Unconventional oil and gas well casing deformation control method

Abstract

The invention discloses an unconventional oil and gas well casing deformation control method, which comprises the following steps of: evaluating casing deformation risks existing in a gas well single section, and judging which casing deformation risks exist in the gas well single section; the casing deformation risk comprises fault development, natural fracture development, micro-structure development, frequent crossing, poor well cementation quality and well diameter expansion; and executing corresponding regulation and control methods according to different quantities of risk types. According to the method, effective control of casing deformation is realized on the premise that geological modeling and fracturing simulation are not carried out and a high-cost monitoring instrument is not put down.

Description

Technical Field

[0001] The present invention belongs to the technical field of unconventional oil and gas production enhancement and transformation, and in particular relates to a method for controlling deformation of unconventional oil and gas well casing. Background Art

[0002] From a geological perspective, the main geological media that cause casing deformation are the natural fractures and faults that are developed in large numbers in the reservoir. During the multi-cluster fracturing process of horizontal wells, a large amount of fracturing fluid enters the formation, activating the fractures and faults to a critical state. The formation slips and dislocates along the natural fractures, bedding planes and faults, causing shear deformation of the casing and making it impossible for conventional bridge plugs to pass through. This paper further demonstrates the changing rules of the influence of the approach angle and length of natural fractures on the degree of casing deformation. From an engineering perspective, the sudden pressure release in the pipe at the end of large-volume fracturing will put the casing in the most dangerous condition of anti-external squeeze failure; the view that cold fracturing fluid causes annular pressure changes that will increase the risk of casing deformation; non-uniform cracks produced by fracturing can easily cause unbalanced formation rock deformation, asymmetric casing force, formation sliding along weak interfaces and fracture surfaces, and casing deformation caused by extrusion loads or stress deficits around the casing; cementing quality problems such as casing eccentricity or missing cement rings will cause the casing to bear asymmetric loads, increasing the risk of heel casing damage under the influence of the fracturing fluid on the temperature difference from the heel to the toe of the horizontal wellbore.

[0003] In the prior art, Patent ZL201610497331.X proposes a method and device for determining the deformation area of ​​fracturing casing, but it requires regional seismic interpretation, which is a huge workload and extremely costly; Patent ZL202010078842.4 proposes a method for determining the risk area of ​​casing deformation, but it requires full understanding of the formation and fine geological modeling, fracturing simulation and other work. The workflow is long and it is difficult to keep up with the development progress; Patent ZL202011170898.9 proposes a real-time monitoring and evaluation method for downhole casing deformation induced by reservoir fracturing transformation. It requires the insertion of a magnetic positioning instrument to receive downhole abnormal signal judgment, but it requires increased equipment costs, a high downhole damage rate, and cannot achieve batch prediction of hundreds or thousands of wells. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a method for controlling casing deformation of unconventional oil and gas wells. By evaluating the development of faults around the well, the development of natural fractures around the well, the development of micro-structures around the well, the penetration of well trajectory, the quality of well cementing, the expansion of well diameter, and the real-time net pressure curve, a casing deformation prediction before fracturing is established, so as to achieve low-cost and high-efficiency casing deformation prediction and ensure the smooth implementation of subsequent construction.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A method for controlling deformation of casing of an unconventional oil and gas well, the method comprising:

[0007] Evaluate the casing deformation risk in a single section of a gas well, and determine which casing deformation risks exist in the single section of the gas well, wherein the casing deformation risks include fault development, natural fracture development, micro-structure development, frequent penetration, poor cementing quality, and wellbore expansion;

[0008] When there is only one risk of casing deformation:

[0009] Take measures not to perform fracturing at the corresponding locations of developed faults;

[0010] Take measures to reduce the scale of fracturing at the corresponding locations where natural fractures develop;

[0011] Take measures not to perform fracturing construction at the corresponding locations where micro-structures are developed;

[0012] Take measures to reduce the scale of fracturing for the corresponding positions of frequent layer penetration, where the frequent layer penetration is located when the number of times of penetrating different layers within a preset length section exceeds a preset threshold;

[0013] For the corresponding positions of well sections with medium cementing quality, the single-stage fracturing fluid volume and the single-stage construction displacement need to be controlled within the preset thresholds. For the corresponding positions of poor well sections, measures without fracturing construction are taken. The cementing quality evaluation results include excellent, medium and poor. The cementing quality evaluation results are determined based on the cementing quality of the first interface and the cementing quality of the second interface at different cementing depths and well sections.

[0014] Take measures to reduce the scale of fracturing at the corresponding positions of well diameter expansion;

[0015] When there are any two to three casing deformation risks, the single-stage fracturing fluid volume and single-stage construction displacement at the corresponding position are controlled within the preset threshold range;

[0016] When there are any four to six risks of casing deformation, measures shall be taken not to carry out fracturing construction.

[0017] Furthermore, the method further comprises:

[0018] During the fracturing process, monitor the real-time net pressure of the fracturing section, establish a net pressure curve, and adjust the construction measures in real time according to the shape of the curve:

[0019] When the curve shows an overall upward trend, there is no risk of casing deformation in the corresponding section, and the construction work continues according to the original fracturing construction parameters;

[0020] When the curve shows a horizontal trend as a whole, the corresponding section needs to monitor the curve shape of the subsequent fracturing section in real time. If there is a low risk of casing deformation, the single-stage fracturing fluid volume and construction displacement should be reduced according to the preset values;

[0021] When the curve shows a downward trend as a whole, there is a risk of casing deformation in the corresponding section. If two consecutive sections show a downward trend, it is determined that casing deformation will occur in the third sequence section, and the single-stage fracturing fluid volume and construction displacement are controlled within the preset threshold.

[0022] Furthermore, the net pressure monitoring method includes:

[0023] The minimum horizontal principal stress, hydrostatic column pressure, real-time operation pressure, real-time friction along the process and real-time borehole friction resistance corresponding to each fracturing stage are collected. The net pressure calculation formula is net pressure = hydrostatic column pressure + real-time operation pressure - real-time friction along the process - real-time borehole friction resistance - small horizontal principal stress.

[0024] Furthermore, the measures for reducing the construction scale of fracturing at the corresponding positions where natural fractures are developed specifically include:

[0025] The natural fractures around the well are graded according to their length, and the single-stage fracturing fluid volume and single-stage construction displacement of the natural fractures in each grade section are controlled according to preset thresholds.

[0026] Furthermore, the measures for reducing the construction scale of fracturing at the corresponding positions with frequent penetration specifically include:

[0027] The penetrations are graded according to the number of times, and the single-stage fracturing fluid volume and single-stage construction displacement are controlled according to preset thresholds for the penetrations in each grade section.

[0028] Furthermore, the measures to reduce the construction scale of fracturing at the corresponding position of the well diameter expansion specifically include controlling the single-stage fracturing fluid volume and the single-stage construction displacement within a preset threshold value.

[0029] Furthermore, the method for determining the fault development includes:

[0030] Obtain a fault characterization map within a preset range of the gas well. The well periphery is defined as the area within a preset radius from any point on the horizontal wellbore to determine whether there are faults around the well. If faults develop around the well, there is a risk of casing deformation caused by the faults.

[0031] Furthermore, the method for determining the development of natural fractures includes:

[0032] Obtain a natural fracture characterization map within a preset range of the gas well. The wellbore periphery is defined as the area within a preset radius from any point on the horizontal wellbore to determine whether there are natural fractures around the wellbore. If natural fractures are developed in the wellbore periphery, there is a risk of casing deformation caused by natural fractures.

[0033] Furthermore, the method for determining the microstructural development includes:

[0034] The seismic profile along the trajectory of the gas well is obtained. The area around the well is defined as the area within a preset radius from any point on the horizontal wellbore. If the change amplitude of the formation dip angle in each preset length on the profile within the well periphery is greater than the amplitude threshold, it is judged that there is micro-structure development. If there is micro-structure development within the well periphery, there is a risk of casing deformation caused by the micro-structure.

[0035] Furthermore, the method for determining the wellbore expansion includes:

[0036] The wellbore logging curve and results of the horizontal section of the gas well are obtained. The average wellbore of the horizontal section is recorded as x. If the average wellbore value deviation within the preset length range on the horizontal section reaches the preset threshold, it is judged as abnormal wellbore expansion, and there is a risk of casing deformation caused by wellbore expansion.

[0037] The beneficial effects of the present invention are:

[0038] The present invention makes full use of the test results that must be carried out on unconventional oil and gas wells, fully combines the relevant parameters of geology, drilling, and fracturing, maximizes the prediction speed and prediction accuracy, and minimizes the prediction cost. During the process, there is no need to carry out tedious work such as geological modeling and numerical simulation, which greatly reduces the workload of scientific researchers. After completing the risk prediction, different management and control measures are adopted for different numbers of risk types to ensure that the deformation of the gas well casing is effectively controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a multi-stage fracture depiction diagram of a gas well according to an embodiment of the present invention;

[0040] Figure 2 It is a schematic diagram of a gas well completion model and micro-structure and frequent penetration positions according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0042] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0043] In the prior art, Patent ZL201610497331.X proposes a method and device for determining the deformation area of ​​fracturing casing, but it requires regional seismic interpretation, which is a huge workload and extremely costly; Patent ZL202010078842.4 proposes a method for determining the risk area of ​​casing deformation, but it requires full understanding of the formation and fine geological modeling, fracturing simulation and other work. The workflow is long and it is difficult to keep up with the development progress; Patent ZL202011170898.9 proposes a real-time monitoring and evaluation method for downhole casing deformation induced by reservoir fracturing transformation. It requires the insertion of a magnetic positioning instrument to receive downhole abnormal signal judgment, but it requires increased equipment costs, a high downhole damage rate, and cannot achieve batch prediction of hundreds or thousands of wells.

[0044] In order to solve the above technical problems, the following embodiments of a method for controlling deformation of casing of an unconventional oil and gas well are proposed in the present invention.

[0045] Example 1

[0046] The present embodiment provides a method for controlling casing deformation of unconventional oil and gas wells, the purpose of which is to establish a method for predicting casing deformation before fracturing by combining the evaluation of the development of faults around the well, the development of natural fractures around the well, the development of micro-structures around the well, the penetration of well trajectory, the quality of well cementing, the expansion of well diameter, real-time net pressure curve, etc., to achieve low-cost and high-efficiency prediction and control of casing deformation, and ensure the smooth implementation of subsequent construction.

[0047] The method specifically includes:

[0048] 1. Evaluate the development of faults around the well:

[0049] Obtain a fault mapping map near the well to determine whether there are faults around the well. The well perimeter is defined as a radius of 300 meters from any point on the horizontal wellbore.

[0050] If there is no fault around the well, it is determined that the well has no risk of casing deformation caused by faults;

[0051] If faults are developed around the well, it is determined that the well is at risk of casing deformation due to the faults, and measures are taken not to perform fracturing construction at the corresponding positions where the faults are developed.

[0052] 2. Evaluate the development of natural fractures around the well:

[0053] Obtain a natural fracture characterization map near the well to determine whether there are natural fractures around the well. The well perimeter is defined as a range with a radius of 150 meters from any point on the horizontal wellbore.

[0054] If there are no natural fractures around the well, it is determined that the well has no risk of casing deformation due to natural fractures;

[0055] If natural fractures are developed around the well, it is determined that the well has a risk of casing deformation caused by natural fractures. For the corresponding positions where natural fractures are developed, measures are taken to reduce the scale of fracturing. When the distance between natural fractures around the well is between 0 and 50 m, the single-stage fracturing fluid volume needs to be controlled at 1400 m. 3 The displacement of a single section is controlled within 12m 3 / min or less; when the distance between natural fractures around the well is between 50 and 100 m, the single-stage fracturing fluid volume should be controlled at 1600 m 3 The displacement of a single section is controlled within 14m 3 / min or less; when the distance between natural fractures around the well is between 100 and 150 m, the single-stage fracturing fluid volume should be controlled at 1800 m 3 The displacement of a single section is controlled within 16m 3 / min or less.

[0056] 3. Evaluate the development of microstructures around the well:

[0057] Obtain seismic profiles along the well trajectory to determine whether there are microstructures around the well. The well perimeter is defined as the change in formation dip angle of more than 10 degrees per 100 meters on the profile.

[0058] If there is no micro-structure development around the well, it is determined that the well has no risk of casing deformation caused by micro-structure;

[0059] If there are micro-structures developed around the well, it is determined that the well is at risk of casing deformation due to the micro-structures, and measures are taken not to perform fracturing construction at the corresponding positions where the micro-structures are developed.

[0060] 4. Evaluation of well trajectory penetration:

[0061] Obtain part of the well trajectory map of the horizontal section of the well to clarify the situation of the trajectory passing through different strata. Define the well trajectory as frequent penetration if it passes through different strata three or more times within 200 meters, and repeatedly passing through the same strata up and down as multiple times;

[0062] If the horizontal well trajectory is basically located in the same layer, or only penetrates at most two layers within a range of 200 meters, it is determined that the well has no risk of casing deformation due to frequent penetration;

[0063] If there are frequent penetrations in the horizontal well trajectory, it is determined that the well has the risk of casing deformation due to frequent penetrations, and measures to reduce the scale of fracturing are taken at the corresponding locations where frequent penetrations occur. When the number of penetrations is 3 to 5, the single-stage fracturing fluid volume needs to be controlled at 1800m 3 The displacement of a single section is controlled within 16m 3 / min or less. When the number of penetrations is 6 to 8, the single-stage fracturing fluid volume should be controlled at 1600m 3The displacement of a single section is controlled within 14m 3 / min or less. When the number of penetrations is more than 8 times, the single-stage fracturing fluid volume should be controlled at 1400m 3 The displacement of a single section is controlled within 12m 3 / min or less.

[0064] 5. Evaluation of well cementing quality:

[0065] The cementing quality evaluation results of the horizontal section of the well are obtained, and the cementing quality of the first interface and the cementing quality of the second interface at different depths and sections are clarified. The section where both the first interface and the second interface have excellent cementing quality is defined as a high-quality section, the section where either the first interface or the second interface has excellent cementing quality and the other has medium cementing quality is defined as a medium section, and the section where either the first interface or the second interface has poor cementing quality is defined as a poor section;

[0066] If the cementing quality of the horizontal section is excellent, it is determined that there is no risk of casing deformation caused by cementing quality in the well;

[0067] If the cementing quality of the horizontal section does not include a poor well section but includes a medium well section, the single-stage fracturing fluid volume should be controlled at 1400m 3 The displacement of a single section is controlled within 12m 3 / min or less;

[0068] If the cementing quality of the horizontal section contains poor well sections, it is determined that the well has the risk of casing deformation due to poor cementing quality, and measures are taken not to perform fracturing construction for the corresponding positions of the poor well sections.

[0069] 6. Evaluation of well diameter expansion:

[0070] Obtain the borehole caliper logging curve and results of the horizontal section of the well, determine the average borehole caliper value of the horizontal section, record it as x inches, and define that if the average borehole caliper value deviation is 3 inches or more within 10 consecutive meters of the horizontal section, that is, it is not within the interval of x+3 inches, then the borehole caliper expansion is abnormal;

[0071] If the wellbore caliper logging values ​​at all positions in the horizontal section of the well are within x+3 inches, it is determined that the well has no risk of casing deformation due to abnormal wellbore;

[0072] If the wellbore diameter is abnormal in the horizontal section of the well, it is determined that the well has the risk of casing deformation due to the abnormal wellbore diameter. For the corresponding position of the abnormal wellbore diameter, measures are taken to reduce the scale of fracturing. The single-stage fracturing fluid volume needs to be controlled at 1400m 3 The displacement of a single section is controlled within 12m 3 / min or less.

[0073] During the fracturing process, a casing deformation prediction method and control method are established according to the real-time net pressure curve:

[0074] Collect the minimum horizontal principal stress corresponding to each fracturing stage, denoted as σ min ;

[0075] Collect the static liquid column pressure corresponding to each fracturing stage, recorded as P o ;

[0076] Collect the real-time construction pressure of each fracturing stage during fracturing, recorded as P1. The real-time construction pressure should be recorded in real time during the construction process;

[0077] Collect the real-time friction resistance along the fracturing path of each fracturing section, recorded as P2. The real-time friction resistance along the fracturing path should be recorded in real time during the construction process.

[0078] Collect the real-time borehole friction resistance of each fracturing stage during fracturing, recorded as P3. The real-time borehole friction resistance should be recorded in real time during the construction process;

[0079] Calculate the net pressure P in real time according to the situation during construction net , the calculation formula is as follows:

[0080] P net =P o +P1-P2-P3-σ min

[0081] Read and identify the shape of the net pressure curve, and judge the three shapes of the curve: when the curve shows an upward trend as a whole, there is no risk of casing deformation in this section; when the curve shows a horizontal trend as a whole, this section needs to monitor the shape of the subsequent fracturing section curve in real time, and the risk of casing deformation is low; when the curve shows a downward trend as a whole, there is a risk of casing deformation in this section. If this situation exists in two consecutive sections, it is determined that casing deformation will occur in the third sequence section.

[0082] Real-time control measures developed based on the curve shape include:

[0083] When the curve shows an overall upward trend, there is no risk of casing deformation in this section, and the construction work continues according to the original fracturing construction parameters;

[0084] When the curve shows a horizontal trend as a whole, the curve shape of the subsequent fracturing section needs to be monitored in real time. The risk of casing deformation is low. At this time, the single-stage fracturing fluid volume is reduced by 200m 3 , construction displacement is reduced by 1~2m 3 / min;

[0085] When the curve shows a downward trend as a whole, there is a risk of casing deformation in this section. If this situation occurs in two consecutive sections, it is determined that casing deformation will occur in the third sequence section, and the single-stage fracturing fluid volume is controlled at 1000m 3 , the construction displacement shall not exceed 12m 3 / min.

[0086] This embodiment makes full use of the test results that must be carried out on unconventional oil and gas wells, fully combines the relevant parameters of geology, drilling, and fracturing, maximizes the prediction speed and prediction accuracy, and minimizes the prediction cost. During the period, there is no need to carry out tedious work such as geological modeling and numerical simulation, which greatly reduces the workload of scientific researchers. After completing the risk prediction, different control measures are adopted for different numbers of risk types to ensure that the deformation of the gas well casing is effectively controlled.

[0087] Example 2

[0088] Well X is taken as an example to carry out casing deformation prediction. Well X has a total of 20 sections. The characteristics of different fracturing are analyzed to achieve early prediction of casing deformation risks.

[0089] Reference Figure 1 ,like Figure 1 Shown is a multi-stage fracture depiction diagram of a gas well in this embodiment.

[0090] It can be seen from the figure that there are no faults around Well X, so it is determined that there is no risk of casing deformation caused by faults.

[0091] It can also be seen from the figure that there are natural fractures around Well X. There is a risk of casing deformation caused by natural fractures at the 3rd, 8th, 10th and 18th sections. Figure 1 Different fracturing scales are formulated according to the distance between natural fractures.

[0092] Reference Figure 2 ,like Figure 2 Shown is a gas well completion model and a schematic diagram of micro-structures and frequent penetration locations in this embodiment.

[0093] As can be seen from the figure, there are micro-structures around Well X, and there is a risk of casing deformation caused by micro-structures in sections 4 and 18. Figure 2 Different fracturing scales are formulated for locations with medium and micro-amplitude structures.

[0094] It can also be seen from the figure that Well X has frequent penetrations, and there is a risk of casing deformation at the 4th and 18th sections due to frequent penetrations. Figure 2 Different fracturing scales are formulated for locations with frequent layer penetration.

[0095] According to the cementing quality table, the cementing quality of Well X is medium or poor in the 18th section. There is a risk of casing deformation due to cementing quality. Different fracturing scales need to be formulated according to the cementing quality.

[0096] The interpretation results of caliper logging show that well X has abnormal caliper in the 9th, 10th and 20th sections. Different fracturing scales are formulated for the abnormal caliper locations.

[0097] The aforementioned analysis results can all be obtained before implementing the control method provided in the aforementioned embodiment.

[0098] According to the above analysis results, the pre-fracturing parameter design is formulated to achieve comprehensive prediction, see Table 1.

[0099] Table 1 Pre-fracturing design of well X fracturing parameters

[0100]

[0101]

[0102] During the 9th and 10th fracturing stages, the net pressure of Well X decreased, and real-time adjustment measures were required.

[0103] By further increasing the construction fluid volume of Section 11 from 1800m 3 Down to 1600m 3 The construction curve shape was stable and in a continuous upward trend, which effectively controlled the casing deformation at the 11th section.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling casing deformation in unconventional oil and gas wells, characterized in that: The method comprises: Evaluate the casing deformation risk in a single section of a gas well, and determine which casing deformation risks exist in the single section of the gas well, wherein the casing deformation risks include fault development, natural fracture development, micro-structure development, frequent penetration, poor cementing quality, and wellbore expansion; When there is only one risk of casing deformation: Take measures not to perform fracturing at the corresponding locations of developed faults; Take measures to reduce the scale of fracturing at the corresponding locations where natural fractures develop; Take measures not to perform fracturing construction at the corresponding locations where micro-structures are developed; Take measures to reduce the scale of fracturing for the corresponding positions of frequent layer penetration, where the frequent layer penetration is located when the number of times of penetrating different layers within a preset length section exceeds a preset threshold; For the corresponding positions of well sections with medium cementing quality, the single-stage fracturing fluid volume and the single-stage construction displacement need to be controlled within the preset thresholds. For the corresponding positions of poor well sections, measures without fracturing construction are taken. The cementing quality evaluation results include excellent, medium and poor. The cementing quality evaluation results are determined based on the cementing quality of the first interface and the cementing quality of the second interface at different cementing depths and well sections. Take measures to reduce the scale of fracturing at the corresponding positions of well diameter expansion; When there are any two to three casing deformation risks, the single-stage fracturing fluid volume and single-stage construction displacement at the corresponding position are controlled within the preset threshold range; When there are any four to six risks of casing deformation, measures shall be taken not to carry out fracturing construction.

2. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 1, characterized in that: The method further comprises: During the fracturing process, monitor the real-time net pressure of the fracturing section, establish a net pressure curve, and adjust the construction measures in real time according to the shape of the curve: When the curve shows an overall upward trend, there is no risk of casing deformation in the corresponding section, and the construction work continues according to the original fracturing construction parameters; When the curve shows a horizontal trend as a whole, the corresponding section needs to monitor the curve shape of the subsequent fracturing section in real time. If there is a low risk of casing deformation, the single-stage fracturing fluid volume and construction displacement should be reduced according to the preset values; When the curve shows a downward trend as a whole, there is a risk of casing deformation in the corresponding section. If two consecutive sections show a downward trend, it is determined that casing deformation will occur in the third sequence section, and the single-stage fracturing fluid volume and construction displacement are controlled within the preset threshold.

3. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 2, characterized in that: The net pressure monitoring method comprises: The minimum horizontal principal stress, hydrostatic column pressure, real-time operation pressure, real-time friction along the process and real-time borehole friction resistance corresponding to each fracturing stage are collected. The net pressure calculation formula is net pressure = hydrostatic column pressure + real-time operation pressure - real-time friction along the process - real-time borehole friction resistance - small horizontal principal stress.

4. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 1, characterized in that: The measures for reducing the scale of fracturing at the corresponding locations where natural fractures are developed specifically include: The natural fractures around the well are graded according to their length, and the single-stage fracturing fluid volume and single-stage construction displacement are controlled according to preset thresholds for the natural fractures in each grade section.

5. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 1, characterized in that: The measures to reduce the scale of fracturing at the corresponding positions with frequent penetration specifically include: The penetrations are graded according to the number of times, and the single-stage fracturing fluid volume and single-stage construction displacement are controlled according to preset thresholds for the penetrations in each grade section.

6. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 1, characterized in that: The measures to reduce the scale of fracturing at the corresponding positions of the wellbore expansion specifically include controlling the single-stage fracturing fluid volume and the single-stage construction displacement within preset thresholds.

7. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 1, characterized in that: The determination method of the fault development includes: Obtain a fault characterization map within a preset range of the gas well. The well periphery is defined as the area within a preset radius from any point on the horizontal wellbore to determine whether there are faults around the well. If faults develop around the well, there is a risk of casing deformation caused by the faults.

8. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 1, characterized in that: The determination method of the development of natural fractures includes: Obtain a natural fracture characterization map within a preset range of the gas well. The wellbore periphery is defined as the area within a preset radius from any point on the horizontal wellbore to determine whether there are natural fractures around the wellbore. If natural fractures are developed in the wellbore periphery, there is a risk of casing deformation caused by natural fractures.

9. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 1, characterized in that: The determination method of the micro-structural development includes: The seismic profile along the trajectory of the gas well is obtained. The area around the well is defined as the area within a preset radius from any point on the horizontal wellbore. If the change amplitude of the formation dip angle in each preset length on the profile within the well periphery is greater than the amplitude threshold, it is judged that there is micro-structure development. If there is micro-structure development within the well periphery, there is a risk of casing deformation caused by the micro-structure.

10. The method for controlling deformation of casing of unconventional oil and gas wells according to claim 1, characterized in that: The determination method of the well diameter expansion includes: The wellbore logging curve and results of the horizontal section of the gas well are obtained. The average wellbore of the horizontal section is recorded as x. If the average wellbore value deviation within the preset length range on the horizontal section reaches the preset threshold, it is judged as abnormal wellbore expansion, and there is a risk of casing deformation caused by wellbore expansion.

Images