation probe device 50 can optionally be placed in the wings 37 of the stabilizer 36. The equalizing valve 60, the shut-off valve 74 and the pull pistons 70, 72 can remain in the same positions as shown in Figure 3B, but it is preferred that they are located close to the formation probe device 50 , and that they are therefore moved closer to the stabilizer 36. A placement of the formation probe devices 50, 200 in the stabilizer wings 37 enables the devices to be placed closer to the borehole wall and still be arranged in a robust part of the tool. The other wings on the stabilizer 36 can be used for repelling the formation probe devices 50, 200 during the execution and pressing against the borehole wall.

The wings on the stabilizer 36 are advantageously used as a counterweight for the execution of the formation probe devices 50, 200, even if the devices are not arranged in the stabilizer 36. In order to provide a sufficient sealing force for the probe packing pad, a reaction force must act on the tool as a counterweight to the force which used for the execution or deployment of the probe. Alternatively, if a stabilizer is not used, centralizing stamps of the type shown and described in US Patent Application No. 10/440,593, May 19, 2003, "Method and Apparatus for MWD Formation Testing", the contents of which are considered as part of the present description.

In the probe devices described above, a position indicator can be arranged for measuring the distance the probe device has been moved from the fully retracted position. Different sensors can be used to detect the position of the probe device when it exits. In one embodiment, such a position indicator can be based on a measurement of the volume of hydraulic fluid that is used to perform the probe device. If the probe device is designed to use hydraulic fluid and a pressure difference for the output, as described above, the volume of the fluid pumped into the probe device can be measured. With a known diameter for the adapter sleeve and the pistons, the distance traveled by the pistons can be calculated using the volume of fluid that has been pumped into the probe device. To make such a measurement more accurate, certain characteristics of the probe device can be taken into account, such as the compression of the packing pad when it is pressed against the borehole wall.

In another embodiment of the probe device position indicator, an optical or acoustic sensor can be arranged in the probe device, for example in an opening in the piston surface 141 in the formation probe device 50, or in the piston surface 242 in the probe device 200. The optical or acoustic sensor can measure the distance the piston moves from a known reference point, such as the piston position when the probe device is fully retracted. Such devices are well known to a person skilled in the art.

In yet another embodiment, electrical means can be used to detect the movement of the reciprocating parts of the probe device, such as a potentiometer, a resistance meter or another known device. The potentiometer or resistance meter can measure voltage or resistance, and such information can be used to calculate the distance.

The distance measurement obtained with the probe position indicator can be used for several purposes. For example, the borehole caliber can be calculated using such a measurement, so that an accurate measure of the borehole diameter can be obtained. Alternatively, a number of probes can be arranged around the drill string or wireline instrument, and one can then take measurements with such probes to thereby find the borehole diameter and shape. An accurate measurement of borehole caliber enables the drill operator to know where borehole breakouts or collapses are taking place. The caliber measurement can also be used for correcting formation evaluation sensors. For example, resistivity measurements will be affected by the size of the borehole. Neutron corrections in a neutron tool are also affected, as are density corrections for a density tool. Other sensor tools may also be affected. An accurate borehole caliber measurement contributes to the correction of such tools, as well as to the correction of other drilling, production and completion processes that require knowledge of the size of the borehole, for example a cementing.

In another embodiment, the probe position indicator can be used to correct for probe flow volume changes. Flow conduits, such as flow conduits 91, 93 in Figures 6A, 6B and 9, will be subject to volume changes as the probe packing pad compresses and decompresses. Especially when the packing pad is placed against the borehole wall and formation testing is taking place, the pressure in connection with the extraction of the formation fluids will cause the packing pad to compress with a corresponding increase in the flow line volume. The flow line volume is used in connection with several types of formation calculations, such as mobility, and the permeability can then be calculated using formation fluid viscosity and density. To correct for such volume changes and to achieve an accurate flow volume measurement, probe positioning can be used. Even if the total flow volume is known, possibly only a part of the volume will be used if the probe is not fully extended before the installation towards the borehole wall, and the amount will then not be known. The probe position can then be used to correct the part of the flow volume that is not used.

Design examples of the position indicator described above can also be used for pull-piston devices, so that one gets to know where in the cylinder the pull-piston is located and how the piston moves. Volume and diameter calculations can be used to provide the movement distance, or sensors can be used as described above. In this way, the exact movement distance for the piston can be obtained, instead of having to rely on the fluid volume used to activate the piston, as an indication of the distance traveled. The stability of the pull can also be achieved with the position indicator. The speed can be calculated on the basis of the measured distance, and the stability of the speed can be used to correct other measurements.

For example, to get a better understanding of the permeability of the formation or of the bubble point of the formation fluids, a reference pressure can be selected, and the distance the draw piston moves before such a reference pressure is reached can be measured using the draw piston position indicator. If the bubble point is reached, the piston's movement distance can be registered and sent to the surface, or to a software in the tool, so that the piston can be ordered to move less, so that the bubble point can be avoided.

Sensors for other purposes can also be arranged in the probe devices. For example, a known temperature sensor can be arranged in the probe device for measuring annulus or formation temperature. In one embodiment, the temperature sensor can be placed in the snorkel extensions 126, 266. In the retracted state of the probe device, the sensor will be close to the annulus environment, and the annulus temperature can then be measured. In the extended state of the probe device, the sensor will be close to the formation, whereby a measurement of a formation temperature is made possible. Such temperature measurements can be used for various reasons, such as for calculation of production or completion, or for evaluation calculations, such as permeability and resistivity. These sensors can also be placed near the probe devices, for example in the stabilizer wings or in the centralizing pistons.

In Figures 3B and 5, it can be seen that the probe weight tube 12 also contains pull-piston devices 70, 72 and a pull-stop valve device 74. In Figure 4, it is shown that the pull-piston device 70 includes an annular gasket 502, a piston 506, a plunger 510 and a end cap 508. The piston 506 is slidably arranged in the cylinder 504, and the plunger 510, which is made in one with and extends out from the piston 506, is slidably engaged in the cylinder 514. In figure 11, the piston 506 is shown in its retracted position, but is typically affected by tension to its upper position at the shoulder 516. A spring, not shown, biases the piston 506 to this upper position or shoulder position and is arranged in the lower cylinder portion 504b between the piston 506 and the end cap 508. Separate hydraulic lines, not shown, connect the cylinder 504 above and below the piston 506 i sy Sub-sections 504a, 504b for moving the piston 506 up or down in the cylinder 504. This will be described in more detail. The plunger 510 is slidably arranged in the cylinder 514, coaxial with the cylinder 504. The cylinder 512 is the upper part of the cylinder 514 which has fluid connection with the longitudinal passage 93 (shown schematically in Figure 9) which has connection with the draw-bar valve assembly 74, the draw-piston 72, the formation probe device 50, 200 and the balancing valve 60. The cylinder 512 is filled with drilling fluid as a result of its connection with the passage 93. The cylinder 514 is filled with hydraulic fluid below the gasket 513 through the connection with the hydraulic circuit 400.

The end cap 508 includes a contact switch (not shown) with a contact facing the piston 506. A lead wire 515 is connected to the contact switch. A plunger 511 is arranged in the piston 506. When the pulling of the piston device 70 is complete, as shown in figure 11, the piston 506 will activate the contact switch by the plunger 511 making contact with the contact switch, whereby the lead wire 515 connects the system to earth via the contact switch, the plunger 511 , the piston 506 and the end cap 508, which are grounded (not shown).

Figure 12 shows a second pull piston device 72. The pull piston 72 is designed like the piston 70, however with the noticeable difference that the pull volume is larger and that the device does not include a tension spring. The pull-piston device 72 includes an annular packing 532, a piston 536, a plunger 540 and an end cap 538. The piston 36 is slidably received in the cylinder 534, and the plunger 540, which is integrally formed with and extends from the piston 536, is slidably engaged in the cylinder 544. The plunger 540 and the cylinder 544 have larger diameters than the corresponding parts of the piston 70.1 figure 12, the piston 536 is shown in its pulling position, but is pressed to its uppermost position or shoulder position at the shoulder 546 by a hydraulic force. Separate hydraulic lines (not shown) connect cylinder sections 534a and 534b above, respectively below piston 536 for movement of piston 536 up or down in cylinder 534. This will be described in more detail. The plunger 450 is slidably received in the cylinder 544, coaxial with the cylinder 534. The cylinder 542 is the upper part of the cylinder 544 which is in fluid communication with the longitudinal passage 93 (shown schematically in Figure 9) which is in communication with the pull rod valve assembly 74, the pull piston 70, the formation probe device 50, 200 and the equalization valve 60. The cylinder 542 is filled with drilling fluid as a result of the connection with the passage 93. The cylinder 544 is filled with hydraulic fluid below the gasket 543, through the connection with the hydraulic circuit 400.

The end cap 538 has a contact switch 548 with a contact 550 facing the piston 536. A lead wire 545 is connected to the contact switch 548. 1 piston 536 a plunger 541 is arranged. When a pulling of the piston device 72 is complete, as shown in figure 12, the piston will 536 activate the contact switch 548 by the plunger 541 going towards the contact 550, whereby the lead wire 545 will connect the system to ground via contact switches 548, the plunger 541, the piston 536 and the end cap 538, which is grounded (not shown).

It should be understood here that the pull stamps can have varying sizes in accordance with varying volumes. The pistons can also be designed for pulling at different pressures. The embodiment just described includes two pull-piston devices, but a formation test tool can have more or fewer devices than two.

The hydraulic circuit 400 which is used to operate the formation probe devices 50, 200, the balancing valve 60 and the draw pistons 70, 72 is shown in Figure 9. A microprocessor-based controller 402 is electrically connected to all of the controlled elements in the one in Figure 9 showed hydraulic circuit 400, but such electrical connections for such elements are conventional and are therefore only shown schematically. The controller 402 is arranged in the electronics module 20 shown in Figure 2A, but can be located elsewhere in the tool 10 or the downhole device 6. The controller 410 detects the control signals that are transmitted from a main controller 401 arranged in the MWD socket 13 in the downhole device 6, which the main controller in turn receives instructions transmitted from the surface using mud pulse telemetry, or using other conventional means of transmitting signals to tools downhole.

When the controller 402 receives an order to start a formation testing, the drill string will be stopped if the drill string 10 is arranged on a drill string. As shown in Figure 9, the motor 404 is connected to a pump 406 which draws hydraulic fluid from a hydraulic reservoir 408 through a filter 410. It will be understood that the pump 406 supplies hydraulic fluid to the hydraulic circuit 400 which includes the formation probe device 50, 200 (both can be used interchangeably), the balancing valve 60, the pull pistons 70, 72 and the solenoid valves 412, 414, 416, 418, 420, 422. Although the description below only refers to a formation probe device 50, the described hydraulic circuit can be used to operate a formation probe device 50 or a probe device 200.

The operation of the formation test 10 is best understood with reference to Figure 9 and Figures 6A-6B, 7A-F, 11 and 12. In response to an electrical control signal, the controller 402 will energize the retraction solenoid valve 412 and valve 414 and start the motor 404. The pump 406 begins then to pressurize the hydraulic circuit 400 and, more particularly, to charge the probe retraction accumulator 424. The charging of the accumulator 424 also ensures that the formation probe assembly 50 will be retracted, that the equalization valve 60 is open and that the draw pistons 70, 72 are in their initial positions as described in connection with Figures 11 and 12. When the pressure in the system 400 reaches a certain value, such as 95,848 Newtons per m2 (1,800 psi) as sensed by the pressure transducer 426a, the controller 402 (which continuously monitors the system pressure) will energize the solenoid valve 416 which causes the formation probe device 50 to start moving outwards towards the borehole wall 16. At the same time, kickback will svalve 428 and relief valve 429 close the probe drawdown accumulator 424 at a pressure load of between approximately 24,000 and 60,000 Newtons per<m2> (500 to 1,250 psi). Solenoid valve 412 is still active.

The formation probe device 50 will, as previously described, move from the position in Figure 6A and to a position before full deployment, as shown in Figure 6B (while the snorkel is still retracted), in which position the packing pad 180 moves against the mud cake 49 on the borehole wall 16. Now the current to the retraction solenoid valve 412 is interrupted, allowing the snorkel 98 to exit while the scraper 160 enters. With continued hydraulic pressure on the plunger 96 and snorkel 98 extension side, the snorkel will penetrate the mud cake and the scraper will retract, as shown in Figure 6B (and Figures 7B-7F for the device 200). The outward movements of the piston 96 and the snorkel 98 continue until the packing pad 180 comes into contact with the borehole wall 16, as described above in connection with the probe device 50. This combined movement continues until the pressure against the piston 96 and the snorkel 98 has reached a predetermined value, for example 57,456 Newton per m<2>

(1,200 psi), as controlled by the relief valve 417, so that thereby the packing pad 80 is clamped. Now a second expansion step will take place as the snorkel 28 moves in the cylinder 120 in the piston 96 for penetration of the mud cake 49 on the bore wall 16 and reception of formation fluid, or for other measurements. A disconnection of the solenoid valve 412 also contributes to a closing of the compensation valve 60, whereby the fluid passage 93 is isolated relative to the annulus. In this way, the valve 412 will ensure that the valve 60 only closes after the packing pad 140 has made contact with the mud cake 49 that sits on the borehole wall 16. The passage 93, which is now closed to the annulus 15, has a fluid connection with the cylinders 512. 542 at the the upper ends of the cylinders 514, 544 in the draw-piston devices 70, 72, which is ordered in Figures 11 and 12.

With the solenoid valve 460 still energized, and with the hydraulic circuit 400 under a pressure of approximately 57,456 Newtons per m<2> (1,200 psi), the probe discharge accumulator 430 will be charged and the controller 402 will provide power to the solenoid valve 414. An energization of valve 414 results in a shutdown of the output section in the hydraulic circuit, so that the output section is thereby held under a pressure of approximately 57,460 Newton per m<2> (1,200 psi) and a draw begins. When the valve 414 is energized, the pressure can be added to the draft circuit, which generally contains the draft accumulator 432, the solenoid valves 418, 420, 422 and the draft piston devices 70, 72.

The controller 402 now ensures the supply of current to the solenoid valve 420, which allows pressurized fluid to now enter the section 504a of the cylinder 504 and cause a withdrawal of the pull piston 70. When this happens, the plunger 510 will move in the cylinder 514 so that the volume in the fluid passage 93 increases correspondingly to the volume which is determined by the area of the plunger 10 forming the length of the stroke of the plunger in the cylinder 514. The volume in the cylinder 512 is increased during this movement, thereby also increasing the volume of fluid in the passage 93. Advantageously, these elements are dimensioned so that the volume of the fluid in the passage 93 is advantageously increased by a maximum of 30 cm when the piston 70 is withdrawn. If the draw piston 70 is to be stopped, for example when there is a need for only a partial draw or in the case of a poorly successful partial draw, the controller 402 can again provide power to the solenoid valve 418 in order to pressurize the pull rod valve arrangement 74. A pressurization of the valve arrangement 74 means that the draw piston 70 no longer draws down formation fluids. The valve device 74 and the pull piston 70 are pressurized up to approximately 95,848 Newton per m (1,800 psi). This ensures that the shut-off valve device 74 holds the draw piston 70 in its draw or partial draw position so that the drawn formation fluid is held and not accidentally ejected.

When it is desired to be able to continue a draw with the draw piston 70, the current to the valve 418 can be interrupted, whereby the shut-off valve 74 is closed. The pulling with the pulling piston 70 then continues until the volume in the cylinder 514 is filled. The pull of the pull piston 70 can be interrupted by valves 418 and 74. Such interruptions may be necessary to change the pull parameters, such as the pull speed and volume.

The controller 402 can be used to command the piston 70 to draw fluid at different speeds and volumes. For example, the draw piston 70 can be ordered to draw down fluid in an amount of 1 cm<3>per second up to 10 cm<3>, and then wait 5 minutes. If the result of this test is unsatisfactory, a signal can be sent by means of mud pulse telemetry, or by means of other wellbore communication means, so that the controller 402 is ordered to o cause the piston 70 to now o draw down fluid by 2 cm<3>per second up to 20 cm<3>, and then wait 10 minutes. These figures are of course only examples. The first test can be interrupted, the parameters changed, and the test can then be restarted with the new parameters sent from the surface to the tool. These parameter changes can be made while the formation probe device 50 is brought out.

When the draft piston 70 is stopped, the controller 402 can supply current to the solenoid valve 422, so that pressure fluid can thereby enter the cylinder part 534a in the cylinder 534 and cause the draft piston 72 to enter. When this happens, the plunger 540 will move in the cylinder 534 so that the volume in the fluid passage 93 increases corresponding to the volume determined by the area of the plunger 540 times the length of the plunger's stroke in the cylinder 544. The volume in the cylinder 542 is increased with this movement, whereby the fluid volume in the passage 93 increases. Advantageously, these elements are dimensioned so that the volume of the fluid passage 93 is increased by 50 cm<3> when the piston 72 enters. Advantageously, the draw piston 72 has no stop and start pull in the same way as the piston 70, and can therefore draw down more fluid faster. The draw piston 72 can be designed for drawing fluid with, for example, a speed of 3.8 or 7.7 cm 3 per second. However, it should be understood that the pistons 70, 72 can have different sizes and that the piston 72 can be designed with stop and start details via the shut-off valve device. The hydraulic circuit 400 can thus be designed to operate several pistons 70 and/or several pistons 72. The pistons 70, 72 can also be operated in another way.

The previously described option for controlling the pull pistons 70, 72 means that the operator can flush fluids into the pull piston devices and into the probe flow lines. If, for example, a pretest volume of fluid has been drawn into the probe, it can be flushed by activating the drawing pistons in the opposite directions. This can be beneficial for the desire to clean out any accumulated residues in the flow lines and in the probe device.

Clean flow lines are important to protect the instruments in the test tool, and to maintain the integrity of the formation tests by flushing out old fluid residues from the lines. In another embodiment, in order to keep the flow lines clean, a mechanical filter is arranged in the flow lines, such as anywhere in these flow lines 91, 93 shown in figures 6A, 6B and 9. Alternatively, the flow lines is flushed by opening the balancing valve 60, pumping out any fluid that may be present in the flow lines, and then closing the balancing valve 60 to prepare for yet another draw sequence.

When the draw piston 70 is activated, 30 cm<3> of formation fluid will thus be drawn through the central passage 127 in the snorkel 98 and through the filter 100. This movement of the piston 70 in the cylinder 504 causes a pressure drop in the closed passage 93, to a pressure below the formation pressure, and thereby, formation fluid will be drawn through the filter 100 and into the openings 106, through the snorkel 98, further through the stem passage 108 and to the passage 91 which has a fluid connection with the passage 93, and forms part of the closed fluid system. In total, the fluid chambers 93 (including the volume of the various connected fluid passages, including the passage in the formation probe device 50, the passage 91, 93, the passage connecting 93 with the draft pistons 70, 72 and the draft shut-off valve 74) will have a volume of approximately 63 cm<3>. If the draw piston 72 is also activated, this volume can be increased by approximately 30 cm<3>, up to a total of approximately 90 cm<3>. Drilling mud in the annulus 15 is not drawn into the snorkel 98, because the packing pads 180 seal against the mud cake. The snorkel 98 serves as a conduit through which formation fluid can pass, and the pressure in the formation fluid can be measured in the passage 93, with the packing pad 180 serving as a seal to prevent annulus fluid from entering the snorkel 98 and destroying the formation pressure measurement.

Reference should now be made for a moment to figure 6B, where formation fluid is first drawn into the central bore 132 in the filter 100. The formation fluid then passes through the slots 134 in the slotted filter segment 133, so that the particles in the fluid are thereby filtered out and not drawn into the passage 93. The formation fluid then passes between the outer surface of the filter 100 and the inner surface of the snorkel extension 126, out through the outlet end 135, through the openings 166 in the scraper 160, through the scraper tube 150 and into the central passage 108 in the stem 92.

The filter 100 (and the filter 290 in the device 200) can be optimized for special applications. If, for example, you have obtained knowledge about the formation, then the filter can be adapted to the rock type or sediment type that is known to be found in the formation. One type of adjustable filter is a gravel-packed filter that can be used instead of or together with a slotted filter 100. A gravel-packed filter will generally consist of two elongated, cylindrical filters with different diameters. These filters are arranged concentrically, and the annulus is filled with gravel or a known sand size.

Regardless of the type of formation encountered, the gravel pack can be designed so that it has a 10-1 ratio between the formation sand size and the gravel pack size, which is a preferred ratio between formation particles and gravel particles. With such a ratio, it is to be expected that the gravel pack filter will be able to take formation particles up to 1/10 of the size of the nominal formation particle diameter that one expects to encounter. With such a design, the sand size of the gravel pack can be adapted to the specific purpose.

In another embodiment, the filters 100, 290 as shown in Figures 6B, 7F can be optimized by changing the size and number of slits, as required for a particular application. The slots, or slots, are shown schematically as an internally slotted section 133 with slots 134 in Figure 6B, and as an internally slotted segment 293 with slots or slots 295. The size and number of slots can be designed in accordance with the particular formation to be - is sought, and on the basis of the nominal sand particle size in the produced sand. For example, for smaller nominal formation particle sizes, it can be chosen to use slits with smaller openings.

In another embodiment, the aforementioned setting of the slot size can take place in real time. In the preceding embodiment, the slot size is selected when the tool 10 is to be placed in the drill hole. The slot size will remain unchanged during the placement of the tool 10. The slot size can be changed at the surface by replacing the filters 100, 290, or manually changing the slot size, but such a change cannot take place in real time, or when the tool 10 is in the wellbore. In the latter embodiment, detection of the formation type can be achieved using the various devices and methods described here. If a detected formation value, such as a particle size, differs from the predetermined value, the slot size can be changed without the tool 10 having to be removed from the well. An order can be given from the surface, or from the tool 10, and the slot size can be changed by moving two concentrically arranged and slotted cylindrical elements in relation to each other, or by, for example, setting closing mechanisms at the slots. In Figure 9, with the packing pad 180 sealing against the borehole wall, the one-way valve 434 will maintain the desired pressure acting on the piston 96 and the snorkel 98, thereby maintaining the sealing effect of the packing pad 180. In addition, because the probe seal accumulator 430 is fully charged, extra hydraulic fluid volume can be supplied to the piston 96 and the snorkel 98, should the tool 10 move, thereby ensuring that the packing pad 180 remains in a tight position against the borehole wall. If the borehole wall 16 were to move in the vicinity of the packing pad 180, then the accumulator 430 would be able to supply more hydraulic fluid to the piston 96 and the snorkel 98 to thereby ensure that the packing pad 180 remains in good sealing against the borehole wall 16. Without the accumulator 430 in the circuit 400, a movement of the tool 10 or the borehole wall 16, and thus of the formation probe device 50, could cause loss of sealing at the packing pad 180, and errors in connection with the formation testing.

With the draw pistons 70, 72 in fully or partially retracted positions, and with from one to 90 cm of formation fluid drawn into the closed system 93, the pressure will be stabilized and enable the pressure transducers 426b, c to sense and measure the formation fluid pressure. The measured pressure is transmitted to the controller 402 in the electronic section where the information is stored in memory and, alternatively or additionally, communicated to the main controller 401 in the MWD tool 13 below the formation tester 10, where the information can be transmitted to the surface using mud pulse telemetry or another suitable, conventional telemetry operation.

When the draw is finished, the pistons 70, 72 will activate their contact switches, as described earlier. When, for example, the contact switch 550 is activated, the controller 402 will respond by shutting down the motor 404 and the pump 406, thereby saving energy. The check valve 436 will hold the hydraulic pressure and hold the pistons 70, 72 in their retracted positions. In the event of a leak of hydraulic fluid, which could cause the pistons 70, 72 to start moving towards their original shoulder positions, the accumulator 432 will provide the necessary fluid volume to compensate for such a leak and thereby maintain a sufficient force ratio of the pistons 70 , 72 in their contracted positions.

In this interval, the controller 402 will continuously monitor the pressure in the fluid passage 93 by means of the pressure transducers 426b, c. When the measured pressure has stabilized, or after a predetermined time interval, the controller 402 will break the current to the solenoid valve 416. When this happens, the pressure will be relieved on the closing side of the balancing valve 60 and on the outlet side of the probe piston 96. The balance valve 60 will return to its normally open state, and the probe retraction accumulator 424 will cause the piston 96 and the snorkel 98 to retract, so that the packing pad 180 is brought out of engagement with the borehole wall. Then the control 402 will again start the motor 404 to operate the pump 406 and ensure that power is supplied to the solenoid valve 412. This ensures that the piston 96 and the snorkel 98 are fully retracted and that the balancing valve 60 is opened. Given such an arrangement, the forming tool will have a redundant probe retraction mechanism. The active retraction force is provided by the pump 406. A passive retraction force is provided by the probe retraction accumulator 424 which can retract the probe even when the energy supply fails. It is preferred that the accumulator 424 be charged on the surface before being lowered into the wellbore to provide pressure for holding the piston and snorkel in the housing 12.

It will be understood that the equalization valve 60 can be opened in a similar way at other times during the interaction of the probe with the borehole wall. If the probe packing pad is in danger of sticking to the borehole wall, the suction can be broken by opening the equalization valve 60 as described above.

After a certain pressure, for example 95,848 Newton per m (1,800 psi) is sensed by the pressure transducer 426a and communicated to the controller 402 (indicating that the balance valve is open and that the piston and snorkel are fully retracted), the controller 402 will de-energize the solenoid valves 418. back to the starting positions. The controller 402 monitors the pressure by means of the pressure transducer 426a, and when a certain pressure is reached, the controller 402 will determine that the pistons 70, 72 have fully retracted. The controller will then shut down the motor 404 and the pump 406 and cut off the power supply to the solenoid valve 412. When all the solenoid valves have returned to their initial positions and the motor 404 has stopped, the tool 10 will be back in the initial state.

The hydraulic circuit 400, which is shown in Figure 9, can also act as a regenerative circuit during the execution of the probe device. With both retraction valve 412 and discharge valve 416 activated, as described above, and with a difference in area between the smaller area on the retraction side of the probe piston, such as piston 96 or piston 240, and the larger area on the discharge side of the piston, there will be a net effect that brings the probe device outwards. The piston continues to extend, while the retraction valve is still open, and there will therefore be a backflow of hydraulic fluid through the retraction valve 412, because there is a lack of a one-way valve behind or after the retraction valve 412. This relatively unobstructed backflow path means that the pressurized hydraulic fluid will flow into the outlet valve 416 and add to the pressure on the outlet side of the circuit, with which the outlet speed of the probe can be increased.

During the execution of the probe device, using the hydraulic circuit 400, the total volume of hydraulic fluid that the pump 406 must displace, and thereby the number of revolutions for the motor 404, will be reduced compared to a non-regenerative circuit. The regenerative nature of the circuit 400 also allows the movable scraper or scraper, such as the scraper 160, to remain engaged during the execution of the probing device, particularly when the snorkel device penetrates the mud cake and formation and thereby there will be an additional force that tries to push the movable scraper back. As shown in Figures 6A, 6B and 7A-7F, the area on the discharge side of the scraper device, for example the bottom of the flange 372 on the scraper tube 278 in Figure 7F, is larger than the area on the retraction side, or the flange 372's upper side. When both valves 412 and 416 are activated, one and the same hydraulic pressure will thus act on different areas, which means that the wiper element will go out, and that the pressurized fluid is regenerated on the discharge side of the scraper pipe 278, as described above.

Furthermore, also as mentioned earlier, the generation of the pressure in the circuit 400 enables a faster deployment or deployment of the probe device. In addition, the regenerated pressure will contribute to a control of the balancing valve activation.

In the probe weight tube 12, as shown in Figure 101, a hydraulic reservoir-accumulator device 600 is arranged. This reservoir-accumulator device 600 will maintain a pressure in the hydraulic system of the tool 10 that is greater than the annulus pressure or the ambient pressure. This state of the hydraulic system compensates for pressure and temperature changes in the tool. The pressure delivered from the device 600 will cause the pump 406 (figure 9) to start working from the annulus pressure, thereby reducing the workload that would otherwise be necessary when starting the pump 406 at atmospheric pressure. The accumulator device 600 can thus be used for communicating the annulus pressure into the tool's hydraulic system. As discussed in more detail below, the device 600 is autonomous and can be easily replaced on site. The device 600 includes a housing 602 with an upper surface 632, a bottom surface 634 (Figure 10C) and an end cover 604 at the end 606, several locking rings 608 and drilling fluid ports 618, 620 at the end 622. The upper surface 632 has additional fluid ports 628, 630 which is covered with a filter 639, as shown in Figure 10F. The filter 639 is held in place by means of a retaining ring 637, and the filter prevents larger particles in the drilling fluid from entering the cylinders and disrupting the piston movements. The end cover 604 includes a pressure plug 638 for connecting the device 600 to the probe weight tube 12, which helps to lock the device 600 in place, as shown in Figure 10H. The end cover 604 also includes one-way valves 640, 642 for fluid connection with the tool's hydraulic circuit, and for holding fluid in the device 600 and in the tool's hydraulic system when the device 600 is removed from the neck tube 12.

In Figure 10F it can be seen that the device 600 is internally divided into two cylinders 626, 646.

Figure 10C shows the cylinder 626 with a piston 636 which divides the cylinder 626 into a section 626a with hydraulic fluid and a section 626b with drilling fluid. The piston 636 can reciprocate between the position shown in Figure 10C and the position of the piston 656 shown in Figure 10D. In the cylinder section 626b, a spring 624 is arranged between the piston 636 and the end 622. The spring 624 extends past the piston end 636b and over the piston 636 and bears against a piston part 633 whose diameter is increased. This piston part 633 designed with an increased diameter corresponds to the larger piston part 633 on the piston 656, see Figure 10G. At the end 622, the opening 620 will enable drilling fluid to enter the cylinder section 626b and thereby bring the surrounding annulus pressure to action against the piston side 636b of the piston 636. Because the spring 624 also acts against the piston side 636b, the hydraulic fluid pressure in the cylinder section 626a will be greater than the annulus pressure. The pressure of the hydraulic fluid in the cylinder section 626a will be equal to the annulus pressure plus the pressure provided by the spring 624. The spring 624 can, for example, exert a pressure of approximately 2,800 to 3,800 Newtons per m<2> (60-80 psi).

The cylinder 646 in figure 10D works in a similar way to the cylinder 626. Drilling fluid enters the cylinder section 646b through the opening 622 and will apply an annulus pressure on the piston side 656b of the piston 656. The spring 644 will increase the pressure on the piston 656, thereby causing the hydraulic fluid pressure in the cylinder 646a, and thereby the hydraulic fluid pressure in the tool hydraulic system, to be greater than the annulus pressure. The spring 644 is shown in its fully compressed position in Figure 10D.

As shown in Figure 10G, the extended piston end 656a has a gasket 659 that provides a seal between drilling mud and hydraulic system fluid. Furthermore, there is a scraper 661 here which cleans the cylinder bore 646 when the piston 656 reciprocates. The spring 644 rests against the larger diameter part 653. The piston end 636a is designed like the piston end 656a shown in Figure 10G.

Advantageously, the pistons 636, 656 reciprocate independently of each other, maintaining the thickness of the tool's hydraulic system. Both pistons communicate with the tool's hydraulic system.

In figure 10H, the accumulator device 600 is shown placed in the neck tube 12, but is not locked. When placing the device 600 in the cavity 601 in the neck tube 12, the device 600 is placed over the cavity 601, and the locking wings 608 (Figure 10A) are brought into alignment with recesses 664. The recesses 664 have a large L-shape (not shown), as the end parts of L' one extends towards the end cover 604 and the end 603 in the cavity 601. The device 600 is introduced into the cavity 601 as the locking wings 608 slide down into the recesses 664 until the device 600 is brought into place at the bottom of the cavity 601 and the top surface 632 will essentially be flush with the carrier's 12 surface. The device 60 is then guided towards the end of the cavity 603 so that the locking wings 608 enter the protruding female parts of the recesses 664 and the pressure plug 638 (figure 10A) is pressed into an opening (not shown) in the end 603 of the cavity 601. This forward movement also means that the a gap 678 is formed between the end 605 of the cavity and the end 622 of the device.

To lock the device 600 in place, a wedge 670 is placed in the gap 678. The chamfered end 622 (shown in Figure 10C) cooperates with the inclined side 676 of the wedge 670. The wedge action between these surfaces causes the device 600 to move completely forward in the cavity 601. The bolts 674 and nuts 672 are used to lock the wedge 670. L-shaped locking pieces 668 are placed in the recesses 664, and bolts 666 are used to lock the wings 608. The final locked position of the device 600 is shown in figure 101 The fluid ports 628, 630 have a connection with drilling fluid in the annulus 15. Fluid entering the cylinder sections 626b and 646b through the openings 618, 620 is filtered by means of slits in the wedge 670 (such slits are not shown).

A withdrawal of the accumulator device 600 takes place in the reverse order of that described above. The one-way valves 640, 642 will close and thereby keep the oil in the tool's hydraulic system. The device 60 can then be cleaned and/or replaced. The one-way valves 640, 642 are opened again as soon as the device 600 is locked in place. Hydraulic fluid can then be supplied to replace any fluid loss, and fluid is advantageously supplied to such an extent that the pistons 636, 656 are pushed back to the position shown in figure 10D.

Order for the tool 10 is not limited to the use of mud pulse telemetry. Other applicable telemetry systems may include manual methods, pump cycles, flow/

pressure band, tube rotation or combinations of these. Other possible methods include electromagnetic (EM), acoustic and wire telemetry. An advantage of using alternative telemetry methods is that mud pulse telemetry (both up and down) requires a pump, which other telemetry systems do not.

The downhole receiver for orders or data from the surface may reside in the formation test tool or in an MWD tool 13 with which the test tool communicates. Correspondingly, the wellbore transmitter for orders or data from the hole can be located in the formation testing tool 10 or in an MWD tool 13 with which the testing tool communicates. In the preferred embodiment described herein, the receivers and transmitters are located in the MWD tool 13, and the receiver signals are processed, analyzed and sent to a master controller 401 in the MWD tool 13 before being sent to the local controller 402 in the form test tool 10.

Claims (13)

1. Wellbore device (10) including: a weight tube (12) with an outer surface for cooperation with a foundation formation, an executable test device with a bore and arranged below said outer surface in a first position for execution beyond the outer surface and to a second position, a first traction cylinder (504) in which a first piston (506) is slidably arranged, which first piston can be activated between a first position and a second position, the first traction cylinder having a fluid connection with the executable test device, a flow line (91, 93) between the executable test device and the first traction cylinder, the borehole and the flow line being designed to receive at least formation fluid from the basic formation, characterized by a second traction cylinder (534) which slidably accommodates a second piston (536), which second traction cylinder is fluid series connected with the first traction cylinder (504) and with the executable test device. 2. Device (10) according to claim 1, characterized by the wood controller (402) which is programmed to order the first piston (506) to stop in a third position in the first traction cylinder (504) between the first and the second position, and to order the piston to be moved again. 3. Device (10) according to claim 1, characterized by a filter arranged in the flow line (91, 93). 4. Device (10) according to claim 1, characterized by a hydraulic circuit (400) in fluid communication with the executable test device and the first traction cylinder (504), and which hydraulic circuit includes an accumulator (424) for supplying fluid to at least one of the executable test device and the first traction cylinder. 5. Device (10) according to claim 4, characterized in that the hydraulic circuit (400) includes valves (412, 416) for directing fluid from a withdrawal side of the executable test device and towards an output side of the executable test device when the executable test device is activated from the aforementioned first position and to the second position. 6. Device (10) according to claim 1, characterized by a wood position indicator for signaling a position for the first traction cylinder (506). 7. The wellbore device (10) according to claim 1, including: a drill string (5) with a drill bit (7) at a distal end of the drill string, and with a collar pipe (12), which collar pipe is arranged close to the drill bit, a hydraulic circuit (400 ) with a fluid pressure, and a hydraulic reservoir accumulator (600), which hydraulic reservoir accumulator is configured for fluid communication with an annulus (15) that surrounds the drill string and has an annulus fluid pressure, and the hydraulic circuit is configured so that the reservoir accumulator can supply annulus fluid pressure to the hydraulic circuit. 8. Procedure for operating a wellbore device (10), including: placement of a shock tube (12) in a borehole (8), which shock tube includes an operable sampling device, a hydraulic circuit (400) and a first draw piston device, execution of a sampling element from the executable test device outside the collar tube, movement of a piston (506) in the draw piston device, drawing of a fluid in the executable test device and a flow line (91, 93) between the executable test device and the draw piston device, accumulation of a fluid pressure in the hydraulic circuit, characterized by diverting a hydraulic fluid from a retraction side of the sampling element, directing the fluid to the sampling element's discharge side, and providing an additional discharge force on the sampling element's discharge side. 9. Method according to claim 8, characterized in that the accumulated fluid pressure is supplied to at least one of the executable test device and the first draft piston device (70). 10. Method according to claim 8, characterized by indicating a position for the draw piston (506) at any point during the draw piston movement. 11. Method according to claim 10, characterized by calculation of a speed for the draw piston movement and correction of another wellbore measurement. 12. Method according to claim 8, characterized in that the pulling piston (506) can be moved between a first and a second position and that it further includes: stopping the pulling piston in a third position, and starting the movements of the pulling piston again. 13. Method according to claim 8, characterized in that a balancing valve (60) is arranged in the neck tube (12), which balancing valve has a fluid connection with the flow line (91, 93), opening of the balancing valve, pumping the fluid in the flow line out through the balancing valve, and cleaning the flow line.