NO316886B1 - Underground formation drilling apparatus and method for drilling a subsurface formation - Google Patents

Description

The present invention relates to an underground formation drilling apparatus with a pipe sleeve which includes a structure at its upper end for connection to a drill string, and which delimits a longitudinal borehole, as well as a core drill bit which is arranged at the lower end of the pipe casing, formation evaluation instrumentation which can be influenced to obtain data associated with at least one formation characteristic parameter at the same time as cutting out a core from a formation. It also includes a method for drilling an underground formation.

The invention is generally intended for use in cable-core drilling of underground formations in combination with a drilling system that enables replaceable placement and withdrawal of inner tube assemblies for core drilling and drill-plug assemblies for forward drilling, the latter also possibly being equipped with logging options for evaluation of borehole parameters, and in particular the ability to simultaneously log a formation that is cored and the core sample that is cut from the formation.

Cable core drilling has been known for many years. The basic concept of cable core drilling is to use a core casing which includes an outer casing assembly which is arranged at the end of a drill string and has a core drill bit at its base. An inner tube assembly adapted to receive a core cut by the core drill bit is releasably secured in the outer sleeve assembly. This device makes it possible to place the inner tube assembly in the outer hole assembly by means of cable, gravity or hydraulic flow, and to pull it up from the outer hole assembly via cable. Examples of such known cable core drilling systems are shown in US patents 3 127 943 and 5 020 612, which are hereby referred to, as well as NO B1 311 047.

A problem with many such known systems is the need to use a special drill string with an enlarged diameter to allow the insertion and withdrawal of an inner tube assembly used to cut relatively large cores, greater than 5.08 cm (2 in.) in diameter.

Although coring systems that cut small or "slim-hole" cores of 4.45 cm (1%") diameter or less are known, it should be understood that such cores are very fragile and conventional core drilling systems are limited in length, so that cores can reasonably be cut without breaking. This limitation appears to be mainly due to the instability of the entire core casing, which is initiated by lateral and vertical movement of the drill bit in the borehole, which produces vibrations. A main phenomenon caused by such drill bit movement and vibration is the so-called drill bit -"vortex", although vibration without vortex is also harmful. The term drill bit "vortex" occurs with drill bits that have unbalanced shear forces, As these forces cause the bit to rotate or "whirl" in the borehole about a center point at a distance from the geometric center of the bit, in such a way that the bit tends to swirl backwards around the borehole.It has been observed that the swirling phenomenon is exacerbated in the presence of ca liber cutters or trimmers at certain places on the outer dimensions of the drill bit, as such cutters also create frictional forces during drilling. Whirling is a dynamic and self-sustaining phenomenon which, in many cases, is very harmful to bit cutters. The vortex phenomenon also leads to spiraling of the borehole during drilling, which, in core drill bits, leads to a non-cylindrical, spiral-shaped core that is more prone to breakage and wedging in the core casing inner tube.

Considering the relatively small clearances between the core and the guide shoe, the core catcher and the inner tube components of the inner sleeve, small lateral and vertical movements of the core sleeve will easily lead to breakage in small diameter cores with consequent core wedging and degradation of the core sample. For this reason, small diameter core casings are usually of limited length due to the short (e.g., 3.05 to 3.96 m (ten to thirteen feet)) core samples that could be cut without being subject to the above-mentioned core breakage, wedging, and degradation. Attempts have been made to cut longer cores, up to 7.92 m (twenty-six feet), but the apparatus used has never been considered workable, due to the above problems.

It has been recognized that certain improvements in drill bit design, including but not limited to so-called "anti-swirl" polycrystalline diamond cutter (PDC) bits introduced by Amoco and improved by applicant, could be achieved for core drill bits to improve the reliability of a core drilling operation and the quality of the cores. Patents disclosing anti-whirl bits include, without limitation, US Patents 4,982,802, 5,010,789, 5,042,596, 5,099,934, 5,109,935, 5,111,892, 5,119,892, 5,131,478, 5,165,494, and 52,178 2 , to which reference is hereby made. SPE (Society of Petroleum Engineers) Document No. 24587 by L. A. Sinor et al at Amoco Production Co., entitled a "Development of an Anti-Whirl Core Bit", deals with improvements and potential improvements in core drilling capability believed to be achieved by using of antivlrvel core drill bits.

Other solutions for bit stabilization have been used by Amoco and others. One solution is to attempt perfect balancing of a drill bit, as shown in US patent 4,815,342 to which reference is hereby made. Another solution is to mechanically "lock" the protrusions on the drill bit surface in circular grooves cut by cutters on the end surface, as shown in US patent 5,090,492 to which reference is hereby made.

All the above-mentioned developments in drill bit stabilization have been concentrated on individual elements during the drilling operation, either drilling of the nominal borehole diameter or during core drilling.

A few years ago, the Eastman Christensen Company, a predecessor of the present applicant, developed a combined hole and core drilling system with a "Drill-Core System" capability, which allowed drilling operations for alternating core drilling and hole drilling without withdrawal of the drill string. According to the drill-core system, both the inner casing assembly for coring and a replacement center plug assembly with a "crowsfoot" (English: crowsfoot) and cutters for converting the core-bit to a hole-bit could be deployed and pulled up by cable. The drill core system used natural diamond core drill bits and was only marginally applicable for several reasons. First, the maximum core length that could be drilled at a time was only 3.96 m (13 ft), which provided very short intervals for analysis without multiple runs of the inner-tube assembly, and required combining different lengths of tube to drill the drive tube down to the rotary drill as a pipe joint. In addition, the introduction of more accurate electrical well logs and analysis techniques for logging data reduced the need for core analyses. Finally, the industry would not accept the relatively small diameter (2") cores taken using the system, which were necessary to deploy and pull the inner sleeve assembly and center plug assembly through standard tubing stock.

In recent years, however, the development and industry acceptance of sidewall core drilling techniques of the punch and rotary type, which result in 1" diameter cores from the side of the borehole being drilled, as well as the increasing use of "slim-hold" drilling for exploration wells , eliminated the earlier skepticism regarding the acceptance and use of small-diameter cores. These changes in industry practice have led to a renewed interest in core drilling, but today the state of the art with respect to core drilling systems has not provided an acceptable "slim-hole"- coring and well drilling system that can cut pristine, undamaged cores of desired length (e.g. 9.14 m (thirty feet)), substantially avoid core wedging, and furthermore allow for forward drilling between intervals to be cored without extracting In addition, there is no known core drilling system with performance capabilities and operating characteristics similar to those of PDC drill bits.

Another disadvantage of known core drilling systems is their tendency to treat extraction (excision) of the core and assessment of borehole parameters as separate, only peripherally related operations instead of two coherent segments of the overall formation evaluation process. Even bm US patent 4 955 438, which belongs to the applicant and is hereby referred to, shows how to take "measured values" of borehole characteristics during a core drilling operation and acquire such data from the core drilling rig physically, by means of cable or by means of mud pulse telemetry , the applicant is not aware of any such system being suitable for use in oil and gas exploration wells. Furthermore, it should be noted that although it would be desirable to log certain characteristics of a core while it is being cut and at the same time with logging of directional parameters as well as characteristics of the formation on the outside of the core drilling apparatus, no core drilling system with such capabilities is known to exist.

The purpose of the present invention is to avoid or reduce the disadvantages of the state of the art as discussed above, and this is achieved according to the invention by a subsoil formation drilling apparatus as stated in subsequent claim 1, and a method as stated in subsequent claim 17, while advantageous embodiments of the invention is stated in the other subsequent claims.

The present invention enables alternating core drilling and hole drilling without extracting the drill string and extracting long cores with a small diameter.

The core sleeve according to the invention comprises an outer sleeve assembly with a PDC core drill bit disposed at its lower end and a drill bit end bearing assembly immediately above the core drill bit in the core sleeve to alternately receive the end of an inner tube assembly or a center plug assembly. A locking coupling is located on the upper inside of the outer sleeve assembly. The inner tube assembly includes a socket coupling member at the upper end, a lock assembly thereunder for engagement with the outer sleeve lock coupling and a bearing assembly below the lock assembly to allow rotation between the outer sleeve assembly and the inner tube. The lower end of the inner tube assembly, which engages the bit bearing assembly, includes a conventional core catcher.

The PDC core drill bit used in the invention is preferably of an "anti-swirl" construction, although other stabilized drill bit constructions as discussed above may also be suitable. Use of an anti-swirl core drill bit in the invention leads to the demonstrated ability to cut and pull at least 9.14 m (30 ft) of high quality core and greatly increased recovery rate. In addition, the use of a PDC core bit with an optional center plug provides a rate of penetration (ROP) similar to that achieved with PDC bits, and weight on the bit (WOB), rotational speed and hydraulic volume flows similar to those achieved with PDC bits. Thus, large quantities of high-quality cores can be obtained cost-effectively and the total ROP during the drilling operation is not significantly reduced compared to drilling without core drilling, as the operator benefits from time and cost savings as well as information available from the high-quality cores. quality.

The use of the drill bit end bearing assembly results in accurate alignment of the inner tube to receive the core being cut out, as well as a seating arrangement for the lower end of the center plug assembly which contains a number of PDC cutters and fluid outlets for drilling fluid.

An eventual feature of the invention, which is nonetheless important, is the placement of a suitable logging tool, such as a gamma ray or directional logging tool, in the center plug assembly to enable logging during a drilling operation. Data may be stored in the logging tool joint during drilling and periodically retrieved by cable transmission or when the center plug assembly is pulled to the surface, or a mud pulse or other suitable data transmission system may be included as part of the center plug assembly to allow real-time transfer of data. One or more sensing possibilities can be included in the tool, as such possibilities include, without limitation, pressure and temperature measurement in addition to others mentioned above. It should be noted that logging tool sensors and especially sensors for detecting formation characteristics can be arranged immediately next to the lower end of the center plug assembly, literally in the neck of the core drill bit, for extremely close adjacency to the bit surface and thereby to the formation being drilled.

It is also contemplated that sensors for measuring directional parameters as well as the above-mentioned borehole parameters and further including others such as (by way of example only) formation resistivity and nuclear magnetic resonance (NMR), as well as power supply, data processing and memory, and downhole data transfer or telemetry capability , shall be included in one or more of a core bore-inner tube assembly, in the wall of the core sleeve between its exterior and bore, or above the core sleeve in a separate pipe section or housing with an axial through bore that is aligned with the bore in the core sleeve. Sensors for measuring drilling parameters such as (here only as an example) torque, rotational speed, weight on the drill bit, vibration and borehole pressure can also be included in one or more components of the device, preferably near the drill bit such as in the wall of the core sleeve.

Another aspect of the invention involves simultaneous, or at least temporally coinciding, logging of borehole parameters at the formation outside the core sleeve and logging of the same or a different borehole parameter at the core that is cut out while it is introduced into the core-inner tube assembly. E.g. one can take gamma ray, resistivity, density, porosity, sound and/or NMR logs. It is advantageous to take such logs for the sake of comparison with respect to the characteristics exhibited by the outer formation as opposed to those exhibited by the core under the controlled environment of the core casing interior and at extremely small distance. Moreover, it is desirable to carry out such chemical logs immediately after the core has passed through the core bit throat when the core is in its most pristine condition and least prone to being heavily contaminated by drilling mud or having lost its physical integrity. Furthermore, it is contemplated that the orientation of the core will be determined, both in absolute terms and with respect to the surrounding formation from which it is cut, using the directional instrumentation of the apparatus.

It is further contemplated that a short-range, wireless telemetry system can be used to transmit data over a short distance from a location in the core sleeve wall to the inner tube assembly, or vice versa, for subsequent transmission using a long-range telemetry system located in the other part of the apparatus, or from one or the other of these locations to a long-range telemetry module located a short distance above the core casing in the borehole. Data can be relayed by mud pulse, acoustics, or electromagnetic telemetry, or by cable extending to the surface. Furthermore, data can be stored in electronic memory located in the inner tube assembly or in the above-mentioned center plug assembly and with this physically retrieved to the surface instead of being forwarded in essential real time. Of course, data is preferably stored in an inner tube assembly, center plug assembly, core sleeve or in a separate housing associated with the core drilling apparatus, even if transmitted to the surface in real time, to prevent data loss due to poor transmission or transmission failure.

Yet another aspect of the present invention lies in a method for drilling and simultaneously obtaining directional formation and possibly drilling parameter data before a core drilling operation is carried out, with the aim of locating a zone or layer of potential interest, such as a hydrocarbon-producing zone, before the inner tube assembly is driven in to begin core drilling. Likewise, it is intended that obtaining such data during the core drilling operation will give the operator the opportunity to identify when core drilling should cease, and without core drilling of rock mainly outside a zone of potential interest. When practicing this side of the invention, it will of course be desirable to communicate the data that is produced to the surface on a real-time basis, particularly when drilling in a potentially producing zone. During core drilling, it may be sufficient to obtain data for each interval that is cored at the time when the inner tube assembly containing the core sample is pulled to the surface,

but it would clearly be preferable to locate the endpoint of the zone of interest as accurately as possible, indicating that real-time data transfer may also be preferable in such a situation.

In the following, the invention will be described in more detail with reference to the drawing where: Fig. 1 is a schematic longitudinal section through the core sleeve according to the present invention; Fig. 2 is a longitudinal section on a larger scale through the lower end of the core sleeve according to the invention, with the inner tube assembly in place for core drilling; Fig. 3 is a schematic elevational view showing cutter placement, looking down through the bit end face of an anti-swirl core bit suitable for use with the present invention; Fig. 4 is a vertical section on a larger scale through one example of an Inner Diameter cutter in a low penetration core drill bit and a cooperating core drill shoe device suitable for use with the present invention. Fig. 5 is a schematic view of a first embodiment of a core drilling apparatus with an inner tube assembly in place in a device suitable for simultaneous core drilling and logging of borehole parameters and transmission of recorded borehole parameter data to the earth's surface;

Fig. 6 is a schematic diagram showing surface instrumentation combined

with a receiver and a computer;

Fig. 7 is a schematic view of a second preferred embodiment of a core drilling apparatus with an inner tube assembly in place in a device suitable for simultaneous core drilling and logging of borehole parameters and transmission of recorded borehole parameter data to the earth's surface; Fig. 8 is a schematic diagram of a third preferred embodiment of a core drilling apparatus with an inner tube assembly in place in a device suitable for simultaneous core drilling and logging of borehole parameters and transmission of recorded borehole parameter data to the earth's surface; and Fig. 9 is a schematic view of the lower end of a preferred, instrumented center plug assembly according to the invention.

A core sleeve 10 according to the present invention is shown in fig. 1 is shown suspended in a borehole 12 from a weight pipe 14 at the bottom of a drill string that extends to the surface.

The core sleeve 10 comprises an outer sleeve assembly 16 with a tubular outer sleeve 18. At the top of the outer sleeve 18 there is a threaded coupling sleeve 20 for attaching the core sleeve 10 to the threaded coupling pin 22 of the weight tube 14. A PDC core bit 24 of anti-swirl or other stabilized design as above described, is attached to the bottom of the sleeve 18. PDC cutters 26 on the core drill bit 24 cut the formation as the drill string is rotated, and also cut a core 28 from the formation being drilled, the core 28 extending up into the throat opening 30 of the core drill bit 24 as the drill bit drilling forward in the formation. If desired, the core drill bit 24 can be of the low penetration type, as shown in US patent 4,981,183, which belongs to the applicant and to which reference is hereby made. On the inside of the sleeve 18 is a locking coupling 32, under which there are a number of axially spaced groups of bearing ribs 34 which extend circumferentially around the interior of the sleeve 18. Inside the core drill bit 24 is a rotary bearing assembly 36 for the bit end. Fluid channels 38 extend from the inside of the bit to its end face.

An inner tube assembly 40 is shown arranged in the core casing 10 as it would be during coring operations. The inner tube assembly 40 includes at its lower end an inner tube 42 which is engaged in the rotary bearing assembly 36. The inner tube 42 extends up into the outer sleeve 18 through the group of bearing ribs 34, which provides support against lowering and bending of the inner tube 42. At the top of the inner tube 42 is the inner tube bearing assembly 44 which allows the upper and lower portions of the inner sleeve assembly 40 to rotate relative to each other and thus, in combination with the bit end bearing assembly 36, allows the outer sleeve assembly 16 to rotate while the inner tube assembly 40 remains stationary. Above the bearing assembly 44 is a locking assembly 46 in releasable engagement with the locking coupling 32 on the inside of the outer sleeve 18. At the top of the inner sleeve assembly 40, a hook coupling 50 is arranged for selective engagement with and release of the inner sleeve assembly 40 by means of a cable-supported fishing sleeve.

In fig. 2 are the parts that have previously been numbered in connection with fig. 1, given the same reference numbers.

As shown in fig. 2, the bearing assembly 36 comprises an outer housing 60, the bearing

62, and an inner housing 64 which rotates freely relative to the outer housing 60 due to the bearing 62. Ribs 66 with chamfered shoulders 68 at their lower ends extend radially inwards from the inner housing 64, the ribs 66 and shoulders 68 laterally and axially supporting the inner tube the lower end of the assembly 40. The distance between the ribs 66 allows drilling fluid to flow into the neck opening 30 of the core drill bit 24 and around the core 28 during core drilling. If this flow is not desirable, a low-penetration core drill bit of cooperating shoe construction of the type shown in the above-mentioned '183 patent and shown in the application's fig. 4 is used to minimize drilling fluid contact with the core. At the lower end of the inner tube 42, either a wedge-type core catcher 70 as shown on the left in the drawing or a basket-type core catcher 72 as shown on the right in the drawing (both are previously known) can be used. PDC cutters 26 are omitted from FIG. 2, but as shown in fig. 1 they are arranged on the core drill bit 24 to carve out a core which is dimensioned to move upwards in the neck opening 30 of the core drill bit 24 and into the bore 74 in the inner tube 42.

When it is desired to core drill with the device according to the present invention, the inner pipe assembly 40 is driven into the drill string on a cable and locked in the outer casing assembly 16. Drilling fluid is then circulated down through the drill string and into the annulus 100 between the inner pipe assembly 40 and the outer casing -the assembly 16, where it exits from the end face of the core bit 24 through conventional fluid channels and nozzles (not shown) to clean and cool the cutters and clean the bit surface as the string is rotated and the formation and core are cut. When the maximum core length is reached, the inner tube assembly is pulled out of the borehole via a cable with a fishing sleeve at its end for engagement with the coupling part 50, and another inner tube assembly inserted into the drill string if further core drilling is desired.

Temperature measurement is particularly desirable and useful if a gel core drilling operation is carried out, with non-penetrating gel for encapsulating the core sample which is passed through the inner tube 42 before entering the drill string. The temperature-sensitive nature of such gels, as well as their ability to increase viscosity and also to a significant extent solidify over a relatively narrow temperature drop range, make the ability to measure core-shell depth temperature a very desirable capability, which allows formulation or selection of gels that will become viscous at the desired depth and not too early. A more complete explanation of the formulation and use of non-penetrating gels for core sample encapsulation can be found in concurrently referenced US Patent No. 5,360,074.

In fig. 3, examples of anti-swirl core bit 24 are shown, viewed down through the bit end face 200, when oriented in the borehole. Placement of PDC cutters 26 is schematically shown on the drill bit surface 200, certain cutters 26 extending radially inward from the inner diameter 202 which delimits the channel mouth 30 in the core drill bit 24, whereby a core with a smaller diameter than the diameter of the mouth 30 can be cut. Channels 204 are provided around the inner diameter 202 to allow flow of drilling fluid, if desired, past the outside of the core. Other fluid channels 220 extend through the bit surface 200. Although anti-swirl bits are well known in the art, it should be noted that the blades 206 and 208 of the core bit 24 are without cutters at the outer diameter 210, and that diameter pads 212 and 214 on the blades 206 and 208 are used as bearing surfaces for the core drill bit 24 against the borehole wall. Selected size, location, and orientation of the cutters 26 on the bit face 200 results in a cumulatively directed lateral or transverse force vector oriented in a direction perpendicular to the bit axis and between the blades 206 and 208, which causes the diameter pads 212 and 214 to yaw substantially constantly against the borehole wall and eliminate vibration and tendency to bit swirl.

Fig. 4 shows an arrangement consisting of a low-penetration inner diameter cutter on a low-penetration core drill bit 248 with cooperating core drill shoe 246 as shown in the above-mentioned US patent 4,981,183. The core drill bit 248 can have different shapes, but preferably has a parabolic profile as generally indicated at 251. Alternatively, other profiles can advantageously be used. For example, generally flat sides that give the drill bit a generally conical shape can be used. The main body 256 of the core bit 248 comprises a number of channels 252 which form a fluid connection between the annulus 100 in the core sleeve 10 and outlet openings 240 in the end surface of the core bit 248. A number of cutters 26, preferably PDC cutters, are preferably distributed along the core bit 248 profile.

The main part 256 preferably comprises a lower bore 257. At least one inner diameter cutter 226, and preferably two or three such cutters 226 spaced apart in the circumferential direction, extend within the surface which delimits the lower bore 257 of the core drill bit 248 to cut an inner diameter, i.e. the outer diameter of a core 28. Each individual diameter cutter 226 is preferably designed with a flat portion 264 at this diameter dimension which is smaller than the bore 257. The lip or guide section 262 of the core shoe 246 can thus extend downwards to such a position that its end tip 266 is located immediately next to the upper edge 268 of the cutters 226 in the annular space formed by the cutters 226 between the various diameters formed by the flat parts 264 and the lower bore 257. The core drill bit 248 comprises a ledge 258 on its inner surface above the lower bore 257. A bearing surface 260 abuts the landing 258 and thereby forms a constriction, and ideally essentially a fluid seal, between the rotating drill bit and the stationary core sleeve. With the arrangement described above, the outside of the core is precisely cut and the core 28 penetrates the core drill shoe 246 immediately after leaving the upper edges of the planar cutter portions 264. The preferred profile 251 combined with the orientation and location of the outlet of the channels 252 away from the inner diameter of the core drill bit 248, provides better flushing of formation casing and at the same time works to make the core less exposed to drilling fluid, thus improving the mechanical as well as chemical integrity of the core sample. It will be clear to a person skilled in the art that the arrangement according to fig. 2 can be modified to a low penetration design by designing the inner diameter of the core crown 24 differently and using an extended shoe with a guide portion, both as shown in FIG. 4. The inner housing 64 in the bit end rotary bearing assemblies 36 may be designed with channels that are positioned and oriented to direct fluid to channels that direct fluid to the bit face, instead of to the throat opening or inner diameter. Of course, the channels 204 on the inner diameter, as shown in fig. 3, is omitted.

Fig. 5 shows a first preferred embodiment 300a of a core drilling apparatus with the possibility of obtaining different data in connection with various borehole parameters ("borehole data") during a core drilling operation. The apparatus 300a comprises a core sleeve 302 with a core drill bit 304 attached to its lower end and an inner tube assembly 306 arranged in the core sleeve 302's longitudinal bore 308 flush with the core drill bit's bore neck 310. As mentioned and described above, it is preferred that the core drill bit 304 comprises a PDC core drill bit, and preferably a stabilized core drill bit. The coring apparatus 300a is suspended in a borehole from a casing 312 by means of a typical API threaded connection 314.

The core sleeve 302 includes a locking coupling 320 on its upper interior, with which the inner tube assembly locking assembly 322 can be releasably engaged to retract the inner tube assembly 306 via a hook coupling 324 or other construction such as a fish neck adapted to be gripped by a retracting mechanism like a fishing socket at the end of a cable. The main part of the inner tube assembly 306 is rotatably suspended from the upper, locked part by means of a rotary bearing assembly 330 of a known type. If desired, a drill bit end bearing assembly (not shown) as described above can also be used to stabilize the lower end of the inner tube assembly 306. The bearing assembly 330 and the optional bit end bearing assembly allow rotation of the core sleeve 302 about the inner tube assembly 306 below the bearing assembly 330 for to cut a core of formation material without subjecting it to rotationally induced stress, a technique well known in the art.

The core drill pipe 332 with an open mouth 333 at its lower end is positioned to receive a formation core through the core bit neck 310.

Just as an example, the device 300a can include instrumentation 336 for determining borehole position and orientation (azimuth, slope, etc), the following being generally referred to as "directional instrumentation", as well as instrumentation 338 for obtaining data in connection with formation characteristics, such as ( only as an example) borehole temperature, borehole pressure, formation resistivity, formation gamma radiation, formation nuclear magnetic resonance, density and porosity, hereinafter referred to as "formation evaluation instrumentation". The above-mentioned instrumentation is at least to some extent equipped with processing capability and electronic machine-readable memory, both denoted by 340, for storing acquired data, and is in connection with data transmission device 342 for transmission of real-time data to the earth's surface.

Those skilled in the art will recognize that the directional instrumentation, in addition to being used to follow borehole direction, can (and is desired) be used to develop and maintain a record of the orientation of the core as it is cut, thereby correlating the core data with the borehole data obtained from the formation surrounding the core drilling apparatus 300d and from which the core sample is cut.

In the apparatus 300a, a formation evaluation instrumentation 338 is contained in the wall of the core sleeve 302, and may comprise a series of pressure housings arranged circumferentially around the sleeve 302, or a continuous, toroidal pressure housing. As shown by the arrows pointing inward and outward from the instrumentation 338, such an arrangement will facilitate the simultaneous acquisition of formation evaluation data from the surrounding formation and from a core 350 as it enters the mouth 333 of the core pipe 332 and moves relatively upward therein (at due to the forward or backward movement of the core drilling assembly). Any or all of the above types of formation evaluation instrumentation may be used, it being understood that gamma radiation, porosity, density, residual stiffness, nuclear magnetic resonance and sonic logs are believed to be particularly suitable for performance in conjunction with the core 350 characteristics. The core sleeve 302 and its wall and exterior may be similarly designed for "transparency" to the relevant incoming and (in some cases) outgoing fields, waves, subatomic particles, and other signals used in performing such logs. It should be understood that the different locations shown and described for sensors for measuring different borehole parameters can be varied depending on the logical location for each to best obtain data, and thus assemblies will vary accordingly.

As previously mentioned, it is also highly desirable, and most would say crucial, to ensure the orientation of the core (azimuth, angle in relation to the vertical direction), both in absolute terms and also for correlation with the surrounding formation being logged. In the apparatus 300a, processors) and electronic memory 340a as well as a power supply 346 are located in the core sleeve 302, and a wireless telemetry transmitter 354 is used to transmit data to the receiver 356 located in the inner tube assembly 306 for forwarding to the surface via data transmission -or the telemetry device 342, which may comprise a slurry pulser or any of the above system types. Furthermore, the inner tube assembly 306 occupies another power supply 346 for operation not only of the data transfer device 342, but also of additional processors and memory 340b and directional instrumentation 336. Thus, both formation and directional data can be sent to the surface in real time, and one or the other or , if desired both, may be stored in memory 340b for periodic pull-up with inner tube assembly 306 for download at the surface. It is also contemplated that the location of the formation evaluation instrumentation 338 immediately adjacent to the core drill bit 304 provides an extremely favorable location for the drilling parameter instrumentation 360 to monitor such characteristics as torque, rotational speed, weight on the drill bit, vibration and pressure, as well as directional parameters as noted above, the latter being favorable for total tracking of the borehole trajectory and to point out the location and orientation of potential zones or strata of interest. As shown, the directional instrumentation 336 can optionally be accommodated in the core sleeve 302 instead of being carried by the inner tube assembly 306.

Fig. 7 shows a second preferred embodiment 300b of a core drilling apparatus according to the present invention, where features and components previously described will be denoted by the same reference number, and the only differences between the apparatus 300b and 300a will be explained in more detail. As shown, the apparatus 300b includes an instrumentation tubing portion 370 above the core casing 302, which constitutes one or more of the directional instrumentation 336, the formation evaluation instrumentation 338, and the drilling parameter instrumentation 360. The tubing portion 370 may include a modified reservoir navigation tool, or RNT, provided by the 1NTEQ operating unit of Baker Hughes , i.e. the applicant. The pipe part 370 comprises a power supply

346 as well as data processing and memory electronics 340a. Data from the pipe part 370 is transferred via a short-range transmitter/receiver combination 354 and 356 to the data transmission assembly 342 in the inner pipe assembly 306, which also contains a power supply 346 and preferably at least one memory 340b, if processing capability is otherwise not required in the draw-up system I li ng. Furthermore, and as shown, the directional instrumentation 336 can be occupied in the inner tube assembly 306 instead of in the tube part 370, and a further power supply 346 for operation of the directional instrumentation 336. Communication link 362, which extends from the directional instrumentation 336 and memory 340b, can comprise a hard wire link which uses a slip ring coupling to pass the bearing assembly 330, or if desired, a wireless, electromagnetic, short-range link. A further possibility is to use a telemetry assembly 342 in the tube part 370 and from there transfer to the surface data from the instrumentation in the inner tube assembly 306, which is transmitted wirelessly short-range to the tube part 370 in an arrangement that is the reverse of what is shown.

Fig. 8 shows a third preferred embodiment 300c of the core drilling apparatus according to the present invention. As in the previous figures, features and elements will be designated where possible with reference numbers that have already been used, and only significant differences in the apparatus according to fig. 9 will be described in more detail. The apparatus 300c uses a telemetry pipe part 380 located above the core casing 302, the pipe part 380 preferably accommodating an acoustic or electromagnetic telemetry or data transmission device 342. Formation evaluation instrumentation 338 and drilling parameter instrumentation 360 are occupied in the core casing 302 and, as in the embodiment according to fig. 7, the formation evaluation instrumentation may have the ability to perform a "look-in" log of a core sample 350 as it travels into the core drill pipe 332. A hardwire telemetry link 382 may be used to transmit data from the core casing-borne instrumentation to the telemetry pipe section 380 via connections between the casing 302 and the pipe part 380 as known in the art, or a short-range wireless arrangement can be used. Likewise, the directional instrumentation can 336

(optionally occupied in either inner tube assembly 306 or core sleeve 302)

wireless short-range transfer to the telemetry tube part 380, such an arrangement preferably being a hard wire link between the inner tube assembly 306 and the core sleeve 302 or the telemetry tube part 380.

It should be understood that the center plug for drilling a full borehole diameter can replace the inner tube assembly 306 until the interval to be cored is reached. Furthermore, such a center plug including a data transmission device, electronic memory and a short-range receiver can be used to transmit data to the surface from the formation evaluation instrumentation 338, the drilling parameter instrumentation 360, or also the directional instrumentation 336 which is occupied in the core sleeve 302 as previously shown in the embodiments according to fig. 5-8. By real-time evaluation of formation characteristics during drilling of the borehole, a suitable place to start core drilling at a potential zone or layer of interest can thus be identified literally instantly and with relatively high precision compared to known techniques. At such a point, the center plug will be pulled up and instead an inner tube assembly 306 inserted into the core casing 302. Similarly, and with appropriate formation evaluation instrumentation in place during the coring operation, a relatively accurate termination of the interval or zone of interest can be determined. At such a point, coring can be stopped, the last core pulled up and a center plug reinserted into the core sleeve to drill forward without coring. In this way, a number of zones of interest can be located and drilled during core drilling, while the intervals between the zones of interest are only logged and drilled without taking coresAs shown in fig. 9, it may be desirable to design the core drilling apparatus according to the invention in an embodiment 400, here shown with a center plug 402 in place, so that formation evaluation instrumentation 338 is arranged in the actual neck 310 of the core drill bit 304 itself immediately next to the front surface 404 of the plug 402 where cutters 406 is placed. Such sensor proximity to the formation in front of the core drilling apparatus may require a redesign of the internal fluid channels 408 in the core drill bit 304 as shown, as it may no longer be possible to pass such channels through the end of the center plug. The channels 408 will be operative only with a center plug 402 which is blocked by suitable design of an inner tube assembly to avoid contamination of the core. Of course, as previously mentioned, directional and/or drilling parameter instrumentation can also be included in a center plug such as the 402.

Although short-range and long-range telemetry systems have been described above in terms of a single transmitter and receiver, for simplicity, it will be readily understood that two-way transmission may be desirable in many cases, e.g. to enable or disable instrumentation, to change instrumentation to another mode of operation, or to request instrumentation for calibration or testing purposes.

Although all the instrumentation described above has been arranged in the borehole as part of the core drilling apparatus according to the invention, it will also be understood and appreciated by those skilled in the art that surface instrumentation on or below rig decks can be used to monitor drilling-related parameters that can be correlated and used in combination with data obtained from the downhole instrumentation. The surface instrumentation 500 as shown in FIG. 6, can thus be used in combination with a computer 502 and with data received from down in the borehole through a receiver 504 to provide data to the operator via the screen display 506, which can perceive digital or graphic display in transient form (so such as on a video screen) or permanent form (paper, film, electronic memory including magnetic or optical, etc.) and, if desired, transmitted further via wires on land, radio telemetry or satellite links or elsewhere for further evaluation.

As cables, fishing sockets, hook couplings, locking couplings and locking assemblies, core catchers, bearing assemblies and other core sleeve components of a wide variety of constructions are well known in the art, these elements are not described in more detail. Likewise, various bypass valve assemblies of various designs may be used with core sleeves according to the invention to alternately direct drilling fluid flow through or around inner tube assemblies and to allow displacement of fluid by means of the core, but such devices are also entirely conventional, well known to those skilled in the art, and will thus not be shown or described. Finally, as the various types of directional, drilling and formation parameter instrumentation discussed here are previously known, as are associated data transmission and other electronics (processors, memory, power supplies, etc.), no further description of such is necessary .

Claims (21)

1. Subsurface formation drilling apparatus with a pipe sleeve (302) which includes a structure at its upper end for connection to a drill string, and which defines a longitudinal borehole (308), as well as a core drill bit (304) which is arranged at the pipe sleeve (302)'s lower end, formation evaluation instrumentation (336, 338) which can be influenced to obtain data associated with at least one formation characteristic parameter simultaneously with cutting a core from a formation, characterized in that the formation evaluation instrumentation (336, 338) is at least partially arranged in the pipe wall of the pipe sleeve (302). 2. Underground formation drilling apparatus according to claim 1, characterized in that at least part of the formation evaluation instrumentation (336, 338) is located close to the core drill bit (304). 3. Subsurface formation drilling apparatus according to claim 1, characterized in that the formation evaluation instrumentation (336, 338) is aligned to and positioned to obtain data associated with at least one formation characterizing parameter from a core segment located in the longitudinal borehole (308) next to the instrumentation (336, 338). 4. Subsurface formation drilling apparatus according to claim 1, characterized by a retractable inner tube assembly (306) which is designed for placement in the casing bore and includes a lower part which is designed to receive a core which is cut out by the core drill bit (304). 5. Underground formation drilling apparatus according to claim 4, characterized by a transmitter (342,344,354) for sending data to a location at a distance from the formation evaluation instrumentation (336, 338). 6. Subsurface formation drilling apparatus according to claim 5, characterized in that the transmitter (342, 344, 354) is located above the lower part of the inner tube assembly (306). 7. Underground formation drilling apparatus according to claim 6, characterized in that the transmitter (342, 344, 354) is part of the inner tube assembly (306). 8. Underground formation drilling apparatus according to claim 5, characterized in that the transmitter (342, 344, 354) is a slurry pulser, an acoustic transmitter and/or an electromagnetic transmitter. 9. Subsurface formation drilling apparatus according to claim 1, characterized by directional instrumentation (336) which can be influenced to obtain data related to the position and orientation of the apparatus. 10. Subsurface formation drilling apparatus according to claims 4 and 9, characterized in that the directional instrumentation and the lower part of the inner tube assembly (306) are cooperatively designed to produce orientation data for the received core. 11. Subsurface formation drilling apparatus according to claim 1, characterized by a machine-readable memory (340) for storing borehole data in the apparatus. 12. Underground formation drilling apparatus according to claim 5, characterized by an underground receiver (356) placed above the sleeve to receive data transmitted by the transmitter, and a second transmitter which is connected to the receiver for onward transmission of data to the earth's surface. 13. Underground formation drilling apparatus according to claim 1, characterized by instrumentation (500) at the earth's surface for obtaining drilling data, a transmitter near the sleeve for sending data from the formation evaluation instrumentation to the earth's surface, a receiver at the earth's surface for receiving data from the transmitter, and a computer for processing the received data and data from the surface instrumentation. 14. Underground formation drilling apparatus according to claim 5, characterized in that the transmitter is located above the pipe sleeve (302). 15. Subsurface formation drilling apparatus according to one of the preceding claims, characterized by drilling parameter instrumentation that can be influenced to obtain information data associated with torque, rotational speed, weight of drill bit, vibration and/or pressure. 16. Subsurface formation drilling apparatus according to claim 13, characterized by directional instrumentation which is located close to the pipe sleeve (302) and which can be influenced to obtain data related to the pipe sleeve (302) and which can be influenced to obtain data related to the position and orientation of the apparatus for transmission to the earth's surface by means of the transmitter. 17. Method for drilling a subsurface formation, characterized by: drilling a first borehole interval in the subsurface formation with a drill string that includes a pipe sleeve (302) equipped with formation evaluation instrumentation (336, 338) which is at least partially arranged in the pipe wall of the pipe sleeve (302) and which can be influenced to obtain data associated with at least one formation characteristic parameter at the same time as cutting a core from a formation; and, without removing the drill bit from the borehole, coring a second borehole interval extending from an end point in the first borehole interval while acquiring borehole data. 18. Method according to claim 17, characterized in that the acquisition of borehole data comprises the acquisition of formation characteristic parameter data. 19. Method according to claim 18, characterized in that it further comprises: drilling the first borehole interval in the underground formation simultaneously with cutting out a formation core sample along a longitudinal axis of the drilled borehole interval from a front end thereof; and simultaneously with said drilling and cutting, sensing at least one borehole formation characteristic parameter from a location close to a location where the core sample is separated from the formation. 20. Method according to claim 19, characterized by simultaneously with said drilling and cutting, sensing of at least one drilling parameter from a place close to a place where the core sample is separated from the formation. 21. Method according to claim 20, characterized by simultaneously with said drilling and cutting, sensing of at least one directional parameter from a place close to a place where the core sample is separated from the formation.