Method of operating a water injection well and water injection well

Abstract

The present invention relates to a method for operating a water injection well, which can achieve relatively balanced water injection between different strata of the water injection well. The method comprises arranging a flow control screen in a well cavity, and filling a packer particle carrying fluid into an annular space between the flow control screen and the well wall through a wellhead. The present invention also relates to a water injection well suitable for water injection using the method.

Description

Technical Field

[0001] The present invention relates to a method for operating a water injection well, which can realize relatively balanced water injection between different strata of the water injection well. The present invention also relates to a water injection well suitable for water injection using the method. Background Art

[0002] In the process of oil field development, as the energy of the oil layer decreases, the production capacity of the oil wells is also continuously reduced. In order to restore the production of oil wells, a water injection development model that increases the energy of the oil layer by injecting water has gradually been formed. Water is injected into the oil reservoir through a special water injection well to maintain or restore the oil layer pressure, so that the oil reservoir has a stronger driving force to increase the production speed and recovery rate of the oil reservoir.

[0003] like Figure 1 As shown in the figure, both the injection well and the production well penetrate multiple formations, and the permeability of each formation is different, and the viscosity of the oil in each formation is also different. In the process of water injection, between the injection well and the production well, under the condition of the same pressure difference, the seepage rate of different formations may differ by several times, dozens of times or even higher, which will cause the production well of the high permeability formation to see water quickly (ineffective water injection). The viscosity of water is lower than that of oil. After the water penetrates, the seepage rate of the high permeability formation is hundreds of times that of the low permeability formation, and the corresponding production well liquid production is greatly increased, and the water content is further increased. Since the water in the high permeability formation has been conducted, a short circuit is formed between the injection well and the production well, so the pressure difference cannot be accumulated between the injection well and the production well, resulting in the water in the low permeability formation can only drive the oil to flow to the production well at a very low level, and the oil production is greatly reduced. At the same time, the water in the high permeability formation is ineffectively circulated, which causes a great waste to the oil field and reduces the economic limit of the oil field. The high water content reduces the recovery rate of the oil field, and the oil field has to be abandoned. Horizontal water injection wells also have the problem of serious uneven water injection in each section, because the permeability of each section is different, there are cracks in each section, and the water breakthrough time of each section is different.

[0004] In the actual production process, a technology is needed to enable the water injection well to achieve the purpose of balanced water injection. At present, there are generally two methods for balanced water injection: chemical method and mechanical method.

[0005] The chemical method, also known as the chemical profile control method, is a method of injecting chemicals (such as polymer solutions, gels, etc.) into injection wells to increase the viscosity of water and improve the water absorption profile of the injection wells, but it has a short effective period and a small scope of application.

[0006] The mechanical method refers to using packers to separate the corresponding positions of the corresponding layers in the water injection well into multiple independent flow units, and installing water nozzles to achieve a layered and segmented balanced water injection effect. This method has a wide range of applications. For example, the water injection section of a water injection well in an oil field has 20 formations, which can be divided into 5 units using 4 packers, with an average of 4 formations in each unit. The mechanical isolation method is used to control the daily water inflow of the high-permeability unit through the water nozzles on the water injection string. For high-permeability units, the water injection flow rate is large, and the water nozzles have a greater flow restriction, which greatly reduces the water inflow flow rate. For low-permeability units, the water nozzles have a smaller resistance and the water inflow flow restriction is correspondingly smaller, so that different permeability sections of the formation can achieve relatively uniform water injection (see Figure 2 ). This method is widely used, with more than hundreds of thousands of wells around the world using this technology.

[0007] However, the water injection technology of the currently used mechanical isolation method mainly has the following technical defects:

[0008] 1. Due to the difficulty in inserting the packer into the well, only 4-5 packers can be put in. During the implementation process, there are 4 strata between every two packers on average, and the sections cannot be subdivided, and it is impossible to realize an independent water injection unit for each layer. The heterogeneity of these 4 strata is several times different, so these 4 strata can only be injected with water in general, and the sections cannot be subdivided, resulting in serious uneven water injection in the flow unit;

[0009] 2. The packers put into the well need to be tested, and the test can only be done from the wellhead, such as the annulus test. However, only the first packer can be tested for leaks, and the second packer cannot be tested. Therefore, it is impossible to ensure that each packer after entering the well can be effectively sealed. It is possible that the packer put in does not play an effective role in isolating the layers. In addition, over time, due to the timeliness of the packer, the sealing rubber will leak. If one packer fails, more layers will be flooded.

[0010] 3. In different flow units, the pressure in the water injection string is the same. Due to the different resistances of the water nozzles, different water nozzle pressure drops will be formed, resulting in inconsistent water pressure outside the water injection string, which in turn leads to pressure differences between flow units. Long-term pressure differences will cause damage to the cement sheath and cause crossflow problems (see Figure 7 ), segmented water injection failure;

[0011] 4. In cased wells where casing has been deformed and is not circular, the packer cannot be inserted into the well. In cased wells where casing is severely deformed, the packer cannot be lowered to the required position, so the traditional mechanical isolation method cannot be used. And for open hole wells, due to the irregular wellbore, the traditional mechanical isolation method cannot be implemented. If the mechanical isolation method is to be used, the open hole well needs to be casingd, and then cementing, perforating, completion and other cumbersome operation processes are carried out, which is expensive. If it is implemented offshore, one more day of delay will cause millions of dollars in costs;

[0012] 5. Due to the limited isolation effect of the packer, some oil fields need to adopt multiple sets of injection and production well networks for development, which greatly increases the number of wells drilled and increases other costs such as well management and maintenance;

[0013] 6. It is difficult to lower the packer, and once the packer is installed, it is extremely difficult to remove it, especially in some deep wells and wells with high mineralization, which is not conducive to the adjustment of the completion method of the water injection well in the later stage. If a major overhaul is required in the later stage, it will incur huge costs;

[0014] 7. After a period of water injection, the impurities in the injected water are likely to clog the sand control net. Acidification treatment is required to remove the blockage in the later stage, which is costly and damages the casing oil. The effect decreases with increasing number of times, and the impurities in the borehole are also difficult to clean.

[0015] Therefore, in the art, there is a need to provide an improved water injection method for oil wells, which can overcome one or more of the above-mentioned drawbacks. Summary of the invention

[0016] According to one aspect of the present invention, a method for operating a water injection well is provided, the water injection well comprising a wellhead and a well wall extending underground from the wellhead, the well wall defining a well cavity, the method comprising arranging a flow control screen in the well cavity. The flow control screen comprises: a hollow base pipe, the base pipe comprising a pipe wall impermeable to fluid, the pipe wall of the base pipe defining a base pipe inner cavity; a hollow filter tube, the filter tube comprising a pipe wall permeable to fluid, the filter tube being arranged around the outer side of the base pipe so that a first annular space is formed between the filter tube and the well wall and a second annular space is formed between the filter tube and the base pipe; and a flow control device, the flow control device having a flow cross-sectional area allowing fluid to flow through. The method also includes filling the first annular space with a sealing body particle carrying fluid via the wellhead, the sealing body particle carrying fluid includes sealing body particles and a liquid for carrying the sealing body particles, a portion of the liquid enters the second annular space via the wall of the filter tube, enters the inner cavity of the base pipe via the flow control device, and returns via the wellhead, another portion of the liquid penetrates into the formation via the well wall, the filter tube blocks the sealing body particles, so that the sealing body particles accumulate in the first annular space.

[0017] In one embodiment, placing the flow control screen in the wellbore includes placing two or more flow control screens connected end to end in the wellbore, so that each formation corresponds to one or more flow control screens. Preferably, the flow cross-sectional areas of the flow control devices of the flow control screens corresponding to the same formation are the same.

[0018] In one embodiment, the method further comprises setting the flow cross-sectional area of ​​the flow control device of the flow control screen located at the bottom of the water injection well to be larger than the flow cross-sectional area of ​​the flow control device of other flow control screens. Preferably, the flow cross-sectional area of ​​the flow control device of the flow control screen located at the bottom of the water injection well is 1.1 to 5 times the flow cross-sectional area of ​​the flow control device of other flow control screens.

[0019] In one embodiment, the method further comprises setting flow cross-sectional areas of the flow control devices of at least two of the flow control screens to be different from each other.

[0020] In one embodiment, the water injection well further comprises a first valve and a second valve, wherein the first valve is used to open or close the fluid communication between the first annular space and the wellhead, and the second valve is used to open or close the fluid communication between the inner cavity of the base pipe and the wellhead, and the method further comprises: closing the first valve and opening the second valve; and injecting water into the inner cavity of the base pipe via the second valve, so that water enters the first annular space via the flow control device, the second annular space and the filter tube.

[0021] In one embodiment, the method further comprises pressurizing the first annular space before closing the first valve and opening the second valve.

[0022] In one embodiment, the water injection well further includes a first valve and a second valve, the first valve being used to open or close the fluid communication between the first annular space and the wellhead, and the second valve being used to open or close the fluid communication between the inner cavity of the base pipe and the wellhead, and the method further includes: opening the first valve and opening the second valve; and injecting water into the inner cavity of the base pipe via the second valve, so that water enters the first annular space via the flow control device, the second annular space and the filter tube, so as to disperse the isolation body particles accumulated in the first annular space, and allow the isolation body particles to be discharged back to the ground via the first valve.

[0023] In one embodiment, the method further comprises: opening the first valve and opening the second valve; and refilling the first annular space with a packer particle carrier fluid via the first valve.

[0024] In one embodiment, the method further comprises placing a hanging packer around the flow control screen at the top and hanging it on the wellbore wall.

[0025] In one embodiment, the method further comprises adjusting a flow cross-sectional area of ​​the flow control device.

[0026] In one embodiment, the method further comprises replacing the flow control device with another flow control device having a different flow cross-sectional area.

[0027] In one embodiment, the water injection well further comprises a casing arranged in the wellbore and a cement ring arranged between the casing and the wellbore wall, and wherein, arranging the flow control screen in the wellbore comprises arranging the flow control screen in the casing, and filling the first annular space with a sealing body particle carrying fluid via the wellhead comprises filling the annular space between the filter tube and the casing with a sealing body particle carrying fluid via the wellhead.

[0028] In one embodiment, the water injection well further comprises a casing disposed in the wellbore, a cement ring disposed between the casing and the wellbore wall, a flow control string disposed in the casing, and a mechanical packer disposed between the flow control string and the casing, the method further comprising removing the mechanical packer and the flow control string from the wellbore before disposing the flow control screen in the wellbore, and disposing the flow control screen in the wellbore comprises disposing the flow control screen in the casing.

[0029] In one embodiment, the tube wall of the filter tube has a pore size, the particles of the packing body have a particle size, and the pore size is greater than or equal to 1 / 2 of the particle size and less than or equal to 2 / 3 of the particle size.

[0030] According to another aspect of the present invention, a water injection well is provided. The water injection well comprises: a wellhead; a well wall, the well wall extending from the wellhead to the underground, the well wall defining a well cavity; a flow control screen, the flow control screen is arranged in the well cavity. The flow control screen comprises: a hollow base pipe, the base pipe comprises a pipe wall impermeable to fluid, the pipe wall of the base pipe defines the base pipe inner cavity; a hollow filter tube, the filter tube comprises a pipe wall permeable to fluid, the filter tube is arranged around the outer side of the base pipe, so that a first annular space is formed between the filter tube and the well wall and a second annular space is formed between the filter tube and the base pipe; and a flow control device, the flow control device having a flow cross-sectional area allowing fluid to flow through. The water injection well also comprises packer particles, the packer particles are filled in the first annular space.

[0031] In one embodiment, the water injection well comprises two or more flow control screens connected end to end, and the two or more flow control screens are arranged in the well cavity so that each formation corresponds to one or more flow control screens. Preferably, the flow cross-sectional areas of the flow control devices of the flow control screens corresponding to the same formation are the same.

[0032] In one embodiment, the flow cross-sectional area of ​​the flow control device of the flow control screen located at the bottom of the water injection well is greater than the flow cross-sectional area of ​​the flow control device of other flow control screens. Preferably, the flow cross-sectional area of ​​the flow control device of the flow control screen located at the bottom of the water injection well is 1.1 to 5 times the flow cross-sectional area of ​​the flow control device of other flow control screens.

[0033] In one embodiment, the flow cross-sectional areas of the flow control devices of at least two of the flow control screens are different from each other.

[0034] In one embodiment, the water injection well further comprises a casing disposed in the wellbore and a cement ring disposed between the casing and the wellbore wall, the flow control screen is disposed in the casing, and the packing particles are filled in the annular space between the filter tube and the casing.

[0035] In one embodiment, the tube wall of the filter tube has a pore size, the particles of the packing body have a particle size, and the pore size is greater than or equal to 1 / 2 of the particle size and less than or equal to 2 / 3 of the particle size.

[0036] The present invention has the following advantages:

[0037] 1. Each section of the stratum can be separated by continuous sealing particles. For example, if there are 20 strata in the water injection section of a well, it can be divided into 20 independent units, further refining the flow unit and realizing independent balanced water injection of 20 strata.

[0038] 2. A good axial isolation is achieved without the problem of packer leakage. Because there are continuous packer particles outside the flow control filter string, and the packer particles will automatically fill the leaking areas through migration, solving the problems of casing channeling and casing leakage;

[0039] 3. Filling in open hole. Whether the open hole is big or small, the packer particles will fill it up (see Figure 5 ), can adaptively fill wells of various shapes (including deformed casing wells), solving problems that packers cannot achieve;

[0040] 4. The process is simple and reduces the operating cost;

[0041] 5. It can effectively reduce the pressure difference of high permeability formations, reduce the injection volume of high permeability sections, and increase the pressure difference of low permeability sections of injection wells and production wells under the same liquid volume, which is conducive to driving the oil volume of low permeability formations and improving oil field recovery;

[0042] 6. The packer particles in the wellbore have a separation function in the axial direction to prevent axial crossflow; they act as filters in the radial direction to effectively filter the impurity particles injected into the water. Under the premise of avoiding blockage of the sand control net, they can effectively intercept the impurities in the pores and throats between the packer particles; at the same time, they can also have a blocking effect, because the packer particles can blow away the impurities that are blocked and accumulated in the pores and throats between the packer particles when they are returned, and mix with the packer particles in the carrying liquid medium and return to the ground together. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of an injection well and a production well is shown;

[0044] Figure 2 A water injection well using a mechanical isolation method in the prior art is schematically shown;

[0045] Figure 3 A water injection well according to an embodiment of the present invention is schematically shown;

[0046] Figure 4 The tube wall of the filter tube and the packing body particles located outside the filter tube according to one embodiment of the present invention are schematically shown;

[0047] Figure 5 A water injection well according to an embodiment of the present invention is schematically shown;

[0048] Figure 6-Figure 13 Some embodiments according to the invention are schematically shown. DETAILED DESCRIPTION

[0049] Figure 3 A water injection well 100 according to an embodiment of the present invention is schematically shown. The water injection well 100 may include a well head 110 and a well wall 120. The well wall 120 extends underground from the well head 110 and defines a well cavity 130.

[0050] The water injection well 100 may also include a flow control screen 140 disposed in the wellbore 130. The flow control screen 140 may include a hollow base pipe 150, a hollow filter tube 160, and a flow control device 170. The base pipe 150 may include a fluid-impermeable wall 152. The wall 152 of the base pipe 150 defines a base pipe lumen 154. The filter tube 160 may include a fluid-permeable wall 162. The filter tube 160 may be disposed around the outside of the base pipe 150 so that a first annular space S1 is formed between the filter tube 160 and the wellbore wall 120 and a second annular space S2 is formed between the filter tube 160 and the base pipe 150. The flow control device 170 has a flow cross-sectional area that allows fluid to flow through. The flow cross-sectional area of ​​the flow control device 170 may be various suitable shapes, such as circular, elliptical, rectangular, etc. The flow cross-sectional area of ​​the flow control device 170 may include a plurality of separate parts. The flow cross-sectional area of ​​the flow control device 170 may vary in the flow direction.

[0051] The water injection well 100 may further include packer particles 180. The packer particles 180 may be filled in the first annular space S1. Preferably, the packer particles 180 may completely fill the first annular space S1. During the water injection process, water injected into the base pipe inner cavity 154 via the wellhead 110 may enter the second annular space S2 via the flow control device 170, then pass through the pipe wall 162 of the filter pipe 160 into the first annular space S1, and then flow into the formation between the water injection well and the production well.

[0052] The filter tube 160 may also be referred to as a screen tube. The tube wall 162 of the filter tube 160 may be in the form of a screen. The tube wall 162 of the filter tube 160 may allow formation fluid (such as water, oil) to pass through, while being able to block the packer particles 180 from passing through. Figure 4 The tube wall 162 of the filter tube 160 and the packer particles 180 located outside the filter tube 160 (ie, located in the first annular space S1 ) are schematically shown. Figure 4 It also schematically shows impurities with smaller particle sizes, for example, from the injected water. In one embodiment, the pore size of the tube wall 162 of the filter tube 160 is greater than or equal to 1 / 2 of the particle size of the packer particles 180 and less than or equal to 2 / 3 of the particle size of the packer particles 180. Since the pore throat size between the packer particles 180 is approximately 1 / 5 of the particle size of the packer particles, the packer particles 180 can act as a filter in the radial direction, and most of the impurities in the injected water can pass through the tube wall 162 of the filter tube 160 (to avoid clogging of the filter tube 160), but are effectively intercepted at the pore throats between the packer particles 180.

[0053] In one embodiment, the water injection well 100 may include two or more flow control screens 140 connected end to end. In this embodiment, two or more flow control screens 140 are arranged in the wellbore 130, so that each formation corresponds to one or more flow control screens 140. Preferably, the flow cross-sectional areas of the flow control devices 170 of the flow control screens 140 corresponding to the same formation may be the same. During the water injection process, the water injected into the base pipe cavity 154 through the wellhead 110 may enter the second annular space S2 through the flow control devices 170 of each flow control screen 140, then pass through the pipe wall 162 of the filter pipe 160 to enter the first annular space S1, and then flow into the corresponding formation.

[0054] The working principle of the packing particles 180 of the present invention is based on the Darcy formula of seepage mechanics: , where K is the permeability of the rock, Q is the flow rate, μ is the viscosity of the fluid, L is the length of the core, A is the cross-sectional area of ​​the core, and △P is the pressure difference between the two ends of the core. According to Darcy's formula, the magnitude of the seepage resistance is proportional to the seepage distance and inversely proportional to the seepage area.

[0055] In the present invention, the accumulation body formed by the packing body particles 180 in the first annular space S1 is thin in thickness, small in cross section and large in axial length. When the formation fluid flows radially in the packing body particles 180, the seepage distance is relatively short and the seepage area is relatively large, so the resistance is relatively small. However, when the formation fluid flows axially in the packing body particles 180, the seepage distance is relatively long and the seepage area is relatively small, so the resistance is relatively large. By appropriately selecting the particle size of the packing body particles 180 and setting the radial thickness of the first annular space S1, the flow resistance of the formation fluid flowing axially for several meters to tens of meters can be made greater than the flow resistance flowing radially for several centimeters, for example, several thousand times or even tens of thousands of times. Due to the presence of the packing body particles 180, there is a huge difference between the axial and radial flow resistances. Therefore, under the action of the same pressure difference, the flow rate of the axial flow is much smaller than the flow rate of the radial flow, so that the packing body particles 180 have radial permeability and axial blocking properties. On the one hand, due to the radial permeability of the packer particles 180, the injected water can easily pass through the packer particles 180 in the first annular space S1 in the radial direction and flow into each formation, ensuring that the packer particles 180 will not affect the normal function of the water injection well. On the other hand, due to the axial blocking property of the packer particles 180, the axial crossflow of water flowing out of the flow control device 170 of each flow control screen 140 is reduced or prevented (axial crossflow refers to the water from one flow control screen flowing axially to the formation where another flow control screen is located after entering the first annular space S1). In the present invention, radial and axial are relative to the wellbore 130. Specifically, radial refers to the direction perpendicular to the wellbore 130, and axial refers to the direction along the wellbore 130.

[0056] In one embodiment, the flow cross-sectional area of ​​the flow control device 170 of the flow control screen 140 located at the bottom of the water injection well 100 may be greater than the flow cross-sectional area of ​​the flow control device 170 of other flow control screens 140. Preferably, the flow cross-sectional area of ​​the flow control device 170 of the flow control screen 140 located at the bottom of the water injection well 100 may be 1.1 to 5 times the flow cross-sectional area of ​​the flow control device 170 of other flow control screens 140.

[0057] In one embodiment, the flow cross-sectional areas of at least two flow control devices 170 in the flow control screen 140 are different from each other. Preferably, the flow cross-sectional area of ​​the flow control device 170 of the flow control screen 140 can be designed based on the physical property parameters (such as permeability, porosity, oil saturation, phase permeability curve, etc.) of the formation in which each flow control screen 140 is located, so that the flow limiting capacity of the flow control device 170 of each flow control screen 140 matches the formation in which it is located. In one embodiment, the flow cross-sectional area of ​​at least one flow control device 170 is adjustable, so that the flow cross-sectional area of ​​the flow control device 170 can be adjusted according to the changes in the formation physical property parameters during production, so as to better match the flow limiting capacity of the flow control device 170 with the formation in which it is located.

[0058] In one embodiment, Figure 3 As shown, the water injection well 100 can be an open hole well. That is, the packer particles 180 are directly filled in the first annular space S1 formed between the filter tube 160 of the flow control screen 140 and the well wall 120. In the case where the water injection well 100 is an open hole well, the well wall 120 can have an irregular shape, that is, it can have different diameters at different depths. Correspondingly, the first annular space S1 also has an irregular shape, that is, it has different radial thicknesses at different depths. The packer particles 180 of the present invention are particularly advantageous when filling an open hole well. As shown in FIG. Figure 3 As shown, no matter what the shape of the wellbore wall 120 is, the packer particles 180 can adaptively fill the first annular space S1 of various shapes due to their fluidity, thereby being able to adapt to well conditions that mechanical packers cannot cope with.

[0059] In one embodiment, Figure 5 As shown, the water injection well 100 may be a cased well. That is, the water injection well 100 may further include a casing 190 disposed in the well cavity 130 and a cement ring 195 disposed between the casing 190 and the well wall 120. In the case where the water injection well 100 is a cased well, the flow control screen 140 may be disposed in the casing 190, and the packer particles 180 may be filled in the annular space between the filter tube 160 of the flow control screen 140 and the casing 190.

[0060] The following is a detailed description of a method 200 for operating a water injection well according to the present invention. The water injection well includes a wellhead 110 and a well wall 120 extending from the wellhead 110 to the underground. The well wall 120 defines a well cavity 130. The method 200 may include setting a flow control screen 140 in the well cavity 130. The method 200 may also include filling a first annular space S1 with a packer particle carrying fluid via the wellhead 110, the packer particle carrying fluid including packer particles 180 and a liquid for carrying the packer particles 180, a portion of the liquid entering the second annular space S2 via the wall of the filter tube 160, entering the base pipe inner cavity 154 via the flow control device 170, and returning via the wellhead 110, another portion of the liquid permeating into the formation via the well wall 120, the filter tube 160 blocking the packer particles 180, so that the packer particles 180 are accumulated in the first annular space S1.

[0061] In one embodiment, two or more flow control screens 140 connected end to end may be arranged in the wellbore 130, so that each formation corresponds to one or more flow control screens 140. Preferably, the flow cross-sectional areas of the flow control devices 170 of the flow control screens 140 corresponding to the same formation may be the same.

[0062] In one embodiment, the method 200 may further include the step of setting the flow cross-sectional areas of at least two flow control devices 170 in the flow control screens 140 to be different from each other.

[0063] like Figure 3 As shown, the water injection well may further include a first valve V1 and a second valve V2. The first valve V1 is used to open or close the fluid communication between the first annular space S1 and the wellhead 110. The second valve V2 is used to open or close the fluid communication between the base pipe lumen 154 and the wellhead 110. In one embodiment, the method 200 may further include the following steps: closing the first valve V1 and opening the second valve V2; and injecting water into the base pipe lumen 154 via the second valve V2, so that water enters the first annular space S1 via the flow control device 170, the second annular space S2 and the filter tube 160. The water injection process can play a role in compacting the particles of the packing body in the first annular space S1.

[0064] In one embodiment, the method 200 may further include the following step: before closing the first valve V1 and opening the second valve V2, pressurizing the first annular space S1. By appropriately pressurizing the first annular space S1 before water injection, the compaction effect of the packer particles 180 can be further improved.

[0065] As described above, most of the impurities in the water injected from the wellhead can pass through the tube wall 162 of the filter tube 160, but are effectively intercepted at the pores and throats between the packer particles 180. After a period of water injection using the water injection well of the present invention, the pores and throats between the packer particles may become blocked. When blockage is found, the packer particles need to be replaced. The replacement of the packer particles can be completed by first removing the original packer particles and then refilling with new packer particles. When removing the packing body particles, the following operations are performed: open the first valve V1 and open the second valve V2; and inject water into the base pipe inner cavity 154 through the second valve V2, so that the water enters the first annular space S1 through the flow control device 170, the second annular space S2 and the filter tube 160, so as to disperse the packing body particles 180 accumulated in the first annular space S1, so that the impurities intercepted and filtered out of the throat of the packing body particles 180 are dispersed and mixed with the packing body particles 180, and the packing body particles 180 and impurities 182 are returned to the ground through the first valve V1. Next, the first annular space S1 can be refilled with new packing body particle carrying fluid. When refilling the packing body particle carrying fluid, the following operations are performed: open the first valve V1 and open the second valve V2; and refill the packing body particle carrying fluid into the first annular space S1 through the first valve V1.

[0066] In one embodiment, the flow cross-sectional area of ​​the flow control device 170 of the flow control screen 140 located at the bottom of the water injection well can be set to be larger than the flow cross-sectional area of ​​the flow control device 170 of other flow control screens 140. By making the flow control device located at the bottom of the water injection well have a larger flow cross-sectional area, it can be ensured that a larger water flow flows out of the flow control device at the bottom of the water injection well when removing the packer particles, so that the packer particles can be returned more thoroughly. This is beneficial for eliminating the blockage phenomenon.

[0067] In one embodiment, the method 200 may further include the step of disposing a hanging packer TP around the flow control screen 140 located at the top and hanging the hanging packer TP on the wellbore wall 120 . Figure 3 The hanging packer TP is schematically shown. The hanging packer TP can further prevent the packer particles from escaping from the first annular space S1 and entering the flow control screen 140, thereby causing blockage.

[0068] In one embodiment, the method 200 may further include the following step: adjusting the flow cross-sectional area of ​​the flow control device, so as to better match the flow limiting capacity of the flow control device with the formation in the production process.

[0069] In one embodiment, the method 200 may further include the following step: replacing the original flow control device with another flow control device having a different flow cross-sectional area, so that the flow limiting capacity of the flow control device can be better matched with the formation during the production process.

[0070] The method 200 of the present invention can also be used in the above-mentioned cased well. In the case where the water injection well 100 is a cased well, the flow control screen 140 can be set in the casing 190, and the annular space between the filter tube 160 and the casing 190 can be filled with the packer particle carrying fluid through the wellhead 110.

[0071] The method 200 of the present invention can also be used to transform an existing cased well using a mechanical packer and a conventional flow control string. Such a cased well, in addition to a wellhead 110 and a well wall 120 extending underground from the wellhead 110, also includes a casing 190 disposed in a well cavity 130 defined by the well wall 120, a cement ring 195 disposed between the casing 190 and the well wall 120, a conventional flow control string disposed in the casing 190, and a mechanical packer disposed between the conventional flow control string and the casing 190. When the cased well is transformed, the mechanical packer and the conventional flow control string are first removed from the well cavity 130, and then the flow control screen 140 of the present invention is disposed in the casing 190, and then the annular space between the filter tube 160 of the flow control screen 140 and the casing 190 is filled with a packer particle carrying fluid via the wellhead 110.

[0072] Example 1 (vertical well, new open hole well)

[0073] A certain offshore directional open hole water injection well has 20 water injection layers and the size of the open hole wellhead is 8.5 inches. The method and water injection well of the present invention are used. A 5.5-inch flow control screen 140 is lowered into the open hole, and 40-70 mesh packer particles are filled in the first annular space between the flow control screen 140 and the well wall. The concentration of the packer particle carrying liquid is 5%, and the filling pressure is 6MPa. After the packer particle carrying liquid carries the packer particles into the first annular space, the packer particles are continuously accumulated and filled in the first annular space until the packer particles fill the entire first annular space (see Figure 3 ). A part of the liquid in the particle-carrying fluid of the packer enters the second annular space through the wall of the filter tube of the flow control screen 140, enters the inner cavity of the base pipe through the flow control device, and returns from the wellhead, and another part of the liquid in the particle-carrying fluid of the packer penetrates into the formation through the well wall. After production, the corresponding oil well pressure difference reached 5MPa, with a daily oil production of 42 cubic meters / day, a daily liquid production of 120 cubic meters / day, a water content of 65%, and no water has been seen for 2 years. In contrast, the water injection wells in the same block that use traditional mechanical isolation methods have a corresponding oil well production pressure difference of only 3MPa, a daily oil production of 5 cubic meters / day, a daily liquid production of 100 cubic meters / day, and a water content of 95%.

[0074] Example 2 (vertical well, traditional cased well)

[0075] There is a traditional cased well in an oil field. The production layer is more than 30 layers. The reservoir condition is covered by sandstone and mudstone interlayers (one layer of sandstone and one layer of mudstone. The sandstone layer contains oil, and the mudstone layer is not permeable). Balanced water injection development is required to achieve the ideal development effect. The cased well adopts the traditional mechanical isolation method. The completion structure is casing perforation. Four mechanical packers are used to divide the formation into five sections (see Figure 6 ). In the initial stage of production, the corresponding oil well production pressure difference was 1MPa, the production well produced 80 cubic meters of water per day, 5 cubic meters of oil per day, and the water content was 94%. Due to the low daily oil production, the well had to be shut down and production stopped.

[0076] The cased well was transformed by the method of the present invention. First, the original mechanical packer and flow control column were removed. Then, a 3.5-inch flow control screen 140 was lowered into the 7-inch casing, and 40-70 mesh packer particles were filled in the annular space between the flow control screen 140 and the casing. The packer particle carrying liquid concentration was 5%, and the filling pressure was 6MPa. After the well was completed, the production pressure difference of the corresponding oil well reached 10MPa, the production well produced 50 cubic meters of water per day, and 45 cubic meters of oil per day, with a water content of 53%. The comparison of the effects before and after the transformation is shown in the following table:

[0077] .

[0078] Implementation 3 (vertical wells, traditional cased wells, interlayer crossflow, and packer leakage problems)

[0079] There is a traditional cased well in an oil field. The well structure is 7-inch casing perforation, and the traditional mechanical method is used for separation and water injection. In the early stage of production, the pressure difference of the corresponding oil well reached 3MPa, the production well produced 100 cubic meters of water per day, 20 cubic meters of oil per day, and the water content was 83%. After a period of production, problems such as interlayer crossflow and packer leakage occurred (see Figure 7 ). Due to the existence of perforations and channeling slots, if water comes out at the perforation channel a, the water in the formation will enter the channel b through the perforation channel a, and flow axially in the channel along the arrow direction to the perforation channel c, and enter the casing through the perforation channel c. Water will enter the corresponding flow control filter d in the casing, thereby destroying the sealing effect of the cement sheath. At the same time, due to the timeliness of the use of the packer, the sealing rubber will leak over time, such as Figure 7 If the packer in the well leaks, it will also cause the packer to fail, and water will flow from the low-permeability formation to the high-permeability formation, resulting in general water injection. As a result, the pressure difference between the injection well and the production well is reduced to 0.5MPa, and the production well produces 120 cubic meters of water per day and 2 cubic meters of oil per day, with a water content of up to 98%.

[0080] The cased well was reconstructed by the method of the present invention. First, the original mechanical packer and flow control column were removed. Then, a 3.5-inch flow control screen 140 was lowered into the 7-inch casing, and 30-50 mesh packer particles were filled in the annular space between the flow control screen 140 and the casing. The packer particle carrying liquid concentration was 5%, and the filling pressure was 6 MPa. The fluidity of the packer particles enables the packer particles to timely block the channeling leakage points in the well wall, and has the effect of self-repairing the well wall. Figure 8 The figure shows the cased well after the transformation. After the transformation, the pressure difference of the corresponding oil well reaches 10MPa, the production well produces 60 cubic meters of water per day, 42 cubic meters of oil per day, and the water cut is reduced to 59%. The comparison of the effect before and after the transformation is shown in the table below.

[0081]

[0082] Example 4 (Horizontal Well, Conventional Cased Well)

[0083] A horizontal water injection well in an offshore oil field, spanning 600 meters, uses traditional mechanical isolation for balanced water injection (see Fig. 9 ). Due to water breakthrough in the high permeability layer and casing leakage due to casing damage, the water content reached 95%, corresponding to a production pressure difference of 0.2MPa, a daily water production of 100 cubic meters and a daily oil production of 5 cubic meters.

[0084] The method of the present invention is used to transform the casing well. First, the original mechanical packer and flow control string are removed. Then, a 3.5-inch flow control screen 140 is lowered into the 7-inch casing, and 20-40 mesh packer particles are filled in the annular space between the flow control screen 140 and the casing. The concentration of the packer particles carrying liquid is 5%, and the filling pressure is 6MPa. The fluidity of the packer particles enables the packer particles to adaptively control the problem of casing leakage, without considering the location and quantity of casing leakage, and new casing leakage points in the future. Fig.10 The figure shows the cased well after the transformation. After the transformation, the corresponding oil well production pressure difference reached 5MPa, the daily water production was 203 cubic meters / day, the daily oil production was 60 cubic meters / day, and the water content was reduced to 77%. The comparison of production data before and after the transformation is shown in the table below.

[0085]

[0086] Embodiment 5 (In a cased well using the water injection method of the present invention, the flow control device is replaced after a period of production)

[0087] There is a new well in an offshore oil field. The oil layer viscosity of the well is 142 centipoise, the formation water viscosity is 0.6 centipoise, the oil-water viscosity ratio is 237:1, and the wellbore diameter is 6 inches. The completion structure obtained by using the technology of the present invention is as follows: Fig.11As shown. A 3.5-inch flow control screen 140 is lowered into the casing, and 20-40 mesh sealing body particles are filled in the annular space between the flow control screen 140 and the casing. The concentration of the sealing body particles carrying liquid is 5%, and the filling pressure is 6MPa. After the well is opened, the daily liquid production is 176 cubic meters / day, the daily oil production is 172 cubic meters / day, the water content is 2.3%, and the corresponding oil well production pressure difference is 3MPa. After 30 months of stable production, the water content gradually increased to 90%, and the corresponding oil well production pressure difference was reduced to 1MPa, with a daily liquid production of 200 cubic meters / day and a daily oil production of 20 cubic meters / day. After comprehensive analysis, it is necessary to take measures to increase liquid and stabilize production, and replace the flow control devices of different specifications for the flow control screen 140. The casing well using the water injection method of the present invention is easy to remove the flow control screen 140 from the well, the process is simple, and the operation is convenient (such as Fig.12 as shown).

[0088] The specific operations are as follows:

[0089] Unseal the lifting suspension packer (if any);

[0090] Inject water into the inner cavity of the base pipe of the flow control screen to return the particles of the packer from the annulus;

[0091] Remove the flow control screen;

[0092] Replace the flow control device of the flow control screen;

[0093] The flow control screen is re-run and the packer particles are re-packed.

[0094] After replacing the flow control device and refilling the packer particles, the corresponding oil well pressure difference reached 5MPa, the daily liquid production was 500 cubic meters / day, the daily oil production was 62 cubic meters / day, and the water content was reduced to 87%. The production data before and after replacing the flow control device are compared in the table below.

[0095]

[0096] Example 6 (Cased well using the water injection method of the present invention without a hanging packer at the top)

[0097] There is a water injection well in a certain oil field, and the water injection layer involves 20 wells. The well is completed by 7-inch casing perforation, and the water injection method of the present invention is used. A 3.5-inch flow control screen 140 is lowered into the casing, and the flow control screen 140 is directly suspended at the wellhead (no need to hang the packer). The first valve V1 and the second valve V2 are opened, and 40-70 mesh packer particles are filled into the annular space between the flow control screen and the casing through the first valve V1. The concentration of the packer particle carrying liquid is 5%, and the filling pressure is 6MPa. After the packer particle carrying liquid carries the packer particles into the first annular space, the packer particles are continuously accumulated and filled in the first annular space until the packer particles fill the entire first annular space (see Fig.13A portion of the liquid in the particle-carrying fluid of the packer enters the second annular space through the wall of the filter tube of the flow control screen 140, enters the inner cavity of the base pipe through the flow control device, and returns from the wellhead through the second valve V2, and another portion of the liquid in the particle-carrying fluid of the packer penetrates into the formation through the well wall.

[0098] During the water injection process, the first annular space is appropriately pressurized and the first valve V1 is closed. Water is injected from the second valve V2, which can better compact the particles of the packer to obtain a better separation effect. In the early stage of water injection, the injection pressure is 10 MPa and the water injection volume is 136 cubic meters / day; but after 3 years of water injection, when the water injection pressure increases to 20 MPa, the water injection volume is 80 cubic meters / day. After analysis, there may be blockage, and the water injection well needs to be unblocked.

[0099] The specific operations are as follows:

[0100] Open the first valve V1 and the second valve V2;

[0101] Inject water into the inner cavity of the base pipe of the flow control screen to flow back the packer particles, so that the impurities intercepted and accumulated at the pore throats between the packer particles are returned to the ground together with the packer particles through the first valve V1. The flow cross-sectional area of ​​the flow control device of the flow control screen located at the bottom of the injection well can be set to be larger than the flow cross-sectional area of ​​the flow control devices of other flow control screens. By making the flow control device at the bottom of the injection well have a larger flow cross-sectional area, it can be ensured that a larger water flow flows out of the flow control device at the bottom of the injection well when the packer particles are flowed back, so that the packer particles can be returned more thoroughly;

[0102] Replace the new 40-70 mesh packer particles and refill.

[0103] After the above measures, the water injection pressure was restored to 12 MPa, and the water injection volume was 150 cubic meters per day. The comparison of production data before and after unblocking is shown in the table below.

[0104]

[0105] Although the present invention has been described with reference to (one or more) exemplary embodiments, it will be understood by those skilled in the art that the present invention is not limited to the exact structure and components described herein, and that various modifications, changes and variations may be apparent from the foregoing description without departing from the spirit and scope of the present invention as defined in the appended claims. The present invention is not limited by the illustrated order of steps, as some steps may be performed in a different order and / or simultaneously with other steps. Therefore, the present invention is not limited to the specific (one or more) embodiments disclosed, but will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for operating a water injection well (100), the water injection well (100) comprising a wellhead (110) and a well wall (120) extending underground from the wellhead (110), the well wall (120) defining a well cavity (130), the method comprising: A flow control screen (140) is arranged in the wellbore (130), wherein the flow control screen (140) comprises: A hollow base pipe (150), the base pipe (150) comprising a fluid-impermeable wall (152), the wall (152) of the base pipe (150) defining a base pipe lumen (154); a hollow filter tube (160), the filter tube (160) comprising a fluid-permeable tube wall (162), the filter tube (160) being arranged around the outer side of the base tube (150) so that a first annular space (S1) is formed between the filter tube (160) and the well wall (120) and a second annular space (S2) is formed between the filter tube (160) and the base tube (150); and a flow control device (170), wherein the flow control device (170) has a flow cross-sectional area allowing a fluid to flow therethrough; and The first annular space (S1) is filled with a packing particle carrying fluid via the wellhead (110), the packing particle carrying fluid comprising packing particles (180) and a liquid for carrying the packing particles (180), a portion of the liquid enters the second annular space (S2) via the pipe wall (162) of the filter tube (160), enters the base pipe inner cavity (154) via the flow control device (170), and returns via the wellhead (110), another portion of the liquid penetrates into the formation via the well wall (120), the filter tube (160) blocks the packing particles (180), so that the packing particles (180) accumulate in the first annular space (S1).

2. The method according to claim 1, wherein: Placing the flow control screen (140) in the wellbore (130) includes arranging two or more flow control screens (140) connected end to end in the wellbore (130), so that each formation corresponds to one or more flow control screens (140).

3. The method according to claim 2, wherein: The flow cross-sectional areas of the flow control devices (170) of the flow control screen tubes (140) corresponding to the same formation are the same.

4. The method according to claim 2, wherein: The method further comprises: The flow cross-sectional area of ​​the flow control device (170) of the flow control screen (140) located at the bottom of the water injection well is set to be larger than the flow cross-sectional area of ​​the flow control device (170) of other flow control screens (140).

5. The method according to claim 4, wherein: The flow cross-sectional area of ​​the flow control device (170) of the flow control screen (140) located at the bottom of the water injection well is 1.1 to 5 times the flow cross-sectional area of ​​the flow control device (170) of other flow control screens (140).

6. The method according to claim 2, wherein: The method further comprises: The flow cross-sectional areas of the flow control devices (170) of at least two of the flow control screen tubes (140) are set to be different from each other.

7. The method according to claim 1, wherein: The water injection well (100) further comprises a first valve (V1) and a second valve (V2), wherein the first valve (V1) is used to open or close the fluid communication between the first annular space (S1) and the wellhead (110), and the second valve (V2) is used to open or close the fluid communication between the base pipe inner cavity (154) and the wellhead (110). The method further comprises: closing the first valve (V1) and opening the second valve (V2); and Water is injected into the inner cavity (154) of the base pipe via the second valve (V2), so that the water enters the first annular space (S1) via the flow control device (170), the second annular space (S2) and the filter tube (160).

8. The method according to claim 7, wherein: The method further comprises pressurizing the first annular space (S1) before closing the first valve (V1) and opening the second valve (V2).

9. The method according to claim 1, wherein: The water injection well (100) further comprises a first valve (V1) and a second valve (V2), wherein the first valve (V1) is used to open or close the fluid communication between the first annular space (S1) and the wellhead (110), and the second valve (V2) is used to open or close the fluid communication between the base pipe inner cavity (154) and the wellhead (110). The method further comprises: opening the first valve (V1) and opening the second valve (V2); and Water is injected into the inner cavity (154) of the base pipe through the second valve (V2), so that the water enters the first annular space (S1) through the flow control device (170), the second annular space (S2) and the filter tube (160), so as to disperse the sealing body particles (180) accumulated in the first annular space (S1), and make the sealing body particles (180) return to the ground through the first valve (V1).

10. The method according to claim 9, wherein: The method further comprises: opening the first valve (V1) and opening the second valve (V2); and The first annular space (S1) is refilled with the packer particle-carrying fluid via the first valve (V1).

11. The method according to claim 1, wherein: The method further comprises: A hanging packer (TP) is arranged around the flow control screen (140) at the top and is hung on the wellbore wall (120).

12. The method according to claim 1, wherein: The method further comprises: The flow cross-sectional area of ​​the flow control device (170) is adjusted.

13. The method according to claim 1, wherein: The method further comprises: The flow control device (170) is replaced with another flow control device (170) having a different flow cross-sectional area.

14. The method according to claim 1, wherein: The water injection well (100) further comprises a casing (190) arranged in the well cavity (130) and a cement ring (195) arranged between the casing (190) and the well wall (120), and wherein, arranging the flow control screen (140) in the well cavity (130) comprises arranging the flow control screen (140) in the casing (190), and filling the first annular space (S1) with a sealing body particle carrying fluid via the wellhead (110) comprises filling the annular space between the filter tube (160) and the casing (190) with a sealing body particle carrying fluid via the wellhead (110).

15. The method of claim 1, wherein: The water injection well (100) further comprises a casing (190) arranged in the well cavity (130), a cement ring (195) arranged between the casing (190) and the well wall (120), a flow control string arranged in the casing (190), and a mechanical packer arranged between the flow control string and the casing (190). The method further includes removing the mechanical packer and the flow control string from the wellbore (130) before placing the flow control screen (140) in the wellbore (130), and Disposing the flow control screen (140) in the wellbore (130) includes disposing the flow control screen (140) in the casing (190).

16. The method according to claim 1, wherein: The tube wall (162) of the filter tube (160) has a pore size, and the packing body particles (180) have a particle size, and the pore size is greater than or equal to 1 / 2 of the particle size and less than or equal to 2 / 3 of the particle size.

17. A water injection well (100), comprising: wellhead(110); A well wall (120), the well wall (120) extending from the well head (110) toward the underground, the well wall (120) defining a well cavity (130); A flow control screen (140), wherein the flow control screen (140) is disposed in the wellbore (130), and the flow control screen (140) comprises: A hollow base pipe (150), the base pipe (150) comprising a fluid-impermeable wall (152), the wall (152) of the base pipe (150) defining a base pipe lumen (154); a hollow filter tube (160), the filter tube (160) comprising a tube wall (162) permeable to fluid, the filter tube (160) being arranged around the outer side of the base tube (150) so that a first annular space (S1) is formed between the filter tube (160) and the well wall (120) and a second annular space (S2) is formed between the filter tube (160) and the base tube (150); and a flow control device (170), wherein the flow control device (170) has a flow cross-sectional area allowing a fluid to flow therethrough; and Packer particles (180), the packer particles (180) are filled in the first annular space (S1).

18. The water injection well (100) according to claim 17, wherein: The water injection well (100) comprises two or more flow control screens (140) connected end to end, and the two or more flow control screens (140) are arranged in the well cavity (130) so that each formation corresponds to one or more flow control screens (140).

19. The water injection well (100) according to claim 18, wherein: The flow cross-sectional areas of the flow control devices (170) of the flow control screen tubes (140) corresponding to the same formation are the same.

20. The water injection well (100) according to claim 18, wherein: The flow cross-sectional area of ​​the flow control device (170) of the flow control screen (140) located at the bottom of the water injection well (100) is greater than the flow cross-sectional area of ​​the flow control device (170) of other flow control screens (140).

21. The water injection well (100) according to claim 20, wherein: The flow cross-sectional area of ​​the flow control device (170) of the flow control screen (140) located at the bottom of the water injection well is 1.1 to 5 times the flow cross-sectional area of ​​the flow control device (170) of other flow control screens (140).

22. The water injection well (100) according to claim 18, wherein: The flow cross-sectional areas of at least two flow control devices (170) in the flow control screen tubes (140) are different from each other.

23. The water injection well (100) according to claim 17, wherein: The water injection well (100) further comprises a casing (190) disposed in the well cavity (130) and a cement ring (195) disposed between the casing (190) and the well wall (120). The flow control screen (140) is disposed in the casing (190), and The packer particles (180) are filled in the annular space between the filter tube (160) and the casing (190).

24. The water injection well (100) according to claim 17, wherein: The tube wall (162) of the filter tube (160) has a pore size, and the packing body particles (180) have a particle size, and the pore size is greater than or equal to 1 / 2 of the particle size and less than or equal to 2 / 3 of the particle size.

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