Well wall stabilizing method based on formation water outflow prevention

Abstract

The invention discloses a well wall stabilizing method based on formation water outflow prevention, and relates to the technical field of petroleum drilling, and the well wall stabilizing method comprises the following steps: 1, connecting a spraying tool on a drilling tool, drilling and expanding the inner diameter of a well wall of a to-be-cured area; 2, putting in a throw-in coating loading cylinder; 3, controlling the throw-in type paint loading cylinder to be connected with the spraying tool; 4, controlling the resin coating to enter the spraying tool and spray the resin coating to the well wall; 5, the drilling tool is static to solidify the curing resin; sixthly, the fourth step is repeated, and the catalytic coating is continuously sprayed to the resin coating; seventhly, the drilling tool is lifted upwards, the resin coating and the catalytic coating enter the microcracks, and a water outlet prevention isolation layer is formed; and 8, downward drilling continues, the step 1-the step 7 are repeated, and stabilization of the well wall of the rest to-be-cured area is completed. According to the method, a tight isolation layer can be formed on the well wall by using the sprayed cured resin in the drilling process, so that the effect of effectively preventing water from flowing out of the well wall is achieved, and an effective technical support is provided for on-site rapid drilling construction.

Description

Technical Field

[0001] This invention relates to the field of oil drilling technology, and more specifically to a wellbore stabilization method based on preventing formation water inflow. Background Technology

[0002] Underbalanced pressure drilling technology is a drilling method that applies drilling fluid pressure at the bottom of the well to be less than the formation pore pressure, effectively controlling the flow of formation fluid into the wellbore and managing it. Underbalanced drilling is suitable for low-pressure, low-permeability reservoirs, fractured oil and gas reservoirs, depleted reservoirs, marginal oil and gas reservoirs, or areas that have experienced drilling fluid loss and differential pressure stuck pipe, where drilling is required to penetrate complex formations.

[0003] Gas drilling is an underbalanced drilling technology that uses pure gas as the circulating medium. It offers advantages such as timely detection and protection of oil and gas reservoirs, increased mechanical drilling rate, prevention of leakage, and reduction of differential pressure sticking risk. Especially when drilling through gas-bearing formations, it can prevent downhole explosions and ensure drilling safety. However, extensive operational experience has shown that in gas drilling environments, real-time wellbore reinforcement is necessary to form a tight surface layer, thereby eliminating the risks of leakage, collapse, and water inrush, and ensuring wellbore stability.

[0004] To effectively prevent formation water inflow, the following technical measures are employed in existing technologies: I. The literature "Overview and Prospect of the Development of Controlled Pressure Drilling Technology in Water Injection Areas" addresses the abnormally high reservoir pressure and high well control risk caused by long-term continuous water injection in the Changqing area. It develops automatic controlled pressure drilling technology suitable for this block, which uses a series of supporting equipment such as small-diameter formation water production control. After its application, it has greatly improved the formation water production control capability of this block.

[0005] II. The literature "Research and Application of Air Drilling and Foam Drilling in the Upper Formations of the Keping Fault Zone" addresses the drilling difficulties in the Keping Fault Zone of the Tarim Basin, such as poor drillability and high risk of well leakage. It proposes for the first time the application of underbalanced drilling technology using air drilling and foam drilling in the Devonian and Silurian strata of this block. Through various analyses of the applicability and risks of underbalanced drilling technology in the upper well sections of the new block, a reasonable construction scheme was found. During the actual drilling of the Ketan-1 well, no well leakage occurred during the underbalanced drilling in the upper section, and the mechanical drilling rate reached 3.07 m / h, with an average mechanical drilling rate of 2.38 m / h for the entire well, demonstrating excellent leakage prevention effect. Simultaneously, the average mechanical drilling rate for the entire well set a new record for mechanical drilling rate in the Keping Fault Zone of the Tarim Basin and the Cambrian subsalt formations of the Bachu Uplift.

[0006] III. The literature "Intelligent Identification Method for Safety Risks in Gas Drilling" analyzes and studies formation water production in gas drilling, identifying four main components: water produced by gas atomization, water absorbed from the wellbore, water absorbed from cuttings, and free water. To calculate the volume of each component, four different experiments were conducted to analyze these four types of water. Furthermore, experimental methods were used to quantitatively analyze the formation water production in gas drilling.

[0007] IV. The study in the literature "Application of Gas Continuous Circulation Cobalt Well Technology in Gravel Layer of Bozi Block" found that stuck drill pipe often occurs after formation water emerges. Formation water emerges is the biggest obstacle to implementing dry gas drilling. Water emerges itself is not the key issue. Current technology can completely solve the problem of how much water emerges. The key is timely monitoring and rapid conversion to prevent stuck drill pipe and wellbore instability caused by formation water emerges.

[0008] V. The literature "Research on Construction Technology of Large-Diameter Mining Wells Using Air Impact Drilling" addresses the problems encountered during the construction of large-diameter mining wells in coalbed methane, such as wellbore instability, incomplete backflow of cuttings, and backflow of rock powder from the bottom of the well clogging the drill bit when connecting drill pipes. It developed and formed a coordinated process centered on improving drill string assembly and changing the way drill pipes are connected. Combined with field practice, it successfully solved the problems of drill bit clogging and cuttings backflow when encountering highly water-rich formations, achieving good results in speeding up drilling, significantly shortening the drilling cycle, and significantly improving economic benefits.

[0009] However, the aforementioned technical measures to prevent formation water inflow mainly focus on improvements such as automated pressure-controlled drilling, timely casing installation, gas atomization of water volume, and modifications to drill string assembly and drill pipe connection methods. They do not specifically disclose the technical means employed to achieve water inflow from the wellbore. Therefore, it is necessary to provide a specific wellbore stabilization method to prevent formation water inflow. Summary of the Invention

[0010] To overcome the aforementioned problems in the existing technology, this invention provides a wellbore stabilization method based on preventing formation water outflow. This method can form a tight isolation layer on the wellbore using sprayed curing resin during the drilling process, thereby effectively preventing water outflow from the wellbore. Not only is the operation simple and easy to implement, but it also ensures a high overall drilling speed, providing effective technical support for rapid drilling operations on site.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A wellbore stabilization method for preventing formation water inrush, which is achieved by spraying a resin coating onto the wellbore during gas drilling, includes the following steps: Step 1: Connect the spraying tool to the drill string. The spraying tool includes a housing with a retractable nozzle inside. The side wall of the housing has a side hole that can be automatically opened and closed corresponding to the nozzle. During gas drilling, when the drill string completes drilling of the area to be cured, the inner diameter of the well wall of the area to be cured is enlarged by short-trip reaming. After the reaming is completed, the spraying tool is located at the spraying starting point above the area to be cured. Step 2: Stop injecting high-pressure gas, remove the square drill pipe at the wellhead, and use the drill pipe to lower the submersible coating loading cylinder. The submersible coating loading cylinder contains resin coating and catalytic coating. The outer diameter of the submersible coating loading cylinder and the inner diameter of the drill pipe form a dynamic seal. Step 3: Control the immersion paint loading cylinder to descend along the inner hole of the drill rod until it reaches above the spraying tool and connects with the spraying tool; Step 4: Control the side hole on the spraying tool housing to open, control the nozzle to extend out of the side hole, increase the pressure above the submersible paint loading cylinder, so that the resin paint in the submersible paint loading cylinder enters the spraying tool and is sprayed onto the well wall through the spraying tool; at the same time, control the spraying device to descend and rotate through the drill string, and when the spraying device reaches the spraying endpoint below the area to be cured, the resin paint is continuously sprayed onto the well wall; Step 5: Control the nozzle and side hole to reset, and stop the drill bit to allow the curing resin to solidify; Step 6: Control the spraying tool to return to the spraying starting point above the area to be cured, and repeat Step 4 to continuously spray the catalytic coating in the immersion coating carrier onto the resin coating. Step 7: Raise the drill string. Under the squeezing action of the drill bit, the resin coating and catalytic coating enter the micro-cracks in the well wall and form a dense water-proof isolation layer, thus stabilizing the well wall in the area to be cured. Step 8: Continue drilling downwards and repeat steps 1-7 to stabilize the remaining areas of the well wall that need to be solidified.

[0012] In step one, the drilling tools include an eccentric tricone drill bit, a MWD, a drill collar, and a drill rod that are fixedly connected in sequence. The spraying tool is fixed between the MWD and the drill collar through a housing.

[0013] In step two, the immersion coating loading cylinder includes a cylinder body for sealing connection with the housing of the spraying tool. The upper part of the cylinder body is provided with an annular piston that communicates with the outside, and the lower part of the cylinder body is provided with an end rupture disc. The catalytic coating and resin coating are arranged in layers between the annular piston and the end rupture disc.

[0014] In step three, the mud pump is turned on to create air circulation inside the drill pipe, and the downward movement of the immersion coating loading cylinder is controlled by the pressure of the gas circulation.

[0015] In step four, after the nozzle extends out of the side hole, the distance between the nozzle and the well wall is 5-6 mm.

[0016] In step four, the spraying device descends at a speed of 3-4 m / min while rotating at a speed of 50-55 rpm.

[0017] In step five, the drill string remains stationary for 5-10 minutes.

[0018] In step seven, the thickness of the waterproof barrier layer is 2-3 mm.

[0019] The length of the area to be cured is 200-300mm, and the spacing between each area to be cured is 200-300mm.

[0020] The automatic opening and closing of the side holes and the automatic extension and retraction of the nozzle in the spraying tool are controlled by the ground system.

[0021] The advantages of using this invention are: 1. This invention enables the sequential spraying of resin coating and catalytic coating onto the wellbore during drilling, forming a tight, water-proof isolation layer that effectively prevents water from seeping out of the wellbore. Furthermore, the entire process can be achieved by controlling the raising and lowering of the drill string and adjusting different air pressures. This not only simplifies the operation and facilitates implementation but also ensures a high overall drilling speed, providing effective technical support for rapid on-site drilling operations.

[0022] 2. This invention employs a complete spraying device consisting of a spraying tool and a movable, immersion-type paint loading cylinder. Using this specific spraying device, the spraying tool is pre-fixed to the drill string and descends with it. The immersion-type paint loading cylinder contains resin paint and is lowered only after drilling has completed the area to be cured. In practical applications, this reduces the overall weight of the drill string, offering advantages such as easier drilling, shorter downhole processing time, reduced material consumption, and lower drilling and completion costs.

[0023] 3. The entire curing process of this invention involves the up-and-down movement of the drill bit. During this movement, the resin coating is squeezed into the micro-cracks by the drill bit and forms a dense water-proof isolation layer, thereby achieving a better wellbore stability effect. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure for gas drilling using drilling tools in step one; Figure 2 This is a schematic diagram of the structure of the immersion-type paint loading cylinder in step two; Figure 3 This is a schematic diagram of the structure where the side hole of the spraying tool is opened in step four; Figure 4 This is a schematic diagram of the downward rotation of the spraying tool in step four; Figure 5This is a schematic diagram of the spraying tool resetting upwards in step six; Figure 6 This is a schematic diagram of the structure after the well wall of the area to be solidified is stabilized in step seven.

[0025] The markings in the diagram are: 1. Drilling tool, 2. Spraying tool, 3. Immersion paint loading cylinder, 4. Waterproof isolation layer. Detailed Implementation

[0026] Example 1 This invention provides a wellbore stabilization method for preventing formation water inflow. This method is achieved by spraying a resin coating onto the wellbore during gas drilling, and includes the following steps: Step 1: As Figure 1 As shown, drill string 1 is prepared, comprising a 215.9-230mm eccentric tricone drill bit, a MWD (measuring wire cutter), a 165mm drill collar, and a 127mm drill pipe, all sequentially and fixedly connected. A spraying tool 2 is connected to drill string 1. The spraying tool 2 includes a housing, which is fixed between the MWD and the drill collar. The housing contains a retractable nozzle, and the sidewall of the housing has an automatically opening and closing side hole corresponding to the nozzle. During gas drilling, when drill string 1 completes drilling into the area to be cured, a short reaming hole is used to enlarge the wellbore diameter of the area to be cured. After the reaming is completed, the spraying tool 2 is positioned at the spraying starting point above the area to be cured.

[0027] It should be noted that the area to be cured has a certain length. When the drill bit 1 completes the drilling of the area to be cured, the drill bit 1 is just located at the spraying endpoint at the bottom of the area to be cured. At this time, the inner diameter of the well wall of the area to be cured can be enlarged by short-tripping and reaming. After the reaming is completed, the spraying tool 2 is just located at the spraying starting point above the area to be cured. In this way, top-down spraying can be carried out during curing, which is beneficial to improving efficiency.

[0028] Step Two: As Figure 2 As shown, stop injecting high-pressure gas, remove the square drill pipe at the wellhead, and use the drill pipe to lower the submersible paint loading cylinder 3. The submersible paint loading cylinder 3 contains resin paint and catalytic paint. The outer diameter of the submersible paint loading cylinder 3 can form a dynamic seal with the inner diameter of the drill pipe, so as to ensure that the submersible paint loading cylinder 3 can quickly and smoothly reach the spraying tool 2 below.

[0029] Preferably, the immersion-type paint loading cylinder 3 includes a cylinder body for sealing connection with the housing of the spraying tool 2. The upper part of the cylinder body is provided with an annular piston communicating with the outside. The catalytic paint and resin paint in each immersion-type paint loading cylinder 3 are sufficient to satisfy the spraying and curing of at least one area to be cured. The lower part of the cylinder body is provided with an end rupture disc, and the catalytic paint and resin paint are arranged in layers between the annular piston and the end rupture disc.

[0030] Step 3: By turning on the mud pump, air circulation is formed in the drill pipe, and the pressure of the gas circulation is used to control the downward movement of the submersible paint loading cylinder 3. When the submersible paint loading cylinder 3 reaches above the spraying tool 2, the submersible paint loading cylinder 3 connects with the spraying tool 2. The specific connection method can be to use existing structures such as chucks.

[0031] When the immersion paint loading cylinder 3 is connected to the spraying tool 2, the upper part of the spraying tool 2 can rupture the end rupture disc through a pre-set lifting structure, thereby allowing the paint in the immersion paint loading cylinder 3 to communicate with the nozzle. In addition, when the pressure on the annular piston is greater than the pressure on the end rupture disc, the end rupture disc will rupture, and the annular piston will push the catalytic paint and resin paint to be sprayed out of the nozzle.

[0032] Step Four: As Figure 3 , 4 As shown, the side hole on the housing of the spraying tool 2 is opened, and the nozzle extends out of the side hole. After the nozzle extends out of the side hole, the distance between the nozzle and the well wall is 5mm. Then, the pressure above the immersion paint loading cylinder 3 is increased. This pressure acts on the annular piston, which moves downward and squeezes the resin paint, thereby allowing the resin paint in the immersion paint loading cylinder 3 to enter the spraying tool 2 and be sprayed onto the well wall through the spraying tool 2. At the same time, the spraying device is controlled to descend and rotate by the drill string 1. The spraying device descends at a speed of 3m / min and rotates at a speed of 50 rpm. When the spraying device reaches the spraying endpoint below the area to be cured, the resin paint is continuously sprayed onto the well wall.

[0033] Step 5: Control the nozzle and side hole to reset, and stop drill bit 1 to allow the curing resin to solidify. The time for drill bit 1 to remain stationary is 5 minutes.

[0034] Step Six: As Figure 5 As shown, control the spraying tool 2 to reset to the spraying starting point above the area to be cured, and repeat step four to continuously spray the catalytic coating in the immersion coating loading cylinder 3 onto the resin coating.

[0035] Step 7: Raise drill string 1. Under the squeezing action of the drill bit in drill string 1, the resin coating and catalytic coating enter the micro-fractures in the well wall and form a structure like... Figure 6 The dense anti-outflow isolation layer 4 shown has a thickness of 2mm, which completes the stabilization of the well wall in the area to be solidified.

[0036] Step 8: Continue drilling downwards and repeat steps 1-7 to stabilize the remaining areas of the well wall that need to be solidified.

[0037] It should be noted that the length of each area to be cured in this scheme can be 200mm, and the spacing between each area to be cured can be 200mm, which can be determined according to the actual situation downhole. In addition, the docking of the submersible paint loading cylinder 3 and the spraying tool 2, the automatic opening and closing of the side holes in the spraying tool 2, and the automatic extension and retraction of the nozzle are all controlled by the surface system.

[0038] In summary, this solution can sequentially spray resin coating and catalytic coating onto the well wall during drilling to form a tight water-proof isolation layer 4, thereby effectively preventing water from emerging from the well wall.

[0039] Example 2 This invention provides a wellbore stabilization method for preventing formation water inflow. This method is achieved by spraying a resin coating onto the wellbore during gas drilling, and includes the following steps: Step 1: As Figure 1 As shown, drill string 1 is prepared, comprising a 215.9-230mm eccentric tricone drill bit, a MWD (measuring wire cutter), a 165mm drill collar, and a 127mm drill pipe, all sequentially and fixedly connected. A spraying tool 2 is connected to drill string 1. The spraying tool 2 includes a housing, which is fixed between the MWD and the drill collar. The housing contains a retractable nozzle, and the sidewall of the housing has an automatically opening and closing side hole corresponding to the nozzle. During gas drilling, when drill string 1 completes drilling into the area to be cured, a short reaming hole is used to enlarge the wellbore diameter of the area to be cured. After the reaming is completed, the spraying tool 2 is positioned at the spraying starting point above the area to be cured.

[0040] It should be noted that the area to be cured has a certain length. When the drill bit 1 completes the drilling of the area to be cured, the drill bit 1 is just located at the spraying endpoint at the bottom of the area to be cured. At this time, the inner diameter of the well wall of the area to be cured can be enlarged by short-tripping and reaming. After the reaming is completed, the spraying tool 2 is just located at the spraying starting point above the area to be cured. In this way, top-down spraying can be carried out during curing, which is beneficial to improving efficiency.

[0041] Step Two: As Figure 2 As shown, stop injecting high-pressure gas, remove the square drill pipe at the wellhead, and use the drill pipe to lower the submersible paint loading cylinder 3. The submersible paint loading cylinder 3 contains resin paint and catalytic paint. The outer diameter of the submersible paint loading cylinder 3 can form a dynamic seal with the inner diameter of the drill pipe, so as to ensure that the submersible paint loading cylinder 3 can quickly and smoothly reach the spraying tool 2 below.

[0042] Preferably, the immersion-type paint loading cylinder 3 includes a cylinder body for sealing connection with the housing of the spraying tool 2. The upper part of the cylinder body is provided with an annular piston communicating with the outside. The catalytic paint and resin paint in each immersion-type paint loading cylinder 3 are sufficient to satisfy the spraying and curing of at least one area to be cured. The lower part of the cylinder body is provided with an end rupture disc, and the catalytic paint and resin paint are arranged in layers between the annular piston and the end rupture disc.

[0043] Step 3: By turning on the mud pump, air circulation is formed in the drill pipe, and the pressure of the gas circulation is used to control the downward movement of the submersible paint loading cylinder 3. When the submersible paint loading cylinder 3 reaches above the spraying tool 2, the submersible paint loading cylinder 3 connects with the spraying tool 2. The specific connection method can be to use existing structures such as chucks.

[0044] When the immersion paint loading cylinder 3 is connected to the spraying tool 2, the upper part of the spraying tool 2 can rupture the end rupture disc through a pre-set lifting structure, thereby allowing the paint in the immersion paint loading cylinder 3 to communicate with the nozzle. In addition, when the pressure on the annular piston is greater than the pressure on the end rupture disc, the end rupture disc will rupture, and the annular piston will push the catalytic paint and resin paint to be sprayed out of the nozzle.

[0045] Step Four: As Figure 3 , 4 As shown, the side hole on the housing of the spraying tool 2 is opened, and the nozzle extends out of the side hole. After the nozzle extends out of the side hole, the distance between the nozzle and the well wall is 5.5 mm. Then, the pressure above the immersion paint loading cylinder 3 is increased. This pressure acts on the annular piston, which moves downward and squeezes the resin paint, thereby allowing the resin paint in the immersion paint loading cylinder 3 to enter the spraying tool 2 and be sprayed onto the well wall. At the same time, the spraying device is controlled to descend and rotate by the drill string 1. The spraying device descends at a speed of 3.5 m / min and rotates at a speed of 53 rpm. When the spraying device reaches the spraying endpoint below the area to be cured, the resin paint is continuously sprayed onto the well wall.

[0046] Step 5: Control the nozzle and side hole to reset, and stop drill bit 1 to allow the curing resin to solidify. The time for drill bit 1 to remain stationary is 8 minutes.

[0047] Step Six: As Figure 5 As shown, control the spraying tool 2 to reset to the spraying starting point above the area to be cured, and repeat step four to continuously spray the catalytic coating in the immersion coating loading cylinder 3 onto the resin coating.

[0048] Step 7: Raise drill string 1. Under the squeezing action of the drill bit in drill string 1, the resin coating and catalytic coating enter the micro-fractures in the well wall and form a structure like... Figure 6The dense anti-water leakage isolation layer 4 shown has a thickness of 2.5 mm, which completes the stabilization of the well wall in the area to be solidified.

[0049] Step 8: Continue drilling downwards and repeat steps 1-7 to stabilize the remaining areas of the well wall that need to be solidified.

[0050] It should be noted that the length of each area to be cured in this scheme can be 240mm, and the spacing between each area to be cured can be 260mm, which can be determined according to the actual situation downhole. In addition, the docking of the submersible paint loading cylinder 3 and the spraying tool 2, the automatic opening and closing of the side holes in the spraying tool 2, and the automatic extension and retraction of the nozzle are all controlled by the surface system.

[0051] In summary, this solution can sequentially spray resin coating and catalytic coating onto the well wall during drilling to form a tight water-proof isolation layer 4, thereby effectively preventing water from emerging from the well wall.

[0052] Example 3 This invention provides a wellbore stabilization method for preventing formation water inflow. This method is achieved by spraying a resin coating onto the wellbore during gas drilling, and includes the following steps: Step 1: As Figure 1 As shown, drill string 1 is prepared, comprising a 215.9-230mm eccentric tricone drill bit, a MWD (measuring wire cutter), a 165mm drill collar, and a 127mm drill pipe, all sequentially and fixedly connected. A spraying tool 2 is connected to drill string 1. The spraying tool 2 includes a housing, which is fixed between the MWD and the drill collar. The housing contains a retractable nozzle, and the sidewall of the housing has an automatically opening and closing side hole corresponding to the nozzle. During gas drilling, when drill string 1 completes drilling into the area to be cured, a short reaming hole is used to enlarge the wellbore diameter of the area to be cured. After the reaming is completed, the spraying tool 2 is positioned at the spraying starting point above the area to be cured.

[0053] It should be noted that the area to be cured has a certain length. When the drill bit 1 completes the drilling of the area to be cured, the drill bit 1 is just located at the spraying endpoint at the bottom of the area to be cured. At this time, the inner diameter of the well wall of the area to be cured can be enlarged by short-tripping and reaming. After the reaming is completed, the spraying tool 2 is just located at the spraying starting point above the area to be cured. In this way, top-down spraying can be carried out during curing, which is beneficial to improving efficiency.

[0054] Step Two: As Figure 2As shown, stop injecting high-pressure gas, remove the square drill pipe at the wellhead, and use the drill pipe to lower the submersible paint loading cylinder 3. The submersible paint loading cylinder 3 contains resin paint and catalytic paint. The outer diameter of the submersible paint loading cylinder 3 can form a dynamic seal with the inner diameter of the drill pipe, so as to ensure that the submersible paint loading cylinder 3 can quickly and smoothly reach the spraying tool 2 below.

[0055] Preferably, the immersion-type paint loading cylinder 3 includes a cylinder body for sealing connection with the housing of the spraying tool 2. The upper part of the cylinder body is provided with an annular piston communicating with the outside. The catalytic paint and resin paint in each immersion-type paint loading cylinder 3 are sufficient to satisfy the spraying and curing of at least one area to be cured. The lower part of the cylinder body is provided with an end rupture disc, and the catalytic paint and resin paint are arranged in layers between the annular piston and the end rupture disc.

[0056] Step 3: By turning on the mud pump, air circulation is formed in the drill pipe, and the pressure of the gas circulation is used to control the downward movement of the submersible paint loading cylinder 3. When the submersible paint loading cylinder 3 reaches above the spraying tool 2, the submersible paint loading cylinder 3 connects with the spraying tool 2. The specific connection method can be to use existing structures such as chucks.

[0057] When the immersion paint loading cylinder 3 is connected to the spraying tool 2, the upper part of the spraying tool 2 can rupture the end rupture disc through a pre-set lifting structure, thereby allowing the paint in the immersion paint loading cylinder 3 to communicate with the nozzle. In addition, when the pressure on the annular piston is greater than the pressure on the end rupture disc, the end rupture disc will rupture, and the annular piston will push the catalytic paint and resin paint to be sprayed out of the nozzle.

[0058] Step Four: As Figure 3 , 4 As shown, the side hole on the housing of the spraying tool 2 is opened, and the nozzle extends out of the side hole. After the nozzle extends out of the side hole, the distance between the nozzle and the well wall is 6mm. Then, the pressure above the immersion paint loading cylinder 3 is increased. This pressure acts on the annular piston, which moves downward and squeezes the resin paint, thereby allowing the resin paint in the immersion paint loading cylinder 3 to enter the spraying tool 2 and be sprayed onto the well wall. At the same time, the spraying device is controlled to descend and rotate by the drill string 1. The spraying device descends at a speed of 4m / min and rotates at a speed of 55 rpm. When the spraying device reaches the spraying endpoint below the area to be cured, the resin paint is continuously sprayed onto the well wall.

[0059] Step 5: Control the nozzle and side hole to reset, and stop drill bit 1 to allow the curing resin to solidify. The time for drill bit 1 to remain stationary is 10 minutes.

[0060] Step Six: As Figure 5As shown, control the spraying tool 2 to reset to the spraying starting point above the area to be cured, and repeat step four to continuously spray the catalytic coating in the immersion coating loading cylinder 3 onto the resin coating.

[0061] Step 7: Raise drill string 1. Under the squeezing action of the drill bit in drill string 1, the resin coating and catalytic coating enter the micro-fractures in the well wall and form a structure like... Figure 6 The dense anti-water leakage isolation layer 4 shown has a thickness of 3mm, which completes the stabilization of the well wall in the area to be solidified.

[0062] Step 8: Continue drilling downwards and repeat steps 1-7 to stabilize the remaining areas of the well wall that need to be solidified.

[0063] It should be noted that the length of each area to be cured in this scheme can be 300mm, and the spacing between each area to be cured can be 300mm, which can be determined according to the actual situation downhole. In addition, the docking of the submersible paint loading cylinder 3 with the spraying tool 2, the automatic opening and closing of the side holes in the spraying tool 2, and the automatic extension and retraction of the nozzle are all controlled by the surface system.

[0064] In summary, this solution can sequentially spray resin coating and catalytic coating onto the well wall during drilling to form a tight water-proof isolation layer 4, thereby effectively preventing water from emerging from the well wall.

[0065] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All features or steps in the disclosed methods or processes may be combined in any way, except for mutually exclusive features and / or steps.

Claims

1. A wellbore stabilization method for preventing formation water inrush, wherein the method is achieved by spraying a resin coating onto the wellbore during gas drilling, characterized in that, Includes the following steps: Step 1: Connect the spraying tool to the drill string. The spraying tool includes a housing with a retractable nozzle inside. The side wall of the housing has a side hole that can be automatically opened and closed corresponding to the nozzle. During gas drilling, when the drill string completes drilling of the area to be cured, the inner diameter of the well wall of the area to be cured is enlarged by short-trip reaming. After the reaming is completed, the spraying tool is located at the spraying starting point above the area to be cured. Step 2: Stop injecting high-pressure gas, remove the square drill pipe at the wellhead, and use the drill pipe to lower the submersible coating loading cylinder. The submersible coating loading cylinder contains resin coating and catalytic coating. The outer diameter of the submersible coating loading cylinder and the inner diameter of the drill pipe form a dynamic seal. Step 3: Control the immersion paint loading cylinder to descend along the inner hole of the drill rod until it reaches the top of the spraying tool and connects with the spraying tool; Step 4: Control the side hole on the spraying tool housing to open, control the nozzle to extend out of the side hole, increase the pressure above the submersible paint loading cylinder, so that the resin paint in the submersible paint loading cylinder enters the spraying tool and is sprayed onto the well wall through the spraying tool; at the same time, control the spraying device to descend and rotate through the drill string, and when the spraying device reaches the spraying endpoint below the area to be cured, the resin paint is continuously sprayed onto the well wall; Step 5: Control the nozzle and side hole to reset, and stop the drill bit to allow the curing resin to solidify; Step 6: Control the spraying tool to return to the spraying starting point above the area to be cured, and repeat Step 4 to continuously spray the catalytic coating in the immersion coating carrier onto the resin coating. Step 7: Raise the drill string. Under the squeezing action of the drill bit, the resin coating and catalytic coating enter the micro-cracks in the well wall and form a dense water-proof isolation layer, thus stabilizing the well wall in the area to be cured. Step 8: Continue drilling downwards and repeat steps 1-7 to stabilize the remaining areas of the well wall that need to be solidified.

2. The wellbore stabilization method based on preventing formation water seepage according to claim 1, characterized in that: In step one, the drilling tools include an eccentric tricone drill bit, a MWD, a drill collar, and a drill rod that are fixedly connected in sequence. The spraying tool is fixed between the MWD and the drill collar through a housing.

3. A wellbore stabilization method based on preventing formation water seepage according to claim 1, characterized in that: In step two, the immersion coating loading cylinder includes a cylinder body for sealing connection with the housing of the spraying tool. The upper part of the cylinder body is provided with an annular piston that communicates with the outside, and the lower part of the cylinder body is provided with an end rupture disc. The catalytic coating and resin coating are arranged in layers between the annular piston and the end rupture disc.

4. A wellbore stabilization method based on preventing formation water outflow according to claim 1, characterized in that: In step three, the mud pump is turned on to create air circulation inside the drill pipe, and the downward movement of the immersion coating loading cylinder is controlled by the pressure of the gas circulation.

5. A wellbore stabilization method based on preventing formation water seepage according to claim 1, characterized in that: In step four, after the nozzle extends out of the side hole, the distance between the nozzle and the well wall is 5-6 mm.

6. A wellbore stabilization method based on preventing formation water seepage according to claim 1, characterized in that: In step four, the spraying device descends at a speed of 3-4 m / min while rotating at a speed of 50-55 rpm.

7. A wellbore stabilization method based on preventing formation water outflow according to claim 1, characterized in that: In step five, the drill string remains stationary for 5-10 minutes.

8. A wellbore stabilization method based on preventing formation water seepage according to claim 1, characterized in that: In step seven, the thickness of the waterproof barrier layer is 2-3 mm.

9. A wellbore stabilization method based on preventing formation water seepage according to claim 1, characterized in that: The length of the area to be cured is 200-300mm, and the spacing between each area to be cured is 200-300mm.

10. A wellbore stabilization method based on preventing formation water seepage according to claim 1, characterized in that: The automatic opening and closing of the side holes and the automatic extension and retraction of the nozzle in the spraying tool are controlled by the ground system.

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