Device and method for testing creep shrinkage of borehole in salt rock stratum

Abstract

The invention provides a rock salt formation borehole creep hole shrinkage testing device and method. The rock salt formation borehole creep hole shrinkage testing device comprises an X-direction pressure loading device, a Y-direction pressure loading device, a Z-direction pressure loading device, a drilling fluid circulating system and a data processing system. During use, the X-direction pressure loading device, the Y-direction pressure loading device and the Z-direction pressure loading device are used for clamping a salt rock sample and changing the compression condition of the salt rock sample. The drilling fluid in the drilling fluid circulating system passes through the borehole of the salt rock sample when flowing, and the temperature of the drilling fluid can be changed. The data processing unit obtains the temperature of drilling fluid in a borehole through the temperature collecting unit, collects strain data of the inner wall of the borehole through the strain collecting unit, and finally obtains the relation between the rock salt stratum creep reducing strain and stress at different temperatures. Therefore, guidance is provided for providing engineering technology countermeasures for keeping the stability of the inner wall of the borehole in the drilling engineering of the salt rock stratum.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas engineering, and in particular to a device and method for testing the creep shrinkage of a wellbore in a salt rock formation. Background Art

[0002] As a rock mass with good air tightness, strong damage recovery ability, and stable chemical and mechanical properties, salt rock is often used as an important storage place for deep energy reservoirs and underground nuclear waste. In the field of oil and gas engineering, salt rock is usually used as the cap rock of oil and gas reservoirs.

[0003] Since salt rock has strong creep properties, creep shrinkage of salt rock formations has always been one of the difficult technical problems to solve in drilling projects. The creep shrinkage rate is restricted by multiple factors, among which the ground stress state and drilling fluid temperature, density, and salt saturation are the main factors affecting wellbore creep shrinkage. However, there is currently no device or method for testing the relationship between wellbore shrinkage in salt rock formations and various influencing factors. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a device and method for testing the creep shrinkage of a wellbore in a salt rock formation, aiming to solve the problem that there is no device or method for testing the relationship between the shrinkage of a wellbore in a salt rock formation and various influencing factors in the related art.

[0005] The present invention provides a salt rock formation borehole creep shrinkage testing device, comprising:

[0006] An X-direction pressure loading device, which is used to clamp the two sides of the salt rock sample perpendicular to the X-direction;

[0007] A Y-direction pressure loading device, the Y-direction pressure loading device is used to clamp the two sides of the salt rock sample perpendicular to the Y direction;

[0008] A Z-direction pressure loading device, the Z-direction pressure loading device is used to clamp the two ends of the salt rock sample perpendicular to the Z-direction, the Z-direction pressure loading device is also provided with a drilling fluid inflow channel and a drilling fluid outflow channel, a wellbore penetrating the salt rock sample is provided in the salt rock sample, when the salt rock sample is clamped between the Z-direction pressure loading devices, the drilling fluid inflow channel and the drilling fluid outflow channel are respectively connected with the two ends of the wellbore;

[0009] A drilling fluid circulation system, wherein a drilling fluid supply end of the drilling fluid circulation system is connected to the drilling fluid inflow channel, a drilling fluid return end of the drilling fluid circulation system is connected to the drilling fluid outflow channel, and a temperature regulating device is provided on the drilling fluid circulation system;

[0010] A data processing system, the data processing system comprises a temperature acquisition unit, a strain acquisition unit and a data processing unit, the temperature acquisition unit and the strain acquisition unit are both arranged in the wellbore and are both electrically connected to the data processing unit, and the strain acquisition unit is arranged on the inner wall of the wellbore.

[0011] According to the salt rock formation borehole creep shrinkage testing device provided by the present invention, the strain acquisition unit includes at least four strain sensors, and the multiple strain sensors are evenly distributed along the circumference of the inner wall of the borehole.

[0012] According to the wellbore creep shrinkage testing device for salt rock formations provided by the present invention, the X-axis pressure loading device includes a pair of relatively arranged X-axis telescopic mechanisms and a pair of first pressure heads, the two first pressure heads are respectively arranged at the telescopic ends of the two X-axis telescopic mechanisms, and the side of the first pressure head in contact with the salt rock sample has the same shape and size as the side of the salt rock sample perpendicular to the X-axis.

[0013] According to the wellbore creep shrinkage testing device for salt rock formations provided by the present invention, the Y-axis pressure loading device includes a pair of relatively arranged Y-axis telescopic mechanisms and a pair of second pressure heads, the two second pressure heads are respectively arranged at the telescopic ends of the two Y-axis telescopic mechanisms, and the side of the second pressure head in contact with the salt rock sample has the same shape and size as the side of the salt rock sample perpendicular to the Y-axis.

[0014] According to the wellbore creep shrinkage testing device for salt rock formations provided by the present invention, the Z-direction pressure loading device includes a pair of relatively arranged Z-direction telescopic mechanisms and a pair of third pressure heads, the two third pressure heads are respectively arranged at the telescopic ends of the two Z-direction telescopic mechanisms, and the side of the third pressure head in contact with the salt rock sample has the same shape and size as the end face of the salt rock sample perpendicular to the Z axis.

[0015] According to the salt rock formation borehole creep shrinkage testing device provided by the present invention, the drilling fluid inflow channel is arranged inside one of the two third pressure heads, and the drilling fluid outflow channel is arranged inside the other one.

[0016] According to the salt rock formation borehole creep shrinkage testing device provided by the present invention, a sealing ring is provided between the third pressure head and the salt rock sample.

[0017] According to the salt rock formation wellbore creep shrinkage testing device provided by the present invention, the drilling fluid circulation system includes a drilling fluid outflow pipe, a circulation pump and a drilling fluid inflow pipe connected in sequence, the end of the drilling fluid outflow pipe away from the circulation pump is connected to the drilling fluid outflow channel, the end of the drilling fluid inflow pipe away from the circulation pump is connected to the drilling fluid inflow channel, and the drilling fluid outflow pipe is also provided with a heating device and a pressure gauge.

[0018] The present invention also provides a method for testing the creep shrinkage of a wellbore in a salt rock formation. Based on the above-mentioned device for testing the creep shrinkage of a wellbore in a salt rock formation, the testing method comprises:

[0019] Installing a temperature acquisition unit and a strain acquisition unit of a data processing system on the inner wall of a wellbore of a salt rock sample;

[0020] Clamping the salt rock sample between an X-direction pressure loading device, a Y-direction pressure loading device, and a Z-direction pressure loading device;

[0021] Pressure setting step: adjusting the pressure applied by the X-direction pressure loading device to the salt rock sample to the target X-direction pressure, adjusting the pressure applied by the Y-direction pressure loading device to the salt rock sample to the target Y-direction pressure, and adjusting the pressure applied by the Z-direction pressure loading device to the salt rock sample to the target Z-direction pressure;

[0022] Temperature setting step: adjusting the temperature of the drilling fluid in the drilling fluid circulation system to a target temperature, and starting the drilling fluid circulation system;

[0023] Data collection step: collecting data from the temperature collection unit and the strain collection unit;

[0024] re-adjusting one or three of the target X-direction pressure, the target Y-direction pressure, and the target Z-direction pressure, or re-adjusting the target temperature, and performing a data acquisition step;

[0025] The data collected in the data collection step are processed to obtain the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at different temperatures.

[0026] The present invention adopts the above technical solution, which has the following advantages:

[0027] The device for testing the creep shrinkage of a wellbore in a salt rock formation provided by the present invention comprises an X-direction pressure loading device, a Y-direction pressure loading device, a Z-direction pressure loading device, a drilling fluid circulation system and a data processing system. When in use, a salt rock sample with a wellbore drilled therein is clamped between the X-direction pressure loading device, the Y-direction pressure loading device and the Z-direction pressure loading device. The X-direction pressure loading device and the Y-direction pressure loading device are used to provide X-direction and Y-direction pressures to the salt rock sample to simulate horizontal ground stress, and the Z-direction pressure loading device is used to provide Z-direction pressure to the salt rock sample to simulate overburden pressure. A drilling fluid inflow channel and a drilling fluid outflow channel are also provided on the Z-direction pressure loading device, and the two ends of the wellbore of the salt rock sample are respectively connected to the drilling fluid inflow channel and the drilling fluid outflow channel. The drilling fluid supply end of the drilling fluid circulation system is connected to the drilling fluid inflow channel, and the drilling fluid return end is connected to the drilling fluid outflow channel, thereby forming a circulation loop for the flow of drilling fluid. The salt rock formation borehole creep shrinkage test device provided by the present invention can change the pressure applied to the salt rock sample by at least one of the X-direction pressure loading device, the Y-direction pressure loading device and the Z-direction pressure loading device to change the stress state of the salt rock sample, and can also change the temperature of the drilling fluid through a temperature regulating device. The data processing system includes a temperature acquisition unit, a strain acquisition unit and a data processing unit. The temperature acquisition unit and the strain acquisition unit are both arranged in the borehole and are both electrically connected to the data processing unit, and the strain acquisition unit is arranged on the inner wall of the borehole. The data processing unit obtains the data detected by the temperature acquisition unit and the strain acquisition unit, and finally obtains the relationship between the creep shrinkage strain and stress of the salt rock formation at different temperatures, thereby providing guidance for proposing engineering and technical countermeasures to maintain the stability of the inner wall of the borehole of the salt rock formation drilling project. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a front view of a wellbore creep shrinkage testing device for salt rock formations provided by one embodiment of the present invention;

[0030] Figure 2 It is a top view of a wellbore creep shrinkage testing device for salt rock formations provided by one embodiment of the present invention;

[0031] Figure 3 is a cross-sectional view of a third pressure head provided by an embodiment of the present invention;

[0032] Figure 4 This is a force analysis diagram of a salt rock sample provided by an embodiment of the present invention.

[0033] Reference numerals:

[0034] 100: salt rock sample; 110: wellbore; 211: X-axis telescopic mechanism; 212: first pressure head; 221: Y-axis telescopic mechanism; 222: second pressure head; 231: Z-axis telescopic mechanism; 232: third pressure head; 310: drilling fluid outflow channel; 320: drilling fluid inflow channel; 410: drilling fluid outflow pipeline; 420: drilling fluid inflow pipeline; 430: circulating pump; 440: heating device; 450: pressure gauge; 510: temperature sensor; 520: strain sensor. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0038] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0040] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0041] The device for testing the creep shrinkage of a wellbore in a salt rock formation provided by the present invention comprises an X-direction pressure loading device, a Y-direction pressure loading device, a Z-direction pressure loading device, a drilling fluid circulation system and a data processing system. When in use, a salt rock sample with a wellbore drilled therein is clamped between the X-direction pressure loading device, the Y-direction pressure loading device and the Z-direction pressure loading device. The X-direction pressure loading device and the Y-direction pressure loading device are used to provide X-direction and Y-direction pressures to the salt rock sample to simulate horizontal ground stress, and the Z-direction pressure loading device is used to provide Z-direction pressure to the salt rock sample to simulate overburden pressure. A drilling fluid inflow channel and a drilling fluid outflow channel are also provided on the Z-direction pressure loading device, and the two ends of the wellbore of the salt rock sample are respectively connected to the drilling fluid inflow channel and the drilling fluid outflow channel. The drilling fluid supply end of the drilling fluid circulation system is connected to the drilling fluid inflow channel, and the drilling fluid return end is connected to the drilling fluid outflow channel, thereby forming a circulation channel for the flow of drilling fluid. The salt rock formation borehole creep shrinkage test device provided by the present invention can change the pressure applied to the salt rock sample by at least one of the X-direction pressure loading device, the Y-direction pressure loading device and the Z-direction pressure loading device to change the stress state of the salt rock sample, and can also change the temperature of the drilling fluid through a temperature regulating device. The data processing system includes a temperature acquisition unit, a strain acquisition unit and a data processing unit. The temperature acquisition unit and the strain acquisition unit are both arranged in the borehole and are both electrically connected to the data processing unit, and the strain acquisition unit is arranged on the inner wall of the borehole. The data processing unit obtains the data detected by the temperature acquisition unit and the strain acquisition unit, and finally obtains the relationship between the creep shrinkage strain and stress of the salt rock formation at different temperatures, thereby providing guidance for proposing engineering and technical countermeasures to maintain the stability of the inner wall of the borehole of the salt rock formation drilling project.

[0042] Combine the following Figures 1 to 4 The invention discloses a device for testing the creep shrinkage of a wellbore in a salt rock formation.

[0043] An embodiment of the present invention provides a salt rock formation borehole creep shrinkage test device, comprising a pressure loading system, a drilling fluid circulation system and a data processing system. The pressure loading system comprises an X-direction pressure loading device, a Y-direction pressure loading device and a Z-direction pressure loading device, and the data processing system comprises a temperature acquisition unit, a strain acquisition unit and a data processing unit.

[0044] During the test, a rectangular salt rock sample 100 with a wellbore 110 drilled therein is clamped in a pressure loading system. Specifically, the X-direction pressure loading device is clamped on both sides of the salt rock sample 100 perpendicular to the X-axis, the Y-direction pressure loading device is clamped on both sides of the salt rock sample 100 perpendicular to the Y-axis, and the Z-direction pressure loading device is loaded on both sides of the salt rock sample 100 perpendicular to the Z-axis.

[0045] A drilling fluid inflow channel 320 and a drilling fluid outflow channel 310 are also provided on the Z-direction pressure loading device. When the salt rock sample 100 is clamped in the pressure loading system, the drilling fluid inflow channel 320 is connected to one end of the wellbore 110 of the salt rock sample 100, and the drilling fluid outflow channel 310 is connected to the other end of the wellbore 110 of the salt rock sample 100.

[0046] The drilling fluid supply end of the drilling fluid circulation system is connected to the drilling fluid inlet channel 320, and the drilling fluid return end of the drilling fluid circulation system is connected to the drilling fluid outflow channel 310. In this way, the wellbore 110 connects the drilling fluid supply end and the return end of the drilling fluid circulation system, so that the drilling fluid circulation system forms a circulation loop, and passes through the wellbore 110 during the drilling fluid circulation process to simulate the working condition of the drilling fluid passing through the wellbore 110 during the drilling process.

[0047] The drilling fluid circulation system is also provided with a temperature regulating device for regulating the temperature of the circulating drilling fluid, thereby changing the temperature of the drilling fluid passing through the wellbore 110 .

[0048] The temperature acquisition unit in the data processing system is disposed in the wellbore 110, and is used to acquire the temperature of the drilling fluid flowing through the wellbore 110. The strain acquisition unit in the data processing system is disposed on the inner wall of the wellbore 110, and is used to acquire strain data of the inner wall of the wellbore 110. The data processing unit in the data processing system is connected to the temperature acquisition unit and the strain acquisition unit, and is used to acquire temperature data and strain data, and obtain the relationship between the creep shrinkage strain and stress of the wellbore 110 at different temperatures based on the temperature data and the strain data.

[0049] In the actual test process, the temperature of the drilling fluid can be heated to a first temperature by the temperature regulating device, and the X-direction pressure applied by the X-direction pressure loading device on the salt rock sample 100, the Y-direction pressure applied by the Y-direction pressure loading device on the salt rock sample 100, and the Z-direction pressure applied by the Z-direction pressure loading device on the salt rock sample 100 are adjusted based on a pressure condition. After the drilling fluid flows for a certain period of time, the data processing unit obtains the drilling fluid temperature data collected by the temperature collection unit and the strain data of the inner wall of the wellbore 110 collected by the strain collection unit.

[0050] Then, based on another pressure condition, the X-direction pressure applied by the X-direction pressure loading device on the salt rock sample 100, the Y-direction pressure applied by the Y-direction pressure loading device on the salt rock sample 100, and the Z-direction pressure applied by the Z-direction pressure loading device on the salt rock sample 100 are adjusted. After the drilling fluid flows for a certain period of time, the data processing unit again obtains the drilling fluid temperature data collected by the temperature collection unit and the strain data of the inner wall of the wellbore 110 collected by the strain collection unit.

[0051] In this way, the drilling fluid temperature data and strain data under various pressure conditions are obtained.

[0052] Finally, the data processing unit obtains the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at the first temperature.

[0053] Then, the temperature of the drilling fluid is heated to a second temperature by the temperature regulating device, and the X-direction pressure applied by the X-direction pressure loading device on the salt rock sample 100, the Y-direction pressure applied by the Y-direction pressure loading device on the salt rock sample 100, and the Z-direction pressure applied by the Z-direction pressure loading device on the salt rock sample 100 are adjusted based on a pressure condition. After the drilling fluid flows for a certain period of time, the data processing unit acquires the drilling fluid temperature data acquired by the temperature acquisition unit and the strain data of the inner wall of the wellbore 110 acquired by the strain acquisition unit.

[0054] Then, based on another pressure condition, the X-direction pressure applied by the X-direction pressure loading device on the salt rock sample 100, the Y-direction pressure applied by the Y-direction pressure loading device on the salt rock sample 100, and the Z-direction pressure applied by the Z-direction pressure loading device on the salt rock sample 100 are adjusted. After the drilling fluid flows for a certain period of time, the data processing unit again obtains the drilling fluid temperature data collected by the temperature collection unit and the strain data of the inner wall of the wellbore 110 collected by the strain collection unit.

[0055] In this way, the drilling fluid temperature data and strain data under various pressure conditions are obtained.

[0056] Finally, the data processing unit obtains the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at the second temperature.

[0057] By analogy, the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at different temperatures is obtained.

[0058] In some embodiments, the strain acquisition unit includes at least four strain sensors 520 , and the plurality of strain sensors 520 are evenly distributed along the circumference of the inner wall of the wellbore 110 .

[0059] The temperature collection unit may be a temperature sensor 510 , and the temperature sensor 510 may also be disposed on the inner wall of the wellbore 110 .

[0060] In some embodiments, the X-direction pressure loading device includes a pair of X-direction telescopic mechanisms 211 and a pair of first pressing heads 212 that are arranged opposite to each other.

[0061] The X-direction telescopic mechanism 211 may be a hydraulic cylinder. The telescopic directions of the two hydraulic cylinders are along the X-direction. When the hydraulic rods of the two hydraulic cylinders are extended, the extended ends approach each other, and when they are retracted, the extended ends move away from each other.

[0062] The two first pressure heads 212 are respectively arranged at the extended ends of the hydraulic rods of the two hydraulic cylinders. The side of the first pressure head 212 away from the hydraulic rod is a plane, and its shape and area are the same as the shape and area of ​​the side of the salt rock sample 100 perpendicular to the X direction, so that the first pressure head 212 can completely cover the side of the salt rock sample 100 perpendicular to the X direction.

[0063] In some embodiments, the Y-direction pressure loading device includes a pair of Y-direction telescopic mechanisms 221 and a pair of second pressing heads 222 that are arranged opposite to each other.

[0064] The Y-direction telescopic mechanism 221 may be a hydraulic cylinder. The telescopic directions of the two hydraulic cylinders are along the Y-direction. When the hydraulic rods of the two hydraulic cylinders are extended, the extended ends are close to each other, and when they are retracted, the extended ends are away from each other.

[0065] The two second pressure heads 222 are respectively arranged at the extended ends of the hydraulic rods of the two hydraulic cylinders. The side of the second pressure head 222 away from the hydraulic rod is a plane, and its shape and area are the same as the shape and area of ​​the side of the salt rock sample 100 perpendicular to the Y direction, so that the second pressure head 222 can completely cover the side of the salt rock sample 100 perpendicular to the X direction.

[0066] In some embodiments, the Z-direction pressure loading device includes a pair of Z-direction telescopic mechanisms 231 and a pair of third pressing heads 232 that are arranged opposite to each other.

[0067] The Z-direction telescopic mechanism 231 may be a hydraulic cylinder. The telescopic directions of the two hydraulic cylinders are along the Z direction. When the hydraulic rods of the two hydraulic cylinders are extended, the extended ends are close to each other, and when they are retracted, the extended ends are away from each other.

[0068] The two third pressure heads 232 are respectively arranged at the extended ends of the hydraulic rods of the two hydraulic cylinders. The side of the third pressure head 232 away from the hydraulic rod is a plane, and its shape and area are the same as the shape and area of ​​the side of the salt rock sample 100 perpendicular to the Z direction, so that the third pressure head 232 can completely cover the side of the salt rock sample 100 perpendicular to the X direction.

[0069] In some embodiments, one of the two third pressure heads 232 is provided with a drilling fluid inflow channel 320, and the other is provided with a drilling fluid outflow channel 310. For example, the drilling fluid outflow channel 310 may be provided in the third pressure head 232 at the top, and the drilling fluid inflow channel 320 may be provided in the third pressure head 232 at the bottom.

[0070] The drilling fluid outflow channel 310 passes through the third pressure head 232, one end of the drilling fluid outflow channel 310 is connected to the wellbore 110, and the other end is used to connect to the drilling fluid return end of the drilling fluid circulation system. The drilling fluid inflow channel 320 passes through the third pressure head 232, one end of the drilling fluid inflow channel 320 is connected to the wellbore 110, and the other end is used to connect to the drilling fluid supply end of the drilling fluid circulation system.

[0071] In some embodiments, a sealing ring is disposed between the third pressure head 232 and the salt rock sample 100 .

[0072] Specifically, the sealing ring may be made of rubber, and its inner diameter needs to be greater than or equal to the inner diameter of the wellbore 110 , and the outer diameter of the sealing ring is smaller than the side length of the salt rock sample 100 .

[0073] When the third pressure head 232 is pressed against the end surface of the salt rock sample 100 , the sealing ring is squeezed between the third pressure head 232 and the salt rock sample 100 , thereby preventing the drilling fluid from leaking.

[0074] In some embodiments, the drilling fluid circulation system includes a drilling fluid outflow pipe 410 , a circulation pump 430 , and a drilling fluid inflow pipe 420 connected in sequence, and a heating device 440 and a pressure gauge 450 are provided on the drilling fluid outflow pipe 410 .

[0075] Specifically, one end of the drilling fluid outflow pipe 410 is connected to the inlet of the circulation pump 430, the other end of the drilling fluid outflow pipe 410 is connected to the drilling fluid outflow channel 310 on the third pressure head 232, one end of the drilling fluid inflow pipe 420 is connected to the outlet of the circulation pump 430, and the other end of the drilling fluid inflow pipe 420 is connected to the drilling fluid inflow channel 320 on the third pressure head 232.

[0076] The heating device 440 is arranged on the drilling fluid outflow pipe 410, and is used to heat the drilling fluid in the drilling fluid circulation system. The heating device 440 is the temperature regulating device mentioned above. The pressure gauge 450 is arranged on the drilling fluid outflow pipe 410, and is used to detect the pressure of the drilling fluid in the drilling fluid circulation system.

[0077] An embodiment of the present invention further provides a method for testing the creep shrinkage of a wellbore in a salt rock formation, which is performed based on the above-mentioned device for testing the creep shrinkage of a wellbore in a salt rock formation. The method comprises the following steps:

[0078] Step S100, installing the temperature acquisition unit and the strain acquisition unit of the data processing system on the inner wall of the wellbore 110 of the salt rock sample 100;

[0079] Step S200, clamping the salt rock sample 100 between the X-direction pressure loading device, the Y-direction pressure loading device and the Z-direction pressure loading device;

[0080] Step S300, pressure setting step: adjusting the pressure applied by the X-direction pressure loading device to the salt rock sample 100 to the target X-direction pressure, adjusting the pressure applied by the Y-direction pressure loading device to the salt rock sample 100 to the target Y-direction pressure, and adjusting the pressure applied by the Z-direction pressure loading device to the salt rock sample 100 to the target Z-direction pressure;

[0081] Step S400, temperature setting step: adjusting the temperature of the drilling fluid in the drilling fluid circulation system to a target temperature, and starting the drilling fluid circulation system;

[0082] Step S500, data collection step: collecting data from the temperature collection unit and the strain collection unit;

[0083] Step S600, readjusting one or three of the target X-direction pressure, the target Y-direction pressure, and the target Z-direction pressure, or readjusting the target temperature, and executing the data collection step;

[0084] Step S700: Process the data collected in the data collection step to obtain the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at different temperatures.

[0085] Specifically, first, the temperature acquisition unit and the strain acquisition unit are installed inside the wellbore 110 of the salt rock sample 100. The strain acquisition unit may include four strain sensors 520, and the four strain sensors 520 are evenly installed on the inner wall of the wellbore 110. Finally, the strain sensor 520, the temperature sensor 510 and the data processing unit are connected, for example, a wireless connection or a Bluetooth connection.

[0086] Then, the salt rock sample 100 with the temperature acquisition unit and the strain acquisition unit installed is installed into the pressure loading system. Specifically, the X-direction pressure loading device is clamped on both sides of the salt rock sample 100 perpendicular to the X-axis, the Y-direction pressure loading device is clamped on both sides of the salt rock sample 100 perpendicular to the Y-axis, and the Z-direction pressure loading device is loaded on both sides of the salt rock sample 100 perpendicular to the Z-axis.

[0087] It should be noted that, before the Z-direction loading device contacts the salt rock sample 100 , a sealing ring needs to be placed between the salt rock sample 100 and the Z-direction loading device.

[0088] Then, the drilling fluid outflow end of the drilling fluid circulation system is connected to the drilling fluid outflow channel 310 on the Z-direction pressure loading device, and the drilling fluid supply end of the drilling fluid circulation system is connected to the drilling fluid inflow channel 320 on the Z-direction pressure loading device to establish a drilling fluid circulation loop.

[0089] Then, the pressure setting step and the temperature setting step are performed, that is, based on a pressure condition, the pressure applied by the X-direction pressure loading device to the salt rock sample 100 is adjusted to the target X-direction pressure, the pressure applied by the Y-direction pressure loading device to the salt rock sample 100 is adjusted to the target Y-direction pressure, and the pressure applied by the Z-direction pressure loading device to the salt rock sample 100 is adjusted to the target Z-direction pressure. Then, the drilling fluid circulation system is opened, and the heating temperature of the temperature regulating device is adjusted so that the drilling fluid is heated to the first temperature.

[0090] After the drilling fluid flows for a certain period of time, the data processing unit acquires the drilling fluid temperature data collected by the temperature acquisition unit and the strain data of the inner wall of the wellbore 110 collected by the strain acquisition unit.

[0091] Then, based on another pressure condition, the X-direction pressure applied by the X-direction pressure loading device on the salt rock sample 100, the Y-direction pressure applied by the Y-direction pressure loading device on the salt rock sample 100, and the Z-direction pressure applied by the Z-direction pressure loading device on the salt rock sample 100 are adjusted. After the drilling fluid flows for a certain period of time, the data processing unit again obtains the drilling fluid temperature data collected by the temperature collection unit and the strain data of the inner wall of the wellbore 110 collected by the strain collection unit.

[0092] In this way, the drilling fluid temperature data and strain data under various pressure conditions are obtained.

[0093] Finally, the data processing unit obtains the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at the first temperature.

[0094] Then, the temperature of the drilling fluid is heated to a second temperature by the temperature regulating device, and the X-direction pressure applied by the X-direction pressure loading device on the salt rock sample 100, the Y-direction pressure applied by the Y-direction pressure loading device on the salt rock sample 100, and the Z-direction pressure applied by the Z-direction pressure loading device on the salt rock sample 100 are adjusted based on a pressure condition. After the drilling fluid flows for a certain period of time, the data processing unit acquires the drilling fluid temperature data acquired by the temperature acquisition unit and the strain data of the inner wall of the wellbore 110 acquired by the strain acquisition unit.

[0095] Then, based on another pressure condition, the X-direction pressure applied by the X-direction pressure loading device on the salt rock sample 100, the Y-direction pressure applied by the Y-direction pressure loading device on the salt rock sample 100, and the Z-direction pressure applied by the Z-direction pressure loading device on the salt rock sample 100 are adjusted. After the drilling fluid flows for a certain period of time, the data processing unit again obtains the drilling fluid temperature data collected by the temperature collection unit and the strain data of the inner wall of the wellbore 110 collected by the strain collection unit.

[0096] In this way, the drilling fluid temperature data and strain data under various pressure conditions are obtained.

[0097] Finally, the data processing unit obtains the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at the second temperature.

[0098] By analogy, the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at different temperatures is obtained.

[0099] An embodiment will be disclosed below to illustrate the data processing process under certain temperature and pressure conditions.

[0100] In the XYZ coordinate system, the X-direction stress is calculated as σ H , the stress in the Y direction is σ h , the Z-direction stress is σ v , the above stress values ​​are converted into stress components in the X'Y'Z' coordinate system by the following formula:

[0101]

[0102] in:

[0103]

[0104] Matrix [L] T represents the transposed matrix of matrix [L]. According to the shear stress reciprocity theorem, the transformed stress components are:

[0105]

[0106] It should be noted that the X axis of the XYZ coordinate system is the aforementioned X direction, the Y axis is the aforementioned Y direction, and the Z axis is the aforementioned Z direction. The Z' axis of the X'Y'Z' coordinate system is the axial direction of the wellbore 110, and the Y' axis and the X' axis are perpendicular to the Z' axis.

[0107] Generally, there is shear stress on the inner wall of the wellbore 110, so that σ H , σ h , σ v The stress component in the X'Y'Z' coordinate system is not a principal stress, and the magnitude of the principal stress on the inner wall of the wellbore 110 is a non-zero solution of the following equation:

[0108]

[0109] The characteristic root of the above equation is the magnitude of the principal stress of the geostress on the inner wall of the wellbore 110: σ1, σ2 and σ3. According to the magnitude of the principal stress on the inner wall of the wellbore 110, the Mises stress generated by the geostress on the inner wall of the wellbore 110 can be calculated:

[0110]

[0111] The data of the strain sensor 520 on the salt rock sample 100 is collected, and the creep shrinkage strain ε of the salt rock formation wellbore is obtained through computer post-processing. e .

[0112] Fitting ε using a computer e and σ e Relationship ε under different drilling fluid temperature and pressure e =f(σ e ), that is, the borehole creep shrinkage chart of salt rock formation is obtained.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A borehole creep shrinkage test device for salt rock formations, characterized in that: include: An X-direction pressure loading device, the X-direction pressure loading device being used to clamp the two sides of the salt rock sample (100) perpendicular to the X-direction; A Y-direction pressure loading device, the Y-direction pressure loading device is used to clamp the two sides of the salt rock sample (100) perpendicular to the Y-direction; A Z-direction pressure loading device, the Z-direction pressure loading device is used to clamp the two ends of the salt rock sample (100) perpendicular to the Z-direction, the Z-direction pressure loading device is also provided with a drilling fluid inflow channel (320) and a drilling fluid outflow channel (310), a wellbore (110) penetrating the salt rock sample (100) is provided in the salt rock sample (100), and when the salt rock sample (100) is clamped between the Z-direction pressure loading device, the drilling fluid inflow channel (320) and the drilling fluid outflow channel (310) are respectively connected to the two ends of the wellbore (110); a drilling fluid circulation system, wherein a drilling fluid supply end of the drilling fluid circulation system is connected to the drilling fluid inflow channel (320), a drilling fluid return end of the drilling fluid circulation system is connected to the drilling fluid outflow channel (310), and a temperature regulating device is provided on the drilling fluid circulation system; A data processing system, the data processing system comprising a temperature acquisition unit, a strain acquisition unit and a data processing unit, the temperature acquisition unit and the strain acquisition unit are both arranged in the wellbore (110) and are both electrically connected to the data processing unit, and the strain acquisition unit is arranged on the inner wall of the wellbore (110).

2. The salt rock formation borehole creep shrinkage test device according to claim 1, characterized in that: The strain acquisition unit comprises at least four strain sensors (520), and the plurality of strain sensors (520) are evenly distributed along the circumference of the inner wall of the wellbore (110).

3. The salt rock formation borehole creep shrinkage testing device according to claim 1, characterized in that: The X-direction pressure loading device comprises a pair of X-direction telescopic mechanisms (211) and a pair of first pressure heads (212) arranged opposite to each other, the two first pressure heads (212) being arranged at the telescopic ends of the two X-direction telescopic mechanisms (211) respectively, and the side of the first pressure head (212) in contact with the salt rock sample (100) having the same shape and size as the side of the salt rock sample (100) perpendicular to the X-axis.

4. The salt rock formation borehole creep shrinkage testing device according to claim 1, characterized in that: The Y-direction pressure loading device comprises a pair of Y-direction telescopic mechanisms (221) and a pair of second pressure heads (222) arranged opposite to each other, wherein the two second pressure heads (222) are respectively arranged at the telescopic ends of the two Y-direction telescopic mechanisms (221), and the side of the second pressure head (222) in contact with the salt rock sample (100) has the same shape and size as the side of the salt rock sample (100) perpendicular to the Y axis.

5. The salt rock formation borehole creep shrinkage testing device according to claim 1, characterized in that: The Z-direction pressure loading device comprises a pair of Z-direction telescopic mechanisms (231) and a pair of third pressure heads (232) arranged opposite to each other, the two third pressure heads (232) being arranged at the telescopic ends of the two Z-direction telescopic mechanisms (231) respectively, and the side of the third pressure head (232) in contact with the salt rock sample (100) having the same shape and size as the end face of the salt rock sample (100) perpendicular to the Z axis.

6. The salt rock formation borehole creep shrinkage testing device according to claim 5, characterized in that: The drilling fluid inflow channel (320) is disposed inside one of the two third pressure heads (232), and the drilling fluid outflow channel (310) is disposed inside the other one.

7. The salt rock formation borehole creep shrinkage testing device according to claim 6, characterized in that: A sealing ring is provided between the third pressure head (232) and the salt rock sample (100).

8. The salt rock formation borehole creep shrinkage testing device according to claim 1, characterized in that: The drilling fluid circulation system comprises a drilling fluid outflow pipe (410), a circulation pump (430) and a drilling fluid inflow pipe (420) which are connected in sequence. The end of the drilling fluid outflow pipe (410) away from the circulation pump (430) is connected to the drilling fluid outflow channel (310), and the end of the drilling fluid inflow pipe (420) away from the circulation pump (430) is connected to the drilling fluid inflow channel (320). A heating device (440) and a pressure gauge (450) are also provided on the drilling fluid outflow pipe (410).

9. A method for testing the creep shrinkage of a wellbore in a salt rock formation, characterized in that: Based on the salt rock formation borehole creep shrinkage testing device according to any one of claims 1 to 8, the testing method comprises: Installing a temperature acquisition unit and a strain acquisition unit of a data processing system on the inner wall of a wellbore (110) of a salt rock sample (100); Clamping the salt rock sample (100) between an X-direction pressure loading device, a Y-direction pressure loading device, and a Z-direction pressure loading device; Pressure setting step: adjusting the pressure applied by the X-direction pressure loading device to the salt rock sample (100) to a target X-direction pressure, adjusting the pressure applied by the Y-direction pressure loading device to the salt rock sample (100) to a target Y-direction pressure, and adjusting the pressure applied by the Z-direction pressure loading device to the salt rock sample (100) to a target Z-direction pressure; Temperature setting step: adjusting the temperature of the drilling fluid in the drilling fluid circulation system to a target temperature, and starting the drilling fluid circulation system; Data collection step: collecting data from the temperature collection unit and the strain collection unit; re-adjusting one or three of the target X-direction pressure, the target Y-direction pressure, and the target Z-direction pressure, or re-adjusting the target temperature, and performing a data acquisition step; The data collected in the data collection step are processed to obtain the relationship between the creep shrinkage strain and stress of the salt rock formation wellbore at different temperatures.

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