A low-cost mechanical pumping to water injection process system, method, and design method

Abstract

This invention provides a low-cost mechanical well-to-water injection process system, method, and design. The system includes an injection pipe, an injection rod string, a wellhead connector, a drive unit, a reciprocating water injection device, and a water supply mechanism. The drive unit and water supply mechanism are both located on the surface. The injection pipe is located inside the well casing and its lower end communicates with the oil layer. The upper end of the injection pipe is sealed to the wellhead connector located at the wellhead. The reciprocating water injection device is located inside the injection pipe and the two are sealed together. The bottom end of the injection rod string is fixedly connected to the reciprocating water injection device, and the top end of the injection rod string passes through the wellhead connector and connects to the drive unit. The water supply mechanism is connected to the injection pipe through the wellhead connector. This invention provides a water source through surface water supply equipment, utilizes the existing drive unit, and, with a suitable rod string combination, efficiently transmits power to the downhole reciprocating water injection device, thereby injecting water into the formation. Furthermore, the pressure loss when the injected water reaches the formation is smaller, providing technical support for the low-cost conversion of mechanical wells to water injection wells.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a low-cost mechanical extraction to water injection process system and method, as well as a design method. Background Technology

[0002] Water injection is one of the important means to replenish the formation with energy and improve the oil recovery rate during the oilfield development process. At present, oilfield water injection mainly adopts the surface water injection method, which involves increasing the pressure of the injected water through a high-pressure water injection pump, and then injecting the injected water into each water injection well through the water distribution room via the water injection pipeline. This is to maintain or restore the formation pressure, drive crude oil into the production well, and improve the crude oil extraction speed and recovery rate.

[0003] In oilfield development, some pumping wells need to be converted into water injection wells. This requires dismantling the surface supporting equipment, installing the necessary water injection equipment, and laying surface water injection pipelines. The construction and maintenance of surface water injection equipment is costly and economically inefficient. Summary of the Invention

[0004] The purpose of this invention is to provide a low-cost mechanical mining to water injection process system to overcome the above-mentioned technical problems existing in the prior art.

[0005] Another objective of this invention is to provide a low-cost mechanical extraction to water injection process method to achieve safe and low-cost downhole water injection.

[0006] Another objective of this invention is to provide a low-cost design method for a mechanical pumping to water injection process system. By utilizing the original well pumping unit and applying a reasonable rod string design method, the original drive device can efficiently transmit power to the reciprocating water injection device to achieve the water injection requirements.

[0007] Therefore, the technical solution provided by the present invention is as follows: A low-cost mechanical mining to water injection process system includes a water injection pipe, a water injection rod string, a wellhead connector, a drive device, a reciprocating water injection device, and a water supply mechanism, wherein the drive device and the water supply mechanism are both located on the ground. The water injection pipe is located inside the well casing and its lower end is connected to the oil layer. The upper end of the water injection pipe is sealed to the wellhead connector located at the wellhead. The reciprocating water injection device is located inside the water injection pipe and the two are sealed to each other. The bottom end of the water injection rod is fixedly connected to the reciprocating water injection device. The top end of the water injection rod passes through the wellhead connector and is connected to the drive device. The water supply mechanism is connected to the water injection pipe through the wellhead connector.

[0008] The driving device is an oil pumping unit, and the top of the water injection rod is movably connected to the donkey head of the oil pumping unit.

[0009] The top of the wellhead connector is connected to a polished rod blowout preventer, and the top of the water injection rod extends through the polished rod blowout preventer, with the two dynamically sealed.

[0010] The wellhead joint is fixedly connected to a polished rod sealing box, and the top of the water injection rod extends out of the polished rod sealing box, with the two dynamically sealing each other.

[0011] A low-cost mechanical extraction to water injection process involves injecting water into the injection pipe through a water supply mechanism and wellhead connector, allowing water to enter the space above the injection pipe. Then, a drive unit drives the piston of a reciprocating water injection device to move up and down, pressing the water in the space above the injection pipe into the space below the injection pipe. Finally, the water is pressed into the oil layer from the space below the injection pipe. This process is repeated to achieve water injection.

[0012] A design method for a low-cost mechanical oil well conversion water injection system is proposed, which determines the pressure that the water injection system must meet for normal water injection based on basic oilfield data. P 注 and water injection volume; Based on water injection volume and pressure P 注 Determine the piston diameter and the required load on the upper part of the piston in the reciprocating water injection device; Considering that the water injection rod is mainly pressure-bearing, the weight of the water injection rod itself is calculated. Then, combined with the piston diameter, mechanical mining parameters, and perforation location, the pump depth and weight rod length are determined to obtain the load at the rod suspension point. It is then determined whether the piston diameter, the required load on the upper part of the piston, and the pressure and injection volume of the water injection process system are reasonably matched. If they are not reasonable, the required load on the upper part of the piston is recalculated until the piston diameter, the required load on the upper part of the piston, and the pressure and injection volume of the water injection process system are matched, thus completing the water injection process design. , In the formula, P 注 Just and P 杆 , P 地层 The force of the springs of the moving valve and the fixed valve on the piston of the water injection device is related to the force of the springs, but not to the depth position of the oil pump. P 注 Pinjection is the water injection pressure, MPa; Pformation is the formation pressure, MPa. P 杆 The pressure generated by the weight of the injection rod acting on the piston, in MPa; P 水 The wellhead water pressure is measured in MPa. P 液1 The pressure of the liquid column from the wellhead to the lower valve port of the reciprocating water injection device piston, in MPa; P 液2 The pressure of the liquid column from the lower valve port of the water injection device piston to the formation, in MPa; P 预紧1 The spring preload pressure of the valve on the upper part of the piston of the water injection device, in MPa; P预紧2 The spring preload pressure of the valve at the bottom of the piston of the water injection device.

[0013] Considering the water injection volume, the piston diameter of the reciprocating water injection device can be calculated using the following formula: In the formula, d p Piston diameter, mm; The density of water; q L m is the injection volume. 3 ; S For stroke, m; n Strokes per minute; η For pump efficiency, %.

[0014] If the load at the suspension point of the water injection rod exceeds the standard value, the rod assembly is readjusted and the strength is checked to ensure that the maximum load meets the operating load of the pumping unit, thus completing the design of the water injection rod.

[0015] The beneficial effects of this invention are: The present invention provides a low-cost mechanical well-to-water injection system. This system converts a mechanically extracted well into a water injection well by using a surface water supply system. Utilizing the existing drive unit and a suitable combination of rods and columns, power is efficiently transmitted to the reciprocating water injection device downhole, thereby injecting water into the formation. It eliminates the need for additional water injection equipment, long-distance surface water injection pipelines, and concerns about the impact of underground high temperatures on electrical equipment. Furthermore, it results in less pressure loss when the injected water reaches the formation, leading to better water injection performance. This provides technical support for low-cost mechanical well-to-water injection system conversion.

[0016] This invention utilizes surface water supply, allowing water to flow by gravity without the need for surface booster devices or associated power grids. Through its integrated water injection process design, it enables the transmission of power from the surface to the underground reciprocating water injection device, ensuring the long-term, efficient operation of the water injection system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of one embodiment of the present invention; Figure 2 This is a design flowchart of the system of the present invention.

[0018] In the diagram: 1. Water injection pipe; 2. Water injection rod; 3. Drive device; 4. Reciprocating water injection device; 41. Upper space; 42. Lower space; 5. Wellhead connector; 51. Polished rod sealing box; 52. Polished rod blowout preventer; 53. First port; 54. Second port; 6. Water supply mechanism; 7. Casing. Detailed Implementation

[0019] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0020] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0021] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning. Example 1

[0022] This invention provides a low-cost mechanical mining to water injection process system, including a water injection pipe 1, a water injection rod 2, a wellhead connector 5, a drive device 3, a reciprocating water injection device 4, and a water supply mechanism 6, wherein the drive device 3 and the water supply mechanism 6 are both located on the ground. The water injection pipe 1 is located inside the well casing 7 and its lower end is connected to the oil layer. The upper end of the water injection pipe 1 is sealed to the wellhead connector 5 located at the wellhead. The reciprocating water injection device 4 is located inside the water injection pipe 1 and the two are sealed to each other. The bottom end of the water injection rod 2 is fixedly connected to the reciprocating water injection device 4. The top end of the water injection rod 2 passes through the wellhead connector 5 and is connected to the drive device 3. The water supply mechanism 6 is connected to the water injection pipe 1 through the wellhead connector 5.

[0023] like Figure 1 As shown, the piston of the reciprocating water injection device 4 is driven by the driving device 3 to press the water in the space 41 above the water injection pipe 1 into the space 42 below the water injection pipe 1, and then flows into the oil layer from the space 42 below the water injection pipe 1.

[0024] This invention provides a water source through a surface water supply mechanism 6 and uses a drive device with a reasonable combination of rods and columns to efficiently transmit power to the reciprocating water injection device 4 in the well. The reciprocating water injection device 4 injects water into the formation through reciprocating motion. It has the advantages of not needing to install the supporting equipment required for water injection, not needing to lay long-distance surface water injection pipelines 1, and not needing to worry about the impact of underground high temperature on electrical equipment. Moreover, the pressure loss when the injected water reaches the formation is smaller, and the water injection effect is better. Example 2

[0025] Based on Example 1, this example provides a low-cost mechanical pumping to water injection process system, wherein the driving device 3 is an oil pumping unit, and the top end of the water injection rod 2 is movably connected to the donkey head of the oil pumping unit.

[0026] The pumping unit provides power, which drives the piston up and down via the water injection rod string 2. When switching from oil well to water injection, the drive device is the original pumping unit installed in the oil well, which can realize the conversion of oil well to water injection well, reducing the work and cost of dismantling oil well equipment. When the piston moves down, it relies on the gravity of the water injection rod string 2 itself, without the need for other energy sources. Example 3

[0027] Based on Example 1, this example provides a low-cost mechanical extraction to water injection process system, wherein the top of the wellhead connector 5 is connected to a polished rod blowout preventer 52, and the top of the water injection rod 2 extends through the polished rod blowout preventer 52 and the two are dynamically sealed.

[0028] The polished rod blowout preventer 52 is used to prevent excessive downhole pressure from causing a blowout, and can also achieve dynamic sealing between the water injection rod string 2 and the wellhead connector 5.

[0029] The wellhead connector 5 is fixedly connected to a polished rod sealing box 51, and the top of the water injection rod 2 extends out of the polished rod sealing box 51 and the two are dynamically sealed.

[0030] The smooth rod sealing box 51 is used to ensure dynamic sealing between the water injection rod 2 and the wellhead joint 5 when the rod moves up and down.

[0031] Among them, the wellhead connector 5 can effectively seal the oil and casing pressure, while the polished rod blowout preventer 52 and the polished rod sealing box 51 achieve dynamic sealing of the annular space between the water injection pipe 1 and the water injection rod string 2, ensuring the smooth operation of the downhole pressurized water injection process system. The wellhead connector 5 has a port connecting the chamber between the casing 7 and the water injection pipe 1, which is normally closed and can be used to release formation pressure before well workover operations, and can also be used for well washing operations.

[0032] Water injection pipe 1 includes an upper outer pipe and a lower outer pipe. The bottom end of the upper outer pipe and the top end of the lower outer pipe are detachably connected and the connection is sealed. A reciprocating water injection device 4 is installed at the connection between the upper outer pipe and the lower outer pipe. Example 4

[0033] Based on Example 1, this example provides a low-cost mechanically operated water injection system. The reciprocating water injection device 4 includes a piston sleeve with a sealed bottom end. A piston is located inside the piston sleeve, and the two are slidably fitted together. The outer wall of the piston and the inner wall of the piston sleeve are dynamically sealed. The bottom end of the piston and the piston sleeve form a pressurization chamber. A first water flow channel is opened on the piston, and a water injection port is opened at the bottom of the piston sleeve. The first water flow channel connects the space 41 above the water injection pipe 1 with the pressurization chamber, and the water injection port connects the pressurization chamber with the space 42 below the water injection pipe 1.

[0034] like Figure 1 As shown, the reciprocating water injection device 4 divides the water injection into an upper space 41 located above the reciprocating water injection device 4 and a lower space 42 located below the reciprocating water injection device 4. A second annulus is formed between the water injection pipe 1 and the sleeve 7. The reciprocating water injection device 4 can achieve pressurization, has a simple structure, and high reliability.

[0035] Wellhead connector 5 is a four-way connector, consisting of a first port 53, a second port 54, a third port, and a fourth port. The first port 53 and the third port are connected to the space 41 above the water injection pipe 1, and the second port 54 and the fourth port are connected to the second annulus. Each of the first port 53, the second port 54, the third port, and the fourth port is equipped with a valve. The valve on the first port 53 is used to control the water volume and is normally open. The valve on the third port is used for well flushing operations in the space 41 above the water injection pipe 1 and is normally closed. The valve on the second port 54 is used for well flushing operations in the second annulus and is normally closed. The valve on the fourth port is used to release formation pressure before well workover operations and is normally closed.

[0036] The water supply mechanism 6 and the first port 53 are connected by a water supply pipeline. Water enters the space 41 above the water injection pipe 1 by gravity flow. A valve can be installed on the water supply pipeline, and there is no need to install a booster device on the ground water supply pipeline. Example 5

[0037] This embodiment provides a low-cost mechanical extraction to water injection process. Water is injected into the water injection pipe 1 through the water supply mechanism 6 and the wellhead connector 5, so that the water enters the space 41 above the water injection pipe 1. Then, the driving device 3 drives the piston of the reciprocating water injection device 4 to move up and down, pressing the water in the space 41 above the water injection pipe 1 into the space 42 below the water injection pipe 1. Finally, the water is pressed into the oil layer from the space 42 below the water injection pipe 1. This process is repeated to achieve water injection.

[0038] When starting the injection, first ensure that there is water in the surface water supply system 6 and that the water supply pipeline is unobstructed, and ensure that the valve on the first port 53 of the wellhead connector 5 and the polished rod blowout preventer 52 are open. Then open the valve on the water supply pipeline, and water is supplied from the water supply equipment to the wellhead through the water supply pipeline, enters the wellhead connector 5, and flows into the space 41 above the water injection pipe 1. At this time, the incoming water gradually fills the space 41 above the water injection pipe 1. Start the pumping unit, drive the water injection rod string 2 to drive the piston of the reciprocating water injection device 4 to move up and down, inject the incoming water into the oil layer, and realize downhole pressurized water injection.

[0039] When stopping injection, first stop the pumping unit, then close the valve on the first port 53 of the wellhead connector 5 and the polished rod blowout preventer 52, and then close the valve on the water supply line to stop water injection. Example 6

[0040] This embodiment provides a design method for a low-cost mechanical pumping to water injection process system, such as... Figure 1 As shown, based on the oilfield's basic data, the pressure required for normal water injection in the water injection system is determined. P 注 and water injection volume; , In the formula, P 注 Just and P 杆 , P 地层 The force of the springs of the moving valve and the fixed valve on the piston of the water injection device is related to the force of the springs, but not to the depth position of the oil pump. P 注 Pinjection is the water injection pressure, MPa; Pformation is the formation pressure, MPa. P 杆 The pressure generated by the piston due to the weight of the water injection rod 2, in MPa; P 水 The wellhead water pressure is measured in MPa. P 液1 The pressure of the liquid column from the wellhead to the lower valve port of the reciprocating water injection device 4 pistons, in MPa; P 液2 The pressure of the liquid column from the lower valve port of the water injection device piston to the formation, in MPa; P 预紧1 The spring preload pressure of the valve on the upper part of the piston of the water injection device, in MPa; P 预紧2 The spring preload pressure of the valve at the bottom of the piston of the water injection device.

[0041] Based on water injection volume and pressure P 注 Determine the piston diameter and the required load on the upper part of the piston of the reciprocating water injection device 4; Considering that the water injection rod 2 is mainly pressure-bearing, the weight of the water injection rod 2 itself is calculated. Then, combined with the piston diameter, mechanical extraction parameters, and perforation position, the pump depth and the length of the weight rod are determined to obtain the suspension point load of the rod (if the suspension point load of the water injection rod 2 exceeds the standard value, the rod assembly is readjusted and the strength is checked to ensure that the maximum load meets the operating load of the pumping unit, thus completing the design of the water injection rod 2). It is also determined whether the piston diameter, the required load on the upper part of the piston, and the pressure and injection volume of the water injection process system are reasonably matched. If it is not reasonable, the required load on the upper part of the piston is recalculated until the piston diameter, the required load on the upper part of the piston, and the water injection process system pressure and injection volume are matched, and the water injection process matching design is completed.

[0042] In particular, according to formulas C.22 and C.25 in SYT5873-2017 "Design and Construction Method of Rod Pump Oil Pumping System", the suspension point load and torque of the water injection rod column 2 are calculated respectively to ensure that the suspension point load and torque are within the rated range of the oil pumping unit equipment.

[0043] Considering the water injection volume, the piston diameter of the reciprocating water injection device 4 is calculated using the following formula: In the formula, d p Piston diameter, mm; The density of water; q L m is the injection volume. 3 ; S For stroke, m; n Strokes per minute; η For pump efficiency, %.

[0044] Through the design of the water injection process, the power is transmitted from the ground to the reciprocating water injection device 4 in the well, ensuring the long-term and efficient operation of the water injection process system.

[0045] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A low-cost mechanical pumping to water injection process system, characterized in that: It includes a water injection pipe, a water injection rod, a wellhead connector, a drive device, a reciprocating water injection device, and a water supply mechanism, wherein the drive device and the water supply mechanism are both located on the ground. The water injection pipe is located inside the well casing and its lower end is connected to the oil layer. The upper end of the water injection pipe is sealed to the wellhead connector located at the wellhead. The reciprocating water injection device is located inside the water injection pipe and the two are sealed to each other. The bottom end of the water injection rod is fixedly connected to the reciprocating water injection device. The top end of the water injection rod passes through the wellhead connector and is connected to the drive device. The water supply mechanism is connected to the water injection pipe through the wellhead connector.

2. The low-cost mechanical pumping to water injection process system according to claim 1, characterized in that: The driving device is an oil pumping unit, and the top of the water injection rod is movably connected to the donkey head of the oil pumping unit.

3. The low-cost mechanical pumping to water injection process system according to claim 1, characterized in that: The top of the wellhead connector is connected to a polished rod blowout preventer, and the top of the water injection rod extends through the polished rod blowout preventer, with the two dynamically sealed.

4. The low-cost mechanical pumping to water injection process system according to claim 1, characterized in that: The wellhead joint is fixedly connected to a polished rod sealing box, and the top of the water injection rod extends out of the polished rod sealing box, with the two dynamically sealing each other.

5. A low-cost mechanical pumping to water injection process method, using the low-cost mechanical pumping to water injection process system described in claim 1, characterized in that: Water is injected into the injection pipe through the water supply mechanism and wellhead connector, allowing water to enter the space above the injection pipe. Then, the drive equipment drives the piston of the reciprocating water injection device to move up and down, pressing the water in the space above the injection pipe into the space below the injection pipe. Finally, the water is pressed into the oil layer from the space below the injection pipe. This process is repeated to achieve water injection.

6. The design method of a low-cost mechanical pumping to water injection process system according to claim 1, characterized in that: Based on the oilfield's basic data, the pressure that the water injection system needs to meet for normal water injection is determined. P 注 and water injection volume; Based on water injection volume and pressure P 注 Determine the piston diameter and the required load on the upper part of the piston in the reciprocating water injection device; Considering that the water injection rod is mainly pressure-bearing, the weight of the water injection rod itself is calculated. Then, combined with the piston diameter, machine extraction parameters, and perforation position, the pump depth and weight rod length are determined to obtain the suspension load of the water injection rod. The piston diameter, the required load on the upper part of the piston, and whether the matching of the water injection process system pressure and injection volume are reasonable are determined. If it is not reasonable, the required load on the upper part of the piston is recalculated until the piston diameter, the required load on the upper part of the piston, and the water injection process system pressure and injection volume are matched, and the water injection process matching design is completed.

7. The design method of a low-cost mechanical pumping to water injection process system according to claim 6, characterized in that: , In the formula, P 注 Just and P 杆 , P 地层 The force of the springs of the moving valve and the fixed valve on the piston of the water injection device is related to the force of the springs, but not to the depth position of the oil pump. P 注 Pinjection is the water injection pressure, MPa; Pformation is the formation pressure, MPa. P 杆 The pressure generated by the weight of the injection rod acting on the piston, in MPa; P 水 The wellhead water pressure is measured in MPa. P 液1 The pressure of the liquid column from the wellhead to the lower valve port of the reciprocating water injection device piston, in MPa; P 液2 The pressure of the liquid column from the lower valve port of the water injection device piston to the formation, in MPa; P 预紧1 The spring preload pressure of the valve on the upper part of the piston of the water injection device, in MPa; P 预紧2 The spring preload pressure of the valve at the bottom of the piston of the water injection device.

8. The design method of a low-cost mechanical pumping to water injection process system according to claim 6, characterized in that: Considering the water injection volume, the piston diameter of the reciprocating water injection device can be calculated using the following formula: In the formula, d p Piston diameter, mm; The density of water; q L m is the injection volume. 3 ; S For stroke, m; n Strokes per minute; η For pump efficiency, %.

9. The design method of a low-cost mechanical pumping to water injection process system according to claim 1, characterized in that: If the load at the suspension point of the water injection rod exceeds the standard value, the rod assembly is readjusted and the strength is checked to ensure that the maximum load meets the operating load of the pumping unit, thus completing the design of the water injection rod.

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