A casing-cement sheath-stratum consolidation body integrity simulation experimental device

Abstract

The present invention discloses a casing-cement ring-formation consolidation body integrity simulation experimental device, which relates to the field of oil and gas drilling and production, including a support structure, a wellbore structure, a cement slurry injection system, a hydraulic system and a test system; a wellbore structure is installed on the support structure, and the wellbore structure includes a formation pipe string and a casing pipe string vertically arranged on a bracket, and a cement ring cavity is between the formation pipe string and the casing pipe string, and the cement ring cavity is connected to the cement slurry injection system; the formation pipe string includes an upper formation pipe string and a lower formation pipe string, and the upper formation pipe string and the lower formation pipe string are fixedly connected by an inclined plate and an inclined plate bolt; the outer wall of the upper formation pipe string is connected to a hydraulic system; the test system includes a DAS monitoring optical fiber, and a DAS monitoring optical fiber is spirally wound on the outer wall of the casing pipe string. The present invention explores the causes of casing-cement ring-formation integrity failure from an experimental perspective, clarifies the mechanism of wellbore integrity failure, and provides theoretical support for proposing corresponding prevention and control mechanisms.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas drilling and production, in particular to a casing-cement ring-stratum consolidation body integrity simulation experimental device. Background Art

[0002] During oil and gas drilling and production, casing-cement sheath-formation is the most typical wellbore structure of oil and gas wells. Its integrity is the key to ensuring wellbore stability and isolating formation fluids. However, with the continuous development of my country's oil and gas resources and the increasing complexity of the geological environment, oil and gas leakage and wellbore integrity failure accidents related to wellbore quality are increasing rapidly. Therefore, the integrity analysis of the casing-cement sheath-formation system has always been a key research area to ensure the safe and efficient production of oil and gas resources.

[0003] The failure of the casing-cement sheath-formation consolidation body is mainly manifested in two aspects: casing deformation and damage, and cement sheath consolidation body defects. There are many reasons for the failure of casing-cement sheath-formation integrity. On the one hand, it depends on complex geological factors: ① The non-uniform ground stress acting on the wellbore is mainly manifested in the activation of faults and interlayer slippage of formations induced by injection and production measures, which in turn causes shear damage to the wellbore; ② The temperature difference between the formation and the wellbore causes the volume expansion or contraction of the annular cement sheath, which leads to cracking and failure of the cement sheath-casing and cement sheath-formation bonding surfaces; ③ Excessive internal pressure in the casing will cause plastic failure of the cement sheath, which starts from the inner wall of the cement sheath and expands outward until complete plastic failure. On the other hand, it depends on the engineering factors in the drilling and completion process: ① During cementing operations, due to the casing's own weight and other reasons, the casing is not completely centered in the wellbore (casing eccentricity), and the cement slurry solidifies in the annulus to form a cement ring with uneven thickness, which will aggravate the uneven external load on the casing, further causing the casing to deform under stress or the cement ring bonding surface to fail; ② During the completion process, cement rings with different wall thicknesses formed by different sizes of casing and wellbore will affect the stress characteristics of the casing; ③ Cement slurries with different formulations show different permeability characteristics after solidification, which in turn affects the sealing of the wellbore. In short, the failure of casing-cement ring-formation integrity is a problem of deformation damage and sealing failure under the combined action of multiple factors.

[0004] Existing related research is mostly focused on the numerical simulation of casing-cement sheath-formation consolidation. By establishing a casing-cement sheath-formation mechanical model under one or several of the above-mentioned influencing factors, the stress distribution and strain damage of the wellbore under external uniform or non-uniform loads are analyzed. However, the numerical simulation results often need to be verified by related tests, and the existing test devices are mostly built with simple consideration of casing strength tests, or devices considering cement sheath sealing tests, and lack of casing-cement sheath-formation integrity failure simulation test devices under the combined effects of the above-mentioned geological and engineering factors. Summary of the invention

[0005] The purpose of the present invention is to provide a casing-cement sheath-formation consolidation body integrity simulation experimental device to solve the problems existing in the above-mentioned prior art, explore the causes of casing-cement sheath-formation integrity failure from an experimental perspective, clarify the mechanism of wellbore integrity failure, and provide theoretical support for proposing corresponding prevention and control mechanisms.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a casing-cement ring-formation consolidation body integrity simulation experimental device, comprising a support structure, a wellbore structure, a cement slurry injection system, a hydraulic system and a test system; the support structure comprises a bracket, the wellbore structure is installed on the bracket, both ends of the wellbore structure are provided with a plugging device, the wellbore structure comprises a formation pipe string vertically arranged on the bracket, a casing pipe string is arranged in the formation pipe string, a cement ring cavity is between the formation pipe string and the casing pipe string, the cement ring cavity is connected to the formation pipe string, and the cement ring cavity is connected to the formation pipe string. The cement slurry injection system is connected; the formation tubular column comprises an upper formation tubular column and a lower formation tubular column, the bottom of the upper formation tubular column and the top of the lower formation tubular column are both inclined surfaces with the same inclination direction, and the inclined surfaces are fixedly provided with inclined plates, and the inclined plates of the upper formation tubular column and the lower formation tubular column are fixedly connected by inclined plate bolts; the outer wall of the upper formation tubular column is connected to the hydraulic system; the test system comprises a DAS monitoring optical fiber, and the DAS monitoring optical fiber is spirally wound on the outer wall of the casing string.

[0008] Optionally, the bracket includes a horizontally arranged bottom bracket, to which a vertically arranged vertical bracket is connected; the sealing device includes a pipe column base and a top cover; the pipe column base is fixedly installed on the bottom bracket by a first bolt, a bottom positioning ring is arranged in the pipe column base, the formation pipe column and the casing pipe column are arranged on the bottom positioning ring, and are fixedly connected to the pipe column base by a fixing ring; the top cover is fixedly connected to the formation pipe column by a second bolt; and a pressure relief valve is provided on the top cover.

[0009] Optionally, a stepped hole with a diameter increasing from bottom to top is opened on the bottom positioning ring, and the formation pipe string and the casing pipe string are fixedly sleeved in the stepped hole.

[0010] Optionally, the cement slurry injection system includes a cement slurry agitator disposed on the bottom bracket, and the cement slurry agitator is connected to the cement ring cavity through a cement slurry injection pipe; an injection pump and a one-way valve are installed on the cement slurry injection pipe.

[0011] Optionally, the cement slurry injection pipe is respectively connected to a pressure gauge, a flow meter and a temperature sensor.

[0012] Optionally, the hydraulic system includes a first hydraulic cylinder connected to the vertical support via a hinge, a hydraulic rod at the end of the first hydraulic cylinder is connected to the upper formation pipe column, a horizontally arranged second hydraulic cylinder is connected to the outer wall above the first hydraulic cylinder, and the second hydraulic cylinder is vertically fixedly connected to the vertical support; the first hydraulic cylinder and the second hydraulic cylinder are respectively connected to hydraulic pumps via hydraulic pipelines.

[0013] Optionally, a movable conical ring is sleeved on the outer wall of the upper formation pipe string, and the hydraulic rod at the end of the first hydraulic cylinder is connected to the conical side wall of the movable conical ring.

[0014] Optionally, a horizontal extension frame is provided on the vertical support, and a claw is connected to the end of the horizontal extension frame through a third bolt, and the claw is clamped on the outer wall of the lower formation pipe column; the hydraulic pump is arranged on the horizontal extension frame.

[0015] Optionally, obliquely arranged reinforcing ribs are connected between the bottom bracket and the vertical bracket.

[0016] Compared with the prior art, the present invention has achieved the following technical effects:

[0017] The experimental device of the present invention can monitor the deformation process and sealing of the casing-cement sheath-formation consolidation body under the influence of complex geological factors and engineering factors, so as to provide basic data and theoretical support for the failure analysis of casing-cement sheath-formation integrity. The cement slurry pumping device has the function of configuring cement slurry and injecting it into the cement sheath cavity from the bottom of the casing at a certain temperature, pressure and flow rate. It simulates the phenomenon that the cement injection starts from the bottom of the annulus during the actual cementing process. In addition, the installation of the top cover pressure relief valve can ensure the discharge of cavity air during the cement slurry injection process and ensure the sealing of the cement after solidification. The formation pipe column is assembled by the upper and lower parts with an inclined section at a certain inclination angle. The hydraulic system will provide an external load parallel to this inclined section to simulate the impact of interlayer slippage of the formation on the integrity of the wellbore after the activation of a certain angle fault. The DAS monitoring optical fiber is placed in the entire wellbore section. Since the DAS optical fiber itself is a sensor, it is equivalent to a row of "microphones" placed in the well section to collect downhole acoustic wave signals, and can identify the deformation and strength characteristics of the entire well section in the simulation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1It is a cross-sectional schematic diagram of the overall structure of the present invention;

[0020] Figure 2 It is a schematic diagram of the casing column and the DAS monitoring optical fiber placed on the surface of the casing column in the device of the present invention;

[0021] Figure 3 It is a cross-sectional view of a pipe column base assembly in the device of the present invention;

[0022] Figure 4 It is a plane schematic diagram of the clamping claw in the device of the present invention;

[0023] Explanation of the reference numerals in the accompanying drawings: top cover 1, air relief valve 2, movable conical ring 3, inclined plate 4, inclined plate bolt 5, pressure gauge 6, injection pump 7, cement slurry agitator 8, flow meter 9, temperature sensor 10, one-way valve 11, cement slurry injection pipe 12, formation tubing string 13, fixing ring 14, bottom positioning ring 15, casing tubing string 16, tubing string base 17, first bolt 18, claw 19, third bolt 20, hydraulic pump 21, hydraulic pipeline 22, hinge 23, first hydraulic cylinder 24, second hydraulic cylinder 25, DAS monitoring optical fiber 26, bracket 27, second bolt 28, cement ring cavity 29. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0025] The purpose of the present invention is to provide a casing-cement sheath-formation consolidation body integrity simulation experimental device to solve the problems existing in the above-mentioned prior art, explore the causes of casing-cement sheath-formation integrity failure from an experimental perspective, clarify the mechanism of wellbore integrity failure, and provide theoretical support for proposing corresponding prevention and control mechanisms.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] The present invention provides a casing-cement ring-stratum consolidation body integrity simulation experimental device, such as Figure 1-Figure 4As shown, the bracket 27 is fixed to the ground, and the bracket 27 is connected and fixed to the pipe column base 17 by the first bolt 18. A fixing ring 14 and a bottom positioning ring 15 are placed inside the pipe column base 17 to determine the position of the formation pipe column 13 and the casing pipe column 16. The groove of the fixing ring 14 is used for the tight assembly of the formation pipe column 13 and the casing pipe column 16. The upper and lower parts of the external formation pipe column 13 are connected by the inclined plate 4 and the inclined plate bolt 5. The DAS monitoring optical fiber 26 is spirally wound around the entire pipe column section of the casing pipe column 16 to monitor the deformation and strength characteristics of the casing pipe column 16 and the cement ring in the cement ring cavity 29 during the experiment. The top of the casing pipe column 16 and the formation pipe column 13 are connected by the top cover 1 and the second bolt 28. The top cover 1 is provided with a vent valve 2 for the discharge of air during the cement slurry injection process. The lower end of the oblique section of the formation pipe string 13 is fixed by a bracket 27 to limit its horizontal displacement, while the upper end of the oblique section of the formation pipe string 13 is connected to the hydraulic loading system through a movable conical ring 3, and an external load from the hydraulic loading system is applied. The hydraulic loading system includes a hydraulic pump 21, a first hydraulic cylinder 24, a second hydraulic cylinder 25, a hydraulic pipeline 22 and a hinge 23. The size and direction of the external load acting on the pipe string system can be adjusted by the coordinated use of these tools, and the degree of freedom of direction adjustment is 0°-90°. Specifically, the bottom of the bracket is used to limit the vertical displacement of the wellbore structure, and the lower end of the vertical bracket is fixed by a claw 19 and a third bolt 20 to fix the lower half of the wellbore structure separated by the oblique section to limit its horizontal displacement. The external load provided to the pipe string by the hydraulic system is parallel to the oblique section of the pipe string. A cement slurry injection pipe 12 is provided at the bottom end of the formation pipe string 13. At this point, a cement ring cavity 29 is formed between the formation pipe string 13 and the casing pipe string 16 for cement slurry injection and curing. The cement slurry injection pipe 12 is connected to the cement slurry injection system, which includes a pressure gauge 6, an injection pump 7, a cement slurry agitator 8, a flow meter 9, a temperature sensor 10 and a one-way valve 11. The cement slurry can be directly prepared and injected into the cement ring cavity 29. The system has the ability to analyze the performance of cement slurries of different formulas from liquid injection into the annulus between the casing string 16 and the formation string 13 to solidification into a solid cement ring, optimize the cement slurry formula for the wellbore structure, and monitor the temperature, pressure and displacement changes of the wellbore structure.

[0028] A plurality of formation pipe strings 13 with oblique cross sections of different inclination angles will be prepared to simulate the effect of slippage between formation layers at a certain inclination angle on casing force. The bottom positioning ring 15 on the inner side of the pipe string base 17 is designed according to the size of the casing pipe string and the formation pipe string. A cement ring cavity 29 is formed between the casing pipe string 16 and the formation pipe string 13 to prepare for cement slurry injection. In addition, a plurality of pipe string bases 17 with different groove positions, i.e., non-concentric stepped holes, are prepared to simulate the eccentricity of the casing, i.e., the effect of uneven thickness of the cement ring caused by the non-centering of the casing on the casing force.

[0029] The experimental principle of the present invention is mainly based on the deformation and damage theory of the casing-cement ring-formation consolidation body under the action of complex formation loads. The complex loads acting on the casing-cement ring-formation consolidation body come from: volume expansion or contraction during the cement slurry solidification process; casing eccentricity and uneven thickness of the cement ring affect the casing load distribution; interlayer slip and non-uniform ground stress of the formation produce non-uniform loads on the casing, etc. The test device of the present invention simulates these complex loads acting on the casing, combines the DAS monitoring optical fiber 26 to monitor the deformation and damage of the wellbore, and simulates the phenomenon that the cement is injected from the bottom of the annulus during the actual cementing process. In addition, the installation of the top cover pressure relief valve can ensure the discharge of cavity air during the cement slurry injection process, ensure the sealing of the cement after solidification, further analyze and explain the failure mechanism of the wellbore integrity, and provide theoretical support for the corresponding prevention and control mechanism.

[0030] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A casing-cement ring-formation consolidation body integrity simulation experimental device, characterized in that: The invention comprises a support structure, a wellbore structure, a cement slurry injection system, a hydraulic system and a test system; the support structure comprises a bracket, the wellbore structure is installed on the bracket, plugging devices are arranged at both ends of the wellbore structure, the wellbore structure comprises a formation pipe string vertically arranged on the bracket, a casing pipe string is arranged in the formation pipe string, a cement ring cavity is formed between the formation pipe string and the casing pipe string, and the cement ring cavity is connected with the cement slurry injection system; the formation pipe string comprises an upper formation pipe string and a lower formation pipe string, the bottom of the upper formation pipe string and the top of the lower formation pipe string are both inclined The inclined surfaces have the same oblique direction, and the inclined surfaces are all fixedly provided with oblique plates, and the oblique plates of the upper formation pipe string and the oblique plates of the lower formation pipe string are fixedly connected by oblique plate bolts; the outer wall of the upper formation pipe string is connected to the hydraulic system; the test system includes a DAS monitoring optical fiber, and the DAS monitoring optical fiber is spirally wound on the outer wall of the casing pipe string; the bracket includes a horizontally arranged bottom bracket, and the bottom bracket is connected to a vertically arranged vertical bracket; the plugging device includes a pipe column base and a top cover; the pipe column base is fixedly installed on the bottom bracket by a first bolt, and the A bottom positioning ring is arranged in the pipe column base, the formation pipe column and the casing pipe column are arranged on the bottom positioning ring and are fixedly connected to the pipe column base through a fixing ring; the top cover is fixedly connected to the formation pipe column through a second bolt; a pressure relief valve is arranged on the top cover; a stepped hole with a diameter increasing from bottom to top is arranged on the bottom positioning ring, the formation pipe column and the casing pipe column are fixedly sleeved in the stepped hole; the cement slurry injection system includes a cement slurry agitator arranged on the bottom bracket, and the cement slurry agitator is connected to the cement ring cavity through a cement slurry injection pipe ; An injection pump and a one-way valve are installed on the cement slurry injection pipe; the hydraulic system includes a first hydraulic cylinder connected to the vertical support through a hinge, a hydraulic rod at the end of the first hydraulic cylinder is connected to the upper formation pipe string, a horizontally arranged second hydraulic cylinder is connected to the outer wall above the first hydraulic cylinder, and the second hydraulic cylinder is vertically fixedly connected to the vertical support; the first hydraulic cylinder and the second hydraulic cylinder are respectively connected to hydraulic pumps through hydraulic pipelines; a movable conical ring is sleeved on the outer wall of the upper formation pipe string, and the hydraulic rod at the end of the first hydraulic cylinder is connected to the conical side wall of the movable conical ring.

2. The casing-cement sheath-stratum consolidation body integrity simulation experimental device according to claim 1 is characterized in that: The cement slurry injection pipe is respectively connected with a pressure gauge, a flow meter and a temperature sensor.

3. The casing-cement sheath-stratum consolidation body integrity simulation experimental device according to claim 1 is characterized in that: A horizontal extension frame is arranged on the vertical support, and a clamping claw is connected to the end of the horizontal extension frame through a third bolt, and the clamping claw is clamped on the outer wall of the lower formation pipe column; the hydraulic pump is arranged on the horizontal extension frame.

4. The casing-cement sheath-stratum consolidation body integrity simulation experimental device according to claim 1, characterized in that: An obliquely arranged reinforcing rib is connected between the bottom bracket and the vertical bracket.

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