Wellbore system biaxial loading test device and evaluation method

Abstract

The application discloses a wellbore system biaxial loading test device and an evaluation method thereof, and belongs to the field of drilling. The cement pouring mode is changed to realize the simulation of the characteristics of a reservoir which cannot be stored. The first guide rail and the second guide rail are beneficial to the movement of the poured rigid sleeve to a biaxial extrusion tool. The first extrusion test cylinder, the second extrusion test cylinder, the third extrusion test cylinder and the fourth extrusion test cylinder are adopted to apply a load. The hydraulic cylinder applies a load along the axial direction of the casing. In cooperation with the second environment simulation layer, the casing-cement sheath system service state under different ground stress conditions can be simulated. Therefore, the wellbore system biaxial loading test device can effectively solve the problems of casing optimization, cementing process optimization and wellbore integrity control. Through real-time test data, the casing service state can be determined. The full-size simulation experiment method is adopted to determine the non-uniform bearing characteristics of the casing-cement sheath system, thereby providing technical support for the selection of casing design.

Description

Technical Field

[0001] This invention belongs to the field of drilling, specifically relating to a biaxial loading test device and evaluation method for wellbore systems. Background Technology

[0002] Shale reservoirs have well-developed pores and fractures. Currently, the most efficient methods for shale oil and gas well development both domestically and internationally employ high-parameter multi-stage hydraulic fracturing technology (Pmax = 140 MPa, displacement 14 m³ / s). 3 / min, single-stage injection volume 2000m 3 High-parameter hydraulic fracturing causes shear displacement of pore fractures in shale reservoirs, leading to a redistribution of near-wellbore stress and increased heterogeneity, resulting in non-uniform external extrusion deformation of the casing. In the Changning and Weiyuan blocks of the Southwest Oil and Gas Field, non-uniform external extrusion caused casing deformation accounts for over 80%. Major oil and gas fields both domestically and internationally use the uniform extrusion resistance strength of casing as the main criterion for casing selection, but this approach has significant errors. Regarding evaluation methods for casing under non-uniform external extrusion load conditions, domestic and international experts and scholars mainly use numerical simulation methods with elliptical loading, which cannot verify the accuracy of their calculation results. ZL201810002596.7 proposes a method for evaluating the non-uniform external extrusion bearing capacity of casing using mechanical loading, but it does not consider the anisotropy of formation loads and the influence of the cement sheath on non-uniform loads. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention aims to provide a biaxial loading test device and evaluation method for wellbore systems. This device can simulate the load-bearing characteristics of the casing-cement sheath system under non-uniform load conditions, providing technical support for casing deformation control technology and wellbore integrity. It can effectively solve the problem of the load-bearing characteristics of the casing-cement sheath system under different lithologies, temperatures, and pressures in downhole, ensuring wellbore integrity and effectively controlling the probability of wellbore failure.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] The present invention discloses a biaxial loading test device for a wellbore system, comprising: a first main frame, a second main frame, a hydraulic cylinder, a first guide rail, a second guide rail, a casing, and a biaxial external extrusion fixture; the first guide rail and the second main frame are provided between the first main frame and the second main frame, the biaxial external extrusion fixture is provided on the first guide rail and the second guide rail, the casing passes through the biaxial external extrusion fixture and connects the first main frame and the second main frame, and the hydraulic cylinder is provided on the second main frame;

[0006] The biaxial extrusion fixture includes: a first extrusion test cylinder, a second extrusion test cylinder, a third extrusion test cylinder, a fourth extrusion test cylinder, a cement ring, a second environmental simulation layer, and a rigid sleeve; the first extrusion test cylinder, the second extrusion test cylinder, the third extrusion test cylinder, and the fourth extrusion test cylinder are mounted on the rigid sleeve, the cement ring is mounted outside the sleeve, the second environmental simulation layer is mounted outside the cement ring, and both the cement ring and the second environmental simulation layer are mounted inside the rigid sleeve.

[0007] Preferably, the first host frame has a blind hole for fixing the sleeve.

[0008] Preferably, the rigid sleeve includes: an outer sleeve of a rigid box, several third guide rails, and several slidable baffles of the rigid box; the third guide rails are disposed on the outer sleeve of the rigid box, the slidable baffles of the rigid box are disposed on the third guide rails, and the first external extrusion test cylinder, the second external extrusion test cylinder, the third external extrusion test cylinder, and the fourth external extrusion test cylinder are all connected to the slidable baffles of the rigid box.

[0009] Preferably, the third guide rail is arranged radially on the outer sleeve of the rigid box.

[0010] Preferably, the sleeve passes through the outer sleeve of the rigid box and is fixed by a half-flange.

[0011] Preferably, the size of the rigid sleeve is >1000mm.

[0012] Preferably, the sleeve is positioned at the center of the rigid sleeve.

[0013] Preferably, the forces applied by the first and third extrusion test cylinders are equal, and the forces applied by the second and fourth extrusion test cylinders are equal.

[0014] This invention also discloses an evaluation method for a biaxial loading test device for a wellbore system, comprising:

[0015] Step 1: Sample preparation. Place the sleeve in the center of the rigid sleeve and fix it. According to the site conditions, strata and mechanical properties of the cement ring, pour the cement ring and the second environmental simulation layer inside the rigid sleeve.

[0016] Step 2: Sample installation. Move the cast rigid sleeve into the biaxial external extrusion fixture.

[0017] Step 3: Non-uniform external extrusion loading test. After the specimen is installed and preliminarily adjusted, loads are applied to the first external extrusion test cylinder, the second external extrusion test cylinder, the third external extrusion test cylinder and the fourth external extrusion test cylinder.

[0018] Preferably, in step three, the load applied to the first extrusion test cylinder is the maximum horizontal principal stress P1; the load applied to the second extrusion test cylinder is the minimum horizontal principal stress P2; the load applied to the third extrusion test cylinder is the maximum horizontal principal stress P3; and the load applied to the fourth extrusion test cylinder is the minimum horizontal principal stress P4.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention discloses a biaxial loading test device for wellbore systems. By altering the cement pouring method, it simulates different reservoir characteristics. First and second guide rails facilitate the movement of the poured rigid sleeve to the biaxial extrusion fixture. Loads are applied using first, second, third, and fourth external extrusion test cylinders, with hydraulic cylinders applying loads along the casing axis. Combined with a second environmental simulation layer, it can simulate the service conditions of the casing-cement sheath system under different geostress conditions. Therefore, the biaxial loading test device for wellbore systems described in this invention can effectively solve problems related to casing selection, cementing process optimization, and wellbore integrity control.

[0021] Furthermore, the first main frame has blind holes for fixing the sleeve, which is beneficial for fixing the sleeve.

[0022] Furthermore, a third guide rail is provided on the outer sleeve of the rigid box, allowing the sliding baffle of the rigid box to move along the guide rail, thereby enabling the application of moving loads and simulating the service status of the sleeve-cement ring system under different ground stress conditions.

[0023] Furthermore, the third guide rail is radially arranged on the outer sleeve of the rigid box, which is beneficial for simulating the application of radial loads.

[0024] Furthermore, the sleeve passes through the outer sleeve of the rigid box and is fixed to the outer sleeve of the rigid box via a semi-flange to ensure the sealing of the rigid sleeve during the test and prevent small cement pieces from falling off during the test, which would affect the test results.

[0025] Furthermore, the rigid sleeve has a size >1000mm to ensure that boundary loading has no effect on the sleeve.

[0026] Furthermore, placing the casing at the center of the rigid sleeve is beneficial to the accuracy of the test results and can better simulate the actual downhole environment and load conditions.

[0027] Furthermore, the forces applied by the first and third external extrusion test cylinders are equal, and the forces applied by the second and fourth external extrusion test cylinders are equal. This facilitates operation while more accurately simulating the biaxial principal stresses of the downhole reservoir, namely the maximum horizontal principal stress and the minimum horizontal principal stress.

[0028] This invention also discloses an evaluation method for a biaxial loading test device for wellbore systems. Through real-time test data, the service status of the casing can be determined. A full-scale simulation experiment method is used to determine the non-uniform load-bearing characteristics of the casing-cement sheath system, providing technical support for casing design and selection. By using far-field stress transfer to the formation and then acting on the casing-cement sheath system, the stress concentration effect caused by direct mechanical loading on the casing is avoided, resulting in more accurate test results. The influence of rock bedding fractures on the determination of the non-uniform load-bearing characteristics of the casing is considered. Simultaneously, temperature and internal pressure loads can be applied, more accurately simulating the downhole service conditions of the casing. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a biaxial loading test device for a well system according to the present invention;

[0030] Figure 2 This is a schematic diagram of the non-uniform external extrusion application tooling structure in this invention;

[0031] Figure 3 This is a front view of the rigid sleeve in this invention;

[0032] Figure 4 This is a side view of the semi-flange connecting the rigid sleeve and the sleeve in this invention.

[0033] Wherein: 1-First main frame; 2-Second main frame; 3-Hydraulic cylinder; 4-First guide rail; 5-Second guide rail; 6-Sleeve; 7-Dual-axis external extrusion fixture; 8-First external extrusion test cylinder; 9-Second external extrusion test cylinder; 10-Third external extrusion test cylinder; 11-Fourth external extrusion test cylinder; 12-Cement ring; 13-Second environmental simulation layer; 14-Rigid sleeve; 15-Rigid box outer sleeve; 16-Third guide rail; 17-Rigid box sliding baffle; 18-Half flange. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] The present invention will now be described in further detail with reference to the accompanying drawings:

[0037] This invention designs a biaxial loading test device for a wellbore system, comprising a main frame, a hydraulic cylinder, a guide rail, a casing, and a non-uniform external extrusion application fixture, such as... Figure 1 As shown. The non-uniform external extrusion application fixture is as follows. Figure 2 As shown, the rigid sleeve structure is as follows Figure 3 As shown.

[0038] See Figure 1 It is known that the well system biaxial loading test device includes a first main frame 1, a second main frame 2, a hydraulic cylinder 3, a first guide rail 4, a second guide rail 5, a casing 6, and a biaxial external extrusion fixture 7; the first guide rail 4 and the second guide rail 5 are arranged between the first main frame 1 and the second main frame 2, the biaxial external extrusion fixture 7 is arranged on the first guide rail 4 and the second guide rail 5, the casing 6 passes through the biaxial external extrusion fixture 7 and connects the first main frame 1 and the second main frame 2, the hydraulic cylinder 3 is arranged on the second main frame 2; the first main frame 1 has a blind hole for fixing the casing 6.

[0039] See Figure 2 It is known that the biaxial external extrusion fixture 7 includes a first external extrusion test cylinder 8, a second external extrusion test cylinder 9, a third external extrusion test cylinder 10, a fourth external extrusion test cylinder 11, a cement ring 12, a second environmental simulation layer 13, and a rigid sleeve 14; the first external extrusion test cylinder 8, the second external extrusion test cylinder 9, the third external extrusion test cylinder 10, and the fourth external extrusion test cylinder 11 are disposed on the rigid sleeve 14, the cement ring 12 is disposed outside the sleeve 6, the second environmental simulation layer 13 is disposed outside the cement ring 12, and both the cement ring 12 and the second environmental simulation layer 13 are disposed inside the rigid sleeve 14.

[0040] See Figure 3It can be seen that the rigid sleeve 14 includes a rigid box outer sleeve 15, a third guide rail 16, and a rigid box sliding baffle 17; the third guide rail 16 is disposed on the rigid box outer sleeve 15, the rigid box sliding baffle 17 is disposed on the third guide rail 16, and the first external extrusion test cylinder 8, the second external extrusion test cylinder 9, the third external extrusion test cylinder 10 and the fourth external extrusion test cylinder 11 are all connected to the rigid box sliding baffle 17.

[0041] See Figure 4 It is known that the rigid sleeve is connected to the sleeve by the semi-flange 18; the sleeve 6 passes through the outer sleeve 15 of the rigid box and is fixed by the semi-flange 18.

[0042] Specifically, the main functions of the biaxial loading test device for the well system are: ① determining the non-uniform load-bearing capacity of the casing; ② determining the non-uniform load-bearing capacity of the casing-cement sheath.

[0043] Specifically, the biaxial loading test device for the well system is suitable for the following conditions: ① different casing specifications and sizes; ② different cement slurry systems; ③ different formation lithology; ④ different non-uniform loads.

[0044] The working principle of the above-mentioned biaxial loading test device for wellbore systems is as follows:

[0045] The actual reservoir stress conditions are simulated by applying equal loads to the four outer surfaces of the rigid sleeve through an external extrusion test cylinder; the cement pouring method is changed inside the rigid sleeve 14 to simulate the physical / mechanical state of the rock under different burial depth conditions; the innermost part of the rigid sleeve 14 is the cement sheath 12-casing 6 system, and the casing 6 and cementing slurry used on site are selected to simulate the on-site wellbore conditions.

[0046] This invention also discloses an evaluation method based on the above-mentioned biaxial loading test device for a wellbore system, the scheme of which is as follows:

[0047] (1) Sample preparation: Determine the mechanical properties of the formation and cement sheath 12 under field conditions, namely elastic modulus and Poisson's ratio. Place the casing 6 in the center of the rigid sleeve 14 and fix it. Cast the formation and cement sheath 12 inside the rigid sleeve 14 in a high-temperature environment, i.e. downhole temperature, to ensure that their elastic modulus and Poisson's ratio are the same as those under field conditions. The size of the rigid sleeve 14 is >1000mm to ensure that the boundary load has no effect on the casing 6.

[0048] (2) Sample installation: The cast rigid sleeve 14 is placed on the first guide rail (4) and the second guide rail (5) between the first main frame (1) and the second main frame (2). It is slowly moved into the non-uniform external extrusion application fixture 7. The four sides of the rigid sleeve 14 along the radial direction of the sleeve 6 are connected to the first external extrusion test cylinder 8, the second external extrusion test cylinder 9, the third external extrusion test cylinder 10, and the fourth external extrusion test cylinder 11, respectively. The two sides of the rigid sleeve 14 along the axial direction of the sleeve 6 are connected to the first main frame 1, the second main frame 2, and the hydraulic cylinder 3. All external extrusion test cylinders are connected to the rigid box sliding baffle 17. The rigid sleeve 14 is fixed to the sleeve 6 by the semi-flange 18 to ensure the sealing of the rigid sleeve 14 during the test and to prevent small cement pieces from falling off during the test and affecting the test results.

[0049] (3) Non-uniform external extrusion loading test: After the specimen is installed and preliminarily adjusted, the first external extrusion test cylinder 8 is subjected to the maximum horizontal principal stress load of P1; the second external extrusion test cylinder 9 is subjected to the minimum horizontal principal stress load of P2; the third external extrusion test cylinder 10 is subjected to the maximum horizontal principal stress load of P3; and the fourth external extrusion test cylinder 11 is subjected to the minimum horizontal principal stress load of P4.

[0050] Evaluation of casing resistance to non-uniform external extrusion: The non-uniformity coefficient of formation load n = P1 / P2 (<1.5) is used to monitor the degree of casing deformation in real time. When the inner diameter of the casing undergoes macroscopic deformation, it is considered that the bearing limit has been reached.

[0051] Example:

[0052] (1) Taking the complex fracturing operation of shale gas wells with high degree of non-uniformity in domestic oil and gas fields as an example, the maximum horizontal principal stress Phmax and minimum horizontal principal stress Phmin of shale reservoir are determined by geophysical methods, the elastic modulus and Poisson's ratio of shale reservoir and cement sheath are determined, the large bedding fractures of shale reservoir are quantified, their relative positions are determined, and the maximum internal pressure value Pmax and maximum temperature value Tmax inside the casing are determined.

[0053] (2) Casting a rigid sleeve to simulate working conditions, using plastic film to simulate large bedding fractures in shale reservoirs, ensuring that the elastic modulus and Poisson's ratio of the cast rock and cement sheath are the same as the actual lithology downhole.

[0054] (3) Pressurize the casing to reach Pmax, and use the casing heating method to ensure that the temperature reaches Tmax. Determine that the load of the second external extrusion test cylinder reaches Phmin. Increase the load of P1 and P3 in sequence, and monitor the change of the casing inner diameter in real time. When the casing inner diameter produces macroscopic deformation, stop loading and determine the non-uniformity coefficient n. When n is less than 1.5, the test ends. When n is greater than 1.5, adjust the load of the second external extrusion test cylinder to reach Phmin+5, and increase the load of P1 and P3 in sequence. Monitor the change of the casing inner diameter in real time. When the casing inner diameter produces macroscopic deformation, stop loading and determine the non-uniformity coefficient n. When n is less than 1.5, the test ends. When n is greater than 1.5, continue loading until the non-uniformity coefficient is less than 1.5.

[0055] (4) Casing selection based on formation non-uniformity: Determine the minimum and maximum horizontal principal stresses of the target reservoir, calculate the target non-uniformity coefficient nf, and calculate the non-uniformity coefficient nc of the casing by using the minimum horizontal principal stress value corresponding to the maximum horizontal principal stress when the casing inner diameter undergoes macroscopic deformation under the working condition. Compare the result of nc / nf with the design safety factor of the casing, i.e. the design standard value. If the nc / nf value is greater than the standard value, the casing can meet the working condition requirements. If not, select a higher-level casing and repeat the test until the nc / nf value is greater than the standard value.

[0056] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A biaxial loading test device for a wellbore system, characterized in that, include: The system comprises a first main frame (1), a second main frame (2), a hydraulic cylinder (3), a first guide rail (4), a second guide rail (5), a sleeve (6), and a biaxial external extrusion fixture (7). The first main frame (1) and the second main frame (2) are provided with a first guide rail (4) and a second guide rail (5). The biaxial external extrusion fixture (7) is provided on the first guide rail (4) and the second guide rail (5). The sleeve (6) passes through the biaxial external extrusion fixture (7) and connects the first main frame (1) and the second main frame (2). The hydraulic cylinder (3) is provided on the second main frame (2). The biaxial external extrusion fixture (7) includes: a first external extrusion test cylinder (8), a second external extrusion test cylinder (9), a third external extrusion test cylinder (10), a fourth external extrusion test cylinder (11), a cement ring (12), a second environmental simulation layer (13), and a rigid sleeve (14); the first external extrusion test cylinder (8), the second external extrusion test cylinder (9), the third external extrusion test cylinder (10), and the fourth external extrusion test cylinder (11) are disposed on the rigid sleeve (14), the cement ring (12) is disposed outside the sleeve (6), the second environmental simulation layer (13) is disposed outside the cement ring (12), and both the cement ring (12) and the second environmental simulation layer (13) are disposed inside the rigid sleeve (14); the rigid sleeve (14) is connected to the sleeve (6) by a semi-flange (18). The rigid sleeve (14) includes: a rigid box outer sleeve (15), a plurality of third guide rails (16) and a plurality of rigid box slidable baffles (17); the third guide rails (16) are disposed on the rigid box outer sleeve (15), the rigid box slidable baffles (17) are disposed on the third guide rails (16), and the first external extrusion test cylinder (8), the second external extrusion test cylinder (9), the third external extrusion test cylinder (10) and the fourth external extrusion test cylinder (11) are all connected to the rigid box slidable baffles (17); The third guide rail (16) is radially arranged on the outer sleeve (15) of the rigid box along the sleeve (6); The sleeve (6) passes through the outer sleeve (15) of the rigid box and is fixed by the half flange (18); The forces applied by the first extrusion test cylinder (8) and the third extrusion test cylinder (10) are equal, and the forces applied by the second extrusion test cylinder (9) and the fourth extrusion test cylinder (11) are equal.

2. The biaxial loading test device for a wellbore system according to claim 1, characterized in that, The first host frame (1) has a blind hole for fixing the sleeve (6).

3. The biaxial loading test device for a wellbore system according to claim 1, characterized in that, The size of the rigid sleeve (14) is >1000mm.

4. The biaxial loading test device for a wellbore system according to claim 1, characterized in that, The sleeve (6) is located at the center of the rigid sleeve (14).

5. The evaluation method for a biaxial loading test apparatus for a wellbore system as described in any one of claims 1 to 4, characterized in that, include: Step 1: Sample preparation. Place the sleeve (6) in the center of the rigid sleeve (14) and fix it. According to the geological conditions and mechanical properties of the cement ring, pour the cement ring (12) and the second environmental simulation layer (13) inside the rigid sleeve (14). Step 2: Sample installation. Move the cast rigid sleeve (14) to the middle of the first external extrusion test cylinder (8), the second external extrusion test cylinder (9), the third external extrusion test cylinder (10), and the fourth external extrusion test cylinder (11). Step 3: Non-uniform external extrusion loading test. After the sample is installed and preliminarily adjusted, loads are applied to the first external extrusion test cylinder (8), the second external extrusion test cylinder (9), the third external extrusion test cylinder (10), and the fourth external extrusion test cylinder (11).

6. The evaluation method for a biaxial loading test device for a wellbore system according to claim 5, characterized in that, In step three, the first external extrusion test cylinder is subjected to the maximum horizontal principal stress P1; the second external extrusion test cylinder is subjected to the minimum horizontal principal stress P2; the third external extrusion test cylinder is subjected to the maximum horizontal principal stress P3; and the fourth external extrusion test cylinder is subjected to the minimum horizontal principal stress P4.

Images