A method for injecting a solution into an oil well using a pipe string

Abstract

The present invention discloses an oil well injection string and a solution injection throughput method. The oil well injection string comprises: an oil pipe and a casing, an oil discharge pipe is arranged at the top of the oil pipe, an injection pipe is arranged at the top of the oil casing annulus space formed between the oil pipe and the casing, a high-pressure sealing device is arranged at the wellhead of the oil pipe, and a flow control valve is arranged at the end of the downhole string of the oil pipe. The present invention can realize high-frequency intermittent injection and production in the same well, increase the frequency of the solution and the formation crude oil, improve the oil production efficiency of a single throughput cycle, and also reduce the construction period between the throughput processes, thereby improving the oil production speed.

Description

Technical Field

[0001] The present invention relates to an oil well injection pipe string and an injection solution throughput method, belonging to the technical field of oil field development. Background Art

[0002] The huff and puff technology for oil production is usually based on gas medium (water vapor). Steam huff and puff is a method of increasing the production of heavy oil by first injecting a certain amount of steam into the oil well, shutting the well for a period of time, and then opening the well for production after the heat energy of the steam diffuses into the oil layer. The process of steam huff and puff operation can be divided into three stages, namely steam injection, well shut-in and recovery. The steam huff and puff method is the most commonly used method in heavy oil production and is also the best thermal recovery method for industrial application. Steam huff and puff is also called steam stimulation or cyclic steam injection. Steam huff and puff mainly utilizes the strong compression / expansion performance of gas, and its effect is good, but the production cost is high and the investment cost of gas injection equipment is large.

[0003] Compared with gas injection and huff-and-puff technology, the development effect of solution injection and huff-and-puff technology is relatively poor. However, due to its low cost and simple operation, it is the best development method for specific oil reservoirs. Therefore, this technology has a certain scope of application.

[0004] Solution injection huff-and-puff technology is mainly used in oil reservoirs that cannot replenish energy. The corresponding relationship between oil and water wells in this reservoir cannot be established due to the complex relationship between oil layers. The solution can have certain functionality. For example, for heavy oil, a solution with viscosity reduction function can be selected.

[0005] Solution injection and huff-and-puff technology is to inject solution into the oil well, shut down the well for a period of time, and then pump out oil for production, using the partial pressure increased by the injected solution and the oil-carrying capacity of the solution to obtain a larger output. As shown in Figure 1, the fluid injected and produced in the latter time basically has to pass through the path of the previous fluid. As the number of times increases, the efficiency of the new production gradually decreases. Summary of the invention

[0006] In view of the technical defects and technical drawbacks in the prior art, the embodiments of the present invention provide an oil well injection string and injection solution throughput method that overcomes the above problems or at least partially solves the above problems.

[0007] An embodiment of the present invention provides a high-pressure sealing device, comprising: an outer cylinder, and a telescopic sealing bag and a positioning ring sleeved inside the outer cylinder;

[0008] The outer cylinder is annular and can be sleeved on the polished rod, and a support platform is provided at the bottom;

[0009] The positioning ring is placed on the top of the telescopic sealing bag to position and fix the telescopic sealing bag;

[0010] The telescopic sealing bag is annular and is placed on the support platform. In the extended state, it is in close contact with the polished rod to achieve sealing, and in the contracted state, it is not in contact with the polished rod to release the sealing.

[0011] Another embodiment of the present invention provides a flow control valve, comprising: a control valve part and a power part;

[0012] The control valve part includes: a valve body, a valve ball and a gear set; the valve ball and the gear set are arranged in the valve body, and a channel for liquid to flow through is opened in the valve ball;

[0013] The power part comprises: a housing and fan blades; the housing is annular and surrounds the valve body, and the fan blades are arranged in the housing;

[0014] The gear set is meshed with the valve ball shaft of the valve ball and the fan blade shaft of the fan blade respectively;

[0015] When the fan blade rotates in one direction under the impact of liquid, it drives the gear set to rotate the valve ball to close the channel; when it rotates in the other direction, it drives the gear set to rotate the valve ball to open the channel.

[0016] Another embodiment of the present invention provides an oil well injection string, comprising: an oil pipe and a casing, an oil discharge pipe is arranged at the top of the oil pipe, and an injection pipe is arranged at the top of the oil casing annulus space formed between the oil pipe and the casing, wherein:

[0017] The above-mentioned high-pressure sealing device is arranged at the wellhead of the oil pipe, and the above-mentioned flow direction control valve is arranged at the end of the downhole pipe string of the oil pipe.

[0018] Another embodiment of the present invention provides a method for injecting solution based on the above-mentioned oil well injection using a tubing string, comprising:

[0019] Sealing the oil pipe by the high pressure sealing device;

[0020] Injecting a solution into the oil sleeve annulus space through the injection pipe to close the flow direction control valve;

[0021] When the injection pressure reaches a first threshold, the solution is discharged through the injection pipe until the injection pressure drops to a second threshold, so that the flow direction control valve is opened;

[0022] releasing the seal of the oil pipe by the high-pressure sealing device;

[0023] Extracting liquid from the oil pipe and discharging it through the oil extraction pipe;

[0024] Repeat the above process until the predetermined injection and production frequency is reached.

[0025] The embodiments of the present invention achieve at least the following technical effects: it can realize high-frequency intermittent injection and production in the same well, increase the frequency of interaction between the solution and the formation crude oil, improve the oil production efficiency of a single throughput cycle, and also reduce the construction period between the throughput processes, thereby increasing the oil production speed.

[0026] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structure described in the written description, claims, and drawings.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] FIG1 (a) is a cross-sectional view of a conventional oil well solution injection injection, and (b) is a cross-sectional view of an oil reservoir;

[0030] Figure 2 A schematic diagram of the structure of a pipe string for oil well injection provided by an embodiment of the present invention;

[0031] FIG3 (a) shows an unsealed state of the high-pressure sealing device, and (b) shows a sealed state;

[0032] FIG. 4 (a) shows a longitudinal cross-sectional view of the telescopic sealing bag, and (b) shows a top view;

[0033] FIG5 (a) shows a longitudinal cross-sectional view of the outer cylinder 31, and (b) shows a top view;

[0034] Figure 6 A schematic diagram of the installation of a flow direction control valve provided by an embodiment of the present invention;

[0035] FIG. 7 (a) shows a longitudinal cross-sectional view of the flow control valve, and (b) shows a top view;

[0036] Figure 8 A flow chart of a method for injecting solution throughput provided by an embodiment of the present invention;

[0037] (a) in FIG. 9 shows a structure for producing an oil pump, and (b) shows a structure for producing a screw pump. DETAILED DESCRIPTION

[0038] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0039] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0040] First, the technical terms of the present invention are briefly introduced:

[0041] Original energy of oil reservoir: refers to the energy of oil reservoir before it is developed. This original energy is a part of the composition of oil reservoir, and is the condition and basis for oil reservoir development, thus becoming another key point in oil reservoir description. Original energy of oil reservoir can be evaluated by oil reservoir energy index. The strength of oil reservoir energy refers to the difficulty of oil reservoir fluid flowing into the wellbore. The easier the flow, the stronger the oil reservoir energy; otherwise, the weaker it is.

[0042] Shaft: refers to a type of vertical or inclined project excavated from the ground to the ore body in underground mining or underground engineering construction. Vertical projects are called vertical shafts, and inclined projects are called inclined shafts. The shaft is the main entrance and exit of the mine to the ground. It is the throat project for lifting and transporting coal (or gangue), transporting personnel, materials and equipment, and ventilation and drainage during mine production.

[0043] Oil-water well: refers to the oil production well or water injection well in the oil field. The water injection well is used to inject water into the oil layer. During the development of the oil field, 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.

[0044] Dynamic seal: refers to the seal between relatively moving parts.

[0045] Static seal: refers to the seal between two stationary surfaces.

[0046] Packing box: When using a pumping unit for production, it is a dynamic sealing device for the wellhead used to seal the annular space between the oil pipe and the polished rod. It uses multi-stage sealing, has good sealing effect and is resistant to high pressure. At the same time, due to the design of a universal joint to adjust the eccentricity and angle, it is particularly suitable for oil wells with deviated wellheads.

[0047] Sealing box: A device used to seal the wellhead when a screw pump is used for production.

[0048] The present embodiment provides a tubing string for oil well injection, as shown in FIG1 , comprising: an oil pipe 10 and a casing 20, an oil discharge pipe 11 is arranged at the top of the oil pipe 10, an oil casing annulus space is formed between the oil pipe 10 and the casing 20, and an injection pipe 21 is arranged at the top of the oil casing annulus.

[0049] A high-pressure sealing device 30 is provided at the wellhead of the oil pipe 10, and a flow control valve 40 is provided at the end of the downhole pipe string of the oil pipe 10. Specifically, the high-pressure sealing device 30 can be provided below the oil pipe sealing component 60 at the top of the oil pipe 10. As shown in FIG. 9(a) described later, when a pumping unit is used for production, the oil pipe sealing component 60 is specifically a packing box; as shown in FIG. 9(b) described later, when a screw pump is used for production, the oil pipe sealing component 60 is specifically a sealing box.

[0050] The specific structure of the high pressure sealing device 30 and the flow direction control valve 40 is described in detail below in conjunction with the accompanying drawings:

[0051] As shown in FIG3 , the high-pressure sealing device 30 includes: an outer tube 31, and a telescopic sealing bag 32 and a positioning ring 33 sleeved inside the outer tube 31. The outer tube 31 is annular and can be sleeved on the oil pumping rod shaft component 50. As shown in FIG9(a) described later, when a pumping unit is used for production, the oil pumping rod shaft component 50 is a bare rod; when a screw pump is used for production, the oil pumping rod shaft component 50 is a smooth shaft. In order to simplify the space, the following description takes the bare rod 50 as an example, and the description is also applicable to the case of a smooth shaft, and no additional elaboration is given.

[0052] A support platform 34 is provided at the bottom of the outer cylinder 31, and the telescopic sealing bag 32 is annular and placed on the support platform 34. The positioning ring 33 is placed on the top of the telescopic sealing bag 32 to position and fix the telescopic sealing bag 32. The telescopic sealing bag 32 is in close contact with the polished rod 50 in the extended state to achieve sealing, and is not in contact with the polished rod 50 in the contracted state to release the sealing.

[0053] Specifically, in order to achieve the expansion and contraction of the telescopic sealing bag 32, a through hole 35 is opened on the side wall of the outer tube 31 at a position corresponding to the telescopic sealing bag 32. The telescopic sealing bag 32 is expanded and contracted by injecting or discharging expansion liquid into or out of the telescopic sealing bag 32 through the through hole 35.

[0054] Optionally, there may be multiple telescopic sealing capsules 32, which are spaced apart from each other by spacer rings 36. Accordingly, each telescopic sealing capsule 32 corresponds to a through hole 35, and the positioning ring 33 is placed on the top of the telescopic sealing capsule 32 located at the top. The diameter of the middle hole of the spacer ring 36 and the positioning ring 33 is preferably larger than the diameter of the polished rod 50 by 4 to 6 mm, which can ensure that there is no contact with the polished rod 50 to cause scratches, and can also maintain effective support for the telescopic sealing capsule 32.

[0055] As shown in FIG. 4 , it is a schematic diagram of the specific structure of the telescopic sealing bag 32 , wherein FIG. 4 (a) shows a longitudinal cross-sectional view of the telescopic sealing bag 32 , and FIG. 4 (b) shows a top view of the telescopic sealing bag 32 ,

[0056] The optional material of the telescopic sealing bag 32 is rubber, which has good wear resistance and certain elasticity, and the thickness is not less than 2mm. As shown in the figure, the telescopic sealing bag 32 is annular, and the two end surfaces have a corrugated structure, and the corrugated surface is formed on both sides of the flat surface, and the axial telescopic distance range is ±5mm. The outside of the telescopic sealing bag 32 is connected to the expansion liquid delivery pipe 47, which extends out from the through hole 35 on the side of the outer tube 31.

[0057] The expansion liquid is, for example, lubricating oil. After being injected, the telescopic sealing bag 32 expands, stretches in the axial direction and comes into close contact with the polished rod 50. The pressure is continuously increased to the designed pressure difference, and the sealing operation is completed, as shown in FIG3(b). When sealing is no longer required and the upward and downward movement of the polished rod 50 is not affected, the lubricating oil inside the telescopic sealing bag 32 is discharged by the expansion liquid delivery pipe 47, and sucked by a vacuum pump, so that the telescopic sealing bag 32 is in a contracted state, as shown in FIG3(a).

[0058] As shown in FIG. 5 , it is a schematic diagram of the specific structure of the outer cylinder 31 , wherein FIG. 5 ( a ) shows a longitudinal cross-sectional view of the outer cylinder 31 , and FIG. 5 ( b ) shows a top view of the outer cylinder 31 .

[0059] The outer cylinder 31 can be made of stainless steel, with a smooth inner wall, which is conducive to improving the sealing performance of the telescopic sealing bag 32. The two ends of the outer cylinder 31 are inner threaded tapered interfaces, the lower part is connected to the oil pipe 10, and the upper part is connected to the oil pipe sealing component (packing box or sealing box). There is a support platform 34 at the bottom of the outer cylinder 31, on which the first telescopic sealing bag 32 is placed, and a spacer ring 36 is placed on it. The second sealing bag 32 is rotated, and a positioning ring 33 is placed on the top, so that the working space of the telescopic sealing bag 32 meets the design requirements.

[0060] FIG7(a) shows a longitudinal cross-sectional view of the flow control valve, and FIG7(b) shows a top view. As shown in FIG7 , the flow control valve 40 includes: a control valve part and a power part. The control valve part includes: a valve body 41, a valve ball 42 and a gear set 43; the power part includes: a housing 44 and a fan blade 45.

[0061] The valve ball 42 and the gear set 43 are arranged in the valve body 41. The valve ball 42 is provided with a channel 46 for liquid to flow through. Specifically, the valve ball 42 can be arranged in the valve body 41 through a support bearing 48. The housing 44 is annular and surrounds the valve body 41. The fan blade 45 is arranged in the housing 44. The gear set 43 is respectively meshed with the valve ball shaft 47 of the valve ball 42 and the fan blade shaft (not shown in the figure) of the fan blade 45.

[0062] Specifically, the top of the valve body 41 may be provided with an upper joint 49 for connecting with the oil pipe 10. Figure 6 As shown, the flow control valve 40 is connected to the end of the downhole tubing of the oil pipe 10 through the upper joint 49, so that the flow control valve 40 is installed on the oil pipe 10. The diameter of the housing 44 is larger than that of the oil pipe 10, so that when the valve body 41 is installed on the oil pipe 10, the fan blade 45 can be exposed outside the radial range of the oil pipe 10.

[0063] During operation, the fan blade 45 rotates in one direction under the impact of liquid, driving the gear set 43 to rotate the valve ball 42 to close the channel 46; when rotating in the other direction, driving the gear set 43 to rotate the valve ball 42 to open the channel 46.

[0064] The flow direction control valve 40 is used in conjunction with the high-pressure sealing device 30 to more accurately control the flow direction of the fluid.

[0065] When the flow control valve 40 is not used in the prior art, during the process of injecting the solution, the solution not only enters the oil layer but also enters the oil pipe 10, and enters the oil pipe 10 and the sucker rod annulus in the reverse direction along the oil pump. The pressure is the same as the injection pressure, and the high-pressure sealing device 30 assumes all the pressure-resistant sealing functions.

[0066] When the flow control valve 40 is used in this embodiment, during the process of injecting the solution, the flow control valve 40 is closed, and the solution only enters the oil layer, and the high-pressure sealing device 30 hardly plays a pressure-resistant sealing role. In the production stage, the flow control valve 40 is opened, and the fluid flowing out of the formation can enter the oil pipe 10. In the case where the formation is prone to sand or has blockages, the flow control valve 40 can reduce the blockage of the oil pump inlet.

[0067] If the high pressure sealing device 30 fails, the downhole fluid can also be controlled downhole through the flow control valve 40.

[0068] In conjunction with the accompanying drawings, an embodiment of a method for injecting solution using a tubing string in an oil well with a high pressure sealing device 30 and a flow control valve 40 is described below. Figure 8 As shown, the method comprises the following steps:

[0069] Step 100 , sealing the oil pipe 10 by using the high pressure sealing device 30 .

[0070] As shown in Fig. 5, the expansion liquid is injected into the telescopic sealing bag 32 through the through hole 35 of the high-pressure sealing device 30, so that the telescopic sealing bag 32 is stretched until it is in close contact with the polished rod 50, thereby sealing the oil pipe 10. The telescopic sealing bag 32 is in close contact with the polished rod 50 under the support of the internal liquid, realizing annular surface sealing, and the pressure difference can reach more than 10MPa, thereby being able to withstand the high pressure during the solution injection process, so that the internal and external pressure difference of the oil pump or the screw pump is in a balanced state.

[0071] In contrast, if only existing oil pipe sealing components (packing box or sealing box) are used to achieve sealing, the effective pressure of the seal under dynamic sealing conditions is no more than 1MPa; the effective pressure under static sealing conditions is no more than 3Mpa, which cannot withstand the high pressure of the solution injection process.

[0072] Step 200, inject solution into the oil sleeve annulus space through the injection pipe to close the flow control valve 40.

[0073] Specifically, the pre-fluid and displacement fluid may be injected in sequence. The pre-fluid usually has special functions, such as viscosity reduction, solubilization, etc.; the displacement fluid is usually formation water or injection water.

[0074] As described above, when the solution is injected into the annular space of the oil sleeve, the fan blade 45 is impacted downward by the solution, causing the fan blade 45 to rotate counterclockwise, driving the gear set 43 to rotate the valve ball 42, and after closing the channel 46, the gear set 43 limits the fan blade 45 to stop rotating further, thereby closing the flow control valve 40. At this time, the solution will only enter the oil layer, but not the oil pipe 10.

[0075] Step 300, when the injection pressure reaches a first threshold, the solution is discharged through the injection pipe until the injection pressure drops to a second threshold, so that the flow control valve is opened.

[0076] This step is a pressure relief process. The first threshold is, for example, 10 MPa, and the second threshold is, for example, 3 MPa. When the oil layer fluid is discharged through the oil sleeve annulus space to relieve pressure, the fan blade 45 is impacted upward by the fluid, and the fan blade 45 rotates clockwise, driving the gear set 43 to rotate the valve ball 42, opening the channel 46, and the gear set 43 limits the fan blade 45 to stop rotating, thereby opening the flow control valve 40.

[0077] Step 400 , releasing the seal of the oil pipe by the high pressure sealing device 30 .

[0078] As shown in Fig. 3, the expansion liquid in the telescopic sealing bag can be discharged through the through hole 35, so that the telescopic sealing bag 32 shrinks and leaves the polished rod, thereby releasing the seal of the oil pipe. When the telescopic sealing bag 32 shrinks, a gap is maintained with the polished rod 50 without friction, and the normal operation of the packing box or the sealing box above is not affected.

[0079] Step 500, extract liquid from the oil pipe 10 and discharge it through the oil extraction pipe.

[0080] Specifically, the oil pump extracts liquid from the oil pipe 10. When the oil pump is working, the fan blade 45 is always impacted upward by the fluid, so the flow control valve 40 is always in an open state. This design avoids construction problems such as cable laying of the electric control valve.

[0081] The above process is repeated until a predetermined injection and extraction frequency is reached, for example, 3 injection and extraction frequencies.

[0082] The following example illustrates the specific implementation process of the injection solution throughput method of the present invention.

[0083] (1) Install the equipment

[0084] The initial installation requires the oil well string to be lifted and lowered. After the oil well injection string is installed, connect the high-pressure pump truck and related injection solution and other supporting equipment at the wellhead casing valve. Figure 2

[0085] (2) High-pressure sealing device implements sealing

[0086] Add lubricating oil to the two injection pipes, connect the external pipeline to the injection pipe, and form a seal with the outer cylinder. When the pressure shows 17MPa, stop filling and observe the pressure change. If it remains stable, it means that the high-pressure sealing device has entered the working state.

[0087] (3) Inject the solution and close the flow control valve

[0088] In this case, the first round of pre-fluid throughput is 20m 3 , displacement fluid 40m 3 .

[0089] The solution is continuously injected into the oil-casing annulus space, with no interval between the pre-fluid and the displacement fluid. The solution has a large drop in the oil-casing annulus space at the beginning and has strong kinetic energy; it still maintains 30m after entering the formation. 3 / d flow rate. Under the impact of this flow rate, the blades flowing to the control valve rotate counterclockwise and close the control valve, preventing the solution from entering the oil pipe.

[0090] After the injection is completed, observe the injection pressure changes. If the pressure decreases slowly, it means that the formation absorption state is saturated. If the pressure decreases quickly, it means that the formation energy has not been fully replenished, which provides a reference for the next throughput design.

[0091] (4) High-frequency intermittent injection and production in the first throughput cycle

[0092] In the prior art, after the solution is injected, the well is shut down and the injection pressure is waited to drop to about 3MPa before the tubing string can be pulled in and out. However, the present method eliminates the well shut down operation. After the solution is injected, repeated injection and production operations are started, i.e., high-frequency intermittent injection and production.

[0093] Assume that the injection pressure after the solution is injected is 10MPa, change the injection direction at the wellhead, and discharge the liquid from the casing valve to the liquid storage tank of the high-pressure pump truck. When discharging the liquid, the blades of the flow control valve downhole rotate clockwise and open the flow control valve to allow part of the solution to enter the tubing. When the casing discharge pressure reaches 3MPa, close the flow control valve and stop discharging. Open the injection pipe valve of the high-pressure sealing device to relieve the pressure. When it is lower than 3MPa, suction is performed to shrink the sealing bag and prevent it from contacting the polished rod.

[0094] When the pumping unit is turned on, the oil-free solution pumped out can enter the pump truck. When the pumped liquid contains oil, the pumping unit is turned off or the liquid enters the production pipeline. The structure of the production using the pumping unit is shown in Figure 9(a), and the structure of the production using the screw pump is shown in Figure 9(b).

[0095] When the total discharge volume reaches 40m 3 , it enters the next injection phase of this throughput round.

[0096] Repeat steps (2) to (4) until the designed frequency is completed, for example, 3 injection and production frequencies. As the throughput cycle is extended, the injection and production frequency gradually decreases.

[0097] (5) The oil pump is working and production continues

[0098] After completing the designed injection and production frequency, it has entered the normal production state. Do a good job in production dynamic monitoring, judge the effectiveness of this method based on the changes in water content of the output fluid, cumulative oil production and other information, and formulate the next work plan.

[0099] (6) Implementing the Second Throughput Cycle

[0100] When the oil well production drops to the designed level, the second throughput plan is implemented. The steps refer to the relevant operations in (1) to (5), and there is no need to trip the pipe string.

[0101] In the existing solution injection and huff-and-puff technology, the tubing in the oil well is first pulled out, and the solution (including functional solvent) is injected into the formation along the oil pipe or the oil / casing annulus space by a high-pressure pump truck until the injection pressure is increased to Pin, and then the well is shut down. When the pressure drops to Pou, a certain amount of liquid is discharged from the injection port, and then the pumping construction is carried out. After the pumping unit or screw pump is installed, mechanical oil production is carried out. It usually takes at least 10 days to shut down the well, mainly to wait for the injection pressure to drop to a recoverable level. When the pressure is higher than Pou, the seal between the packing box of the pumping unit and the bare rod, and the seal box of the screw pump and the motor shaft will fail, resulting in leakage, puncture leakage and even uncontrolled liquid spraying.

[0102] The oil well injection pipe provided by the embodiment of the present invention realizes high-pressure sealing by setting a high-pressure sealing device in the pipe string, which can not only shorten the soaking time, but also eliminate the need to remove components such as the oil pump in the oil well. That is, after the solution is injected into the oil casing annulus, the oil pump can be started at any time. Therefore, the present invention has the following advantages:

[0103] 1. The high-frequency intermittent injection and production method in the same well has been realized, so that the functional solution can interact with the formation crude oil at a high frequency during a huff-and-puff process, changing the one-time contact into a controllable number of reciprocating contacts, and the oil production efficiency of a single huff-and-puff cycle has been increased by more than 2 times;

[0104] 2. It makes the high-frequency intermittent injection and production method in the same well easier to implement, reduces the construction period between the throughput process, improves the oil production rate, and significantly reduces the production cost. The existing technology requires the operation of pulling in and out the pipe string when the throughput pressure is high, and the construction period and waiting time for pressure recovery are at least 1 month;

[0105] 3. The application efficiency and production-increasing effect of solution injection throughput technology have been improved, so that the technology can be promoted and applied in complex small fault blocks, poor oil quality / pressure-incompensable reservoirs, etc.

[0106] The technical effects of the present invention are further illustrated by comparative experiments below.

[0107] When injecting solution, the compressibility of the solution is basically the same as that of water, ranging from 4.0 to 5.0×10 -4 MPa -1 In the range (temperature 20°~120°, pressure 7~42MPa). According to the isothermal compressibility formula (1):

[0108]

[0109] Among them, the isothermal compression coefficient refers to the volume change rate of gas with pressure change under isothermal conditions. When the pressure difference is estimated to be 10MPa, the volume compression of the solution is less than 1%, that is, the liquid has a weak ability to store energy, and the pressure difference mainly serves to push the liquid in the reservoir. The kinetic energy released by the liquid storage energy when the pressure difference decreases is also very low. Therefore, the injection solution throughput method is basically to inject a certain amount of liquid and then produce an equal amount of crude oil by using the injected solution to react with the crude oil in the pores. And with the increase in the number of throughput rounds, the action distance becomes farther and farther, and the invalid flow time becomes longer and longer.

[0110] Taking a well as an example of solution huff and puff, the well depth is 1000m, the oil layer thickness is 5m, the effective reserve radius is 50m, the porosity is 30%, and the oil saturation in the newly affected pores is 70%. The oil reserves Qt can be calculated to be 8242m 3 The highest injection pressure at the wellhead is 15MPa. After the wellhead pressure reaches 3MPa after shut-in, oil is pumped out for production.

[0111] The calculation results are shown in Table 1:

[0112] Table 1 Parameter analysis of existing injection solution injection technology

[0113]

[0114] From the data, it can be seen that when the existing technology is used to perform injection solution huff and puff, as the number of huff and puff increases, the efficiency of a single huff and puff decreases rapidly, and the construction time is prolonged. The recovery factor after 4 huff and puff in Table 1 is only 8%.

[0115] In contrast, the injection solution throughput technology provided by the present invention limits the single oil production efficiency, but can significantly improve the single oil production efficiency by accelerating the frequency of the solution and crude oil reaction, that is, after the injected fluid reaches a predetermined pressure, the pressure is relieved and then pressurized, so that the front edge of the injected solution (functional solution part) contacts the high-saturation crude oil for many times, and at the same time, the fluid in the overall flow channel pores involved in the injected fluid also reciprocates, enhancing the oil film stripping effect. Thus, the effect of significantly increasing production can be achieved within one throughput cycle.

[0116] According to the principles of the present invention, the calculation results of the above example are shown in Table 2:

[0117] Table 2 Parameter analysis of injection solution throughput technology of the present invention

[0118]

[0119] It can be seen from the above data shown in Table 2 that when the injection solution throughput technology of the present invention is adopted, the single throughput efficiency is greatly improved, the recovery factor after 4 throughputs is increased to 15%, and the construction time of tripping and running the pipe string and the well soaking time are saved.

[0120] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0121] The present invention is described with reference to the flowchart and / or block diagram of the method, device (system), and computer program product according to the embodiment of the present invention. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the process and / or box in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0122] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0123] These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An oil well injection string, comprising: The oil pipe and the casing, the top of the oil pipe is provided with an oil drain pipe, and the top of the oil-casing annular space formed between the oil pipe and the casing is provided with a liquid injection pipe, characterized in that: A high-pressure sealing device is provided at the wellhead of the oil pipe, and the high-pressure sealing device comprises: an outer tube, a telescopic sealing bag and a positioning ring sleeved inside the outer tube; the outer tube is annular and can be sleeved on a polished rod, and a support platform is provided at the bottom; the positioning ring is placed on the top of the telescopic sealing bag to position and fix the telescopic sealing bag; the telescopic sealing bag is annular and placed on the support platform, and is in close contact with the polished rod in an extended state to achieve sealing, and is not in contact with the polished rod in a contracted state to release the sealing; A flow control valve is provided at the end of the downhole tubular column of the oil pipe, and the flow control valve comprises: a control valve part and a power part; The control valve part comprises: a valve body, a valve ball and a gear set; the valve ball and the gear set are arranged in the valve body, and a channel for liquid to flow through is opened in the valve ball; The power part comprises: a housing and fan blades; the housing is annular and surrounds the valve body, and the fan blades are arranged in the housing; The gear set is meshed with the valve ball shaft of the valve ball and the fan blade shaft of the fan blade respectively; When the fan blade rotates in one direction under the impact of liquid, it drives the gear set to rotate the valve ball to close the channel; when it rotates in the other direction, it drives the gear set to rotate the valve ball to open the channel.

2. The oil well injection string according to claim 1, characterized in that: The valve ball is arranged in the valve body via a support bearing.

3. The oil well injection string according to claim 1, characterized in that: An upper joint for connecting with an oil pipe is arranged on the top of the valve body.

4. The oil well injection string according to claim 1, characterized in that: The high-pressure sealing device is arranged below the oil pipe sealing component at the top of the oil pipe, and the outer cylinder of the high-pressure sealing device is sleeved on the oil pumping rod shaft component penetrating the oil pipe sealing component.

5. The oil well injection string according to claim 1, characterized in that: The upper joint of the flow direction control valve is connected to the end of the downhole tubing string of the oil pipe.

6. The oil well injection string according to claim 1, characterized in that: A through hole is provided on the side wall of the outer tube at a position corresponding to the telescopic sealing bag, and the telescopic sealing bag is expanded and contracted by injecting or discharging expansion liquid into or out of the telescopic sealing bag through the through hole.

7. The oil well injection string according to claim 1, characterized in that: There are a plurality of telescopic sealing bags, which are spaced apart from each other by spacer rings.

8. The oil well injection string according to claim 1, characterized in that: Both end surfaces of the telescopic sealing bag have a corrugated structure.

9. A method for injecting solution using a tubing string for oil well injection according to any one of claims 1 to 8, characterized in that: include: Sealing the oil pipe by the high pressure sealing device; Injecting a solution into the oil sleeve annulus space through the injection pipe to close the flow direction control valve; When the injection pressure reaches a first threshold, the solution is discharged through the injection pipe until the injection pressure drops to a second threshold, so that the flow direction control valve is opened; releasing the seal of the oil pipe by the high-pressure sealing device; Extracting liquid from the oil pipe and discharging it through the oil extraction pipe; Repeat the above process until the predetermined injection and production frequency is reached.

10. The method according to claim 9, characterized in that The sealing of the oil pipe by the high-pressure sealing device includes: injecting expansion liquid into the interior of the telescopic sealing bag through the through hole of the oil well injection string, so that the telescopic sealing bag is expanded until it is in close contact with the pumping rod shaft component of the oil well injection string, thereby sealing the oil pipe.

11. The method according to claim 9, characterized in that The injecting of solution into the oil casing annulus includes: injecting a pre-fluid and a displacement fluid in sequence.

12. The method according to claim 9, characterized in that Closing the flow control valve includes: injecting a solution into the oil sleeve annulus space to cause the blades in the flow control valve to rotate in one direction so as to close the passage in the valve ball.

13. The method according to claim 9, characterized in that The step of opening the flow direction control valve comprises: the solution discharged through the injection pipe causes the fan blades in the flow direction control valve to rotate in another direction so as to open the channel in the valve ball.

14. The method according to claim 9, characterized in that The method of releasing the seal of the oil pipe by the high-pressure sealing device includes: discharging the expansion liquid inside the telescopic sealing bag through the through hole of the oil well injection string, causing the telescopic sealing bag to shrink and leave the pumping rod shaft component of the oil well injection string, thereby releasing the seal of the oil pipe.

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