CN-121997501-A - Method for evaluating shearing strength of sleeve

CN121997501ACN 121997501 ACN121997501 ACN 121997501ACN-121997501-A

Abstract

The invention discloses a method for evaluating the shearing strength of a sleeve, which comprises the following steps of calculating and analyzing the change rule of temperature and pressure in the sleeve under a fracturing working condition, obtaining the service boundary condition of the sleeve, carrying out temperature-pressure alternating test on the sleeve for a plurality of times based on the service boundary condition, carrying out shearing performance physical simulation test on the sleeve after the temperature-pressure alternating test, recording test values, drawing a load-displacement curve according to the test values, obtaining a maximum shearing load value, recording the maximum shearing load value as an actual test value, establishing a shearing strength calculation model of the sleeve after the shearing performance physical simulation test, obtaining a model calculation value, calculating the difference value between the actual test value and the model calculation value, and evaluating the accuracy of the actual test value. According to the invention, under the condition of complex fracturing cyclic load, the shearing strength of the casing under different fracturing working conditions can be accurately calculated and analyzed, and technical support is provided for casing strength design under different fracturing working conditions.

Inventors

CAO JING
Yang Shangtou
HAN LIHONG
WANG JIANJUN
YAN YAN
MOU YISHENG
LI FANGPO

Assignees

中国石油天然气集团有限公司
中国石油集团工程材料研究院有限公司

Dates

Publication Date: 20260508
Application Date: 20241107

Claims (10)

1. The method for evaluating the shearing strength of the sleeve is characterized by comprising the following steps of: S1, under the fracturing working condition, calculating and analyzing the change rule of the temperature and the pressure in the sleeve; S2, acquiring a temperature extremum T max and a pressure load extremum P max of the service of the sleeve, and recording as service boundary conditions; s3, carrying out temperature and pressure alternating load tests on the sleeve for multiple times based on the service boundary condition, and marking the temperature and pressure alternating load tests as temperature and pressure alternating tests; s4, after the temperature and pressure alternating test, carrying out a shearing resistance physical simulation test on the sleeve, and recording test values; s5, drawing a load-displacement curve according to the test value, obtaining a maximum shear load value, and recording the maximum shear load value as an actual test value; S6, establishing a shear strength calculation model of the sleeve after the shear performance physical simulation test, and obtaining a model calculation value; And S7, calculating a difference value between the actual test value and the model calculated value, and evaluating the accuracy of the actual test value.
2. The method for evaluating the shearing strength of the sleeve according to claim 1, wherein the specific steps of calculating and analyzing the change rule of the temperature and the pressure in the sleeve are as follows: s101, establishing a rheological characteristic equation of fracturing fluid in the fracturing process; s102, calculating a convective heat transfer coefficient between the fracturing fluid and the casing pipe through a Marshall model; S103, calculating the temperature at the position with the well depth h and the radius r n , and marking the temperature as a shaft temperature field; s104, calculating the pressure gradient of the fracturing fluid in the well pipe column, and recording the pressure gradient as a well bore pressure field; s105, analyzing the distribution rule of a shaft temperature field and a shaft pressure field in the multistage fracturing process.
3. The method of claim 2, wherein the rheological property equation is: τ=Kγ n (1) Wherein τ is shear stress, pa, K is consistency coefficient, pa/s, n is fluidity index, n <1 is pseudoplastic fluid, n >1 is expansion fluid, n <1 is pseudoplastic fluid for fracturing fluid, and gamma is shear rate, 1/s.
4. The method for evaluating the shear strength of a casing according to claim 2, wherein the Marshall model calculation equation is: Wherein h is a convection heat transfer coefficient, W/(m 2 ·℃);k m ) is a heat transfer coefficient, W/(m 2 . DEG C), D is the inner diameter of the sleeve, m is ρ a is the fluid density, kg/m 3 ;D eff is the equivalent diameter of the sleeve, m is the ground pump displacement of the fracturing fluid, m 3 /min, K is a consistency coefficient, pa/s, n is a fluidity index, and C m is the specific heat capacity of the fracturing fluid, J/(kg. DEG C).
5. The method of claim 2, wherein the equation for calculating the wellbore temperature field is: Wherein T h is the well depth of h, the radius of r n is the temperature of the outer edge of the cement sheath at the well depth of h, T hso is the temperature of the outer edge of the cement sheath at the well depth of h, r yo is the outer diameter dimension of the injection string, m, U to is the total heat transfer coefficient of fluid to the cement sheath, W/(m·DEG C), T 1 is the temperature of fluid in the string, U no is the heat transfer coefficient of the cement sheath at the well depth of h, W/(m·DEG C).
6. The method of claim 2, wherein the pressure gradient is calculated as: Wherein ρ m is the fluid density, kg/m 3 , v is the flow rate of the fluid in the wellbore, m/s, θ is the well inclination angle, d is the injection string diameter, m, and f is a dimensionless time function.
7. The method for evaluating the shearing strength of the sleeve according to claim 1, wherein the temperature-pressure alternating test comprises the following specific steps: s301, heating and preserving heat of the sleeve, wherein the heating temperature is a temperature extreme value T max of the service of the sleeve, and the range is from room temperature to 200 ℃; S302, filling fracturing fluid or clear water into the sleeve to fill the cavity in the sleeve, and stopping heating while filling the fracturing fluid or the clear water to naturally cool the sleeve; s303, pressurizing and maintaining the pressure of the sleeve, wherein the pressurizing pressure is a pressure load extreme value P max of the sleeve service, and the range is 0-200Mpa; s304, after the pressure maintaining is completed, releasing pressure of the fracturing fluid or clean water on the inner wall of the sleeve; S305, after pressure release is completed, the sleeve is heated again, wherein the heating time is equal to the interval time of on-site multistage fracturing; S306, repeating the steps, wherein the cycle number N is 1-100.
8. The method for evaluating the shearing strength of the sleeve according to claim 1, wherein the sleeve (3) sequentially comprises a sleeve end constraint influence range area (6), a sleeve shearing load application area (7) and a sleeve end constraint influence range area (6) from left to right in the physical simulation test, the total length of the sleeve (3) is larger than 8D, D is the outer diameter of the sleeve, the length of the sleeve end constraint influence range area (6) is l 1 , and the length of the sleeve shearing load application area (7) is l 2 .
9. The method for evaluating the shearing strength of the sleeve according to claim 8, wherein an upper shearing clamp (8) is arranged on one side in the middle of the sleeve shearing load application area (7), a first lower shearing clamp (9) and a second lower shearing clamp (10) are symmetrically arranged on the opposite sides of the upper shearing clamp (8), the width of the upper shearing clamp (8) is l u , the distance between the first lower shearing clamp (9) and the second lower shearing clamp (10) is l d , and the installation deviation (l d /2-l u /2) between the upper shearing clamp (8) and the first lower shearing clamp (9) and the second lower shearing clamp (10) is not more than 5mm.
10. The method for evaluating the shearing strength of a sleeve according to claim 1, wherein the equation of the shearing strength calculation model is: σ Shear with cutting edge ＝-0.73P′ 2 +91.12P′+0.06n 2 -8.75n+1477.73 (5) Wherein P' is the percentage value of the internal pressure load,% > n is the warm-pressing cycle number.

Description

Method for evaluating shearing strength of sleeve Technical Field The invention belongs to the technical field of drilling, and particularly relates to a method for evaluating the shearing strength of a casing. Background In the complex fracturing process of shale oil and gas wells, the deformation of the sleeve can be possibly caused, and the existing method for detecting the deformation of the sleeve is to find out that the radial deformation of the sleeve is asymmetric through monitoring means such as stamping, a multi-arm caliper and the like, and the central axis of the sleeve is translated along the radial direction. Through preliminary researches of expert scholars at home and abroad, natural cracks/faults are considered to be easily activated during volume fracturing, so that the sleeve is subjected to shearing deformation, the inner diameter of the sleeve is reduced, and a downhole tool cannot be normally put in. At present, stress analysis under the sleeve shearing deformation condition is less, the sleeve failure is judged by mainly adopting a sleeve Mises stress yield criterion in the existing research, and the criterion is not applicable to the sleeve large shearing deformation problem. In order to explore the problem of sleeve shearing deformation caused by natural fracture fault sliding, zeng Yijin and the like, a sleeve-cement ring-stratum combination finite element model is established in volume fracturing sleeve shearing deformation load analysis and strength design (science and engineering, 2021, volume 21 (29 nd)) to study the sleeve mechanical behavior under the displacement load working condition, a sleeve external load design method combining sleeve reduction and stress is provided, and the strength check is suggested by adopting shearing load. The current method for evaluating the shearing resistance of the sleeve is mainly a numerical simulation method, and aims to determine the relation between the external shearing load and the inner diameter deformation of the sleeve, but the method lacks physical test verification and has a certain error. In order to more accurately evaluate the shearing resistance of the sleeve, the invention patent with the publication number of CN108279173A provides a sleeve shearing resistance evaluation method, a relation between the sleeve and wall thickness change under different shearing load working conditions is established, and shearing intervals are changed to determine the characteristic diagrams of the shearing resistance of the sleeves with different specifications. However, in the shale oil and gas well fracturing process, large-displacement fracturing fluid is injected into a shaft, the bottom hole temperature can be drastically reduced, and meanwhile, the high pumping pressure also increases the stress of the casing, so that the casing failure risk is increased. The pressure and temperature changes in the casing during the complex fracturing process make the integrity of the casing a serious challenge. Currently, casing string designs belong to static strength design methods, and fatigue effects in the later stage multistage complex fracturing process are not considered. Therefore, the shearing resistance graphic plate under different temperatures and pressure loads needs to be determined by means of a physical simulation test, a multi-stage fracturing casing strength attenuation rule is established, a strength design method is optimized, and then a set of complex fracturing casing shearing resistance evaluation method is formed, so that technical support is provided for casing selection in field shale oil and gas well reservoir volume transformation, and the method is urgent and important. Disclosure of Invention The invention aims to provide a method for evaluating the shearing strength of a sleeve, which solves the problem that the shearing strength of the sleeve under different fracturing working conditions cannot be evaluated accurately in the prior art. The technical scheme adopted by the invention is that the method for evaluating the shearing strength of the sleeve comprises the following steps: S1, under the fracturing working condition, calculating and analyzing the change rule of the temperature and the pressure in the sleeve; s2, acquiring a temperature extremum T max and a pressure load extremum P max of the service of the sleeve, and recording as service boundary conditions; S3, carrying out temperature and pressure alternating load tests on the sleeve for multiple times based on service boundary conditions, and recording the temperature and pressure alternating load tests as temperature and pressure alternating tests; s4, after the temperature and pressure alternating test, carrying out a shearing resistance physical simulation test on the sleeve, and recording test values; s5, drawing a load-displacement curve according to the test value, obtaining a maximum shear load value, and recording the maximum shear load value as an actu