Method and system for evaluating the casing deformation resistance of a cement stone for oil and gas well cementing

Abstract

The application provides a cement sheath anti-casing deformation capacity evaluation method and system for oil and gas well cementing, and the evaluation method specifically comprises the following steps: filling the annulus of a mold with cement slurry for cementing after preparation to obtain a sample; applying non-uniform extrusion or shear load to the sample by using a shear test device to simulate the displacement amount of a formation; determining the relative displacement ΔS and the radial size change amount ΔD of the inner cylinder of the mold; determining the deformation amount ΔL of the sample based on the relative displacement ΔS and the radial size change amount ΔD; and judging whether the deformation amount ΔL of the sample is greater than 25 mm, if yes, it is considered that the cement slurry belongs to a large strain cement slurry, and the cement sheath formed has the ability to inhibit casing deformation, otherwise, it is considered that the cement sheath formed by the cement slurry does not have the ability to inhibit casing deformation. The application can quantitatively evaluate the contribution of the cement slurry to reducing the degree of casing deformation, and provides technical support for selecting a cement slurry to reduce casing deformation caused by formation sliding.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil well cementing engineering, in particular to a method for evaluating the casing deformation resistance of cement stone for oil and gas well cementing and a system for evaluating the casing deformation resistance of cement stone for oil and gas well cementing. BACKGROUND

[0002] With the reservoir reconstruction by high-parameter hydraulic fracturing process to increase productivity, casing deformation has also caused the problem of reducing casing drift, which makes the tools such as bridge plug and perforation rush not to be normally lowered, not only reduces the fracturing time efficiency and increases the fracturing cost, but also seriously affects the fracturing effect and natural gas production. Casing deformation has caused a serious threat to wellbore integrity and shale gas productivity, and has directly affected the development of shale gas industry. In view of the problem of casing deformation in shale gas well fracturing, domestic and foreign experts and scholars have done a lot of research. Studies have shown that casing deformation is caused by geological fracture slip in fracturing, and the casing deformation rate is reduced by changing the formation stress state through multi-cluster temporary plugging fracturing process, but the casing deformation rate is still high. Obviously, shale gas casing deformation is related to geological fractures, non-uniform mechanical environment, fracturing scale, etc. Some people have proposed to form large-strain cement stone by modifying the cement slurry to improve the deformation capacity of the cement sheath and achieve the purpose of reducing casing deformation.

[0003] For example, the Chinese document entitled Key Technology Progress and Prospect of Large Strain Pipeline Steel and Steel Pipe, published on October 28, 2020, records an evaluation method for large-strain steel pipe with four indicators of low yield ratio, high uniform plastic deformation elongation rate, high deformation hardening index and high critical buckling strain capacity. The Chinese patent document entitled A High Polymer Polymer Concrete Fatigue Life Evaluation Method Based on Large Strain, published on November 9, 2018, with the publication number CN108776213A, records a high polymer polymer concrete fatigue life evaluation method based on large strain, which adopts a concrete ultimate deformation capacity evaluation, including the following steps: Step one: design the mix proportion of the high polymer polymer mixture; Step two: determine the aggregate gravel and high polymer binder ratio; Step three: take the aggregate gravel and high polymer binder according to the mix proportion, mix and form a test piece, and determine the curing period age by splitting test; Step four: form a wheel rut test plate according to the determined gradation and glue stone ratio; Step five: after the curing time is reached, cut it into a beam type test piece; Step six: perform four-point loading small beam fatigue test on the formed test piece.

[0004] However, the inventors have found through research that there are still the following technical problems in the deformation capacity evaluation of oil well cement stone: the deformation capacity of oil well cement stone can be measured by the stress and strain curve of the compression test to obtain the maximum strain, but this conventional evaluation method is not suitable for the deformation capacity evaluation of the cement sheath in shale gas casing deformation, and cannot directly reflect the casing deformation resistance of the cement stone. SUMMARY

[0005] An object of the present application is to solve at least one of the above-mentioned problems in the prior art. For example, one object of the present application is to provide an anti-casing deformation capacity evaluation method that can intuitively reflect the ability of cement stone to inhibit casing deformation.

[0006] To achieve the above-mentioned object, in one aspect, the present application provides an anti-casing deformation capacity evaluation method for cement stone used in well cementing of oil and gas wells. A mold is used to prepare a cement stone sample for well cementing, and a sample shear test is performed to determine the deformation performance of the cement sheath under non-uniform external extrusion or shear load conditions. The mold includes an inner cylinder, an outer cylinder, and an axial end sealing cover. The inner cylinder and the outer cylinder are both hollow cylindrical. The inner cylinder has a first inner diameter, a first outer diameter, a first axial length, and a first axial cavity. The outer cylinder has a second inner diameter, a second outer diameter, a second axial length, and a second axial cavity. The first inner diameter is smaller than the second inner diameter. Two shear surface openings are provided on the cylinder wall of the outer cylinder and symmetrically distributed along the second axial cavity. The axial end sealing cover is arranged at both ends of the outer cylinder to enable the inner cylinder to be fixedly installed in the second axial cavity. The evaluation method specifically includes the following steps: filling the annulus of the mold with cement slurry for well cementing after preparation, and curing for more than 7 days at the designed temperature to obtain the sample; applying non-uniform external extrusion or shear load to the sample using a shear test device to simulate the displacement of the formation, and monitoring the shear time and displacement relationship curve data in real time; determining the relative displacement ΔS and the radial dimension change amount ΔD of the inner cylinder of the mold, wherein the radial dimension change amount includes the first inner diameter change amount and the first outer diameter change amount; determining the sample deformation amount ΔL based on the relative displacement ΔS and the radial dimension change amount ΔD; and judging the anti-casing deformation capacity of the formed cement stone according to the sample deformation amount ΔL.

[0007] In one exemplary embodiment of the anti-casing deformation capacity evaluation method for cement stone used in well cementing of oil and gas wells of the present application, the relative displacement ΔS can be set to 40 mm to represent the formation slip amount.

[0008] In one exemplary embodiment of the anti-casing deformation capacity evaluation method for cement stone used in well cementing of oil and gas wells of the present application, it can be determined whether the sample deformation amount ΔL is greater than 25 mm. If yes, it is considered that the cement slurry belongs to a large strain cement slurry, and the formed cement stone has the ability to inhibit casing deformation. Otherwise, it is considered that the cement stone formed by the cement slurry does not have the ability to inhibit casing deformation.

[0009] In one exemplary embodiment of the anti-casing deformation capacity evaluation method for cement stone used in well cementing of oil and gas wells of the present application, the calculation formula of the sample deformation amount can be:

[0010] ΔL = ΔS - (D 1内 -D 2内) = ΔS - (D 1外 -D 2外 ),

[0011] wherein, ΔL is the sample deformation, mm; D 1内 is the first inner diameter of the inner cylinder before the test, mm; D 1外 is the first outer diameter of the inner cylinder before the test, mm; D 2内 is the first inner diameter of the inner cylinder after the test, mm; D 2外 is the first outer diameter of the inner cylinder after the test, mm.

[0012] In one exemplary embodiment of the method for evaluating the casing deformation resistance of the cement stone for cementing oil and gas wells, the density of the large-strain mud can be 1.60 g / cm 3 ~ 1.85 g / cm 3 , the permeability of the cement stone is less than 0.05 mD, the elastic modulus is less than 3.5 GPa, and the maximum strain is not less than 21%.

[0013] In one exemplary embodiment of the method for evaluating the casing deformation resistance of the cement stone for cementing oil and gas wells, the loading speed during the shearing test is ≤ 1 mm / min.

[0014] In one exemplary embodiment of the method for evaluating the casing deformation resistance of the cement stone for cementing oil and gas wells, the radial dimension change amount can be the maximum change of the first inner diameter before and after shearing, or the maximum change of the first outer diameter.

[0015] Another aspect of the present application provides a system for evaluating the casing deformation resistance of the cement stone for cementing oil and gas wells, the evaluation system comprising a mold, a shearing test device and a casing deformation resistance evaluation device, wherein the mold is used to prepare a cement stone sample in the casing for cementing, comprising an inner cylinder, an outer cylinder and an axial end sealing cover, the inner cylinder and the outer cylinder are both hollow cylindrical, the inner cylinder has a first inner diameter, a first outer diameter, a first axial length and a first axial cavity, the outer cylinder has a second inner diameter, a second outer diameter, a second axial length and a second axial cavity, the first inner diameter is smaller than the second inner diameter, two shearing surface openings are provided on the cylinder wall of the outer cylinder and symmetrically distributed along the second axial cavity, the axial end sealing cover is arranged at both ends of the outer cylinder to enable the inner cylinder to be fixedly installed in the second axial cavity; the shearing test device is configured to be able to apply a non-uniform external extrusion or shearing load to the sample to simulate the formation displacement amount; the casing deformation resistance evaluation device is connected with the shearing test device and is configured to be able to calculate the sample deformation ΔL and evaluate whether the cement stone has the ability to inhibit the deformation of the casing based on the sample deformation.

[0016] In one exemplary embodiment of the system for evaluating the casing deformation resistance of a cement sheath for cementing an oil and gas well of the present application, the first axial cavity and the second axial cavity can be coaxial.

[0017] In one exemplary embodiment of the system for evaluating the casing deformation resistance of a cement sheath for cementing an oil and gas well of the present application, the first axial length can be less than the second axial length.

[0018] In one exemplary embodiment of the system for evaluating the casing deformation resistance of a cement sheath for cementing an oil and gas well of the present application, the size of the shear surface opening can be 200mm x 200mm to 400mm x 400mm.

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

[0020] (1) The present application uses physical simulation test, uses non-uniform load shear machine to simulate the formation displacement, uses the change amount of the inner diameter or the outer diameter of the casing before and after shearing to indirectly evaluate the deformation performance of the cement sheath, which is suitable for evaluating the deformation ability of the cement sheath in shale gas casing deformation.

[0021] (2) The present application can quantitatively evaluate the contribution of the cement slurry to reducing the casing deformation, and provides technical support for selecting cement slurry to reduce casing deformation caused by formation sliding. BRIEF DESCRIPTION OF DRAWINGS

[0022] The above and other objects and / or characteristics of the present application will become more apparent by describing in detail the present application with reference to the attached drawings, wherein:

[0023] Figure 1 A flowchart of the casing deformation resistance evaluation method of one exemplary embodiment of the casing deformation resistance evaluation method of a cement sheath for cementing an oil and gas well of the present application is shown.

[0024] Figure 2A A schematic diagram of the overall structure of a mold of one exemplary embodiment of the system for evaluating the casing deformation resistance of a cement sheath for cementing an oil and gas well of the present application is shown. Figure 2B A schematic diagram of the cross-sectional structure of a mold of one exemplary embodiment of the system for evaluating the casing deformation resistance of a cement sheath for cementing an oil and gas well of the present application is shown.

[0025] Explanation of reference numerals:

[0026] 1 - shaft end sealing cover, 2 - outer cylinder, 3 - annulus, 4 - inner cylinder. DETAILED DESCRIPTION

[0027] In the following, the casing deformation resistance evaluation method and system of a cement sheath for cementing an oil and gas well of the present application will be described in detail with reference to exemplary embodiments.

[0028] It should be noted that "first", "second", etc. are only for the convenience of description and differentiation, and cannot be understood as indicating or implying relative importance. "Up", "down", "inner", "outer" are only for the convenience of description and constitute relative positional relationship, and are not intended to indicate or imply that the components must have the specific orientation or position. For ordinary skilled in the art, the term "pressure" in this paper is equivalent to pressure.

[0029] The present application adopts physical simulation test, uses non-uniform load shear machine to simulate formation displacement, uses the change amount of the inner diameter of the casing before and after shearing to indirectly evaluate the deformation performance of the cement sheath, and determines the cement slurry type that is beneficial to reduce the deformation degree of the casing.

[0030] In order to achieve the above-mentioned purpose, the present application provides an evaluation method for the casing deformation resistance of cement stone for oil and gas well cementing.

[0031] In an exemplary embodiment of the evaluation method for the casing deformation resistance of cement stone for oil and gas well cementing, as shown in the figure, the evaluation method for the casing deformation resistance of cement stone for oil and gas well cementing specifically includes the following steps: Figure 1

[0032] S1, after the cement slurry for well cementing is prepared, fill the annulus of the mold, and heat and maintain at the designed temperature for more than 7 days to obtain a test sample. The mold includes an inner cylinder, an outer cylinder and an axial end sealing cover. Both the inner cylinder and the outer cylinder are hollow cylindrical. The inner cylinder has a first inner diameter, a first outer diameter, a first axial length and a first axial cavity; the outer cylinder has a second inner diameter, a second outer diameter, a second axial length and a second axial cavity, and the first inner diameter is smaller than the second inner diameter. Two shear surface openings are provided on the cylinder wall of the outer cylinder and symmetrically distributed along the second axial cavity. The axial end sealing cover is arranged at both ends of the outer cylinder, so that the inner cylinder can be fixedly installed in the second axial cavity.

[0033] For example, the inner cylinder is set as follows: steel grade P110, outer diameter 139.7mm, wall thickness 12.7mm, outer cylinder length 1150mm; the outer cylinder is set as follows: steel grade N80, inner diameter 215.9mm, wall thickness greater than 12.7mm, outer cylinder length 1200mm.

[0034] S2, a shear test device is used to apply non-uniform extrusion or shear load to the test sample to simulate the formation displacement, and the shear time and displacement relationship curve data are monitored in real time. During the shear test process, the loading speed is less than or equal to 1mm / min.

[0035] S3, determine the relative displacement AS and the radial size change amount AD of the inner cylinder of the mold, and the radial size change amount includes the first inner diameter change amount and the first outer diameter change amount.

[0036] ​The relative displacement ΔS can be set to 40 mm; the purpose of setting the relative displacement is to represent the stratum slip amount without losing generality, and more than 80% of the actual stratum slip amounts in a mine field are less than 40 mm, so the relative displacement ΔS is set to 40 mm in this embodiment.

[0037] The radial size change amount can be the maximum change of the first inner diameter before and after shearing, or the maximum change of the first outer diameter.

[0038] S4, determining a sample deformation amount ΔL based on the relative displacement ΔS and the radial size change amount ΔD. The calculation formula of the sample deformation amount can be:

[0039] ΔL = ΔS - (D 1内 -D 2内 ) = ΔS - (D 1外 -D 2外 ),

[0040] wherein ΔL is the sample deformation amount, mm; D 1内 is the first inner diameter of the sample before the test, mm; D 1外 is the first outer diameter of the sample before the test, mm; D 2内 is the first inner diameter of the sample after the test, mm; D 2外 is the first outer diameter of the sample after the test, mm.

[0041] S5, judging the casing deformation resistance of the formed cement stone according to the sample deformation amount ΔL.

[0042] For example, when the relative displacement amount ΔS is set to 40 mm, the sample deformation amount of 25 mm can be used as a judgment standard. That is, whether the sample deformation amount ΔL is greater than 25 mm can be judged, if yes, it is considered that the cement slurry belongs to a large strain cement slurry, and the formed cement stone has the ability to inhibit casing deformation, otherwise, it is considered that the cement stone formed by the cement slurry does not have the ability to inhibit casing deformation. The cement slurry with the deformation amount ΔL value greater than 25 mm is a large strain cement slurry, and the greater the ΔL value, the greater the cement annulus deformation capacity and the stronger the ability of the cement stone to inhibit casing deformation.

[0043] The density of the large strain slurry is 1.60 g / cm 3 ~ 1.85 g / cm 3 , the cement stone permeability is less than 0.05 mD, the elastic modulus is less than 3.5 GPa, and the maximum strain is not less than 21%.

[0044] The casing deformation resistance evaluation method uses a mold to prepare a cement stone sample for cementing, and completes a sample shearing test to determine the cement annulus deformation performance under non-uniform extrusion or shearing load conditions.

[0045] Another aspect of the present application provides a system for evaluating the casing deformation resistance of a cement sheath for oil and gas well cementing.

[0046] In one exemplary embodiment of the system for evaluating the casing deformation resistance of a cement sheath for oil and gas well cementing, the system comprises a mold, a shearing test device, and a casing deformation resistance evaluation device.

[0047] The mold is used to prepare a cement sheath sample in a casing for well cementing, and comprises an inner cylinder, an outer cylinder, and an axial end sealing cover. The inner cylinder and the outer cylinder are both hollow cylinders. The inner cylinder has a first inner diameter, a first outer diameter, a first axial length, and a first axial cavity. The outer cylinder has a second inner diameter, a second outer diameter, a second axial length, and a second axial cavity. The first inner diameter is smaller than the second inner diameter. Two shearing surface openings are provided on the cylinder wall of the outer cylinder and symmetrically distributed along the second axial cavity. The axial end sealing cover is arranged at both ends of the outer cylinder to enable the inner cylinder to be fixedly installed in the second axial cavity.

[0048] The shearing test device is configured to apply a non-uniform external extrusion or shearing load to the sample to simulate the amount of formation displacement.

[0049] The casing deformation resistance evaluation device is connected to the shearing test device and is configured to calculate the deformation amount AL of the sample and evaluate whether the cement sheath has the ability to inhibit casing deformation based on the deformation amount of the sample.

[0050] In this embodiment, the first axial cavity and the second axial cavity can be coaxial.

[0051] In this embodiment, the first axial length can be smaller than the second axial length.

[0052] In this embodiment, the size of the shearing surface opening can be 200mm x 200mm to 400mm x 400mm. The shearing surface opening is provided to facilitate shearing of the cement sheath and to ensure that the outer cylinder is not sheared.

[0053] To better understand the above exemplary embodiments of the present application, further descriptions are provided below in conjunction with the accompanying drawings and specific examples.

[0054] The following examples use field sampling of cementing water, cement, and cementing additives to mix cement slurry according to the designed proportions, and the curing condition is room temperature.

[0055] Example 1

[0056] A method for evaluating the casing deformation resistance of a cement sheath for oil and gas well cementing specifically comprises the following steps:

[0057] (1) Measure the inner diameter of the inner cylinder in the direction of the symmetric shearing surface to be 114.12mm and the outer diameter to be 141.08mm using an inner diameter measuring tool.

[0058] (2) Assemble the mold, center the inner cylinder, and tighten the end caps.

[0059] As shown in Figure 2A and Figure 2B , the mold includes an outer cylinder 2 simulating the outer casing, an inner cylinder 4 simulating the inner casing, and end caps 1 at both ends of the inner and outer cylinders, and an annular space 3 filled with the test cement slurry.

[0060] (3) Prepare the cement slurry according to the API specification, mix 5 kg of Jiahua G-grade cement with 2.2 L of tap water uniformly, and measure the density of the cement slurry to be 1.90 g / cm 3 .

[0061] (4) Open the shear plane door of the outer cylinder, fill the annular space of the mold with the cement slurry after preparation, close the shear plane door of the outer cylinder, and heat and maintain at the designed temperature for more than 7 days.

[0062] (5) Open the 200 mm x 200 mm shear plane symmetrically on the upper and lower parts of the outer cylinder of the mold.

[0063] (6) Place the sample on the shear test device, determine the loading position, connect the displacement sensor, start the shear test, the relative displacement ΔS = 40 mm, the loading speed ≤ 1 mm / min, and monitor the shear hydraulic cylinder time and displacement relationship curve data in real time.

[0064] (7) After loading, unload the sample, and measure the minimum inner diameter of the inner cylinder after the test with the inner diameter measuring tool to be 85.23 mm.

[0065] (8) According to the inner diameter of the inner cylinder in step (1) and the inner diameter of the inner cylinder in step (7), determine the deformation amount of the sample, which is calculated as follows:

[0066] Deformation amount ΔL = 40 - (D 1内 -D 2内 ).

[0067] Wherein: ΔL is the deformation amount of the sample, in millimeters (mm);

[0068] D 1内 is the inner diameter of the inner cylinder before the test, in millimeters (mm);

[0069] D 2内 is the inner diameter of the inner cylinder after the test, in millimeters (mm).

[0070] Therefore, the deformation amount ΔL = 40 - (114.12 - 85.23) = 11.11 mm.

[0071] (9) The deformation amount AL value = 11.11 mm < 25 mm, which does not belong to large strain cement slurry, and the cement stone formed thereby does not have the ability to inhibit casing deformation.

[0072] Example 2

[0073] The method for evaluating the casing deformation resistance of a cement stone for cementing an oil and gas well specifically comprises the following steps:

[0074] (1) The inner diameter of the inner cylinder in the direction of the symmetric shear plane is measured by an inner diameter measuring tool to be 114.05 mm, and the outer diameter is 141.25 mm.

[0075] (2) The mold is assembled with the inner cylinder centered, and the two end sealing covers are tightened.

[0076] (3) The cement slurry is prepared according to the API specification, 7 kg of weighted toughness cement and 2.6 L of cementing water are mixed uniformly, and the density of the cement slurry is measured to be 2.20 g / cm 3 .

[0077] (4) The outer cylinder door of the mold is opened, the annulus of the mold is filled with cement slurry after preparation, the outer cylinder door of the shear plane is closed, and the temperature is raised according to the design temperature for more than 7 days of curing.

[0078] (5) The upper and lower symmetric 200 mm x 200 mm shear planes of the outer cylinder of the mold are opened.

[0079] (6) The sample is placed on the shear test device, the loading position is determined, the displacement sensor is connected, the shear test is started, the relative displacement AS = 40 mm, the loading speed is ≤ 1 mm / min, and the real-time monitoring of the shear hydraulic cylinder time and displacement relationship curve data is performed.

[0080] (7) After the loading is completed, the sample is unloaded, and the minimum inner diameter of the inner cylinder after the test is measured by an inner diameter measuring tool to be 89.58 mm.

[0081] (8) The deformation amount of the sample is determined according to the inner diameter of the inner cylinder in step (1) and the inner diameter of the inner cylinder in step (7), and the specific calculation is as follows:

[0082] The deformation amount AL = 40 - (D 1内 -D 2内 ).

[0083] Wherein: AL is the deformation amount of the sample, in millimeters (mm);

[0084] D 1内 is the inner diameter of the inner cylinder before the sample is tested, in millimeters (mm);

[0085] D 2内 is the inner diameter of the inner cylinder after the sample is tested, in millimeters (mm).

[0086] Therefore, the deformation amount AL = 40 - (114.25 - 89.58) = 15.23 mm.

[0087] (9) The deformation amount AL value = 15.23 mm < 25 mm, which does not belong to the large strain cement slurry, and the cement stone formed thereby does not have the ability to inhibit the deformation of the casing.

[0088] Example 3

[0089] A method for evaluating the anti-casing deformation ability of a cement stone for cementing an oil and gas well specifically includes the following steps:

[0090] (1) The inner diameter of the inner cylinder in the direction of the symmetric shear plane is measured by an inner diameter measuring tool to be 114.18 mm, and the outer diameter is 141.10 mm.

[0091] (2) The mold is assembled with the inner cylinder centered and the two end sealing covers tightened.

[0092] (3) The cement slurry is prepared according to the API specification, 5.5 kg of elastic cement and 2.0 L of cementing water are mixed uniformly, and the density of the cement slurry is measured to be 1.70 g / cm 3 .

[0093] (4) The outer cylinder door of the mold is opened, the annulus of the mold is filled with cement slurry after preparation, the outer cylinder door of the shear plane is closed, and the temperature is raised according to the design temperature for more than 7 days of curing.

[0094] (5) The upper and lower symmetric 200 mm x 200 mm shear planes of the outer cylinder of the mold are opened.

[0095] (6) The sample is placed on the shear test device, the loading position is determined, the displacement sensor is connected, the shear test is started, the relative displacement AS = 40 mm, the loading speed is ≤1 mm / min, and the real-time monitoring of the shear hydraulic cylinder time and displacement relationship curve data is performed.

[0096] (7) After the loading is completed, the sample is unloaded, and the minimum outer diameter of the inner cylinder after the test is measured by an outer diameter measuring tool to be 122.46 mm.

[0097] (8) The deformation amount of the sample is determined according to the outer diameter of the inner cylinder in step (1) and the outer diameter of the inner cylinder in step (7), and the specific calculation is as follows:

[0098] The deformation amount AL = 40 - (D 1外 -D 2外 ).

[0099] Wherein: AL is the deformation amount of the sample, in millimeters (mm);

[0100] D 1外 is the outer diameter of the inner cylinder before the sample is tested, in millimeters (mm);

[0101] D 2外 ---Sample in the test after the inner cylinder outer diameter, unit is millimeter (mm).

[0102] Therefore, the deformation amount ΔL = 40 - (141.10 - 122.46) = 21.36 mm.

[0103] (9) deformation amount ΔL value = 21.36 mm < 25 mm, not a large strain cement slurry, which is formed does not have the ability to inhibit casing deformation cement.

[0104] Example 4

[0105] A method for evaluating the casing deformation resistance of a cement slurry for oil and gas well cementing specifically includes the following steps:

[0106] (1) Measure the inner diameter of the inner cylinder in the direction of the symmetric shear plane with an inner diameter measuring tool, which is 114.32 mm, and the outer diameter is 141.06 mm.

[0107] (2) Assemble the mold, center the inner cylinder, and tighten the two end sealing covers.

[0108] (3) Prepare the cement slurry according to the API specification, mix 5.5 kg of large strain cement (strain agent 20%) and 2.0 L of cementing water uniformly, and measure the density of the cement slurry to be 1.78 g / cm 3 .

[0109] (4) Open the outer cylinder door of the mold with one shear plane, fill the annulus of the mold with cement slurry after preparation, close the shear plane outer cylinder door, and heat and cure at the designed temperature for 7 days or more.

[0110] (5) Open the 200 mm x 200 mm shear plane symmetrically above and below the outer cylinder of the mold.

[0111] (6) Place the sample on the shear test device, determine the loading position, connect the displacement sensor, start the shear test, the relative displacement ΔS = 40 mm, the loading speed ≤ 1 mm / min, and monitor the shear hydraulic cylinder time and displacement relationship curve data in real time.

[0112] (7) After loading, unload the sample, and measure the minimum outer diameter of the inner cylinder after the test with an outer diameter measuring tool, which is 128.94 mm.

[0113] (8) Determine the deformation amount of the sample according to the outer diameter of the inner cylinder in step (1) and the outer diameter of the inner cylinder in step (7), and the specific calculation is as follows:

[0114] Deformation amount ΔL = 40 - (D 1外 -D 2外 ).

[0115] Where: ΔL is the deformation amount of the sample, unit is millimeter (mm);

[0116] D 1外 --- The inner cylinder outer diameter of the sample before testing, in millimeters (mm);

[0117] D 2外 --- The inner cylinder outer diameter of the sample after testing, in millimeters (mm).

[0118] Therefore, the deformation amount ΔL = 40 - (141.06 - 128.94) = 27.88 mm.

[0119] (9) The deformation amount ΔL value = 27.88 mm < 25 mm, which belongs to a large strain cement slurry, and the cement stone formed thereby has the ability to inhibit casing deformation.

[0120] Example 5

[0121] A method for evaluating the casing deformation resistance of a cement stone for well cementing specifically includes the following steps:

[0122] (1) The inner diameter of the inner cylinder in the symmetric shear plane direction is measured to be 114.51 mm, and the outer diameter is 141.01 mm using an inner diameter measuring tool.

[0123] (2) The mold is assembled with the inner cylinder centered, and the two end sealing covers are tightened.

[0124] (3) The cement slurry is prepared according to the API specification, 5.5 kg of large strain cement (strain agent 25%) and 2.0 L of well cementing water are mixed uniformly, and the cement slurry density is measured to be 1.75 g / cm 3 .

[0125] (4) The outer cylinder door of the mold is opened, the annulus of the mold is filled with cement slurry after preparation, the outer cylinder door of the shear plane is closed, and the designed temperature is warmed up for more than 7 days.

[0126] (5) The upper and lower symmetric 200 mm x 200 mm shear planes of the outer cylinder of the mold are opened.

[0127] (6) The sample is placed on the shear test device, the loading position is determined, the displacement sensor is connected, the shear test is started, the relative displacement ΔS = 40 mm, the loading speed is ≤1 mm / min, and the real-time monitoring of the shear hydraulic cylinder time and displacement relationship curve data is performed.

[0128] (7) After loading, the sample is unloaded, and the minimum outer diameter of the inner cylinder after testing is measured to be 130.32 mm using an outer diameter measuring tool.

[0129] (8) The deformation amount of the sample is determined according to the inner cylinder outer diameter in step (1) and the inner cylinder outer diameter in step (7), and the specific calculation is as follows:

[0130] Deformation amount ΔL = 40 - (D 1外 -D2外 )。

[0131] wherein: ΔL - deformation of the sample, in millimeters (mm);

[0132] D 1外 - inner cylinder outer diameter before the test of the sample, in millimeters (mm);

[0133] D 2外 - inner cylinder outer diameter after the test of the sample, in millimeters (mm).

[0134] Therefore, the deformation ΔL = 40 - (141.01 - 130.32) = 29.31 mm.

[0135] (9) The deformation ΔL value = 29.31 mm < 25 mm, which belongs to a large strain cement slurry, and the cement stone formed thereby has the ability to inhibit the deformation of the casing.

[0136] The determination results of the strain performance of the above five example cement stones are shown in Table 1. It can be seen that according to the value of the deformation greater than 25 mm, only the cement slurries of Examples 4 and 5 are large strain cement slurries, and the cement stones thereof have stronger ability to inhibit the deformation of the casing.

[0137] Table 1 Evaluation results of the cement stones of the five examples

[0138]

[0139] It should be noted that the large strain cement slurry for inhibiting the deformation of the casing used in Example 4 and Example 5 is composed of the following components in weight percentage: silica powder 25% to 30.0%, strain agent 25.0% to 35.0%, microsilica 0.5% to 4.0%, expansion agent 2.0% to 4.0%, dispersing agent 0.8% to 1.4%, fluid loss reducer 1.4% to 2.1%, retarder 0.1% to 0.8%, defoamer 0.2% to 0.25%, and water 55% to 67%.

[0140] The strain agent can be spherical borosilicate hollow material with a particle size of 10 um to 150 um, D(0.1) < 15 um, D(0.5) > 35 um, the ratio of particle size to wall thickness should be greater than 25, and the mass percentage of SiO2 is greater than 67%.

[0141] The silica powder can be one of the well cementing silica powders with a density of 2.6 g / cm 3 to 2.7 g / cm 3 .

[0142] The expansion agent can be one of the aluminate or magnesium oxide well cement slurry expansion agents.

[0143] The dispersant can be a formaldehyde and acetone condensate CH2OHCH2COCH3.

[0144] The fluid loss additive can be an AMPS-based polymer oil well cement fluid loss additive.

[0145] The retarder can be one of an organic phosphonate or an AMPS-based polymer oil well cement retarder.

[0146] The defoaming agent can be one of an organosiloxane or a polyoxypropylene polyether modified silicon.

[0147] The cement slurry has good engineering performance, 1.60g / cm 3 ~1.85g / cm 3 Adjustable, good rheological property and stability, API fluid loss is less than 50ml, and thickening time is easy to adjust; the strain agent is a spherical borosilicate hollow material, the elastic modulus is low, with the decrease of the elastic modulus of the modified cement slurry, the elasticity increases, the elastic modulus of the pure cement stone is 9.0GPa, and when the amount of the modified material is 20%, the elastic modulus is reduced to 3.0GPa, and the decrease is 67%, and when the amount of the modified material is further increased to 40-50%, the elastic modulus of the cement stone is reduced to 1.1GPa-1.0GPa, which is beneficial to increase the toughness of the cement stone.

[0148] In summary, the beneficial effects of the present application include at least one of the following:

[0149] (1) The present application adopts physical simulation test, uses a non-uniform load shear machine to simulate the formation displacement, and uses the change amount of the inner diameter or the outer diameter of the casing before and after shearing to indirectly evaluate the deformation performance of the cement sheath, which is suitable for evaluating the deformation capacity of the cement sheath in the shale gas casing deformation.

[0150] (2) The present application can quantitatively evaluate the contribution of the cement slurry to reducing the casing deformation degree, and provides technical support for selecting a cement slurry to reduce the casing deformation caused by the formation slip.

[0151] Although the present application has been described above with reference to the example embodiments and the accompanying drawings, it should be clear to those skilled in the art that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for evaluating the resistance to casing deformation of a cement stone for use in cementing oil and gas wells, characterized in that, The cement stone sample for well cementation is prepared by a mold, and a sample shear test is completed to determine the deformation performance of the cement sheath under non-uniform external extrusion or shear load conditions, wherein the mold comprises an inner cylinder, an outer cylinder and an axial end sealing cover, the inner cylinder and the outer cylinder are both hollow cylinders, the inner cylinder has a first inner diameter, a first outer diameter, a first axial length and a first axial cavity, the outer cylinder has a second inner diameter, a second outer diameter, a second axial length and a second axial cavity, the first inner diameter is smaller than the second inner diameter, two shear surface openings are arranged on the cylinder wall of the outer cylinder and symmetrically distributed along the second axial cavity, and the axial end sealing cover is arranged at both ends of the outer cylinder so that the inner cylinder can be fixedly installed in the second axial cavity. The evaluation method specifically comprises the following steps: After the cement slurry for well cementation is prepared, the mold annulus is filled with the cement slurry, the cement slurry is cured at a designed temperature for more than 7 days, and a sample is obtained; A shear test device is used to apply non-uniform external extrusion or shear load to the sample to simulate the formation displacement amount. Determining relative displacement ΔS and the amount of change in the radial dimension of the inner cylinder of the mold ΔD , the amount of change in the radial dimension including a first inner diameter change amount and a first outer diameter change amount based on the relative displacement ΔS and the amount of change in the radial dimension ΔD , determine the amount of deformation of the test sample ΔL ; and According to the deformation amount of the test sample ΔL , the anti-casing deformation capacity of the formed cement stone is judged; The calculation formula of the sample deformation amount ΔD = (D1 - D2) / 2 L is the sample deformation amount, mm; D 1内 is the first inner diameter of the inner cylinder before the test, mm; D 1外 is the first outer diameter of the inner cylinder before the test, mm; D 2内 is the first inner diameter of the inner cylinder after the test, mm; D 2外 is the first outer diameter of the inner cylinder after the test, mm.

2. The method of evaluating the resistance to casing deformation of a set of cement for use in well cementing according to claim 1, said relative displacement ΔS was set to 40 mm to characterize the amount of formation slip.

3. The method of evaluating the resistance to casing deformation of a cement stone for use in cementing oil and gas wells according to claim 2, characterized in that, The step of judging the casing deformation resistance of the formed cement stone according to the sample deformation amount ΔL includes: judging the deformation amount of the test sample ΔL whether it is greater than 25 mm, if so, it is considered that the cement slurry belongs to a large strain cement slurry, and the formed cement stone has the ability to inhibit the deformation of the casing; otherwise, it is considered that the cement stone formed by the cement slurry does not have the ability to inhibit the deformation of the casing.

4. The method of evaluating the resistance to casing deformation of a cement stone for use in cementing oil and gas wells according to claim 3, characterized in that, The density of the large-strain cement slurry is 1.60 g / cm 3 1.85 g / cm 3 The cement stone has a permeability of less than 0.05 mD, an elastic modulus of less than 3.5 GPa, and a maximum strain of not less than 21%.

5. The method of claim 1, wherein, During the shear test, the loading speed is less than or equal to 1 mm / min.

6. The method of evaluating the resistance to casing deformation of a set of cement for use in cementing oil and gas wells according to claim 1, characterized in that, The radial dimension change amount is the maximum change value of the first inner diameter or the maximum change value of the first outer diameter before and after shearing.

7. A system for evaluating the resistance to casing deformation of a cement stone for use in cementing oil and gas wells, characterized in that it comprises: The evaluation system is used to realize the anti-casing deformation capacity evaluation method of the cement stone for well cementation according to any one of claims 1 to 6, and comprises a mold, a shear test device and an anti-casing deformation capacity evaluation device, wherein The mold is used to prepare a cement stone sample in a casing for well cementation, and comprises an inner cylinder, an outer cylinder and an axial end sealing cover, the inner cylinder and the outer cylinder are both hollow cylinders, the inner cylinder has a first inner diameter, a first outer diameter, a first axial length and a first axial cavity, the outer cylinder has a second inner diameter, a second outer diameter, a second axial length and a second axial cavity, the first inner diameter is smaller than the second inner diameter, two shear surface openings are arranged on the cylinder wall of the outer cylinder and symmetrically distributed along the second axial cavity, the axial end sealing cover is arranged at both ends of the outer cylinder so that the inner cylinder can be fixedly installed in the second axial cavity; the shear test device is configured to be able to apply non-uniform external extrusion or shear load to the sample to simulate the formation displacement amount; The anti-casing deformation ability evaluation device is connected to the shearing test device and is configured to be able to calculate the deformation amount of the test sample Δ L and evaluate whether the cement stone has the ability to suppress deformation of the casing based on the deformation amount of the test sample The calculation formula of the sample deformation amount is: Wherein, Δ L is the sample deformation amount, mm; D 1内 is the first inner diameter of the inner cylinder before the test, mm; D 1外 is the first outer diameter of the inner cylinder before the test, mm; D 2内 is the first inner diameter of the inner cylinder after the test, mm; D 2外 is the first outer diameter of the inner cylinder after the test, mm.

8. The system for evaluating the resistance to casing deformation of a cement stone for use in the cementing of oil and gas wells according to claim 7, characterized in that, The first axial cavity and the second axial cavity are coaxial.

9. The system for evaluating the resistance to casing deformation of a cement stone for use in the cementing of oil and gas wells according to claim 8, characterized in that, The first axial length is smaller than the second axial length.

10. The system for evaluating the resistance to casing deformation of a cement stone for use in the cementing of oil and gas wells according to claim 7, characterized in that, The size of the shear surface opening is 200mm×200mm~400mm×400mm.

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