Method for preventing casing deformation by formation stress resetting

Abstract

The present application discloses a method for preventing casing deformation, comprising the steps of: determining a target position of a formation where the casing is located and which has a fault slip risk, setting a perforation on the casing corresponding to the target position; extending a formation drilling tool provided with a formation rock crushing tool at the front end from the perforation to the target position; and starting the formation rock crushing tool to crush the rock mass at the target position, so that the formation rock at the target position uniformly loads and extrudes the casing. The present application crushes the larger rocks in the formation around the casing into small rock masses, so that the casing outer surface and the formation rock can be in full contact, and the casing changes from non-uniform loading to uniform loading, thereby prolonging the service life of the casing. The method provided by the present application is simple in operation and low in cost, fills the gap in the prior art in this aspect, greatly improves the well completion quality, effectively reduces the occurrence of downhole accidents, and greatly reduces the production cost of oil and gas wells.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and in particular to a method for resetting formation stress to prevent casing deformation. Background Technology

[0002] With the rapid development of the social economy, the demand for petroleum resources is increasing year by year. As the number of oil and gas wells developed increases, drilling and completion engineering faces more challenges. Casing deformation in shale gas wells remains a persistent problem for field personnel and drilling and completion engineers in the petroleum industry. Currently, there are few effective solutions; prevention methods are more commonly used, such as thickening the casing and improving well rail quality. The non-uniform load exerted on the casing by irregular rock blocks around it in the formation is the main cause of casing deformation. The specific load conditions on the casing vary at each location of uneven load. In the narrow downhole casing, there are many locations with non-uniform pressure. Improving well rail quality requires advanced technology, and thickening the casing increases costs significantly. These measures cannot completely solve the problem. Therefore, there is an urgent need to find a method to overcome these difficulties and completely solve the problem of casing deformation in shale gas wells. Summary of the Invention

[0003] To achieve the above-mentioned technical objectives, the present invention provides a formation stress resetting method for preventing casing deformation. By crushing larger rocks in the formation surrounding the casing into smaller rock pieces, the squeezing effect of irregular rocks on the casing is changed, and the outer surface of the casing can fully contact the formation rocks, thereby changing the casing from non-uniform load to uniform load and extending the casing life.

[0004] The present invention specifically discloses the following technical solutions: A formation stress reset method for preventing casing deformation includes the following steps: Identify the target location in the stratum where the casing is located that has a risk of fault slippage, and set a perforation on the casing at the location corresponding to the target location; The formation drilling tool, equipped with a formation rock crushing tool at the front end, is extended from the perforation into the formation to the target location; Activate the rock crushing tool to crush the rock blocks at the target location, so that the rock at the target location exerts a uniform load on the casing.

[0005] In some preferred embodiments, the method for determining the target location of the stratum where the casing is located, which has a risk of fault slip, includes: Using ant-body technology to identify formation fractures and determine their locations; A geomechanical model was established based on formation stress and fault data, and the location of the casing where there is a risk of fault slippage was determined and set as the target location.

[0006] In some preferred embodiments, the number of perforations is 2-12.

[0007] In some preferred embodiments, the step further includes: After crushing is completed, the formation drilling tools are retrieved. Microseismic monitoring technology was used to monitor the formation around the casing and analyze the fault slip.

[0008] In some preferred embodiments, the method for analyzing the location of the stratum where the casing is located, which is at risk of fault slip, includes: The fault slip probability function related to pore pressure was derived using the Mohr-Coulomb criterion. The risk of fault slip is assessed based on the pore pressure disturbance value induced by hydraulic fracturing and the fault slip probability function.

[0009] In some preferred embodiments, the drilling trajectory of the formation drilling tool is determined by an iterative assessment of the fault slip risk at the target points it passes through.

[0010] In some preferred embodiments, the formation drilling tool is also equipped with a stress sensor to collect and transmit the stress data of the broken formation along the way during the recovery process after crushing.

[0011] In some preferred embodiments, the method of crushing the rock at the target location includes either explosive crushing or electrical pulse crushing.

[0012] Beneficial effects This invention breaks down larger rocks in the formation surrounding the casing into smaller rock fragments, altering the squeezing effect of irregular formation rocks on the casing. This allows for full contact between the outer surface of the casing and the formation rocks, transforming the casing from a non-uniformly loaded to a uniformly loaded state, thereby extending the casing's lifespan. Furthermore, the method provided by this invention is simple to operate, low in cost, fills the gaps in existing technologies at this level, significantly improves well completion quality, effectively reduces downhole accidents, and greatly lowers the production costs of oil and gas wells. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a formation stress resetting method for preventing casing deformation in a preferred embodiment of the present invention. Figure 2 This is a schematic diagram of a formation stress reset method for preventing casing deformation in another preferred embodiment of the present invention. Figure 3 This is a schematic diagram illustrating the effect of using ant body technology to identify formation fractures and determine fracture locations in another preferred embodiment of the present invention. Figure 4This is a schematic diagram illustrating the drilling effect of a formation drilling tool with a formation rock crushing tool at its front end, as shown in another preferred embodiment of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings. In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0015] Example 1

[0016] like Figure 1 As shown, this embodiment provides a method for resetting formation stress to prevent casing deformation, specifically including the following steps: S1. Determine the target location of the stratum where the casing is located, which has the risk of fault slippage, and set a perforation on the casing at the location corresponding to the target location. Among them, the existing technologies for determining the target location of the stratum where the casing is located, which has the risk of fault slippage, mainly include: (1) Seismic exploration technology: using the propagation characteristics of seismic waves in the stratum, analyzing the structure, lithology, fractures, stress and other parameters of the stratum, and judging whether the stratum has the risk of slippage. (2) Drilling test technology: using the data from logging, coring, pressure testing and other data during the drilling process, evaluating the mechanical properties, fluid pressure, permeability and other indicators of the stratum, and judging whether the stratum has the risk of slippage. The disadvantage of the above methods is that they are not easy to operate, and the economic and labor costs are high, and the time to obtain the results is long. In some preferred embodiments, a method for determining the target location of the stratum where the casing is located, which has the risk of fault slippage, is provided by using numerical simulation, specifically including: S101. Identify and determine the location of geological fractures using ant colony technology; the ant colony technology refers to a 3D seismic interpretation technique based on an ant algorithm. Its main principle is to simulate the collective foraging behavior of real ant colonies, generating a series of instinctive group actions and information feedback. Utilizing the amplitude and phase differences in seismic data, it moves along possible faults and fractures to characterize and identify them. The identification results are as follows: Figure 3 As shown.

[0017] S102. Based on formation stress and fault data, a geomechanical model is established, and the location of the casing where the strata have fault slip risk is analyzed and set as the target location. It should be understood that there are many methods in this field for assessing fault slip risk. For example, data from seismic data, imaging logging, and multi-arm caliper logging can be used to identify the location, attitude, type, and activity of faults, and fault models can be established for analysis. There are also fault slip risk discrimination methods based on porosity elasticity theory, etc.

[0018] Furthermore, in the design of drilling paths for formation drilling tools, it is necessary to avoid areas with fault slip risk. Moreover, the drilling work will inevitably affect the formation stress on the path. Therefore, it is necessary to assess the fault slip risk on the subsequent path in a timely manner during the drilling process. In some preferred embodiments, it is considered to set up a simulated path fitted by multiple target points between the target location and the perforation, and to determine the optimal drilling trajectory by iteratively evaluating the fault slip risk of the target points passed.

[0019] S2. Extend the formation drilling tool, which has a formation rock crushing tool at the front end, from the perforation into the formation to the target location.

[0020] The rock crushing tool used is a commonly used crushing tool in the field, such as an explosion generator, a high-frequency pulse generator, a vibration sound generator, etc., and the present invention does not make any further limitations.

[0021] The perforation refers to creating channels between the casing, cement sheath, and formation in an oil and gas well, allowing oil and gas to flow out. In this invention, the perforation also includes a drilling tool extending out of the formation, thus avoiding the need for holes previously created in the casing. The principle of perforation is to use a high-energy explosive to form a jet stream, penetrating the casing wall and cement layer at high speed and temperature, and then penetrating to a certain depth in the formation. There are various perforation methods, commonly including cable-driven perforation, tubing-driven perforation, directional perforation, and double-perforation. The effectiveness of perforation depends on factors such as the specifications of the perforating gun, the charge of the perforating cartridge, the perforation density, and the perforation diameter. In some preferred embodiments, the number and location of the perforations are determined by the non-uniform load generated by the formation. The principle is to set them without reducing the original load-bearing limit of the casing; preferably, the number of perforations is 2 to 12.

[0022] The angle between the drilling path direction and the casing of the formation drilling tool is determined based on the actual detection conditions. In some preferred embodiments, the angle between the drilling path direction and the casing ranges from 0° to 90°, and the extension length ranges from 50 meters to 500 meters. Furthermore, the formation drilling tool ensures that the formation rock crushing tool will not activate prematurely or the generator will fail during drilling. The drilling effect is as follows... Figure 4 As shown.

[0023] S3. Activate the formation rock crushing tool to crush the rock blocks at the target location, causing the formation rock at the target location to exert a uniform load on the casing. Large rock blocks in the formation are crushed into smaller rock fragments, resetting the formation stress at the casing location where the non-uniform load is applied, and causing the formation rock to exert a uniform load on the casing. In some preferred embodiments, the method of crushing the rock blocks at the target location includes either explosive crushing or electrical pulse crushing. The specific rock crushing method can be selected and applied by those skilled in the art based on the actual site conditions.

[0024] In some preferred embodiments, such as Figure 2 As shown, it also includes: S4. After crushing is completed, the formation drilling tool is retrieved. During this process, a stress sensor can also be installed on the formation drilling tool to collect and transmit the stress data of the crushed formation along the way during the retrieval process. After collecting the formation stress data, the sensor also needs to transmit the collected data back to the ground for use in subsequent steps.

[0025] S5. Utilize microseismic monitoring technology to monitor the formation condition around the casing and analyze the fault slippage. Specifically, the implementation steps of the microseismic monitoring technology include: Hydraulic fracturing generates microseismic waves that release elastic waves with frequencies ranging from approximately 200 to 2000 Hz. These elastic wave signals can be detected in adjacent wells using appropriate receivers. Through analysis and processing, the specific location, fracture height, fracture length, and azimuth parameters of the microseismic events can be determined, thereby assessing fault slip.

[0026] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for resetting formation stress to prevent casing deformation, characterized in that, Including the following steps: Identify the target location in the stratum where the casing is located that has a risk of fault slippage, and set a perforation on the casing at the location corresponding to the target location; The formation drilling tool, equipped with a formation rock crushing tool at the front end, is extended from the perforation into the formation to the target location; Activate the rock crushing tool to crush the rock blocks at the target location, so that the rock at the target location exerts a uniform load on the casing. It also includes the following steps: After crushing is completed, the formation drilling tools are retrieved. Microseismic monitoring technology is used to monitor the strata around the casing and analyze the fault slip.

2. The formation stress reset method for preventing casing deformation as described in claim 1, characterized in that, The target locations where the casing is located are at risk of fault slip include: Using ant-body technology to identify formation fractures and determine their locations; A geomechanical model was established based on formation stress and fault data, and the location of the casing where the formation has the risk of fault slippage was analyzed and set as the target location.

3. The formation stress resetting method for preventing casing deformation as described in claim 1, characterized in that, The number of perforations is 2-12.

4. The formation stress reset method for preventing casing deformation as described in claim 2, characterized in that, The analysis identified locations in the strata where the casing is located that are at risk of fault slippage, including: The fault slip probability function related to pore pressure was derived using the Mohr-Coulomb criterion. The risk of fault slip is assessed based on the pore pressure disturbance value induced by hydraulic fracturing and the fault slip probability function.

5. The formation stress reset method for preventing casing deformation as described in claim 4, characterized in that: The drilling trajectory of the formation drilling tool is determined by iterative assessment of the fault slip risk at the target points it passes through.

6. The formation stress resetting method for preventing casing deformation as described in claim 1, characterized in that: The formation drilling tool is also equipped with a stress sensor to collect and transmit the stress data of the broken formation along the way during the recovery process after crushing.

7. The formation stress resetting method for preventing casing deformation as described in claim 1, characterized in that, The crushing of rock blocks at the target location includes either explosive crushing or electrical pulse crushing.

Images