Simulation device and simulation monitoring method for deformation of tight oil and gas reservoir casing

Abstract

The invention belongs to the technical field of oil and gas reservoir engineering, and discloses a tight oil and gas reservoir casing deformation simulation device and a simulation monitoring method, and the device comprises a sealing box, an optical fiber monitoring assembly, a fracturing fluid injection assembly and a gas injection assembly. The sealing box can accommodate a simulated rock sample and can seal the simulated wellbore; the optical fiber monitoring assembly comprises a monitor and a plurality of sensing optical fibers, and the sensing optical fibers are connected with the simulation wellbore so as to monitor deformation of the simulation wellbore; the gas injection assembly and the fracturing fluid injection assembly communicate with the simulation wellbore so that gas and fracturing fluid can be injected into the simulation wellbore. According to the simulation monitoring method, the simulation device is utilized, and the sensing optical fiber is arranged on the simulation wellbore, so that the stress deformation condition of the simulation wellbore can be detected in real time through optical fiber strain in the simulation process of formation fracturing, fracturing fluid flowback and high-pressure gas injection; therefore, technical reserve is provided for fracturing of compact oil and gas reservoirs on an actual oil field site.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas reservoir engineering, and in particular to a simulation device and a simulation monitoring method for casing deformation in a dense oil and gas reservoir. Background Art

[0002] At present, the discovery of unconventional oil and gas reservoirs on land has set off a new wave of the oil and gas industry. The oil and gas reserves contained in them are quite considerable and have attracted the attention of oilfield workers. Today, when conventional oil and gas reservoirs are exhausted, the development of tight oil and gas reservoirs represented by shale oil and shale gas has achieved a breakthrough and perfectly replaced conventional oil and gas reservoirs. Although the reserves of unconventional tight oil and gas reservoirs are large, unlike conventional reservoirs, if unconventional oil and gas reservoirs are to be mined, an increase in production and injection process - fracturing - is required. Only after the tight oil and gas reservoirs have been transformed by fracturing construction can they be put into normal oil and gas production.

[0003] During the fracturing fluid flowback process of tight oil and gas wells, the problem of casing damage always exists, and the casing damage problem has become a key and difficult problem affecting oil field production. Shale is a typical tight reservoir. This type of reservoir has relatively developed bedding and strong heterogeneity. During the fracturing fluid flowback process, many complex cracks have been generated near the wellbore. The induced stress generated by the cracks causes the ground stress in the unconventional oil and gas reservoir to change. The magnitude and direction of the ground stress will change to varying degrees, resulting in stress concentration, causing the casing to deform or even damage. In addition to the serious impact on the magnitude and direction of the stress, the properties of the entire tight oil and gas reservoir will also change, causing inconvenience to subsequent construction and mining.

[0004] The damage of casing mainly includes the influence of stress concentration and the damage of fluid-solid coupling effect on casing. In addition, the number of high-temperature and high-pressure gas wells is increasing, and the annular pressure problem is becoming increasingly prominent. However, it is currently impossible to monitor the stress and deformation of casing in real time during production. Summary of the invention

[0005] The purpose of the present invention is to provide a simulation device and a simulation monitoring method for casing deformation in tight oil and gas reservoirs, so as to simulate and monitor the stress and deformation of the casing in the process of formation fracturing, fracturing fluid return and displacement oil production in real time, thereby providing technical reserves for the fracturing of tight oil and gas reservoirs in actual oil fields.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The simulation device for casing deformation in tight oil and gas reservoirs includes:

[0008] A sealed box, the sealed box comprising a box body and a box cover, the box body being capable of accommodating a simulated rock sample, and the box cover being provided with a sealing portion capable of sealing a simulated wellbore located in the simulated rock sample;

[0009] An optical fiber monitoring assembly, the optical fiber monitoring assembly comprising a monitoring instrument and a plurality of sensing optical fibers connected to the monitoring instrument, the sensing optical fibers being connected to the simulated wellbore so as to be able to monitor deformation of the simulated wellbore;

[0010] A fracturing fluid injection assembly, wherein the injection end of the fracturing fluid injection assembly is connected to the simulated wellbore so as to be able to inject fracturing fluid into the simulated wellbore;

[0011] A gas injection component, wherein the gas injection end of the gas injection component is connected to the simulated wellbore so as to be able to inject gas into the simulated wellbore.

[0012] Preferably, the simulated wellbore is provided with a plurality of grooves extending along the length direction of the simulated wellbore, and the sensing optical fiber is arranged in the grooves and is sealed by a sealing portion.

[0013] Preferably, the simulated wellbore comprises a casing and a cement ring sleeved on the outside of the casing, and the outer wall of the casing and the outer wall of the cement ring are both provided with the groove.

[0014] Preferably, a plurality of circular holes are provided on the cement ring, and the plurality of circular holes are arranged at equal distances along the length direction of the cement ring, and the circular holes pass through the outer wall of the casing to communicate with the inner cavity of the casing.

[0015] Preferably, a constant temperature box is provided in the sealed box, and the simulated rock sample is placed in the constant temperature box.

[0016] Preferably, a voltage stabilizing component is further provided, and the voltage stabilizing component has a voltage stabilizing source and a confining pressure portion, and the confining pressure portion is coated on the outside of the constant temperature box to ensure the confining pressure of the simulated rock sample.

[0017] Preferably, the fracturing fluid injection assembly comprises a hydraulic source and an oil-water mixer, the hydraulic source is connected to the oil-water mixer, and the oil-water mixer is connected to the simulated wellbore.

[0018] Preferably, a pipe connected to the casing is provided on the box cover, the pipe passes through the sealing portion and is connected to the casing, and the fracturing fluid injection assembly and the gas injection assembly are respectively connected to the pipe.

[0019] A simulation monitoring method for casing deformation in a tight oil and gas reservoir is also provided, using the simulation device for casing deformation in a tight oil and gas reservoir as described above, comprising the following steps:

[0020] S1. Make a simulated wellbore and arrange the sensing optical fiber;

[0021] S2, preparing a simulated rock sample, drilling a hole in the simulated rock sample to simulate a wellbore, and placing the simulated wellbore in the wellbore to perform cementing simulation;

[0022] S3, placing the simulated rock sample in which the simulated wellbore is placed in a sealed box, and connecting a fracturing fluid injection assembly and a gas injection assembly;

[0023] S4, injecting fracturing fluid into the simulated wellbore through the fracturing fluid injection assembly to simulate the fracturing fluid injection process, during which the deformation of the simulated wellbore is monitored;

[0024] S5. Injecting gas into the simulated wellbore through the gas injection assembly to simulate a fracturing fluid flowback process or a displacement oil production process, during which the deformation of the simulated wellbore is monitored.

[0025] Preferably, the gas injected in the process of simulating the fracturing fluid flowback is nitrogen; and the gas injected in the process of simulating the displacement oil production is CO2.

[0026] Beneficial effects of the present invention:

[0027] By setting up sensing optical fibers on the simulated wellbore, it is possible to detect the stress and deformation of the simulated wellbore in real time through optical fiber strain during the simulation process of formation fracturing, fracturing fluid return and displacement oil production, thereby providing technical reserves for the fracturing of tight oil and gas reservoirs at actual oil fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of a simulation device for tight oil and gas reservoir casing deformation according to the present invention;

[0029] Figure 2 It is a schematic diagram of the simulated wellbore in the simulated rock sample in the present invention.

[0030] In the figure:

[0031] 1. Sealing box; 101. Box body; 102. Box cover; 2. Simulated rock sample; 3. Simulated wellbore; 301. Casing; 302. Cement ring; 4. Monitor; 5. Sensing optical fiber; 6. Constant temperature box; 7. Pressure stabilizing source; 8. Confining pressure part; 10. Hydraulic source; 11. Oil-water mixer; 12. MTS booster; 13. Steam injection source; 14. MTS controller; 15. Control system. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0033] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" 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.

[0034] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0035] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0036] like Figure 1 and Figure 2 As shown, this embodiment provides a simulation device for casing deformation in a tight oil and gas reservoir, which includes a sealing box 1, an optical fiber monitoring assembly, a fracturing fluid injection assembly, and a gas injection assembly. The sealing box 1 includes a box body 101 and a box cover 102, the box body 101 can accommodate a simulated rock sample 2, and the box cover 102 is provided with a sealing portion to seal a simulated wellbore 3 located in the simulated rock sample 2; the optical fiber monitoring assembly includes a monitor 4 and a plurality of sensing optical fibers 5 connected to the monitor 4, and the sensing optical fibers 5 are connected to the simulated wellbore 3 to monitor the deformation of the simulated wellbore 3; the injection end of the fracturing fluid injection assembly is connected to the simulated wellbore 3 to inject fracturing fluid into the simulated wellbore 3; the gas injection end of the gas injection assembly is connected to the simulated wellbore 3 to inject gas into the simulated wellbore 3.

[0037] By setting the sensing optical fiber 5 on the simulated wellbore 3, the sensing optical fiber 5 can detect the stress and deformation of the simulated wellbore 3 in real time during the simulation process of formation fracturing, fracturing fluid return and high-pressure gas injection, thereby providing technical reserves for the fracturing of tight oil and gas reservoirs in actual oil fields.

[0038] In this embodiment, a plurality of grooves extending along the length direction of the simulated wellbore 3 are provided on the simulated wellbore 3, and the plurality of grooves are distributed along the circumference of the simulated wellbore 3. The sensing optical fiber 5 is provided in the groove and is blocked by a blocking portion; illustratively, the blocking portion is a mixed cement of water glass and cement. It should be noted here that the sensing optical fiber 5 is left at the port of the groove located at the simulated wellbore 3 so as to be connected to the monitoring instrument 4 provided outside; in this embodiment, the monitoring instrument 4 is a BOTDR strain analyzer.

[0039] In this embodiment, the simulated wellbore 3 includes a casing 301 and a cement ring 302 sleeved on the outside of the casing 301, and the outer wall of the casing 301 is in contact with the inner wall of the cement ring 302. In addition, in order to detect the deformation of the two at the same time, the outer wall of the casing 301 and the outer wall of the cement ring 302 are both provided with the above-mentioned grooves; wherein, the grooves on the casing 301 are distributed along the circumference of the casing 301, and the angle between adjacent grooves on the casing 301 is 60°; and the grooves on the cement ring 302 are distributed along the circumference of the cement ring 302, and the angle between adjacent grooves on the cement ring 302 is also 60°; in addition, the grooves on the cement ring 302 are located between the grooves on the casing 301, and the angle between the grooves on the cement ring 302 and the grooves on the casing 301 is 30°, so that the deformation of the simulated wellbore 3 can be more comprehensively monitored. Exemplarily, the depth of the groove is 5 mm. Furthermore, a plurality of circular holes are provided on the cement ring 302, and the plurality of circular holes are equidistantly arranged along the length direction of the cement ring 302. For example, the diameter of the circular hole is 6 mm, and the circular hole passes through the outer wall of the casing 301 and is connected to the inner cavity of the casing 301 to simulate the perforation holes.

[0040] In this embodiment, a thermostat 6 is provided in the sealed box 1. During the test, the simulated rock sample 2 needs to be placed in the thermostat 6 to increase the ambient temperature of the simulated rock sample 2, thereby simulating the actual formation temperature and making the monitored deformation data more accurate. It should be noted that one end of the thermostat 6 is open and can be sealed by a sealing portion provided on the box cover 102. The form of the sealing portion is not specifically limited. In other embodiments, the sealed box 1 can be replaced by a true triaxial test frame.

[0041] In this embodiment, in order to ensure that the simulated rock sample 2 can be provided with confining pressure in the simulation experiment, a pressure stabilizing component is also provided, and the pressure stabilizing component includes a pressure stabilizing source 7 and a confining pressure part 8, and the confining pressure part 8 is coated on the outside of the thermostatic box 6 to ensure the confining pressure of the simulated rock sample 2. In this embodiment, the pressure stabilizing source 7 is a hydraulic pressure stabilizing source, and the confining pressure part 8 is a pressure plate. Based on this, the thermostatic box 6 is surrounded by a heating plate, and the heating plate is arranged on the confining pressure plate, so that the simulated rock sample 2 can be heated more conveniently.

[0042] In this embodiment, a pipe connected to the casing 301 is provided on the box cover 102, the pipe passes through the sealing part and is connected to the casing 301, and the fracturing fluid injection assembly and the gas injection assembly are respectively connected to the pipe. In this embodiment, the fracturing fluid injection assembly includes a hydraulic source 10 and an oil-water mixer 11, the hydraulic source 10 is connected to the oil-water mixer 11, and the oil-water mixer 11 is connected to the pipe, so that the fracturing fluid can be injected into the simulated wellbore 3 through the hydraulic source 10, wherein the fracturing fluid uses slippery water or linear glue. Furthermore, in order to ensure the injection pressure, an MTS supercharger 12 is also provided, the MTS supercharger 12 is connected to the oil-water mixer 11 and the hydraulic source 10, so as to increase the injection pressure of the fracturing fluid, and the MTS supercharger 12 is connected to the MTS controller 14.

[0043] In this embodiment, the gas injection assembly includes a steam injection source 13, a gas injection pipeline and a switch valve. The steam injection source 13 is connected to the pipeline on the box cover 102 through the gas injection pipeline. The switch valve is arranged on the gas injection pipeline to control the gas injection time and gas injection amount. In this embodiment, the switch valve is a solenoid valve.

[0044] In this embodiment, a control system 15 is also provided, and the control system 15 is connected to the optical fiber monitoring component, the fracturing fluid injection component and the gas injection component, so as to control the automated operation of each link and analyze and process the collected data.

[0045] This embodiment also provides a simulation monitoring method for tight oil and gas reservoir casing deformation, using the above-mentioned tight oil and gas reservoir casing deformation simulation device, including the following steps:

[0046] S1, manufacturing a casing 301 and a cement ring 302, and opening a plurality of circular holes at equal distances on the cement ring 302 and the casing 301 to simulate perforation holes;

[0047] Then, grooves are cut on the outer walls of the casing 301 and the cement ring 302, and the sensing optical fiber 5 is laid in the grooves. Then, the grooves are sealed with a mixture of water glass and cement, and the sensing optical fiber 5 is connected to the BOTDR strain analyzer. Then, the casing 301 is inserted into the cement ring 302, so that the circular hole on the cement ring 302 is connected with the circular hole on the casing 301 to form a simulated wellbore 3.

[0048] S2, using a PDC diamond saw blade cutting machine to process the large-sized shale outcrop rock into a 500mm×500mm×500mm simulated rock sample 2 required for the simulation experiment, and then using a drill bit to drill a hole in the center of a certain end face of the simulated rock sample 2 along the bedding direction to simulate a drilling hole. The outer diameter of the drilling hole is the same as the outer diameter of the cement ring 302, and the drilling hole does not penetrate the simulated rock sample 2, and the simulated wellbore 3 in S1 is inserted into the drilling hole to complete the cementing simulation;

[0049] S3, placing the rock sample in the simulated wellbore 3 in the sealed box 1, connecting the MTS booster 12, the fracturing fluid injection assembly and the gas injection assembly, and closing the box cover 102 for sealing; then raising the internal temperature to 150° C. through the thermostatic box 6, and adjusting the confining pressure through the pressure stabilizing assembly;

[0050] S4, when the confining pressure is stable, inject fracturing fluid into the simulated wellbore 3 through the fracturing fluid injection assembly, and modify the injection pressure through the MTS booster 12 to simulate the fracturing fluid injection process, during which the deformation of the simulated wellbore 3 during the formation fracturing process is monitored;

[0051] S5. After the fracturing fluid is injected, nitrogen is injected into the simulated wellbore 3 through the gas injection assembly. Based on the monitoring of the monitor 4, the pressure in the wellbore is raised to 80 MPa by increasing the injection pressure, and the fracturing fluid is reversely displaced to simulate the fracturing fluid return process. The displacement time is 24 hours, and the deformation of the simulated wellbore 3 is monitored during the experimental displacement process;

[0052] S6, after the fracturing fluid is returned, the nitrogen in the gas injection system is replaced with CO2, so that the wellbore is filled with CO2, and the pressure inside the wellbore is increased by increasing the injection pressure, simulating the process of CO2 displacement oil production, during which the deformation of the simulated wellbore 3 is monitored;

[0053] S7. Process and analyze the data through the control system 15.

[0054] Therefore, the stress and deformation of the casing 301 during high-temperature formation fracturing, fracturing fluid flowback and displacement oil production can be monitored through the above-mentioned simulation device and simulation monitoring method.

[0055] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A simulation device for casing deformation in tight oil and gas reservoirs, characterized in that: include: A sealed box (1), the sealed box (1) comprising a box body (101) and a box cover (102), the box body (101) being capable of accommodating a simulated rock sample (2), the box cover (102) being provided with a sealing portion so as to be capable of sealing a simulated wellbore (3) located in the simulated rock sample (2); An optical fiber monitoring assembly, the optical fiber monitoring assembly comprising a monitoring instrument (4) and a plurality of sensing optical fibers (5) connected to the monitoring instrument (4), the sensing optical fibers (5) being connected to the simulated wellbore (3) so as to be able to monitor the deformation of the simulated wellbore (3); A fracturing fluid injection assembly, wherein the injection end of the fracturing fluid injection assembly is connected to the simulated wellbore (3) so as to be able to inject fracturing fluid into the simulated wellbore (3); A gas injection component, wherein a gas injection end of the gas injection component is connected to the simulated wellbore (3) so as to be able to inject gas into the simulated wellbore (3).

2. The simulation device for casing deformation in tight oil and gas reservoirs according to claim 1, characterized in that: The simulated wellbore (3) is provided with a plurality of grooves extending along the length direction of the simulated wellbore (3), and the sensing optical fiber (5) is arranged in the grooves and is blocked by a blocking portion.

3. The simulation device for casing deformation in tight oil and gas reservoirs according to claim 2, characterized in that: The simulated wellbore (3) comprises a casing (301) and a cement ring (302) sleeved on the outside of the casing (301), and the outer wall of the casing (301) and the outer wall of the cement ring (302) are both provided with the groove.

4. The simulation device for casing deformation in tight oil and gas reservoirs according to claim 3, characterized in that: The cement ring (302) is provided with a plurality of circular holes, which are arranged at equal distances along the length direction of the cement ring (302). The circular holes pass through the outer wall of the casing (301) and are connected to the inner cavity of the casing (301).

5. The simulation device for casing deformation in tight oil and gas reservoirs according to claim 1, characterized in that: A constant temperature box (6) is arranged in the sealed box (1), and the simulated rock sample (2) is placed in the constant temperature box (6).

6. The simulation device for casing deformation in tight oil and gas reservoirs according to claim 5, characterized in that: A voltage stabilizing component is also provided, the voltage stabilizing component comprising a voltage stabilizing source (7) and a confining pressure portion (8), the confining pressure portion (8) being coated on the outside of the constant temperature box (6) so as to ensure the confining pressure of the simulated rock sample (2).

7. The simulation device for casing deformation in tight oil and gas reservoirs according to claim 1, characterized in that: The fracturing fluid injection assembly comprises a hydraulic source (10) and an oil-water mixer (11), wherein the hydraulic source (10) is connected to the oil-water mixer (11), and the oil-water mixer (11) is connected to the simulated wellbore (3).

8. The simulation device for casing deformation in tight oil and gas reservoirs according to claim 3, characterized in that: The box cover (102) is provided with a pipeline connected to the casing (301), the pipeline passes through the sealing portion and is connected to the casing (301), and the fracturing fluid injection assembly and the gas injection assembly are respectively connected to the pipeline.

9. A simulation monitoring method for casing deformation in tight oil and gas reservoirs, using the simulation device for casing deformation in tight oil and gas reservoirs as claimed in any one of claims 1 to 8, characterized in that: The steps include: S1, making a simulated wellbore (3) and arranging a sensing optical fiber (5); S2, preparing a simulated rock sample (2), drilling a hole in the simulated rock sample (2) to simulate a wellbore, and placing the simulated wellbore (3) in the wellbore to perform cementing simulation; S3, placing the simulated rock sample (2) in which the simulated wellbore (3) is placed in a sealed box (1), and connecting a fracturing fluid injection assembly and a gas injection assembly; S4, injecting fracturing fluid into the simulated wellbore (3) by connecting the fracturing fluid injection assembly to simulate the fracturing fluid injection process, during which the deformation of the simulated wellbore (3) is monitored; S5. Injecting gas into the simulated wellbore (3) through a gas injection assembly to simulate a fracturing fluid flowback process or a displacement oil production process, during which the deformation of the simulated wellbore (3) is monitored.

10. The simulation monitoring method for casing deformation in tight oil and gas reservoirs according to claim 9, characterized in that: The gas injected in the simulation of the fracturing fluid flowback process is nitrogen; the gas injected in the simulation of the displacement oil production process is CO2.

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