A heavy oil well sand flushing and steam injection process and its supporting device

Abstract

The invention discloses a sand flushing and steam injection process for a heavy oil well and its supporting device. Before steam injection, the sand impurities in the well are first flushed away, and then steam is injected. After the well is shut down, oil is pumped out to avoid sand jamming the pump during oil pumping, thereby making the operation stable. During steam injection, the heat energy in the steam is efficiently absorbed because the oil layer permeability is high. At the same time, the required steam injection time is also significantly shortened, which reduces the heat absorbed by other pipe sections, reduces invalid heat loss, and is more energy-efficient. The supporting device is a sand flushing and steam injection tool, comprising an oil pipe column, a sucker rod is arranged in the oil pipe column, the lower end of the sucker rod is connected to an oil production assembly, and the lower end of the oil pipe column is connected to a bridge-type steam injection assembly. The lower end of the oil production assembly is connected to a sand flushing inner pipe, and the lower end of the bridge-type steam injection assembly is connected to a sand flushing outer pipe. The upper end of the sand flushing outer pipe is provided with an oil inlet steam sealing valve on the outer side and is connected to the inside. The advantages of the invention are that stable, efficient and energy-saving production is achieved.

Description

Technical Field

[0001] The invention relates to a heavy oil well steam injection process, in particular to a heavy oil well sand flushing steam injection process and a matching device thereof, belonging to the field of heavy oil well steam injection. Background Art

[0002] In the rod production wells in the oil field, as the oil is pumped, the formation oil flows toward the pump, and the sand is also brought to the vicinity of the pump by the oil flow. Because the density of the sand is large, it will gradually settle, causing the sand surface to move up. The sand will increase the resistance to oil flow. When the depth of the accumulated sand reaches a certain level, it will lead to insufficient fluid intake of the pump, air lock, or even dry grinding, resulting in shutdown and pump inspection.

[0003] The production of heavy oil wells usually uses the steam huff and puff process, which injects steam into the ground, shuts down the well and then switches to pumping for oil production. However, conventional steam injection equipment and processes have the following problems:

[0004] First, the commonly used dual-purpose pumps for injection and extraction include feedback pumps and double-inlet oil pumps. When injecting steam, the steam passes through the inner hole of the pump barrel. If the inner wall of the pump barrel is scaled, it will cause the plunger to be stuck when switching to pumping. Double-inlet oil pumps open holes on the side of the pump barrel to inject steam. When washing the well, the sand impurities below the fixed valve cannot be washed out;

[0005] Second, several tail pipes are connected below the oil pump. When washing the well, if the tail pipe is full of sand, the washing fluid cannot be washed through, resulting in failure of well washing and failure of steam injection. The oil pipe needs to be lifted for maintenance.

[0006] Third, if steam is injected directly after well washing through the tail pipe, some impurities will be left behind because the tail pipe is not flushed evenly in the annular direction. This will reduce the permeability of steam in the oil layer and even block the steam injection channel, reducing the steam efficiency;

[0007] If the sand in the well is not cleaned before steam injection, the permeability of the oil layer will be reduced, and even the steam injection channel will be blocked, reducing the steam efficiency. After steam injection, the sand layer will be compacted, and the oil pump will be dry after the pumping, which will require shutdown for maintenance and waste steam injection costs. Figure 1-2 shown. Summary of the invention

[0008] In order to solve the above problems, the present invention designs a heavy oil well sand flushing and steam injection process and its supporting device. Before steam injection, the sand impurities in the well are first flushed away, and then steam is injected. The well is then soaked and oil is pumped out to avoid sand jamming the pump during oil pumping, thereby making the operation stable. During steam injection, the heat energy in the steam is efficiently absorbed because the permeability of the oil layer is high. At the same time, the required steam injection time is also significantly shortened, which reduces the heat absorbed by other pipe sections, reduces ineffective heat loss, and is more energy-efficient.

[0009] The technical solution of the present invention is:

[0010] A heavy oil well sand flushing and steam injection process comprises the following steps:

[0011] (1) Through positive well washing, the sand impurities in the tail pipe and at the bottom of the oil layer are flushed away;

[0012] (2) The sand is washed out layer by layer through the uniform through holes. Because the depth of the uniform through holes buried by sand is different and the flow resistance is different, the sand will be washed away layer by layer in the order of the uniform through holes from bottom to top.

[0013] (3) Steam is then injected evenly into each oil layer through the equalizing hole. During steam injection, the steam does not pass through the inner wall of the oil pump barrel to avoid scale jamming after steam injection.

[0014] Since the aperture of the average through hole increases gradually from top to bottom along the vertical direction, and the opening direction is different, because the steam comes from the upper part of the oil pipe, the average through hole closest to the heat source is designed to be the smallest, and it is larger further down, and the largest at the bottom. The specific aperture is determined according to the sand production of the oil layer and the well depth. In this way, the amount of steam passing through the average through holes at different heights can be relatively uniform. The steam passes through the annular space between the pump barrel and the outer pipe, and does not pass through the inner wall of the pump barrel.

[0015] A supporting device for a heavy oil well sand flushing and steam injection process comprises a bridge-type sand injection and suction prevention pump, a sand flushing and steam injection tool is arranged at the lower part of the bridge-type sand injection and suction prevention pump, the sand flushing and steam injection tool comprises an oil pipe string, a sucker rod is arranged in the oil pipe string, the lower end of the sucker rod is connected to an oil production assembly, and the lower end of the oil pipe string is connected to a bridge-type steam injection assembly; the lower end of the oil production assembly is connected to a sand flushing inner tube, the lower end of the bridge-type steam injection assembly is connected to a sand flushing outer tube, and the upper end of the sand flushing outer tube is provided with an oil inlet steam sealing valve on the outer side and is connected to the interior.

[0016] The oil pipe string is connected from the wellhead to the downhole oil pump, usually by multiple oil pipes connected by threads. Its function is to connect the wellhead and the oil layer, and to transport oil, well washing fluid, and steam.

[0017] The rod of the oil pump is connected to the sucker rod string, which is composed of multiple sucker rods connected from the wellhead bare rod to the well. With the cooperation of the plunger part and the pump barrel part, the up and down reciprocating motion of the plunger generates a pumping force to transport the oil to the ground.

[0018] Under the action of the oil inlet steam seal valve, the oil in the oil layer can enter, so that the oil pump can not only suck the oil in the bottom layer, but also suck the oil near the oil inlet steam seal valve, which increases the oil inlet channel and improves the pump efficiency. The role of the steam seal is that when injecting steam, since there is a valve ball seat inside the oil inlet steam seal valve, which is equivalent to a one-way valve, it only allows steam to enter but not exit, and steam will not be ejected from the oil inlet steam seal valve.

[0019] Furthermore, the side surface of the sand-blasting outer tube is provided with uniform through holes of different sizes at different depths along the circumferential direction.

[0020] The aperture of the average through hole increases gradually from top to bottom, and the opening direction is different. Because the steam comes from the upper part of the oil pipe, the average through hole closest to the heat source is designed to be the smallest, and the larger one is further downward, and the largest one is at the bottom, so that the amount of steam passing through the average through holes at different heights is relatively uniform. The steam passes through the annular space between the pump barrel and the outer tube, and does not pass through the inner wall of the pump barrel.

[0021] The function of the sand flushing outer pipe is to guide the flow of oil, well washing fluid, steam and other media. In combination with the uniform through hole, stratified well washing and uniform steam injection are achieved.

[0022] The sand flushing inner pipe is connected to the lower part of the oil production assembly and functions to guide the flow of oil, well washing fluid, steam and other media.

[0023] Furthermore, a sand flushing steam injection channel is provided between the sand flushing inner tube and the sand flushing outer tube. When the pumping rod string is lifted, the oil production assembly is driven upward, and the sand flushing inner tube follows the upward movement, forming a sand layer cavity at the lower part of the sand flushing inner tube, providing an initial channel for sand flushing and well washing.

[0024] When the oil production assembly is lifted, the inner sand flushing tube will also move upward. If there are sand impurities in the inner sand flushing tube and the outer sand flushing tube, the lifting action can loosen the sand. When the inner sand flushing tube is lifted out of the wellhead, the sand in the inner sand flushing tube will also be lifted out, which is convenient for analyzing the composition of the sand layer. It is a mandatory physical sand cleaning. It is more efficient than sand flushing with well washing fluid and reduces the cost of well washing fluid.

[0025] The workflow is as follows:

[0026] (1) When the bottom of the oil pump is clogged by sand, lift the sucker rod and lift the oil production assembly into the bridge steam injection assembly;

[0027] (2) Through positive well washing, the sand at the bottom is washed out; through the uniform through hole, the sand is washed out layer by layer; and through the uniform through hole, steam is evenly injected into each oil layer;

[0028] (3) After steam injection, lower the sucker rod, adjust the anti-impact distance, and then pump oil.

[0029] The beneficial effects of the present invention are as follows: through positive well washing, the sand impurities in the tail pipe and the bottom of the oil layer are washed clean; through the uniform through hole, the sand is washed out layer by layer; and then through the uniform through hole, steam is uniformly injected into each oil layer. During steam injection, the steam does not pass through the inner wall of the oil pump barrel, avoiding scale jam after steam injection. Stable, efficient and energy-saving production is achieved.

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the sand accumulation state diagram of the oil well pump during the oil pumping process;

[0032] Figure 2 This is a diagram showing the steam injection channel being blocked by sand accumulation in the oil well pump during the oil pumping process;

[0033] Figure 3 It is a structural schematic diagram of a supporting device according to an embodiment of the present invention;

[0034] Figure 4 It is a structural schematic diagram of a well pump bottom blocked by sand according to an embodiment of the present invention;

[0035] Figure 5 This is a structural schematic diagram of the sand flushing and steam injection channel opening state diagram according to an embodiment of the present invention;

[0036] Figure 6 This is a state diagram of sand flushing and steam injection according to an embodiment of the present invention;

[0037] Figure 7 This is a state diagram after steam injection according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0039] Example 1

[0040] A heavy oil well sand flushing and steam injection process comprises the following steps:

[0041] (1) Through positive well washing, the sand impurities in the tail pipe and at the bottom of the oil layer are flushed away;

[0042] Positive well washing: The well washing fluid is injected through the opening of the oil pipe on the oil tree. After passing through the oil layer, the well washing fluid returns to the ground through the annular space between the oil pipe and the casing.

[0043] Backwashing: The well-washing fluid is injected through the opening of the casing on the Christmas tree. After passing through the annular space between the tubing and the casing to reach the oil layer, it returns to the ground through the inner hole of the tubing.

[0044] (2) The sand is washed out layer by layer through the uniform through holes. Because the depth of the uniform through holes buried by sand is different and the flow resistance is different, the sand will be washed away layer by layer in the order of the uniform through holes from bottom to top.

[0045] (3) Then, steam is uniformly injected into each oil layer through the equalizing hole. During steam injection, the steam does not pass through the inner wall of the oil pump barrel to avoid scale jam after steam injection;

[0046] Since the aperture of the average through hole increases gradually from top to bottom along the vertical direction, and the opening direction is different, because the steam comes from the upper part of the oil pipe, the average through hole closest to the heat source is designed to be the smallest, and it is larger further down, and the largest at the bottom. The specific aperture is determined according to the sand production of the oil layer and the well depth. In this way, the amount of steam passing through the average through holes at different heights can be relatively uniform. The steam passes through the annular space between the pump barrel and the outer pipe, and does not pass through the inner wall of the pump barrel.

[0047] like Figure 3 As shown, a supporting device for the sand flushing and steam injection process of a heavy oil well comprises a bridge-type sand injection and pumping anti-sand pump, wherein a sand flushing and steam injection tool is provided at the lower part of the bridge-type sand injection and pumping anti-sand pump.

[0048] The specific structure of the sand flushing and steam injection tool includes: an oil pipe string 6, the oil pipe string (oil pipe assembly) 6 is connected from the wellhead to the downhole oil pump, usually by multiple oil pipes connected by threads. The function is to connect the wellhead and the oil layer, and to transport oil, well washing fluid, and steam;

[0049] A sucker rod (sucker rod column) 1 is provided in the oil pipe string 6, the lower end of the sucker rod 1 is connected to the oil production assembly 2, the lower end of the oil pipe string 6 is connected to the bridge-type steam injection assembly 3, the lower end of the oil production assembly 2 is connected to a sand flushing inner tube 7, the lower end of the bridge-type steam injection assembly 3 is connected to a sand flushing outer tube 8, and the upper end of the sand flushing outer tube 8 is provided with an oil inlet steam sealing valve 9;

[0050] The rod of the plunger assembly of the oil pump (the oil production assembly includes the plunger part and the pump barrel part) is connected to the sucker rod column 1. The sucker rod column is a rod column composed of multiple sucker rods connected from the wellhead bare rod to the bottom of the well. During installation, the sucker rod column 1 is lowered to make the leather cup assembly at the bottom of the pump barrel assembly seal and position at the bottom of the outer tube. Under the cooperation of the plunger part and the pump barrel part, the up and down reciprocating motion of the plunger generates a pumping force to transport the oil to the ground.

[0051] Under the action of the oil inlet steam seal valve 9, the oil in the oil layer can enter, so that the oil pump can not only suck the oil in the bottom layer, but also suck the oil near the oil inlet steam seal valve, thereby increasing the oil inlet channel and improving the pump efficiency. The role of the steam seal is that when injecting steam, since there is a valve ball seat inside the oil inlet steam seal valve, which is equivalent to a one-way valve, it only allows steam to enter but not exit, and steam will not be ejected from the oil inlet steam seal valve.

[0052] The side of the sand-blasting outer tube 8 is provided with equalizing holes 81 of different sizes at different depths along the circumferential direction. The aperture of the equalizing holes gradually increases from top to bottom along the height direction, and the opening directions are different. Because the steam comes from the upper part of the oil pipe, the equalizing holes closest to the heat source are designed to be the smallest, and the holes further down are larger, and the largest at the bottom, so that the amount of steam passing through the equalizing holes at different heights is relatively uniform. The steam passes through the annular space between the pump barrel and the outer tube, and does not pass through the inner wall of the pump barrel.

[0053] The function of the sand flushing outer pipe 8 is to guide the flow of oil, well washing fluid, steam and other media. In combination with the uniform through hole, stratified well washing and uniform steam injection are achieved.

[0054] The sand flushing inner tube 7 is connected to the lower part of the oil production assembly 2, and its function is to guide the flow of oil, well washing fluid, steam and other media.

[0055] A sand flushing steam injection channel 4 is provided between the sand flushing inner tube 7 and the sand flushing outer tube 8. When the pumping rod string is lifted, the oil production assembly is driven upward, and the sand flushing inner tube (central tube) 7 follows the upward movement, and a sand layer cavity 5 is formed at the lower part of the sand flushing inner tube 7, providing an initial channel for sand flushing and well washing.

[0056] When the oil production assembly is lifted, the inner sand flushing tube will also move upward. If there are sand impurities in the inner sand flushing tube and the outer sand flushing tube, the lifting action can loosen the sand. When the inner sand flushing tube is lifted out of the wellhead, the sand in the inner sand flushing tube will also be lifted out, which is convenient for analyzing the composition of the sand layer. It is a mandatory physical sand cleaning. It is more efficient than sand flushing with well washing fluid and reduces the cost of well washing fluid.

[0057] The workflow is as follows:

[0058] (1) When the bottom of the oil pump is clogged by sand, lift the sucker rod 1 and lift the oil production assembly 2 into the bridge steam injection assembly 3 to straighten it. Figure 5 As shown;

[0059] (2) Through positive well washing, the sand at the bottom is washed out; through the uniform through hole, the sand is washed out layer by layer; and then through the uniform through hole, steam is injected evenly into each oil layer, such as Figure 6 As shown;

[0060] (3) After steam injection, lower the sucker rod 1, adjust the anti-shock distance, and start pumping oil. Figure 7 shown.

Claims

1. A sand flushing and steam injection process for a heavy oil well, characterized in that: The following steps are involved: (1) Through positive well washing, the sand impurities in the tail pipe and at the bottom of the oil layer are flushed away; (2) The sand is washed out layer by layer through the uniform through holes. Because the depth of the uniform through holes buried by sand is different and the flow resistance is different, the sand will be washed away layer by layer in the order of the uniform through holes from bottom to top. (3) Steam is then uniformly injected into each oil layer through the uniform through hole. During steam injection, the steam does not pass through the inner wall of the oil pump barrel to avoid scale jamming after steam injection. The side surface of the sand flushing outer pipe is provided with uniform through holes of different sizes at different depths along the circumferential direction. The aperture of the uniform through hole gradually increases from top to bottom, and the opening directions are different.

2. A supporting device for a heavy oil well sand flushing and steam injection process as claimed in claim 1, characterized in that: It comprises a bridge-type injection and suction sand prevention pump, a sand flushing and steam injection tool is provided at the lower part of the bridge-type injection and suction sand prevention pump, the sand flushing and steam injection tool comprises an oil pipe string, a sucker rod is provided in the oil pipe string, the lower end of the sucker rod is connected to the oil production assembly, and the lower end of the oil pipe string is connected to the bridge-type steam injection assembly; the lower end of the oil production assembly is connected to a sand flushing inner tube, the lower end of the bridge-type steam injection assembly is connected to a sand flushing outer tube, and the upper end of the sand flushing outer tube is provided with an oil inlet steam sealing valve on the outer side and is communicated with the interior.

3. The matching device according to claim 2, characterized in that: The pull rod of the oil pump is connected to the oil pump rod string, and the oil pump rod string is a rod string composed of a plurality of oil pump rods connected from the wellhead polished rod to the well bottom.

4. The matching device according to claim 2, characterized in that: A sand flushing steam injection channel is provided between the sand flushing inner tube and the sand flushing outer tube. When the pumping rod column is lifted to drive the oil production assembly upward, a sand layer cavity is formed at the bottom of the sand flushing inner tube.

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