Sand prevention and water plugging method and system for oil well

Abstract

The invention discloses an oil well sand prevention and water plugging method and system, and belongs to the technical field of oil development. The method comprises the following steps: establishing a water plugging barrier at a pore channel of a target layer through a plugging agent; a water blocking barrier is built on the side, close to the screen pipe, of the water plugging barrier through consolidation precipitation particles; a first sand blocking barrier is built on the side, close to the screen pipe, of the water blocking barrier through quartz sand or ceramsite with the second particle size; a second sand blocking barrier is built on the side, close to the screen pipe, of the first sand blocking barrier through quartz sand or ceramsite with the first particle size, and the first particle size is larger than the second particle size; and a well completion production pipe column is put down. According to the method, multi-stage barriers including the water plugging barrier, the water blocking barrier, the first sand blocking barrier and the second sand blocking barrier are built on a target layer, pore channels can be plugged, sand can be prevented from entering an oil well, the effects of water plugging, water lowering and sand prevention are achieved, and the production water content of the oil well is effectively reduced.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of oil development, and in particular to a method and system for preventing sand and water blocking in oil wells. Background Art

[0002] With the rapid development of oil development technology, the amount of oil produced is increasing. In the middle and late stages of the development of loose sandstone reservoirs, oil wells will produce sand and the water content will increase. Therefore, it is necessary to prevent sand and water from entering the oil wells during the oil development process. Summary of the invention

[0003] The embodiment of the present application provides a method and system for preventing sand and blocking water in oil wells, which can be used to prevent sand and block water in oil wells. The technical solution is as follows:

[0004] On the one hand, an embodiment of the present application provides a method for preventing sand and water blocking in an oil well, the method comprising:

[0005] The sand control string is lowered into a target layer in a wellbore of an oil well, wherein the target layer includes a pore, and the sand control string includes a screen pipe and a gravel packing service tool to block quartz sand or ceramsite of a first particle size through the screen pipe;

[0006] Pumping a plugging agent into the target layer through a pipeline and the gravel packing service tool to establish a water blocking barrier at the pores of the target layer through the plugging agent;

[0007] Pumping a sand-carrying fluid containing consolidation and dewatering particles into the target layer through the pipeline and the gravel packing service tool, so as to establish a water blocking barrier on a side of the water blocking barrier close to the screen pipe through the consolidation and dewatering particles;

[0008] Pumping a sand-carrying fluid containing quartz sand or ceramsite of a second particle size into the target layer through the pipeline and the gravel packing service tool, so as to establish a first sand retaining barrier on a side of the water blocking barrier close to the screen pipe through the quartz sand or ceramsite of the second particle size;

[0009] A sand-carrying fluid containing quartz sand or expanded clay of the first particle size is pumped into the target layer through the pipeline and the gravel packing service tool to establish a second sand retaining barrier on the side of the first sand retaining barrier close to the screen pipe through the quartz sand or expanded clay of the first particle size, and the first particle size is larger than the second particle size.

[0010] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:

[0011] The technical solution provided in the embodiment of the present application is through a water blocking barrier, a water blocking barrier, a first sand retaining barrier, and a second sand retaining barrier established in sequence in the direction close to the screen pipe of the target layer of the oil well, wherein the particle size of quartz sand or expanded clay of the first particle size in the second sand retaining barrier is larger than the particle size of quartz sand or expanded clay of the second particle size in the first sand retaining barrier. The water blocking barrier, the water blocking barrier, the first sand retaining barrier, and the second sand retaining barrier can both block the channel and prevent sand and gravel from entering the oil well, thereby achieving the effects of water blocking, dewatering, and sand prevention, and effectively reducing the production water content of the oil well. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0013] Figure 1 This is a flow chart of a method for preventing sand and blocking water in oil wells provided in an embodiment of the present application;

[0014] Figure 2 It is a schematic diagram of an oil well sand prevention and water plugging scenario provided in an embodiment of the present application;

[0015] Figure 3 It is a schematic diagram of an oil well sand prevention and water blocking structure provided in an embodiment of the present application. DETAILED DESCRIPTION

[0016] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0017] It should be noted that the terms "first", "second", etc. (if any) in the specification of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are only examples of devices and methods consistent with some aspects of the present application.

[0018] With the rapid development of oil development technology, the amount of oil produced is increasing. In the middle and late stages of the development of loose sandstone reservoirs, oil wells will produce sand and the water content will increase. Therefore, it is necessary to prevent sand and water from entering the oil wells during the oil development process.

[0019] See also Figure 1, an embodiment of the present application provides a method for preventing sand and water blocking in oil wells, the method including but not limited to steps 101 to 105.

[0020] Step 101, lowering a sand control string into a target layer in a wellbore of an oil well, wherein the target layer includes a pore, and the sand control string includes a screen pipe and a gravel packing service tool to block quartz sand or ceramsite of a first particle size through the screen pipe.

[0021] The target layer in the embodiment of the present application may be an oil layer production layer of an oil well with high water content and sand production. Since the oil layer cement, which is mainly clay, in the oil layer production layer of the oil well with high water content and sand production expands and loosens when it encounters water, the cement strength of the oil layer cement is reduced, which in turn causes sand production in the formation. As the formation produces sand, the formation collapses and forms pores, which further increases the water content in the oil layer production layer.

[0022] A sand control string is lowered into the wellbore of the oil well. The sand control string is used to improve the pipeline of the sand production problem in the oil well. The sand control string is used to cover or fix around the production layer of the oil well to limit the particles in the formation from entering the wellbore of the oil well. The structure and installation method of the sand control string are not limited in the embodiment of the present application. The sand control string can adopt different structural designs and installation methods to adapt to different geological conditions and oil well characteristics. The lowering position of the sand control string is determined at the target layer, and it is ensured that the screen pipe of the sand control string is aligned with the oil layer of the target layer, so as to collect the liquid in the oil layer through the screen pipe.

[0023] Exemplarily, the sand control pipe column includes but is not limited to a screen and a gravel packing tool. The screen can be made of metal or plastic, etc. The screen has many holes. The screen can filter solid particles and allow fluid to pass through. In the embodiment of the present application, the screen is used to prevent quartz sand or ceramsite of the first particle size from entering the screen. In the embodiment of the present application, the quartz sand or ceramsite of the first particle size is used to establish a second sand barrier to block sand and gravel in the target layer liquid.

[0024] The role of the gravel filling tool includes but is not limited to serving as a channel for pumping plugging agents and sand-carrying fluid into the target layer. In the embodiment of the present application, the plugging agent includes but is not limited to micron-level suspended solid phase materials, and the micron-level suspended solid phase materials refer to materials in which solid substances with particle diameters at the micron level exist in a suspended state in a fluid medium. The role of the plugging agent includes but is not limited to blocking water in the oil layer production layer of high-water-content sand-producing oil wells. Sand-carrying fluid refers to the liquid that carries solid materials to the target layer after the pores are formed in the target layer. Sand-carrying fluid can be divided into two categories according to its sand suspension capacity: fully suspended sand-carrying and sedimentation-type sand-carrying. Fully suspended sand-carrying means that the sand does not settle in the sand-carrying fluid, and sedimentation-type sand-carrying means that the sand slowly sinks in the sand-carrying fluid. The embodiment of the present application does not limit the type of sand-carrying fluid.

[0025] For example, when the sand control string is lowered into the target layer in the wellbore of the oil well, a Christmas tree is installed at the wellhead of the oil well. The Christmas tree is a component located at the opening leading to the top of the oil well. The Christmas tree includes but is not limited to valves for measurement and maintenance, a safety system and a series of monitoring equipment. The Christmas tree serves as a barrier to isolate the top of the oil well from the external environment. There are many types of Christmas trees due to different working environments, and the embodiments of the present application do not limit the types of Christmas trees.

[0026] In order to ensure the normal operation of the subsequent steps, the embodiment of the present application performs a pressure test on the construction pipeline before the construction pipeline is inserted into the wellbore of the oil well. The pressure test is to pressurize the construction pipeline when the construction pipeline is closed, so as to determine whether the construction pipeline can work normally. The construction pipeline includes but is not limited to the oil pipe mentioned in step 101 and the pipeline mentioned in step 102 of the embodiment of the present application.

[0027] Exemplarily, the pressure test operation of the construction pipeline may include checking the integrity and effectiveness of the pressure test equipment and tools used to perform the pressure test operation on the construction pipeline. Ensure that all valves connecting the construction pipeline and the pressure test equipment and tools can be properly installed and closed. Connect the pressure test equipment to the interface of the construction pipeline. Set up a plugging device in the area of ​​the construction pipeline that needs to be blocked, such as a plugger or valve for the construction pipeline, to ensure that the plugging device is safe and reliable. Fill the construction pipeline with a pressure test medium by pumping it into the construction pipeline through the pressure test equipment until the pressure in the construction pipeline reaches the pressure test pressure required for the pressure test. The pressure test medium can be air or water, etc. Maintain the test pressure to determine whether the construction pipeline is damaged or has other abnormal conditions.

[0028] Use the pressure test equipment to determine the pressure changes inside the construction pipeline during the pressure test, record the pressure test results, release the pressure test pressure at the specified pressure test pressure release rate, and ensure the safe decompression of the construction pipeline. Determine whether the pressure test results meet the pressure test conditions, which are determined according to the design requirements of the construction pipeline. If the pressure test results meet the pressure test conditions, the pressure test operation is confirmed to be successful; if the pressure test results do not meet the pressure test conditions, it is necessary to check whether there are any problems with the construction pipeline, and take corresponding treatment measures for the construction pipeline such as replacement or repair. Clean and maintain the pressure test equipment and tools to ensure that the pressure test equipment and tools are intact and stored in accordance with the storage requirements of the pressure test equipment and tools.

[0029] When the pressure test result meets the pressure test conditions, the wellbore filling operation is performed to drain the air in the wellbore of the oil well and balance the pressure in the construction pipeline and the wellbore of the oil well. Exemplarily, the oil pipe valve and the casing valve are opened to inject the supporting sand-carrying fluid from the oil pipe into the wellbore of the oil well. The oil pipe is a pipeline for transporting liquid or gas. The material of the oil pipe includes but is not limited to metal, etc. In the embodiment of the present application, the oil pipe is used to transport the supporting sand-carrying fluid, that is, to pump the supporting sand-carrying fluid into the channel of the wellbore of the oil well. The oil pipe is located in the wellbore of the oil well and does not contact the wellbore wall of the oil well.

[0030] The supporting sand-carrying fluid is a special liquid mixture, including but not limited to water and other additives. After the supporting sand-carrying fluid is injected into the wellbore of the oil well, it can provide sufficient support and pressure to the wellbore wall of the oil well to prevent the wellbore wall of the oil well from collapsing and promote further construction work. When the oil pipe valve and casing valve are open, the flow rate and pressure of the pumped supporting sand-carrying fluid are controlled to ensure that the supporting sand-carrying fluid enters the wellbore of the oil well at the specified supporting sand-carrying fluid pumping speed. During the pumping of the supporting sand-carrying fluid, it is necessary to observe the situation of the casing outlet. When the casing outlet begins to return liquid, that is, when the supporting sand-carrying fluid flows back from the casing outlet, the casing valve is closed to avoid continued pumping of the supporting sand-carrying fluid to damage the wellbore wall of the oil well. The casing and the wellbore wall of the oil well are sealed by sealing materials, and the casing is used to support the wellbore wall of the oil well. A Christmas tree is installed at the wellhead of the oil well. The Christmas tree is a device for controlling and regulating the production of the oil well. The Christmas tree is used to hang the oil pipe and seal the space between the oil pipe and the casing.

[0031] When the valve of the casing is closed, the oil pipe is connected to the construction pipeline leading to the target layer, and the parameters of the pre-fluid are determined. The parameters of the pre-fluid include but are not limited to flow rate and pressure to ensure that the parameters of the pre-fluid meet the parameters of the pre-fluid required by the operation. The pre-fluid is pumped into the target layer through the oil pipe and the construction pipeline leading to the target layer to facilitate the breaking of the target layer, and the specified target layer cracks formulated according to the actual situation of the oil well are formed in the target layer, thereby expanding the caliber of the pores of the target layer to facilitate the subsequent pumping operation. When the pre-fluid pumping volume reaches the pre-fluid reference pumping volume, the pumping of the pre-fluid is stopped, and the operation of pumping the pre-fluid is confirmed and recorded.

[0032] Step 102: Pump a plugging agent into the target layer through a pipeline and a gravel packing service tool to establish a water blocking barrier at the pores of the target layer through the plugging agent.

[0033] A channel leading to the target layer is formed by connecting the pipeline and the gravel packing tool, and the plugging agent is pumped into the pores of the target layer through the channel leading to the target layer. This application does not limit the type of pipeline and the material and connection method of the gravel packing tool.

[0034] Exemplarily, before pumping the plugging agent, ensure that the pipeline and the filling service tool are intact, and ensure that the pipeline and the filling service tool are tightly connected. The plugging agent is pumped into the pores of the target layer through the channel leading to the target layer. The plugging agent will gradually fill and solidify in the pores to form a water blocking barrier. In the process of pumping the plugging agent, it is necessary to control the injection speed and pressure of the plugging agent to ensure that the plugging agent is evenly distributed in the pores of the target layer. In addition, it is possible to avoid the pressure applied by the plugging agent to the pores of the target layer exceeding the reference pressure of the pores of the target layer, thereby causing the pore wall to rupture. The embodiment of the present application does not limit the shape and thickness of the water blocking barrier.

[0035] When the plugging agent is pumped into the target layer, a reference amount of slug sand-carrying liquid is pumped into the target layer through the channel leading to the target layer. The slug sand-carrying liquid is used to squeeze the plugging agent into the pores of the target layer. The slug sand-carrying liquid is a category of sand-carrying liquid. The slug sand-carrying liquid is used as a slug to squeeze other liquids. The sand-carrying liquid is used to carry other liquids or solid particles. In the process of pumping the plugging agent into the pores of the target layer, there may be uneven flow rates during the pumping process or complex pore environments, which may cause the water blocking barrier established by the plugging agent to not fit tightly enough with the pores, and thus fail to achieve the specified plugging effect of the plugging agent. Therefore, by pumping the slug sand-carrying liquid into the target layer, pressure is applied to the water blocking barrier, and then the water blocking barrier is made to fit with the pores to achieve the specified plugging effect. The present embodiment of the application does not limit the components of the slug sand-carrying liquid. In addition, the reference amount of the slug sand-carrying liquid described in the embodiment of the application is set based on the specific construction conditions.

[0036] When the pumping of the slug carrying fluid is completed, the blocking effect of the water blocking barrier is determined by means of a water blocking barrier quality detection method. When the blocking effect does not reach the specified blocking effect, the water blocking barrier is repaired or reinforced to ensure the reliability of the water blocking barrier. The embodiment of the present application does not limit the method of the repair or reinforcement operation.

[0037] In the embodiments of the present application, the plugging agent is described by taking a plugging agent configured with a micron-scale suspended solid phase material as an example. The plugging agent configured with a micron-scale suspended solid phase material is pumped into the pores of the target layer through the channel leading to the target layer. In the pores of the target layer, the plugging agent configured with a micron-scale suspended solid phase material meets water to form a colloid or gel-like object. The formed colloid or gel-like object will establish a water blocking barrier at the pores of the target layer. The water blocking barrier is used to block the water in the pores of the target layer. The process of establishing a water blocking barrier in the embodiments of the present application is only for illustrative purposes.

[0038] Step 103, pumping a sand-carrying fluid containing consolidation and dewatering particles into the target layer through pipelines and gravel packing service tools, so as to establish a water blocking barrier on the side of the water blocking barrier close to the screen tube through the consolidation and dewatering particles.

[0039] When the water blocking barrier is established, the sand-carrying fluid containing consolidation and water-reducing particles is pumped into the target layer through the channel formed by the connection of the pipeline and the gravel packing tool. Among them, the consolidation and water-reducing particles are used for consolidation and waterproofing in oil collection projects.

[0040] Exemplarily, the sand-carrying liquid containing the consolidation precipitation particles is pumped into the target layer through the channel leading to the target layer, and the pumping pressure of the sand-carrying liquid containing the consolidation precipitation particles is determined during the pumping process, and it is determined that the pressure of the sand-carrying liquid containing the consolidation precipitation particles will not destroy the established water blocking barrier and the structure of the target layer. The sand-carrying liquid containing the consolidation precipitation particles is evenly distributed on the side of the water blocking barrier close to the screen tube established in step 102. The consolidation precipitation particles will be filled and solidified on the side of the water blocking barrier close to the screen tube to establish a water blocking barrier. The water blocking barrier is used to reduce the water content in the target layer liquid.

[0041] Step 104, pumping a sand-carrying liquid containing quartz sand or ceramsite of the second particle size into the target layer through a pipeline and a gravel packing service tool, so as to establish a first sand retaining barrier on the side of the water blocking barrier close to the screen pipe through the quartz sand or ceramsite of the second particle size.

[0042] When the water barrier is established, the sand-carrying liquid containing quartz sand or ceramsite of the second particle size is pumped into the target layer through the channel leading to the target layer formed by connecting the pipeline and the gravel packing service tool. The quartz sand or ceramsite of the second particle size described in the embodiment of the present application refers to a granular material of a specific particle size, which is used to establish a first sand barrier to block the sand in the target layer. During the pumping process, the sand-carrying liquid will flow to the target layer along the channel leading to the target layer, and accumulate on the side of the water barrier close to the screen.

[0043] When the quartz sand or ceramsite of the second particle size in the sand-carrying liquid contacts the position of the water-blocking barrier close to the screen pipe, the quartz sand or ceramsite of the second particle size will accumulate at the position of the water-blocking barrier close to the screen pipe. Then the quartz sand or ceramsite of the second particle size will establish a barrier on the side of the water-blocking barrier close to the screen pipe, namely the first sand barrier. The function of the first sand barrier is to block the sand in the liquid in the target layer.

[0044] Step 105, pumping a sand-carrying fluid containing quartz sand or ceramsite of a first particle size into the target layer through a pipeline and a gravel packing service tool, so as to establish a second sand barrier on the side of the first sand barrier close to the screen pipe through the quartz sand or ceramsite of the first particle size, wherein the first particle size is larger than the second particle size.

[0045] When the first sand barrier is established, the sand-carrying liquid containing quartz sand or ceramsite of the first particle size is pumped into the target layer through the channel leading to the target layer formed by connecting the pipeline and the gravel packing service tool. The quartz sand or ceramsite of the first particle size described in the embodiment of the present application refers to a granular material of a specific particle size, which is used to establish a second sand barrier to block the ceramsite or quartz sand of the second particle size in the first sand barrier. During the pumping process, the sand-carrying liquid will flow to the target layer through the channel leading to the target layer, and establish a second sand barrier near the screen.

[0046] When the quartz sand or ceramsite of the first particle size in the sand-carrying liquid contacts the side of the first sand barrier close to the screen tube, the quartz sand or ceramsite of the first particle size will be concentrated and accumulated on the side of the first sand barrier close to the screen tube. The quartz sand or ceramsite of the first particle size will form a barrier, namely the second sand barrier. The function of the second sand barrier is to further prevent the water and sand and gravel particles in the target layer from entering through the gaps around the sand control pipe column. The first sand barrier and the second sand barrier work together to form a multi-layer barrier structure, which improves the ability to prevent sand and gravel from infiltrating. The embodiment of the present application does not limit the number of layers of the sand barrier. According to different construction conditions, any layer of sand barrier can be established by quartz sand or ceramsite of different particle sizes to block the sand in the liquid, wherein, from the water barrier to the sand control pipe column, the particle size of the quartz sand or ceramsite corresponding to the sand barrier is from small to large.

[0047] After the second sand barrier is established, the displacement fluid is injected into the target layer through the channel leading to the target layer formed by the connection of the pipeline and the gravel packing tool. During the pumping process, the displacement fluid will be continuously injected into the wellbore in order to maintain a certain pressure. With the injection of the displacement fluid, the pressure will gradually rise. The displacement fluid can be the above-mentioned sand-carrying fluid, that is, the sand-carrying fluid that is continuously pumped to maintain the pressure is called the displacement fluid. When the pressure inside the oil well reaches the reference pressure, the pumping process ends.

[0048] Exemplarily, after establishing the second sand barrier, continue to pump sand-carrying fluid into the target layer as a displacement fluid, and apply pressure to the wellbore of the oil well by pumping the displacement fluid, so as to apply pressure to the water blocking barrier established in step 102, the water blocking barrier established in step 103, the first sand blocking barrier established in step 104, and the second sand blocking barrier established in step 105, thereby reinforcing the water blocking barrier, the water blocking barrier, the first sand blocking barrier, and the second sand blocking barrier. The embodiment of the present application applies pressure to the wellbore of the oil well until a reference pressure is reached, and the reference pressure is set based on the oil production rate at the wellhead of the oil well. The embodiment of the present application does not limit the process of setting the oil production rate based on the wellhead of the oil well, and the reference pressure obtained based on the oil production rate may not be the same depending on the implementation environment. When the pressure reaches the reference pressure, the well is shut in so that the pressure in the well can diffuse into the formation to achieve the reinforcement of the four barriers.

[0049] Optionally, after the water blocking barrier, the water blocking barrier, the first sand retaining barrier, and the second sand retaining barrier are established through the above steps 101 to 105, the pressure inside the oil well can also be obtained. When the pressure reaches the pressure threshold, a completion production tubing is lowered into the wellbore of the oil well, and the completion production tubing is connected to the screen pipe.

[0050] After the well shut-in operation is completed, the internal pressure in the oil well is obtained. The embodiment of the present application does not limit the method of obtaining the internal pressure in the oil well. For example, it is obtained through a pressure gauge at the wellhead. The internal pressure in the oil well diffuses into the formation. When the internal pressure in the oil well reaches the pressure threshold, it means that the reinforcement operation of the barrier in the well is completed and the oil well can be opened. If the pressure in the well does not reach the pressure threshold, opening the oil well will cause the pressure in the barrier to be spit back, thereby causing the barrier structure to loosen.

[0051] When the pressure reaches the pressure threshold, the completion production string is lowered into the wellbore in sections or as a whole. The process of lowering the completion production string into the wellbore in sections or as a whole requires the use of lifting equipment such as a derrick, a drilling rig, etc., and the completion production string is gradually lowered to the bottom of the well through relevant tools and connection methods. The completion production string consists of a series of pipe sections for the production and transportation of oil and gas. The design and selection of the completion production string will be determined according to factors such as the characteristics of the oil well, geological conditions and production requirements. Once the production string is lowered into the wellbore, corresponding installation work needs to be carried out, for example, the completion production string and the screen pipe of the sand control string are docked. The embodiment of the present application does not limit the docking method of the completion production string and the screen pipe of the sand control string. It can be directly docked or docked through a docking connection device. For example, the docking process of the completion production string and the screen pipe of the sand control string includes operations such as connecting pipe sections, tightening threads, testing sealing, and fixing tools.

[0052] In summary, the method for preventing sand and blocking water in oil wells provided in the embodiments of the present application includes a water blocking barrier, a water blocking barrier, a first sand blocking barrier, and a second sand blocking barrier established in sequence in the direction close to the screen pipe in the target layer of the oil well, wherein the particle size of quartz sand or expanded clay of the first particle size in the second sand blocking barrier is larger than the particle size of quartz sand or expanded clay of the second particle size in the first sand blocking barrier. The water blocking barrier, the water blocking barrier, the first sand blocking barrier, and the second sand blocking barrier can both block the pores and prevent sand and gravel from entering the oil well, thereby achieving the effects of water blocking, dewatering, and sand prevention, and effectively reducing the production water content of the oil well.

[0053] For ease of understanding, Figure 2 Taking the scenario shown in the figure as an example, the method provided in the embodiment of the present application is illustrated. Figure 2 As shown, the process of the oil well sand prevention and water plugging method includes the following steps 1 to 12. Among them, the implementation of steps 1 to 4 can refer to the relevant description of the above step 101, the implementation of step 5 can refer to the relevant description of the above step 102 to step 105, the implementation of steps 6 and 7 can refer to the relevant description of the above step 102, the implementation of step 8 can refer to the relevant description of the above step 103, the implementation of step 9 can refer to the relevant description of the above step 104 and step 105, and the implementation of steps 10 to 12 can refer to the relevant description of the above step 105, which will not be repeated here.

[0054] See also Figure 3 An embodiment of the present application provides an oil well sand prevention and water blocking structure, which is located in a target layer 308 within a wellbore 302 of the oil well. The target layer 308 includes a pore. The structure includes: a sand prevention pipe column 301, a water blocking barrier 303, a water blocking barrier 304, a first sand blocking barrier 305 and a second sand blocking barrier 306.

[0055] The sand control pipe column 301 includes a screen and a gravel packing service tool. The screen is used to block quartz sand or ceramsite of a first particle size. The gravel packing service tool is used as a channel for pumping plugging agents and sand-carrying fluid into the target layer 308. The water blocking barrier 303 is established based on the plugging agent. The water blocking barrier 304 is established based on consolidated precipitation particles. The first sand retaining barrier 305 is established based on quartz sand or ceramsite of a second particle size. The second sand retaining barrier 306 is established based on quartz sand or ceramsite of a first particle size, and the first particle size is larger than the second particle size.

[0056] In a possible implementation, the plugging agent includes a micron-sized suspended solid material. The micron-sized suspended solid material forms a colloid or gel-like object when it meets water at the target layer. The colloid or gel-like object establishes a water plugging barrier 303 .

[0057] In a possible implementation, the casing and the well wall of the oil well are sealed by a sealing material; the oil pipe is used to pump sand-carrying fluid into the casing, and the oil pipe is located inside the casing and does not contact the casing.

[0058] In a possible implementation, a reference amount of sand-carrying fluid is pumped into the target layer 308 through a pipeline, and the plugging agent is squeezed into the pores of the target layer 308 based on the sand-carrying fluid.

[0059] In a possible implementation, after the second sand barrier 306 is established, a displacement fluid is pumped into the target layer 308 through a pipeline, and pressure is applied to the oil well based on the displacement fluid. When the pressure inside the oil well reaches a reference pressure, the pumping of the displacement fluid is terminated. The reference pressure is determined according to the oil production rate of the oil well. The pressure inside the oil well is obtained to determine whether the pressure reaches a pressure threshold; and a completion production string 307 is lowered.

[0060] Furthermore, the use of the oil well sand and water blocking method in the embodiments of the present application and the effects produced are explained in conjunction with the following embodiments.

[0061] The present application embodiment is described using the X17-7-1 well as an example.

[0062] The outer diameter of the well casing of the X17-7-1 well is 139.7 mm, and the inner diameter is 121.36 mm. Since the oil well is seriously sanded, it cannot be produced normally, and the production water content reaches 91.88% due to the pores formed in the target layer. The oil well sand prevention and water plugging method described in the above embodiment is used to prevent sand and water plugging in the oil well. The specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0063] Before sand control, the X17-7-1 well produced 30.4 cubic meters of liquid and 2.47 tons of oil per day, with a water content of 91.88%. After implementing the oil well sand control and water plugging method, the daily liquid production was 15.3 cubic meters, the daily oil production was 8.72 tons, the water content was 43%, and the water content decreased by 48.88 percentage points.

[0064] The present application embodiment is described using the X17-6-2 well as an example.

[0065] The outer diameter of the well casing of the X17-6-2 well is 139.7 mm, and the inner diameter is 124.1 mm. Since the oil well is seriously sanded, it cannot be produced normally, and the production water content is 89.59% due to the formation of the pores of the target layer. The oil well sand prevention and water plugging method described in the above embodiment is used to prevent sand and water plugging in the oil well. The specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0066] Before sand control, the X17-6-2 well produced 27.2 cubic meters of liquid and 2.83 tons of oil per day, with a water content of 89.59%. After implementing the oil well sand control and water plugging method, the daily liquid production was 24.39 cubic meters, the daily oil production was 8.31 tons, the water content was 65.93%, and the water content decreased by 23.66 percentage points.

[0067] The present application embodiment is described using the X52-3-6 well as an example.

[0068] The outer diameter of the well casing of the X52-3-6 well is 139.7 mm, and the inner diameter is 121.36 mm. Due to the serious sand production in the oil well, normal production cannot be achieved, and the production water content reaches 96.98% due to the pores formed in the target layer. The oil well sand prevention and water plugging method described in the above embodiment is used to prevent sand and water plugging in the oil well. The specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0069] Before sand control, the X52-3-6 well produced 4.67 cubic meters of liquid and 0.14 tons of oil per day, with a water content of 96.98%. After implementing the oil well sand control and water plugging method, the daily liquid production was 8.93 cubic meters, the daily oil production was 3.99 tons, the water content was 55.23%, and the water content decreased by 65.11 percentage points.

[0070] The above description is only for the purpose of facilitating those skilled in the art to understand the technical solution of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0071] It should be understood that the "plurality" mentioned in this article refers to two or more. "And / or" describes the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0072] The above description is only an exemplary embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preventing sand and water blocking in oil wells, characterized in that: The method comprises: The sand control string is lowered into a target layer in a wellbore of an oil well, wherein the target layer includes a pore, and the sand control string includes a screen pipe and a gravel packing service tool to block quartz sand or ceramsite of a first particle size through the screen pipe; Pumping a plugging agent into the target layer through a pipeline and the gravel packing service tool to establish a water blocking barrier at the pores of the target layer through the plugging agent; Pumping a sand-carrying fluid containing consolidation and dewatering particles into the target layer through the pipeline and the gravel packing service tool, so as to establish a water blocking barrier on a side of the water blocking barrier close to the screen pipe through the consolidation and dewatering particles; Pumping a sand-carrying fluid containing quartz sand or ceramsite of a second particle size into the target layer through the pipeline and the gravel packing service tool, so as to establish a first sand retaining barrier on a side of the water blocking barrier close to the screen pipe through the quartz sand or ceramsite of the second particle size; A sand-carrying fluid containing quartz sand or expanded clay of the first particle size is pumped into the target layer through the pipeline and the gravel packing service tool to establish a second sand retaining barrier on the side of the first sand retaining barrier close to the screen pipe through the quartz sand or expanded clay of the first particle size, and the first particle size is larger than the second particle size.

2. The method according to claim 1, characterized in that The plugging agent includes micron-sized suspended solid-phase material; the micron-sized suspended solid-phase material meets water at the pores of the target layer to form a colloid or gel-like object, and the water blocking barrier is established by the colloid or gel-like object.

3. The method according to claim 1, characterized in that The oil well includes an oil pipe and a casing, the casing and the well wall of the oil well are sealed by a sealing material, and the oil pipe is located inside the casing and does not contact the casing; before the plugging agent is pumped into the target layer through the pipeline and the gravel packing service tool, it also includes: Performing a pressure test on the pipeline and obtaining a pressure test result; When the pressure test result meets the pressure test condition, a supporting sand-carrying fluid is pumped into the casing through the oil pipe, and the supporting sand-carrying fluid is used to balance the pressure in the pipeline and the wellbore of the oil well.

4. The method according to claim 3, characterized in that: After obtaining the pressure test result, the method further includes: When the pressure test result does not meet the pressure test condition, the pipeline is repaired according to the pressure test result, or the pipeline that meets the pressure test result is replaced.

5. The method according to claim 3, characterized in that: After the supporting sand-carrying fluid is pumped into the casing through the oil pipe, the method further comprises: When the supporting sand-carrying fluid flows back at the casing outlet, closing the valve of the casing; A pre-fluid is pumped into the target layer through the oil pipe, and the pre-fluid is used to expand the caliber of the pore.

6. The method according to claim 3, characterized in that The wellhead of the oil well comprises an oil tree, and the oil tree is used to hang the oil pipe and seal the space between the oil pipe and the casing.

7. The method according to claim 1, characterized in that After the plugging agent is pumped into the target layer through the pipeline and the gravel packing service tool, the method further comprises: A reference amount of slug-carrying fluid is pumped into the target layer through the pipeline and the gravel packing service tool, and the reference amount of slug-carrying fluid is used to squeeze the plugging agent into the pores of the target layer.

8. The method according to claim 1, characterized in that: After the sand-carrying liquid containing quartz sand or ceramsite of the first particle size is pumped into the target layer through the pipeline and the gravel packing service tool, the method further includes: Pumping displacement fluid into the target layer through the pipeline and the gravel packing service tool, wherein the displacement fluid is used to apply pressure to the oil well; When the pressure inside the oil well reaches the reference pressure, the pumping of the displacement fluid is terminated.

9. The method according to claim 8, characterized in that The reference pressure is determined according to the oil production rate of the oil well.

10. The method according to any one of claims 1 to 9, characterized in that: After the sand-carrying liquid containing quartz sand or ceramsite of the first particle size is pumped into the target layer through the pipeline and the gravel packing service tool, the method further includes: Obtaining the pressure inside the oil well; When the pressure reaches the pressure threshold, a completion production string is lowered into the wellbore of the oil well, and the completion production string is connected to the screen pipe.

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