NO20170117A1

NO20170117A1 - Non-magnetic survey instrument for boreholes, casings or drill strings

Info

Publication number: NO20170117A1
Application number: NO20170117A
Authority: NO
Inventors: Lennart Jönsson; Rune Lindhjem; Viktor Tokle
Original assignee: Devico As
Priority date: 2017-01-26
Filing date: 2017-01-26
Publication date: 2018-07-27
Also published as: AU2018212302A1; NO342875B1; CA3046456A1; WO2018139935A1; AU2018212302B2

Abstract

Non-magnetic survey instrument (100) for borehole, casing or drill string formed by a body (110) accommodating centralizer assemblies (120-122) and measuring systems (170-190), the non-magnetic survey instrument (100) being arranged for continuous survey ing as the non-magnetic survey instrument (100) travels downwards or upwards in a borehole, casing or drill string.

Description

Non-magnetic survey instrument for boreholes, casings or drill strings

The present invention is related to a non-magnetic survey instrument for boreholes, casings or drill strings, according to the preamble of claim 1.

The present invention is especially related to a non-magnetic survey instrument arranged for surveying inside of boreholes, casings and drill strings by the use of a wireline system.

Background

The closest prior art of the present invention is DeviFlex™ — Non-magnetic Multishot, a product offered by the applicant.

The DeviFlex is a survey instrument for measuring borehole deviation both in magnetically disturbed and undisturbed areas. Over the length of the instrument there are three centralizers with wheels. The wheels are positioned approximately 120 degrees apart, and are always in contact with the drill string inner wall. This secures that the instrument is centralized in the drill string at the location of each centralizer. The distance between the centralizers is fixed (e.g. at 2 meters).

Onboard the instrument is arranged measuring systems for detecting rotational angle and inclination angle of the instrument, as well as "straightness" of the instrument. If there is a bend in the drill string (borehole) the same amount of bend will be transferred to the instrument, and the strain/stress this creates can be measured and converted into an angle. The rotational angle of the instrument is used to determine which direction the angle is pointing.

To start up a survey the instrument is connected to a PDA via a cable. On the PDA the logging frequency is set and then sent to the instrument along with a start command. The instrument will now start to log data from the onboard measuring systems at the set interval. By pressing a button on the PDA the local time is recorded. When the recorded time is combined with the time the survey instrument was started and the logging frequency, the specific data point may be extracted from the instrument.

A borehole survey with the DeviFlex is performed by measuring in overlapping depth intervals. The length of the instrument must be known (e.g. 4 meters), and the distance between each survey station cannot be longer than the length of the instrument. The instrument must be stationary at each survey station for a certain amount of time for sensors of the measuring systems to stabilize and measure correctly.

At each station the deviation over the length of the survey instrument is measured and combined with the deviation measured at the previous station. When the full borehole, or a section of, is measured, the instrument is retrieved to surface and connected back with the PDA. The data points of interest are transferred to the PDA, and the full deviation calculated by combining the sensor data with the depth of each survey station. Depth data is e.g. achieved by using a winch with counter measuring the amount of wire spooled out and thus the length of the wire which corresponds to the depth in the borehole.

The above described survey instrument suffer from that external or internal bias which may cause false deviation readings, e.g. due to tear and wear of wheels, different spring-load, misalignment in the instrument, load from overshot, misalignment on the drill string, etc.

A drawback with the above-described survey instrument is further that it is required to be stationary at every survey station for making measurements, which results in that the survey is time-consuming.

A further drawback is the use of cable communication between the survey instrument and handheld unit (PDA) which is sensitive to dirt and rough treatment.

Further, it is based on using only accelerometers to detect rotation angle, something which is impossible or inaccurate in vertical and near vertical boreholes.

A lack of the above-described survey instrument is that the survey is not performed as part of the drilling process, and therefore affects the daily drilling production rate, as it is required to run separately.

Accordingly, there is a need for a non-magnetic survey instrument for boreholes, casings or drill strings which improves and solves the above mentioned drawbacks and lacks.

Object

The main object of the present invention is to provide a non-magnetic survey instrument for boreholes, casings or drill strings partly or entirely solving the above mentioned drawbacks and lacks of prior art.

It is further an object to provide a non-magnetic survey instrument for boreholes, casings or drill strings enabling continuous surveying.

Another object of the present invention is to provide a non-magnetic survey instrument for boreholes, casings or drill strings arranged for compensation of internal and external bias.

An object of the present invention is to provide a non-magnetic survey instrument for boreholes, casings or drill strings capable of performing detection of rotation angle in vertical and near vertical boreholes.

An object of the present invention is to provide a non-magnetic survey instrument for boreholes, casings or drill strings which can be a part of the drilling process.

Another object of the present invention is to provide a non-magnetic survey instrument for boreholes, casings or drill strings capable of retrieving an inner tube with core samples from the core barrel.

It is further an object to provide a non-magnetic survey instrument for boreholes, casings or drill strings håving a shorter length compared to prior art solutions, as well as increased manageability.

Further objects of the present invention will appear from the following description, claims and attached drawings.

The invention

A non-magnetic survey instrument for boreholes, casings or drill strings according to the present invention is described in claim 1. Preferable features of the non-magnetic survey instrument are described in the dependent claims.

The present invention is related to improvement of the above described survey instrument for measuring borehole deviation in magnetically disturbed and undisturbed areas. The non-magnetic survey instrument for boreholes, casings or drill strings according to the present invention includes a body formed by a front and rear tube arranged for mechanical connection. Over the length of the non-magnetic survey instrument there are arranged centralizer assemblies including wheel assemblies ensuring that the non-magnetic survey instrument at all times will be in contact with inner wall of a borehole, casing or drill string. At rear end of the non-magnetic survey instrument is typically arranged a pump in assembly, and further a spear head assembly for connection to a wireline system.

The non-magnetic survey instrument is further provided with measuring systems for performing measurements in the borehole, casing or drill string. According to the present invention the non-magnetic survey instrument includes at least two independent measuring systems, wherein a first measuring system includes accelerometers in at least three axes for measuring rotational angle and inclination angle of the non-magnetic survey instrument, while a second measuring system includes strain gauge sensors for measuring deviation in the borehole, casing or drill string. Deviation in the borehole, casing or drill string will be transferred to the non-magnetic survey instrument and the strain/stress is measured by the strain gauge sensors and converted to an angle, while the rotational angle of the non-magnetic survey instrument can be used to determine which direction the converted angle is pointing. The deviation angle may be projected to the horizontal and vertical plane for conversion to azimuth and inclination angles.

According to the present invention the non-magnetic survey instrument is according to a further embodiment of the present invention further provided with a third measuring system including at least one gyro sensor for measuring rotational angle of the non-magnetic survey instrument in vertical or near vertical positions. A gyro sensor is subject to drift, but according to the present invention drift is corrected by comparing with sensor data from the accelerometer(s) when the non-magnetic survey instrument is no longer in a vertical position, accordingly providing self-calibration of the gyro sensor(s). The rotational angle from the at least one gyro sensor will enable the non-magnetic survey instrument according to the present invention to detect the direction of the borehole deviation also in fully vertical boreholes.

According to the present invention, the non-magnetic survey instrument is arranged for continuous surveying, as opposite to prior art solutions which require that the survey instrument is stationary at each measurement station. According to the present invention continuous surveying is achieved by that damping is added to the measuring systems and by logging filtering/averaging measured sensor data over a specific (short) time frame. Damping may be added by accommodating the sensors of the measuring systems in a shock absorbing material or arranging them to shock absorbing devices, making them less sensitive to shock and movement as the non-magnetic survey instrument travels inside the borehole, casing or drill string. As the non-magnetic survey instrument is arranged for continuous or discrete logging measured sensor data from the measuring systems, the measured sensor data may be integrated and processed over specific (short) time frames, further reducing the effect of shock and movement.

To provide accuracy in the continuous surveying it is important to compensate for internal and external bias, as discussed above under background. According to the present invention this compensation is achieved by that the centralizer assemblies are arranged to rotate the non-magnetic survey instrument around its longitudinal axis when it travels downwards or upwards inside the borehole, casing or drill string. According to a preferred embodiment of the present invention the non-magnetic survey instrument is preferably rotated 90 degrees over a distance equalling non-magnetic survey instrument length.

The rotation of the non-magnetic survey instrument is according to the present invention achieved by that the centralizer assemblies includes at least three wheel assemblies arranged in circumferential direction thereof and comprising longitudinally angled wheels, wherein the wheels rotate in a plane exhibiting an angle in relation to the longitudinal direction/moving direction of the non-magnetic survey instrument.

According to a further embodiment of the present invention at least one of the wheel assemblies is a spring-loaded wheel assembly.

According to a further embodiment of non-magnetic survey instrument the present invention it is preferably arranged a rear swivel assembly at upper end of the non-magnetic survey instrument to prevent unscrewing of the non-magnetic survey instrument as it rotates.

According to a further embodiment of the non-magnetic survey instrument according to the present invention, the non-magnetic survey instrument is provided with short range wireless communication means, such as Bluetooth, IR or similar wireless transceiver, enabling wireless communication through an area with non-conductive material or a material that electromagnetic waves can penetrate in the non-magnetic survey instrument, enabling wireless communication with a handheld unit/external unit, such as a PDA.

According to a further embodiment of the non-magnetic survey instrument according to the present invention there is arranged an inner tube overshot head assembly at front end of the non-magnetic survey instrument, preferably with a shock absorber assembly, between the non- magnetic survey instrument and the inner tube overshot head assembly. As the non-magnetic survey instrument is sent to the bottom of the borehole, casing or drill string, it will connect with and attach to an inner tube of a wireline-operated core barrel drill, as e.g. described in NO 168962, NO 316286, NO334083, WO2013028074, WO2013028075 and WO2011056077, all in the name of the applicant. As the non-magnetic survey instrument is pulled out, the inner tube with the core sample will follow with. Accordingly, making the survey a part of the drilling process, as the survey is performed and the core retrieved at the same time.

In a further embodiment of the non-magnetic survey instrument according to the present invention is a front swivel assembly arranged between at lower end thereof, between the non-magnetic survey instrument and the overshot head assembly to reduce amount of rotation of the inner tube with the core sample as it is retrieved.

Accordingly, by the present invention is achieved a non-magnetic survey instrument for boreholes, casing or drill strings enabling continuous surveying which reduces the time required for surveying of the borehole, casing or drill string.

By the present invention is further achieved a non-magnetic survey instrument for boreholes, casings or drill strings which provides increased accuracy by that it is arranged for compensation of internal and external bias.

The present invention also provides a solution where a survey can be a part of a drilling process by that the non-magnetic survey instrument is arranged for retrieving inner tube with core samples at the same time as performing a survey, accordingly increasing the daily drilling production rate.

By the present invention is achieved a non-magnetic survey instrument capable of detecting rotation angle also for vertical or near vertical positions (boreholes), which is not achievable with prior art solutions.

A further advantage with the present invention is that the overall length of the non-magnetic survey instrument can be reduced, compared to prior art solutions, increasing the manageability of the non-magnetic survey instrument, as well as the costs.

By the present invention is also achieved a more easy communication between the non-magnetic survey instrument and handheld/external units, such as a PDA, by that it is arranged for short range wireless communication.

Further preferable features and advantageous details of the present invention will appear from the following example description, claims and attached drawings.

Example

The present invention will below be further described with references to the attached drawings, where: Fig. 1 is a principle drawing of a non-magnetic survey instrument for boreholes, casings or drill strings according to the present invention, Fig. 2 is a principle drawing of the non-magnetic survey instrument for boreholes, casings or drill strings revealing details of components therein, and Fig. 3a-b are principle drawings of a centralizer assembly according to the present invention.

Reference is now made to Figures 1, 2 and 3a-b showing principle drawings and details of a non-magnetic survey instrument 100 for boreholes, casings or drill strings according to the present invention.

The non-magnetic survey instrument 100 for boreholes, casings or drill strings according to the present invention includes a body 110 formed by a front tube 111 provided with a front centralizer assembly 120 and a rear tube 112 provided with centralizer assemblies 121, 122 at both ends thereof, which front 111 and rear 112 tube at ends thereof are provided with connections for mechanical connection, as well as arranged for connection to front 130 and rear 131 swivel assemblies, respectively, pump in assembly 140, shock absorber assemblies, spear head adapter 150 for spear head 151 enabling connection to a wireline system and operation of the non-magnetic survey instrument 100 via a wireline system (not shown).

Accordingly, when the front tube 111 and rear tube 112 are connected together the centralizer assembly 120 forms a front centralizer, the centralizer assembly 121 forms a middle centralizer and the centralizer assembly 122 forms a rear centralizer in the body 110 of the non-magnetic survey instrument 100.

In the shown example embodiment an overshot head assembly 160 is arranged to the front swivel 130, preferably via a shock absorber assembly (not shown), enabling retrieval of an inner tube (not shown) with a core sample at the same time as a survey is performed. Inner tubes are well known in prior art wireline-operated core barrel drills, as e.g. described in NO 168962, NO 316286, NO334083, WO2013028074, WO2013028075 and WO2011056077, to which publications are referred to for further description of inner tube.

The front swivel assembly 130 is arranged for reducing the amount of rotation of the inner tube with the core sample, when the non-magnetic survey instrument 100 is retrieved from the borehole, casing or drill string.

The rear swivel 131 is arranged for preventing unscrewing of the non-magnetic survey instrument 100 as it rotates in its way downwards or upwards the borehole, casing or drill string.

The non-magnetic survey instrument 100 for borehole, casing or drill string according to the present invention further includes at least two independent measuring systems accommodated in the body 110.

A first measuring system 170 comprises accelerometers in at least three axes for detecting rotational angle and inclination angle of the non-magnetic survey instrument 100, the accelerometer-based measuring system 170 preferably being arranged close to the middle of the rear tube 112.

A second measuring system 180 comprises strain gauges, preferably at least four strain gauges, for measuring deviation in the borehole, casing or drill string by that deviation in the borehole, casing or drill string is transferred to the body 110 of the non-magnetic survey instrument 100 and the resulting strain/stress is measured by the strain gauges and converted to an angle, the strain gauge based measuring system 180 preferably being arranged close to the centralizer assembly 121, i.e. close to the middle of the non-magnetic survey instrument 100.

According to the present invention the non-magnetic survey instrument 100 can further include a third measuring system 190 including at least one gyro sensor for measuring rotational angle of the non-magnetic survey instrument 100 in vertical and near vertical positions (boreholes). Gyro sensors are subject to drift. According to the present invention the drift is corrected by comparing with sensor data from the accelerometers when the non-magnetic survey instrument 100 is no longer in a vertical position. Accordingly, the gyro sensor based measuring system 190 can be seif- calibrating. The gyro sensor based measuring system 180 is arranged in the rear tube 112, preferably in a middle area thereof.

According to the present invention the non-magnetic survey instrument 100 is arranged for continuous surveying. According to an embodiment of the non-magnetic instrument 100 according to the present invention this is achieved by accommodating the sensors of the measuring systems 170-190 in a shock absorbing material 300 or arranging them to shock absorbing devices (not shown), making them less sensitive to shock and movement as the non-magnetic survey instrument 100 travels inside the borehole, casing or drill string.

The non-magnetic survey instrument 100 according to the present invention is further provided with an energy source 200, preferably in the form of chargeable batteries, arranged in the body 110, powering the measuring systems 170-190, which batteries can be charged via a charging connector 201 and/or via suitable energy harvesters arranged in the non-magnetic survey instrument 100.

The non-magnetic survey instrument 100 according to the present invention is further provided with short range wireless communication means 210, such as Bluetooth, IR or similar wireless short range transceiver, enabling communication with a handheld/external unit, such as a PDA. In the shown example, the body 110 is provided with at least one slit 211 for communication. The slit 211 is preferably covered with a material (e.g. a non-conductive material or a material that electromagnetic waves can penetrate) to create a fully watertight tube without impairing the data signal. The slit(s) 211 is/are preferably supported by a ceramic "button" to increase pressure tolerance. Other suitable similar solutions will be within the knowledge of a skilled person.

The above mentioned charging connector 201 can also be arranged for data transfer to and from the non-magnetic survey instrument 100. In this way the non-magnetic survey instrument 100 will have redundancy in the communication means.

The non-magnetic survey instrument 100 is further provided with a control unit 220, arranged for controlling the measuring systems 170-190, as well as provided with a memory unit, integrated with the control unit 220 or a separate unit, for storing of sensor data, as well as gravity vector, temperature, and battery capacity, and further arranged for controlling the wireless short range communication means 210. The control unit 220 is further provided with means and/or software for integrating and processing measured sensor data over specific (short) time frames, further reducing the effect of shock and movement, as described above.

The non-magnetic survey instrument 100 can further include a magnetic sensor (not shown) arranged for activating the short range wireless transceiver 210 for data communication with a handheld/external unit (PDA) (not shown) when magnetic field of a given size is applied thereto. The body 110 can for this be provided with a slot (not shown) adapted for receiving a dedicated magnet for providing the given magnetic field.

Reference is now made to Figures 3a-b showing details of the centralizer assemblies 120-122 according to the present invention which are arranged for rotating the non-magnetic survey instrument 100 as it travels downwards or upwards a borehole, casing or drill string. The centralizer assemblies 120-122 according to the present invention are provided with at least three wheel assemblies 240, 250 arranged in circumferential direction thereof and comprising longitudinally angled wheels 243, 253, wherein the wheels 243, 253 rotate in a plane exhibiting an angle in relation to the longitudinal direction/moving direction of the non-magnetic survey instrument 100. It should be noted that it in Figure 3a is shown a overdimensioning of the angle, which typically will be between 0-10 degrees.

The centralizer assemblies 120-122 are further formed by a tubular sleeve 230, formed by one or more parts, which tubular sleeve 230 is provided with longitudinal recesses 231 for accommodating the wheel assemblies 240, 250. According to the present invention the wheel assemblies can be fixed wheel assemblies 240 or spring-loaded wheel assemblies 250 or a combination thereof, chosen according to desired properties.

In a preferred embodiment of the non-magnetic survey instrument 100 according to the present invention at least one of the at least three wheel assemblies is a spring-loaded wheel assembly 250.

In Fig. 3b is shown an embodiment with two fixed wheel assemblies 240 and one spring-loaded wheel assembly 250 comprising longitudinally angled wheels 243, 253, respectively, illustrating a possible implementation of the wheel assemblies 240, 250.

The fixed wheel assemblies 240 are e.g. formed by a main body 241 exhibiting a longitudinal recess 242 for accommodating a wheel 243, rotatably arranged in the longitudinal recess 242 by means of a shaft 244 and bearings, wherein the shaft 244 is arranged to the main body 241 such that the wheel 243 extends out of the main body 241 and thus the tubular sleeve 230, wherein the shaft 242 is arranged such that the wheel 243 is longitudinally angled and rotates about a plane exhibiting an angle in relation to the longitudinal direction/moving direction of the tubular sleeve 230/non-magnetic survey instrument 100.

The spring-loaded wheel assembly 250 is e.g. formed by a main body 251 exhibiting a longitudinal recess 252 for accommodating a wheel 253, rotatably arranged in the longitudinal recess 252 by means of a shaft 254 and bearings, wherein the shaft 254 is arranged such that the wheel 253 is longitudinally angled and rotates about a plane exhibiting an angle in relation to the longitudinal direction/moving direction of the tubular sleeve 230/non-magnetic survey instrument 100. The shaft 254 is further arranged on a carrier 255 movable along a transversal axis of the tubular sleeve 230 in a compartment 256 håving its longitudinal extension along a transversal axis of the tubular sleeve 230. Further, a spring 257 is arranged in the compartment 256 providing the carrier 255 and thus the wheel 253 with a spring-loaded movement along the transversal axis of the tubular sleeve 230.

According to the present invention the circumference of the centralizer assemblies 120-122 can be divided in sectors corresponding to the number of wheel assemblies 240, 250, wherein one wheel assembly 240, 250 is arranged in each sector. In the shown embodiment there are smaller circumferential distance between the fixed wheel assemblies 240 than between the spring-loaded wheel assembly 250 and the fixed wheel assemblies 240. In the shown embodiment the fixed wheel assemblies 240 are arranged laterally reversed about a ventral axis through the spring-loaded wheel assembly 250. This is only an example and different configurations will be within the knowledge of a skilled person.

By the arrangement of the fixed wheel assemblies 240 and/or spring-loaded wheel assembly 250 with longitudinally angled wheels 243, 253, respectively, exhibiting a rotational plane exhibiting an angle in relation to the longitudinal direction/moving direction of the non-magnetic survey instrument 100, achieved is that the non-magnetic survey instrument 100 will rotate as it travels downwards or upwards in the borehole, casing or drill string. According to an embodiment of the present invention, the angle of the longitudinally angled wheels 243, 253 is chosen such that the non-magnetic survey instrument 100 is arranged to rotate 90 degrees over a distance equalling the non-magnetic survey instrument 100 length to compensate for external and internal bias. The angle of the wheel assemblies 240, 250 in relation to the longitudinal direction/moving direction of the tubular sleeve 230/non-magnetic survey instrument 100 will be dependent on inner diameter of the borehole, casing or drill string, and calculated as follows:

Angle = atan("inner dimeter"<*>Pl<*>(90°/360°) / "non-magnetic survey instrument length")

The angle is preferably the same for all the wheel assemblies 240, 250.

By using at least one spring-loaded wheel assembly 250 this will ensure that all the wheels 243, 253 of the wheel assemblies 240, 250 at all time is in contact with the inner surface/wall of the borehole, casing or drill string, centralizing the non-magnetic survey instrument 100 in the borehole, casing or drill string, as well as it will adapt to irregularities at the inner surface/wall of the borehole, casing or drill string.

According to the present invention the non-magnetic survey instrument 100 can be adapted to different borehole, casing or drill string sizes by exchanging the centralizer assemblies 120-122 adapted to the different borehole, casing or drill string dimensions. Accordingly, the user will only need to have one non-magnetic survey instrument 100 with a set of tubular sleeves 230 with wheels 243, 253 of various sizes to adjust for different dimensions of the borehole, casing or drill string.

By means of the present invention a survey may be performed by running the non-magnetic survey instrument 100 continuously in the borehole, casing or drill string without stopping to record measurements. Upon starting the survey, the non-magnetic survey instrument 100 is connected to a handheld/external unit, such as a PDA, and continuous or discrete logging is initiated. The non-magnetic survey instrument 100 will now log sensor data lines with high frequency. The handheld/external unit, such as a PDA, may further be connected to a wireless wire counter for continuous depth reference as the non-magnetic survey instrument 100 is lowered or pulled out of the borehole, casing or drill string with the wireline. Optionally, the wire counter may be time synchronized with the handheld/external unit, such as a PDA, and depth reference merged with the sensor data lines as the survey is finished.

Due to the longitudinally angled wheels 240, 250, the non-magnetic survey instrument 100 according to the present invention will spiral as it travels downwards or upwards the borehole, casing or drill string, compensating for external and internal bias. The swivel 140 between the pump in assembly 140 and non-magnetic survey instrument 100 will secure that all threads remain secure if the non-magnetic survey instrument 100 requires to be pumped to hole bottom, e.g. in horizontal boreholes.

Upon landing the front overshot assembly 160 may engage with an inner tube spearhead, and, upon retrieval of the wireline, the inner tube disengages from the core barrel and is pulled out along with the non-magnetic survey instrument 100. Survey data may be collected both as the non-magnetic survey instrument 100 travels downwards to pick up the inner tube, and upwards with the inner tube engaged. In such way the survey operation becomes an integrated part of the drilling process.

After the survey is completed, the non-magnetic survey 100 instrument, when retrieved from the borehole, casing or drill string can communicate wirelessly with the handheld/external unit, such as a PDA, for transfer of measured sensor data.

When the sensor data is downloaded the results can be viewed on a monitor of the handheld/external unit, such as PDA, in the field. The data can thereafter be further processed, analysed, plotted and reported to the client by means of software in the handheld/external unit, such as PDA, suitable for this, such as Devisoft.

Claims

1. Non-magnetic survey instrument (100) for borehole, casing or drill string formed by a body (110) provided with centralizer assemblies (120-122) provided with wheel assemblies (240, 250), wherein the body (110) accommodates power source (200), at least two measuring systems (170-190), control unit (220) and communication means (210),characterized in thatthe non-magnetic survey instrument (100) is arranged for performing continuous surveying by that the measuring systems (170-190) are provided with dampening means and that the control unit (220) is arranged for continuous or discrete logging filtering/averaging of measured values over a specific time frame.

2. Non-magnetic survey instrument (100) according to claim 1,characterized in thatthe centralizer assemblies (120-122) includes at least three wheel assemblies (240, 250) provided with longitudinally angled wheels (243, 253) rotating in a plane exhibiting an angle in relation to longitudinal direction/moving direction of the non-magnetic survey instrument (100).

3. Non-magnetic survey instrument (100) according to claim 2,characterized in thatat least one of the wheel assemblies is a spring-loaded wheel assembly (250).

4. Non-magnetic survey instrument (100) according to claim 2,characterized in thatthe longitudinally angled wheels (243, 253) are arranged to rotate the non-magnetic survey instrument (100) as it travels downwards or upwards in a borehole, casing or drill string.

5. Non-magnetic survey instrument (100) according to claim 1,characterized in thatthe non-magnetic survey instrument (100) includes a measuring system (170) comprising accelerometers in at least three axes and a measuring system (180) comprising at least four strain gauges.

6. Non-magnetic survey instrument (100) according to claim 1,characterized in thatat the non-magnetic survey instrument (100) further includes a measuring system (190) comprising at least one gyro sensor.

7. Non-magnetic survey instrument (100) according to claim 1,characterized in thatthere is arranged an overshot head assembly (160) at lower part of the non-magnetic survey instrument (100) for retrieving an inner tube with a core sample.

8. Non-magnetic survey instrument (100) according to claim 7,characterized in thata front swivel (130) is arranged between lower part of the non-magnetic survey instrument (100) and the overshot head assembly (160), possibly via shock absorber assembly.

9. Non-magnetic survey instrument (100) according to claim 1,characterized in thatthere is arranged a rear swivel (131) between upper part of the non-magnetic survey instrument (100) and a pump in assembly (140).

10. Non-magnetic survey instrument (100) according to claim 1,characterized in thatthe non-magnetic survey instrument (100) is provided with short range wireless communication means (210).

11. Non-magnetic survey instrument (100) according to claim 2,characterized in thatthe angle of the longitudinally angled wheels (243, 253) in relation to longitudinal direction/moving direction of the non-magnetic survey instrument (100) is given by Angle = atan("inner diameter of borehole, casing or drill string"<*>Pl<*>(90°/360°) / "non-magnetic survey instrument length").

12. Non-magnetic survey instrument (100) according to claim 1,characterized in thatthe dampening means is a shock absorbing material (300) accommodating sensors of the measuring systems (170-190) in a shock absorbing material or a shock absorber device.