Under-pump immovable string flushing sand control screen string and well flushing method and device for oil and gas exploitation

Abstract

The invention belongs to the technical field of oil and gas exploitation, and particularly discloses an under-pump immovable pipe column washing sand control screen pipe column, a well washing method and a device for oil and gas exploitation, the under-pump immovable pipe column washing sand control screen pipe column comprises at least one section of sand control screen pipe, and each section of sand control screen pipe comprises an upper connector, a lower connector and a lower connector; the central pipe is connected with the upper joint; the lower joint is connected with the central pipe; and the spring type filtering structure is arranged in the central pipe, and the spring type filtering structure is configured to filter part of stratum sand carried by output liquid entering the sand control screen pipe from the lower connector in the production process and deform under the pressure effect in the well washing process to remove the stratum sand blocking the spring type filtering structure. During well flushing, the sucker rod is lifted upwards, the plunger is lifted out of the pump cylinder, then flushing fluid is pumped into the oil sleeve annulus from the ground, the spring type filtering structure is lengthened under the pressure effect, the overflowing gap is enlarged, blockages are backwashed out of the ground, and the sand control screen does not need to be pulled out of the ground.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas production, and relates to a sand control screen pipe under the pump, in particular to a sand control screen pipe string and a well flushing method without moving the pipe string under the pump, as well as a device for oil and gas production, which is applicable to various wells producing heavy oil or light oil with sand production. Background Art

[0002] Most of the reservoirs in Liaohe Oilfield are unconsolidated sandstone oil and gas reservoirs, and the sand production problem is serious. Necessary sand control measures must be taken during the production process. The screen pipe sand control technology, as a simple and effective sand control method, has been widely used. The sand control process of the screen pipe is divided into two levels of sand control. The first level is the sand control screen pipe in the oil layer part, and the second level is the sand control of the sand filtration pipe under the pump.

[0003] According to different sand control precisions of the screen pipe, the particle size of the formation sand that can be blocked is also different. There are the following contradictions under the initial complete sand control concept: If the sand control precision of the screen pipe is too high, that is, the sand control particle size of the screen pipe is too small, fine sand can be blocked, but the screen pipe is easily blocked; if the sand control precision of the screen pipe is reduced, that is, the sand control particle size of the screen pipe is larger, only medium and coarse sand can be blocked, and fine sand cannot be blocked. With the progress of the sand control concept, the sand control technology has also changed from the initial complete sand control to moderate sand control. That is, in the case of the formation produced sand particle size becoming smaller and smaller in the later stage of development, and even a large amount of fine silt sand appears, and sand control becomes more and more difficult, allowing some small particle formation sand to enter the wellbore with the produced fluid, and be discharged from the formation by the sand discharge pump or enter a special sand settling cylinder. Generally, the method of suspending the sand control screen pipe under the pump is adopted for two-level sand control.

[0004] At present, the sand control screen pipe under the pump is widely used, with an annual application of more than 1000 meters. Its advantages are mainly two: ① For wells with not serious sand production, setting a sand filtration pipe under the sucker rod pump can effectively control sand, and the cost is also reduced compared with the sand control of the screen pipe in the oil layer section; ② After multiple rounds of injection and production in the sand production block, the sand production becomes finer and the content of fine silt sand increases. The screen pipe sand control generally adopts the principle of moderate sand control, allowing a part of fine silt sand to enter the wellbore. The sand control screen pipe under the pump can avoid pump jamming and extend the pump inspection period.

[0005] However, the current sand filtration pipe under the pump still has the following problems: ① Difficulty in designing the sand control precision: If the sand control precision is too large, finer formation sand enters the pump barrel, resulting in pump jamming, pump barrel abrasion, etc.; if the sand control precision is too small, it is easy to cause screen pipe blockage and a decrease in liquid production. ② In case of screen pipe blockage and other situations, the screen pipe cannot be flushed, and the pipe string must be pulled out, increasing the operation cost.

[0006] Based on this, there is still room for improvement in the existing technology. Summary of the Invention

[0007] This application summarizes aspects of the embodiments and should not be used to limit the claims. Other embodiments can be envisioned in accordance with the technology described herein, which will be apparent to those skilled in the art after studying the following drawings and detailed description, and these embodiments are intended to be included within the scope of this application.

[0008] The object of the present invention is to provide a spring - type screen pipe filtration structure with adjustable sand control precision, solve the problem of difficult design of sand control precision of the down - hole screen pipe, block formation sand from entering the pump barrel to the maximum extent, and when the screen pipe is blocked, it can be flushed and unblocked without pulling out the pipe string, avoiding the operation of pulling out the pipe string, extending the pump inspection period, and reducing the measure cost. It should be understood that the "formation sand" described in the present invention broadly includes any impurities such as gravel, mud, and oil sludge from the formation that may have a negative impact on oil and gas production.

[0009] Specifically, according to the first aspect of the present invention, there is provided a down - hole non - pulling - out - pipe - string flushing sand control screen pipe string, which includes: at least one sand control screen pipe, and each sand control screen pipe includes: an upper joint; a central pipe connected to the upper joint; a lower joint connected to the central pipe; and a spring - type filtration structure disposed in the central pipe, the spring - type filtration structure being configured to filter a part of the formation sand carried by the produced fluid entering the sand control screen pipe from the lower joint during production and deform under pressure during the well flushing process to remove the formation sand blocking itself.

[0010] In an embodiment of the present invention, the upper joint includes an internal cavity disposed therein, and the sand control screen pipe further includes an upper pressing cap capable of moving in the internal cavity, and the upper pressing cap is connected to the spring - type filtration structure.

[0011] In an embodiment of the present invention, the spring - type filtration structure includes a spring and a plurality of gaskets filling the gaps between the spring wires of the spring, the thickness of the gaskets corresponding to the sand control precision of the sand control screen pipe, and the gaskets being evenly distributed circumferentially along the spring wires.

[0012] In an embodiment of the present invention, the spring is a compression spring, the cross - section of its spring wire is a trapezoid with a smaller inner side and a larger outer side, the angle between the two waists of the trapezoidal cross - section of the spring wire is set to be approximately 3°, and the cross - section of the gap between the spring wires is a trapezoid with a smaller inner side and a larger outer side to filter the formation sand flowing through it from the inside to the outside.

[0013] In an embodiment of the present invention, the shape of the gasket is a trapezoid with a smaller inner side and a larger outer side.

[0014] In an embodiment of the present invention, the cross - sectional area of the spring wire is determined based on the hydraulic pressure generated during the well flushing process, and it is required that the pressure received at the top of the spring when it is pulled apart is 8 - 10 MPa.

[0015] In an embodiment of the present invention, the length of the spring is set to be 0.5 - 1 m.

[0016] In an embodiment of the present invention, the spring includes a first end and a second end opposite to the first end. The first end is fixedly connected to the upper pressing cap to move together with the upper pressing cap under the pressure and deform, and the second end is fixedly connected to the lower joint.

[0017] In an embodiment of the present invention, the internal cavity has a depth in the axial direction of the sand control screen pipe, and the depth is configured to limit the movement of the upper pressing cap, thereby limiting the deformation of the spring.

[0018] In an embodiment of the present invention, the depth is determined based on the total length of the gaps between the spring wires after the spring is stretched.

[0019] In an embodiment of the present invention, the upper joint further includes a first through hole provided therein. The first through hole extends around and parallel to the internal cavity along the axial direction of the sand control screen pipe, and the first through hole communicates with the annulus between the internal cavity and the central pipe.

[0020] In an embodiment of the present invention, the lower joint includes a second through hole and a third through hole provided therein. The third through hole extends along the axial direction of the sand control screen pipe and communicates with the first through hole.

[0021] In an embodiment of the present invention, a part of the second through hole extends along the axial direction of the sand control screen pipe, one end thereof communicates with the spring - type filtering structure, and the other end extends to the side wall of the lower joint to form a liquid inlet hole.

[0022] In an embodiment of the present invention, the angle of the liquid inlet hole with respect to the radial surface of the sand control screen pipe is greater than 60°.

[0023] In an embodiment of the present invention, the first through hole and the third through hole are crescent - shaped holes, and the second through hole is a circular hole.

[0024] In an embodiment of the present invention, the areas of the second through hole and the third through hole are the same, and the diameter of the second through hole is slightly larger than the outer diameter of the spring.

[0025] In an embodiment of the present invention, at least one sand control screen pipe includes a first sand control screen pipe, a second sand control screen pipe... an nth sand control screen pipe, and the downhole stationary string flushing sand control screen pipe string further includes a short joint and a coupling sequentially connected to the upper joint of the first sand control screen pipe, and a sand settling pipe connected to the lower joint of the nth sand control screen pipe. The short joint and the coupling head form a lifting short joint. The n sand control screen pipes are in parallel independent liquid inlet to avoid the influence of the relatively small size of the liquid inlet hole on the oil well production capacity.

[0026] In an embodiment of the present invention, the number of the sand control screen pipes is determined based on the liquid production volume of the oil well to ensure that the flow capacity of the downhole stationary string flushing sand control screen pipe string meets the oil well production capacity.

[0027] According to the second aspect of the present invention, there is provided a well flushing method based on a downhole stationary string flushing sand control screen pipe string, which includes the following steps: S10. In response to the blockage of at least one sand control screen pipe in the downhole stationary string flushing sand control screen pipe string or in response to the use of the downhole stationary string flushing sand control screen pipe string exceeding a predetermined time length, lift the sucker rod to lift the plunger out of the pump barrel; S20. Pump a well flushing fluid from the ground into the annulus between the casing and the tubing. The well flushing fluid enters the interior of each sand control screen pipe through the liquid inlet hole at the lower joint of each sand control screen pipe of the downhole stationary string flushing sand control screen pipe string. Set the pumping displacement range of the well flushing fluid and the pumping pressure warning value. Set the initial pumping displacement of the well flushing fluid to the lower limit value of the pumping displacement range of the well flushing fluid, and increase the pumping displacement of the well flushing fluid from low to high to the upper limit value of the pumping displacement range of the well flushing fluid, and observe whether the ground pumping pressure changes significantly; S30. In response to the significant change in the ground pumping pressure and exceeding the pressure warning value, further increase the pumping displacement of the well flushing fluid from low to high. The well flushing pressure increases. The increased well flushing pressure deforms the spring-type filtering structure in the sand control screen pipe to remove the formation sand blocking itself. Then the well flushing pressure decreases. Continue to increase the pumping displacement of the well flushing fluid. In response to the well flushing pressure no longer changing, lower the sucker rod to put the plunger back into the pump barrel, and the construction ends.

[0028] In an embodiment of the present invention, in step S20, the increased well flushing pressure deforms the spring-type filtering structure in the sand control screen pipe to remove the formation sand blocking itself, including: the increased well flushing pressure pushes the spring of the spring-type filtering structure and the upper pressing cap connected thereto to move towards the inner cavity of the upper joint, so that the spring is stretched, resulting in an increase in the gap between the spring wires of the spring. The well flushing fluid passes through the gap, carries the blocked formation sand and flows upward, passes through the first through hole of the upper joint, flows upward through the pump barrel, and returns to the ground along the tubing.

[0029] According to the third aspect of the present invention, there is provided a device for oil and gas exploitation, which includes the downhole stationary string flushing sand control screen pipe string as described above.

[0030] When the sieve tube is blocked, the present invention can flush and remove the blockage without pulling out the tubing string, avoid the operation of pulling out the tubing string, extend the pump inspection period, reduce the measure cost, and has a wide range of on-site requirements.

[0031] After studying the following specification, claims and drawings, those skilled in the art will understand and recognize these and other aspects, objects and features of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To more fully understand the embodiments of the present application, reference should be made to the more detailed description in the drawings and the embodiments described by way of example below, where:

[0033] Figure 1 A cross-sectional schematic view of a sand control sieve tube string for flushing without pulling out the tubing string under the pump according to an embodiment of the present invention is shown;

[0034] Figure 2 Shown is Figure 1 A cross-sectional schematic view of one of the sand control sieve tubes of the sand control sieve tube string for flushing without pulling out the tubing string under the pump described in

[0035] Figure 3a A cross-sectional schematic view of the upper joint of the sand control sieve tube according to an embodiment of the present invention is shown;

[0036] Figure 3b An end view of the upper joint of the sand control sieve tube according to an embodiment of the present invention is shown;

[0037] Figure 3c Shown is Figure 3b The cross-sectional view of A-A in

[0038] Figure 4a A cross-sectional schematic view of the lower joint of the sand control sieve tube according to an embodiment of the present invention is shown;

[0039] Figure 4b An end view of the lower joint of the sand control sieve tube according to an embodiment of the present invention is shown;

[0040] Figure 4c Shown is Figure 4b The cross-sectional view of A-A in

[0041] Figure 5a A cross-sectional schematic view of the spring-type filtering structure of the sand control sieve tube according to an embodiment of the present invention is shown;

[0042] Figure 5b Shown is Figure 5a A structural schematic view of the spring wire and gasket of the spring-type filtering structure in

[0043] Figure 6The flowchart of the well flushing method based on the downhole stationary string flushing sand control screen pipe string according to an embodiment of the present invention is shown;

[0044] Figure 7 The schematic diagram of the downhole stationary string flushing sand control screen pipe string and fluid production according to an embodiment of the present invention is shown;

[0045] Figure 8 The schematic diagram of the downhole screen pipe and fluid production in the prior art is shown. Detailed implementation manners

[0046] Embodiments of the present disclosure are described below. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various alternative forms. The drawings are not necessarily drawn to scale; certain features may be exaggerated or minimized to show details of particular components. Thus, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to use the present application in various ways. As those skilled in the art will understand, the various features shown and described with reference to any one of the drawings may be combined with the features shown in one or more other drawings to produce embodiments that are not explicitly shown or described. The combinations of the shown features provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desirable for certain specific applications or implementations.

[0047] In addition, in this document, relational terms such as first and second are only used to distinguish one entity or action from another entity or action, and do not necessarily require or imply any actual such relationship or order between these entities or actions. The terms "comprising", "including" or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article or apparatus comprising a series of elements includes not only those elements, but also elements not expressly listed or inherent to such process, method, article or apparatus.

[0048] One or more embodiments of the present application will be described below in conjunction with the drawings. The flowchart illustrates the process performed by the system according to the present application. It can be understood that the execution of the flowchart does not need to be in sequence, one or more steps may be omitted, one or more execution steps may be added, and may be in sequence or reverse order, and even in some embodiments, one or more steps may be executed simultaneously.

[0049] According to a first aspect of the present invention, a downhole stationary string flushing sand control screen pipe string 10 is provided, as Figure 1 and 2As shown in the figure, it includes: at least one sand control screen pipe 100, and each sand control screen pipe 100 includes: an upper joint 110; a central pipe 120 connected to the upper joint 110; a lower joint 130 connected to the central pipe 120; and a spring-type filtering structure 140 disposed within the central pipe 120. The spring-type filtering structure 140 is configured to filter a portion of the formation sand carried by the produced fluid entering the sand control screen pipe 100 from the lower joint 130 during the production process and deform under pressure to remove the formation sand clogging itself during the well washing process. The entire downhole non-movable string for washing the sand control screen pipe string 10 is composed of an unequal number of single-section sand control screen pipes 100. The length of the entire downhole non-movable string for washing the sand control screen pipe string 10 is determined by the amount of produced fluid in the oil well, ensuring that the flow capacity of the downhole non-movable string for washing the sand control screen pipe string 10 meets the production capacity of the oil well.

[0050] In an embodiment of the present invention, as Figures 3a - 3c shown, the upper joint 110 includes an internal cavity 111 disposed therein, and the sand control screen pipe 100 further includes an upper pressing cap 150 capable of moving within the internal cavity 111. The upper pressing cap 150 is connected to the spring-type filtering structure 140. The upper pressing cap 150 is disposed within the internal cavity 111 of the upper joint 110. The diameter of the upper pressing cap 150 is smaller than the inner diameter of the internal cavity 111, and the outside of the upper pressing cap 150 is smooth, allowing it to slide within the internal cavity 111 of the upper joint 110.

[0051] In an embodiment of the present invention, as Figure 5a and 5b shown, the spring-type filtering structure 140 includes a spring 141 and a gasket 143 filling the gap between the spring wires 142 of the spring 141. The thickness of the gasket 143 corresponds to the sand control precision of the sand control screen pipe 100, and the gasket 143 is evenly distributed circumferentially along the spring wire 142. In Figure 5b the embodiment shown, three gaskets 143 are provided circumferentially along the spring wire 142.

[0052] In an embodiment of the present invention, the spring 141 is a compression spring, and the cross-section of its spring wire 142 is a trapezoid with a smaller inner side and a larger outer side. The angles of the two waists of the trapezoidal cross-section of the spring wire are set to be approximately 3°. The cross-section of the gap between the spring wires 142 is a trapezoid with a smaller inner side and a larger outer side to filter the formation sand flowing through it from the inside to the outside. Correspondingly, the shape of the gasket 143 is a trapezoid with a smaller inner side and a larger outer side.

[0053] In an embodiment of the present invention, the cross-sectional area of the spring wire 142 is determined based on the hydraulic pressure generated during the well washing process, and it is required that the pressure received at the top of the spring when it is stretched is 8 - 10 MPa.

[0054] In an embodiment of the present invention, the length of the spring 141 is set to 0.5 - 1 m to ensure the stability of the spring 141 and avoid uneven stretching of the spring wire 142 during the well washing process.

[0055] In an embodiment of the present invention, the spring 141 includes a first end 144 and a second end 145 opposite to the first end 144. The first end 144 is fixedly connected (e.g., welded) to the upper pressing cap 150 to move together with the upper pressing cap 150 under pressure and deform, and the second end 145 is fixedly connected to the lower joint 130. Under pressure, at least a part of the first end 144 of the spring 141 can move together with the upper pressing cap 150 within the internal cavity 111.

[0056] In an embodiment of the present invention, the internal cavity 111 has a depth d along the axial direction of the sand control screen pipe 100 (shown in Figure 3c ), and the depth d is configured to limit the movement of the upper pressing cap 150, thereby limiting the deformation of the spring 141. The depth d is determined based on the total length of the gaps between the spring wires 142 after the spring 141 is stretched. The purpose is to avoid excessive elongation of the spring of each single sand control screen pipe 100 during the later flushing process of the sand control screen pipe 100, resulting in uneven flow rates of the produced fluid through each sand control screen pipe 100 and preventing other sand control screen pipes 100 from being unblocked.

[0057] In the present invention, the spring is set as a trapezoidal spring. The cross-sectional area of the spring wire 142 is determined by the hydraulic pressure generated during later well flushing. It is required that the pressure received at the top when the spring is stretched is 8 - 10 MPa. To ensure that when a certain amount of well flushing fluid is pumped into the ground under a certain pressure, the spring 141 can be stretched, the gap between the spring wires 142 becomes larger, and the well flushing fluid can clean the sludge and sand-containing sludge blocking the sand control screen pipe 100. A gasket 143 is arranged between the spring wires 142, and the thickness of the gasket 143 is the sand control precision of the sand control screen pipe 100. The cross-section of the spring wire 142 is designed as a trapezoid, and the formed gap between the spring wires 142 is a trapezoid with a smaller inner part and a larger outer part. After the produced fluid carries formation sand into the screen pipe during the production process, the large-particle formation sand is blocked, and very few tiny-particle formation sands pass through the spring-type filtering structure 140. Due to the trapezoidal structure of the gap between the spring wires 142 with a smaller inner part and a larger outer part, once the formation sand enters, it is easily discharged and will not get stuck in the gap between the spring wires 142. Therefore, it has a self-cleaning function.

[0058] In an embodiment of the present invention, the upper joint 110 further includes a first through hole 112 provided therein. The first through hole 112 extends around and parallel to the internal cavity 111 along the axial direction of the sand control screen pipe 100, and the first through hole 112 communicates with the annulus between the internal cavity 111 and the central pipe 120.

[0059] In an embodiment of the present invention, as Figures 4a - 4cAs shown, the lower joint 130 includes a second through hole 131 and a third through hole 132 disposed therein. The third through hole 132 extends along the axial direction of the sand control screen pipe 100 and communicates with the first through hole 112. When multiple sections of the sand control screen pipe 100 are connected together, the first through hole 112 of the upper joint 110 of each section of the sand control screen pipe 100 communicates with the third through hole 132 of the lower joint 130, and further communicates with the first through hole 112 of the upper joint 110 of the previous and next sections of the sand control screen pipe 100, and the first through hole 112 of the upper joint 110 of the previous and next sections of the sand control screen pipe 100 communicates with the third through hole 132 of the lower joint 130.

[0060] In an embodiment of the present invention, a part of the second through hole 131 extends along the axial direction of the sand control screen pipe 100, one end thereof communicates with the spring type filtering structure 140, and the other end extends to the side wall of the lower joint 130 to form a liquid inlet hole 133. As Figure 4b and 4c shown, the second through hole 131 has a wall thickness, a part of it extends along the axial direction of the sand control screen pipe 100, while the other part deviates from the axial direction of the sand control screen pipe 100, and finally a liquid inlet hole 133 is formed on the side wall of the lower joint 130. The liquid inlet hole 133 is the inlet of the produced liquid and the well flushing liquid, and at the same time is the outlet of part of the settled sand.

[0061] In an embodiment of the present invention, the included angle of the liquid inlet hole 133 with respect to the radial surface of the sand control screen pipe is greater than 60°. In the Figure 4c shown embodiment, this angle is 70°. The design angle of the liquid inlet hole 133 is greater than 60°, and the large particle formation sand blocked by the spring type filtering structure 140 during the production of the oil well can settle downward through the liquid inlet hole 133, and will not cause blockage at the outlet.

[0062] In an embodiment of the present invention, the first through hole 112 and the third through hole 132 are crescent-shaped holes, and the second through hole 131 is a circular hole. The areas of the second through hole 131 and the third through hole 132 are the same, ensuring smooth flow of the formation produced liquid during the production process. The diameter of the second through hole 131 is slightly larger than the outer diameter of the spring 141, and the lower joint 130 and the spring 141 can be connected by welding.

[0063] In an embodiment of the present invention, at least one section of the sand control screen pipe includes the first section of the sand control screen pipe, the second section of the sand control screen pipe... the nth section of the sand control screen pipe. The n sections of the sand control screen pipe adopt parallel independent liquid inlet to avoid the influence of the relatively thin liquid inlet hole size on the oil well production capacity. In Figure 1In the illustrated embodiment, the first sand control screen pipe and the second sand control screen pipe are shown. The downhole stationary string flushing sand control screen pipe string 10 further includes a short joint 102 and a coupling 101 that are sequentially connected to the upper joint 110 of the first sand control screen pipe. The short joint 102 and the coupling 101 together form a lifting short joint, whose function is to cooperate with tools such as elevators to facilitate the lowering of the downhole stationary string flushing sand control screen pipe string 10 into the well. In addition, the downhole stationary string flushing sand control screen pipe string 10 may further include a sand settling pipe (not shown in the figure) connected to the lower joint 130 of the nth sand control screen pipe (i.e., the last sand control screen pipe).

[0064] In an embodiment of the present invention, the number of sand control screen pipes is determined based on the oil well production fluid volume to ensure that the flow capacity of the downhole stationary string flushing sand control screen pipe string meets the oil well productivity. The sand control screen pipes are connected to each other through, for example, a double-coupling 103.

[0065] According to a second aspect of the present invention, there is provided a well flushing method for the downhole stationary string flushing sand control screen pipe string 10 based on the foregoing embodiment, as Figure 6 described, the method includes the following steps:

[0066] S10. In response to at least one sand control screen pipe in the downhole stationary string flushing sand control screen pipe string being blocked or in response to using the downhole stationary string flushing sand control screen pipe string for more than a predetermined time period, lift the sucker rod to lift the plunger out of the pump barrel;

[0067] S20. Pump a well flushing fluid from the surface into the annulus between the tubing and the casing. The well flushing fluid enters the interior of each sand control screen pipe through the liquid inlet hole at the lower joint of each sand control screen pipe of the downhole stationary string flushing sand control screen pipe string. Set the well flushing fluid pumping displacement range and the pumping pressure warning value. Set the initial well flushing fluid pumping displacement as the lower limit value of the well flushing fluid pumping displacement range, and increase the well flushing fluid pumping displacement from low to high to the upper limit value of the well flushing fluid pumping displacement range, and observe whether the surface pumping pressure changes significantly;

[0068] S30. In response to the surface pumping pressure changing significantly and exceeding the pressure warning value, further increase the well flushing fluid pumping displacement from low to high. The well flushing pressure increases, and the increased well flushing pressure causes the spring-type filtering structure in the sand control screen pipe to deform and remove the formation sand blocking itself. After that, the well flushing pressure decreases. Continue to increase the well flushing fluid pumping displacement. In response to the well flushing pressure no longer changing, lower the sucker rod to put the plunger back into the pump barrel, and the construction is completed.

[0069] In an embodiment of the present invention, in step S10, the predetermined time period may be one month, one quarter, or half a year, or other time periods, which can be set according to actual needs.

[0070] In an embodiment of the present invention, in step S20, the pumping displacement range of the well flushing fluid can be set to 0.5 - 3 m 3 / min, and the warning pressure of the pumping pressure is set to a maximum of 12 MPa. The initial pumping displacement of the well flushing fluid is set to 0.5 m 3 / min, and the pumping displacement of the well flushing fluid is increased from low to high until 3 m 3 / min, and the ground pumping pressure is observed. If the screen pipe is not blocked or the blockage is not serious, the ground pumping pressure does not change significantly. After flushing for a period of time, the pump is stopped, the sucker rod is lowered, and the plunger is put back into the pump barrel, and the construction is completed.

[0071] In an embodiment of the present invention, in step S30, if the ground pumping pressure changes significantly and exceeds the pressure warning value, it indicates that the surface sand control screen pipe is severely blocked. Further increase the pumping displacement of the well flushing fluid from low to high. The flushing pressure becomes larger, and the increased flushing pressure deforms the spring - type filtering structure 140 in the sand control screen pipe 100 to remove the formation sand blocking itself. After that, the flushing pressure becomes smaller. Continue to increase the displacement, and the flushing pressure no longer changes. The screen pipe is flushed clean. After flushing for a period of time, the pump is stopped, the sucker rod is lowered, and the plunger is put back into the pump barrel, and the construction is completed.

[0072] In an embodiment of the present invention, in step S20, the increased flushing pressure deforming the spring - type filtering structure in the sand control screen pipe to remove the formation sand blocking itself includes: the increased flushing pressure pushes the spring of the spring - type filtering structure and the upper pressing cap connected thereto to move into the inner cavity of the upper joint, causing the spring to be stretched, resulting in an increase in the gap between the spring wires of the spring. The well flushing fluid passes through the gap, carries the blocked formation sand and flows upward, passes through the first through - hole of the upper joint, flows upward through the pump barrel, and returns to the ground along the tubing.

[0073] According to the third aspect of the present invention, a device for oil and gas exploitation is provided, which includes the down - hole stationary pipe string flushing sand control screen pipe string 10 described in the foregoing embodiments.

[0074] The present invention is further illustrated by the following specific embodiments:

[0075] Reference Figures 1 - 6 , the present invention provides a down - hole stationary pipe string flushing sand control screen pipe string 10 and a well flushing method based on the down - hole stationary pipe string flushing sand control screen pipe string 10. The down - hole stationary pipe string flushing sand control screen pipe string 10 includes at least one section of sand control screen pipe 100. Each section of sand control screen pipe 100 is composed of an upper joint 110, a central pipe 120, an upper pressing cap 150, a spring - type filtering structure 140, a lower joint 130, etc. (as Figure 1 and 2As shown. The entire downhole non-movable string flushing sand control screen string 10 is composed of unequal numbers of single-section sand control screens 100. The length of the entire downhole non-movable string flushing sand control screen string 10 is determined by the oil well production fluid volume, ensuring that the flow capacity of the downhole non-movable string flushing sand control screen string 10 meets the oil well production capacity. For the first section of sand control screen 100, its upper joint 110 is connected to the short joint 102 and the coupling 101. The coupling 101 is located at the uppermost part and is connected to the pump barrel above, with a coupling type of flush tubing coupling. The upper part of the short joint 102 is connected to the coupling 101. The short joint 102 and the coupling 101 together form a lifting short joint, whose function is to cooperate with tools such as elevators to facilitate the lowering of the downhole non-movable string flushing sand control screen string 10 into the well.

[0076] The double-coupling 103 has a double-male coupling structure, with a coupling type of flush tubing coupling. Its main function is to connect the upper lifting short joint and the lower downhole non-movable string flushing sand control screen string 10. The sand control screens 100 can also be connected through the double-coupling 103.

[0077] The upper part of the upper joint 110 is connected to the double-coupling 103, and the lower part is connected to the central pipe 120. The upper joint 110 is designed (as Figure 3b shown) to have a crescent-shaped first through hole 112 that is connected up and down and a non-connected internal cavity 111. The internal cavity 111 is the space for the upper compression cap 150 to move axially.

[0078] The lower part of the upper joint 110 is connected to the central pipe 120. The central pipe 120 is a standard tubing, with flush tubing couplings at both the upper and lower ends. The lower part of the central pipe 120 is connected to the lower joint 130, and the inside of the central pipe 120 is the channel of the spring-type filtering structure 140.

[0079] The lower joint 130 is designed to have a circular second through hole 131 and a crescent-shaped third through hole 132 that are connected up and down (as Figure 4b shown). The designed size is such that the areas of the circular second through hole 131 and the crescent-shaped third through hole 132 are the same, ensuring smooth flow of the formation produced fluid during production. The diameter of the circular second through hole 131 of the lower joint 130 is slightly larger than the outer diameter of the spring-type filtering structure 140. The lower joint 130 and the spring-type filtering structure 140 are connected by welding. The circular second through hole 131 is designed to be laterally connected to the outside to form an inlet hole 133. During production, both the formation produced fluid and the well flushing fluid during well flushing enter through this inlet hole 133. The designed angle of the inlet hole 133 is greater than 60°. Large particles of formation sand blocked by the spring-type filtering structure 140 during oil well production can settle downward through this inlet hole 133 and will not cause blockage at the outlet.

[0080] The spring - type filtering structure 140 is arranged inside the central pipe 120 and is connected to the lower joint 130 at the lower part by welding. The upper part of the spring - type filtering structure 140 is welded to the upper pressing cap 150. The spring - type filtering structure 140 includes a spring 141, which can also be called a flow - through spring. The flow - through spring is set as a trapezoidal spring, and the cross - sectional area of the spring wire 142 is determined by the hydraulic pressure generated during later well flushing. It is required that the pressure at the top of the spring when it is stretched is 8 - 10 MPa. When a certain amount of well - flushing fluid is pumped into the well from the ground, the spring 141 can be stretched under a certain pressure, and the gap between the spring wires 142 becomes larger, so that the well - flushing fluid can clean the sludge and sand - containing sludge in the sand - control screen pipe 100. A gasket 143 is arranged between the spring wires 142, and the thickness of the gasket 143 is the sand - control precision of the screen pipe. As Figure 5b shown, the cross - section of the spring wire 142 is designed as a trapezoid, and the gap formed by the spring wires 142 is a trapezoid with a smaller inner part and a larger outer part. After the produced fluid carries formation sand into the sand - control screen pipe 100 during the production process, the large - particle formation sand is blocked, and very few tiny - particle formation sands pass through the spring - type filtering structure 140. Due to the trapezoidal structure of the gap between the spring wires 142 with a smaller inner part and a larger outer part, the formation sand will not get stuck in the gap between the spring wires 142, and it has a self - cleaning function.

[0081] The lower joint 130 of the last sand - control screen pipe 10 at the end of the pump - down non - moving pipe string for flushing the sand - control screen pipe string 10 is connected to a sand - settling pipe (not shown in the figure) to collect the settled sand.

[0082] Figure 8 The figure shows a schematic diagram of a down - hole screen pipe and produced fluid in the prior art. Currently, the down - hole sand - control pipe has at least the following problems: ① It is difficult to design the sand - control precision: If the sand - control precision is too large, finer formation sand will enter the pump barrel, resulting in situations such as pump jamming and pump barrel abrasion; if the sand - control precision is too small, it is easy to cause screen - pipe blockage and a decrease in fluid production. ② When there is a situation such as screen - pipe blockage, the screen pipe cannot be flushed and the pipe string must be pulled out, increasing the operation cost.

[0083] In contrast, the pump - down non - moving pipe string for flushing the sand - control screen pipe described in the embodiment of the present invention can solve the above - mentioned technical problems. Specifically, referring to Figure 7 Specifically, the working principle of the pump - down non - moving pipe string for flushing the sand - control screen pipe 10 described in the present invention is described as follows:

[0084] The upper part of the pump - down non - moving pipe string for flushing the sand - control screen pipe 10 is connected to the pump barrel and lowered into the well, and the lower part is connected to the sand - settling pipe.

[0085] (1) Production process:

[0086] During the production process, the produced fluid carries formation sand and flows upward along the wellbore. It flows to the outside of the stationary pipe string for washing the sand control screen pipe string 10 below the pump, enters the sand control screen pipe 100 through the lateral liquid inlet holes 133 of the lower joints 130 of each section of the sand control screen pipe 100 of the stationary pipe string for washing the sand control screen pipe string 10 below the pump, and then enters the inside of the spring-type filtering structure 140.

[0087] Gaskets 143 are arranged in the gaps between the spring wires 142 of the spring-type filtering structure 140, and the thickness of the gaskets 143 is the sand control precision of the sand control screen pipe string 10. The cross-section of the spring wire 142 is designed as a trapezoid, and the gap formed by the spring wires 142 is a trapezoid with a smaller inner side and a larger outer side. During the production process, when the produced fluid carries formation sand into the sand control screen pipe string 10, the large-particle formation sand is blocked, and very few tiny-particle formation sands pass through the spring-type filtering structure 140. Due to the trapezoidal structure with a smaller inner side and a larger outer side of the gap between the spring wires 142, the sand grains will not get stuck in the gap between the spring wires 142, and it has a self-cleaning function.

[0088] The large-particle formation sand is blocked by the spring-type filtering structure 140, settles downward, and sinks into the wellbore through the liquid inlet holes 133. The produced fluid carries very few small-particle formation sands through the spring-type filtering structure 140 and enters the annulus between the spring-type filtering structure 140 and the central pipe 120. Under the suction of the sucker rod pump, it flows upward, passes through the crescent-shaped first through hole 112 of the upper joint 110 and enters the upper section of the sand control screen pipe 100, and then flows upward through the pump barrel and is produced to the ground along the tubing. During the upward flow process, a small part of the tiny formation sand settles, sinks downward through the crescent-shaped first through hole 112 of the upper joint 110, and the third through hole 132 of the lower joint 130, and then enters the first through hole 112 of the upper joint 110 and the third through hole 132 of the lower joint 130 of the upper joint 110 of the next section of the sand control screen pipe 100 until finally entering the sand settling pipe.

[0089] The production process ends.

[0090] (2) Well washing process:

[0091] After the oil well has been exploited for a period of time, if there is more sand and shale in the formation, it is easy to block the spring-type filtering structure 140.

[0092] After the blockage occurs, lift the sucker rod and lift the plunger out of the pump barrel.

[0093] Then use a pump truck to pump the well washing fluid from the ground into the annulus between the casing and the tubing. The well washing fluid flows downward along the annulus between the casing and the tubing, and finally flows to the outside of the sand control screen pipe 100 and enters the inside of the sand control screen pipe 100 through the liquid inlet holes 133 at the lower joint 130. The pumping displacement of the well washing fluid is set to 0.5 - 3 m 3 / min, and the early warning pressure of the pumping pressure is set to a maximum of 12 MPa. The initial pumping displacement of the well washing fluid is set to 0.5 m 3 / min, increase the displacement of the well flushing fluid pumped in from low to high until it reaches 3 m 3 / min, and observe the ground pumping pressure. If the screen pipe is not blocked or is not severely blocked, the ground pumping pressure will not change significantly. After flushing for a period of time, stop the pump, lower the sucker rod, and put the plunger back into the pump barrel to end the construction.

[0094] If the sand control screen pipe is severely blocked and the well flushing fluid cannot flow through the spring - type filtering structure 140 to the annulus between the spring - type filtering structure 140 and the central pipe 120, the well flushing pressure of the pump truck will increase.

[0095] As the well flushing pressure increases, the spring - type filtering structure 140 is stretched, the gap between the spring wires 142 becomes larger, the well flushing fluid flows through the gap between the spring wires 142, carries the blockage upward, passes through the crescent - shaped first through - hole 112 of the upper joint 110, flows upward through the pump barrel, and returns to the ground along the tubing.

[0096] The sand control screen pipe 100 is unblocked and the well flushing process ends. Lower the sucker rod, put the plunger back into the pump barrel to end the construction.

[0097] In the present invention, by designing that the spring - type filtering structure 140 is stretched under pressure, the flow - through gap becomes larger, and the blockage is back - washed out of the ground without lifting the sand control screen pipe 100 out of the ground. Among them, due to the design of the depth d of the internal cavity 111 of the upper joint 110, the stretching distance of the spring 141 of the spring - type filtering structure 140 is limited, avoiding the problem that during the later well flushing process of the sand control screen pipe 100, the single - section spring is stretched too much, resulting in uneven flow - through rates of the produced fluid through each section of the sand control screen pipe 100 and the inability to unblock other sand control screen pipes 100.

[0098] The present invention provides a downhole non - moving string well flushing sand control screen pipe string and a well flushing method, as well as a device for oil and gas exploitation including the downhole non - moving string well flushing sand control screen pipe string, which can effectively solve the problems existing in the prior art. Among them, each section of the sand control screen pipe of the downhole non - moving string well flushing sand control screen pipe string includes a spring - type filtering structure. The spring - type filtering structure includes a spring, there is a gap between the spring wires of the spring, and a gasket is arranged in this gap. The thickness of the gasket is the sand control precision of the screen pipe. The flow - through direction is set from inside to outside. An upper pressure cap is arranged on the upper part of the spring - type filtering structure, and a liquid inlet hole is arranged on the lower part. The produced fluid enters the sand control screen pipe from the liquid inlet hole, the formation sand is blocked, settles to the wellbore through the liquid inlet hole, the produced fluid is filtered by the spring - type filtering structure and enters the annulus, and then enters the pump barrel upward and is produced to the ground. After the sand control screen pipe is blocked, lift the sucker rod, lift the plunger out of the pump barrel, and then pump the well flushing fluid into the oil - casing annulus from the ground. Under pressure, the spring of the spring - type filtering structure is stretched, the flow - through gap becomes larger, and the blockage is back - washed out of the ground without lifting the sand control screen pipe out of the ground.

[0099] This application document is intended to illustrate how to use the disclosed technology and various embodiments, and is not intended to limit the scope and spirit of what it actually refers to and what is equivalent thereto. Moreover, the above description does not exhaust all possibilities or limit the scope of protection to the exact forms disclosed. According to the above teachings, changes and variations are possible. The selected and described embodiments provide the best illustration of the principles of the technology and its practical applications, and enable those skilled in the art to make various changes to the disclosed technology for various conceivable specific applications. Therefore, all changes and modifications made to the above embodiments are intended to be included within the scope of the present disclosure without materially departing from the spirit and principles of the technology described herein.

Claims

1. A downhole non-movable string flushing and sand control screen string, characterized in that, it includes: At least one section of sand control screen pipe, and each section of the sand control screen pipe includes: An upper joint; A central pipe connected to the upper joint; A lower joint connected to the central pipe; and A spring-type filtering structure arranged in the central pipe, and the spring-type filtering structure is configured to filter part of the formation sand carried by the produced fluid entering the sand control screen pipe from the lower joint during production and deform under pressure during well flushing to remove the formation sand blocking itself.

2. The downhole non-movable string flushing and sand control screen string according to claim 1, characterized in that, The upper joint includes an internal cavity provided therein, and the sand control screen pipe further includes an upper pressing cap capable of moving in the internal cavity, and the upper pressing cap is connected to the spring-type filtering structure.

3. The downhole non-movable string flushing and sand control screen string according to claim 2, characterized in that, The spring-type filtering structure includes a spring and a plurality of gaskets filling the gaps between the spring wires, the thickness of the gaskets corresponds to the sand control precision of the sand control screen pipe, and the gaskets are evenly distributed along the circumferential direction of the spring wires.

4. The downhole non-movable string flushing and sand control screen string according to claim 3, characterized in that, The spring is a compression spring, the cross-section of its spring wire is a trapezoid with a smaller inner side and a larger outer side, the angles of the two waists of the trapezoid of the spring wire cross-section are set to be approximately 3°, and the cross-section of the gap between the spring wires is a trapezoid with a smaller inner side and a larger outer side to filter the formation sand flowing through it from the inside to the outside.

5. The downhole non-movable string flushing and sand control screen string according to claim 4, characterized in that, The shape of the gasket is a trapezoid with a smaller inner side and a larger outer side.

6. The downhole non-movable string flushing and sand control screen string according to claim 3, characterized in that, The cross-sectional area of the spring wire is determined based on the hydraulic pressure generated during well flushing, and it is required that the pressure received at the top of the spring when it is stretched is 8 - 10 MPa.

7. The downhole non-movable string flushing and sand control screen string according to claim 3, characterized in that, The length of the spring is set to be 0.5 - 1 m.

8. The downhole non-movable string flushing and sand control screen string according to claim 3, characterized in that, The spring includes a first end and a second end opposite to the first end, the first end is fixedly connected to the upper pressing cap to move and deform together with the upper pressing cap under the pressure, and the second end is fixedly connected to the lower joint.

9. The downhole non-movable string flushing and sand control screen string according to claim 3, characterized in that, The internal cavity has a depth in the axial direction of the sand control screen pipe, and the depth is configured to limit the movement of the upper pressing cap, thereby limiting the deformation of the spring.

10. The downhole non-movable string flushing and sand control screen string according to claim 8, characterized in that, The depth is determined based on the total length of the gaps between the spring wires after the spring is stretched.

11. The downhole non-movable string flushing and sand control screen string according to claim 3, characterized in that, The upper joint further includes a first through hole disposed therein, the first through hole extending axially along the sand control screen pipe around and parallel to the inner cavity, and the first through hole communicating with the annulus between the inner cavity and the central pipe.

12. The downhole non-movable string flushing sand control screen pipe string according to claim 11, characterized in that the lower joint includes a second through hole and a third through hole disposed therein, the third through hole extending axially along the sand control screen pipe and communicating with the first through hole.

13. The downhole non-movable string flushing sand control screen pipe string according to claim 12, characterized in that a part of the second through hole extends axially along the sand control screen pipe, one end thereof communicating with the spring type filtering structure, and the other end extending to the side wall of the lower joint to form a liquid inlet hole.

14. The downhole non-movable string flushing sand control screen pipe string according to claim 13, characterized in that the included angle of the liquid inlet hole with respect to the radial surface of the sand control screen pipe is greater than 60°.

15. The downhole non-movable string flushing sand control screen pipe string according to claim 13, characterized in that the first through hole and the third through hole are crescent-shaped holes, and the second through hole is a circular hole; the areas of the second through hole and the third through hole are the same, and the diameter of the second through hole is slightly larger than the outer diameter of the spring.

16. The downhole non-movable string flushing sand control screen pipe string according to claim 1, characterized in that at least one section of the sand control screen pipe includes a first section of the sand control screen pipe, a second section of the sand control screen pipe... an nth section of the sand control screen pipe, and the downhole non-movable string flushing sand control screen pipe string further includes a short joint and a coupling sequentially connected to the upper joint of the first section of the sand control screen pipe and a sand settling pipe connected to the lower joint of the nth section of the sand control screen pipe, the short joint and the coupling head forming a lifting short joint, and the n sections of the sand control screen pipes are in parallel independent liquid inlet to avoid the influence of the fine liquid inlet hole size on the oil well productivity.

17. The downhole non-movable string flushing sand control screen pipe string according to claim 16, characterized in that the number of the sand control screen pipes is determined based on the oil well produced liquid volume to ensure that the flow-through capacity of the downhole non-movable string flushing sand control screen pipe string meets the oil well productivity.

18. A well flushing method for the downhole non-movable string flushing sand control screen pipe string according to any one of the foregoing claims 1-17, characterized in that it includes the following steps: S10. In response to the blockage of at least one section of the sand control screen pipe in the downhole non-movable string flushing sand control screen pipe string or in response to the use of the downhole non-movable string flushing sand control screen pipe string exceeding a predetermined time length, lift the sucker rod to lift the plunger out of the pump barrel; S20. Pump the well flushing fluid from the ground into the oil-casing annulus, the well flushing fluid entering the inside of each section of the sand control screen pipe through the liquid inlet hole at the lower joint of each section of the sand control screen pipe of the downhole non-movable string flushing sand control screen pipe string, set the well flushing fluid pumping displacement range and the pumping pressure warning value, set the initial well flushing fluid pumping displacement to the lower limit value of the well flushing fluid pumping displacement range, and increase the well flushing fluid pumping displacement from low to high to the upper limit value of the well flushing fluid pumping displacement range, and observe whether the ground pumping pressure changes significantly; S30. In response to a significant change in the surface pumping pressure that exceeds the pressure warning value, further increase the pumping displacement of the well flushing fluid from low to high. The well flushing pressure increases. The increased well flushing pressure causes the spring-type filtering structure in the sand control screen pipe to deform and remove the formation sand that blocks itself. After that, the well flushing pressure decreases. Continue to increase the pumping displacement of the well flushing fluid. In response to the well flushing pressure no longer changing, lower the sucker rod, place the plunger back into the pump barrel, and the construction ends.

19. The well flushing method according to claim 18, wherein, in step S20, the increased well flushing pressure causing the spring-type filtering structure in the sand control screen pipe to deform and remove the formation sand that blocks itself includes: the increased well flushing pressure pushes the spring of the spring-type filtering structure and the upper pressure cap connected thereto to move towards the inner cavity of the upper joint, causing the spring to be stretched, resulting in an increase in the gap between the spring wires of the spring. The well flushing fluid passes through the gap, carries the blocked formation sand and flows upward, passes through the first through hole of the upper joint, flows upward through the pump barrel, and returns to the ground along the tubing.

20. A device for oil and gas exploitation, wherein, the device for oil and gas exploitation includes the downhole stationary pipe string for flushing the sand control screen pipe string according to any one of the preceding claims 1-17.

Images