High-pressure small-flow balance gas injection control system and method

Abstract

The invention discloses a high-pressure small-flow balance gas injection control system and method, and belongs to the technical field of oil and gas field ground engineering construction. Comprising a gas injection manifold; the gas injection manifold is respectively connected with a plurality of single well injection pipelines which are arranged in parallel; outlets of the single well injection pipelines are connected with a gas production wellhead device; a flow meter, a flow adjusting valve and a third pressure transmitter are sequentially arranged on the single well injection pipeline in the gas injection transmission direction. The flow regulating valves, the electric stop valves, the pressure transmitters and the flowmeters are arranged at well mouths of all the injection wells, flow limiting control is carried out on the wells with low pressure, pressure control is carried out on the wells with the highest pressure, and therefore dynamic balance gas injection control over all the injection wells of an injection well site is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field surface engineering construction, and relates to a high-pressure and small-flow balanced gas injection control system and method. Background Art

[0002] As oilfield exploitation continues, the reservoir is dense and water injection development cannot establish an effective pressure displacement system, resulting in a gradual decline in crude oil production in the oil wells. In order to quickly replenish formation energy, establish an effective pressure displacement system, and improve the development level, gas phase injection (associated gas or oxygen-reduced air) is carried out in the reservoir to increase reservoir energy and thereby increase the crude oil production of a single well.

[0003] See also Figure 2 At present, the gas phase injection method of the oil field is to set up a control system at the gas injection station to monitor the entire gas injection process. The compressor of the gas injection station pressurizes the injected gas phase medium, and the pressurized gas is transported from the gas injection station to the downstream gas injection wells. The gas main pipe of each well field then distributes the gas to each injection well. When the flow meter of the first injection well in the well field measures that the gas volume injected into the well reaches the daily injection volume, an alarm signal is sent to the control system of the gas injection station, and then the on-site operator goes to the well field to close the gas injection pipeline valve of the gas injection well to achieve daily quantitative injection of the gas injection well. When the second well in the well field reaches the daily injection volume, the above operation is performed in the same way. When all the injection wells in the well field reach the daily injection volume, the gas injection pipeline valves of all injection wells are closed, and the main pipe valve of the well field is closed at the same time. The gas injection control process of each well field is analogous. When all well fields reach the daily injection volume, the control system of the gas injection station stops the compressor, and the gas injection of the block ends on that day.

[0004] However, the above-mentioned gas injection control method has the following disadvantages: 1) It is impossible to control the speed of gas injection into each well: Since the wellhead pressure of each injection well is different, when the injection is started, due to the principle of least resistance, the gas in the gas main pipe of the well site will first enter the well with the lowest wellhead pressure, and the well with high wellhead pressure will hardly have any gas injected. This will cause the well with low wellhead pressure to reach the daily injection volume in a very short time, and cause the gas volume injected into the well to be too high instantly, resulting in the risk of gas channeling. 2) Large manual workload: At present, domestic oil field ground stations have moved towards the unmanned mode of small stations. After each gas injection well reaches the daily injection volume, the gas injection station needs to send operators to the well site to close the gas injection well. The time for each well to reach the daily injection volume is different, so personnel need to be frequently sent to the well site to close the wells that have reached the injection volume, which is time-consuming and labor-intensive.

[0005] Therefore, it is urgent to propose a new gas injection control method to achieve uniform gas injection in each injection well and effectively improve the level of oilfield development. Summary of the invention

[0006] The purpose of the present invention is to solve the technical problems in the prior art that gas is easily blowby in the gas injection well field, the injection speed of the high-pressure well is too slow, it is difficult to adjust in real time, and the manual workload is large, and to provide a high-pressure, small-flow balanced gas injection control system and method.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a high-pressure, small-flow balanced gas injection control system, including a gas injection manifold; the gas injection manifold is respectively connected to a number of single-well injection pipelines, and the several single-well injection pipelines are arranged in parallel; the outlets of the single-well injection pipelines are all connected to a gas production wellhead device; the single-well injection pipelines are sequentially provided with a flow meter, a flow regulating valve and a third pressure transmitter along the gas injection transmission direction.

[0009] Furthermore, a first pressure transmitter is provided on the gas injection manifold.

[0010] Furthermore, a switch valve is also provided on the single well injection pipeline; the inlet of the switch valve is connected to the gas injection manifold through a pipeline.

[0011] Furthermore, a second pressure transmitter is also provided on the single well injection pipeline; the second pressure transmitter is located on the pipeline between the switch valve and the flow meter.

[0012] Furthermore, a check valve is also provided on the single well injection pipeline; the check valve is located on the pipeline between the flow regulating valve and the third pressure transmitter.

[0013] Furthermore, an electric shut-off valve is also provided on the single well injection pipeline; the electric shut-off valve is located on the pipeline between the check valve and the third pressure transmitter.

[0014] Furthermore, the electric shut-off valve is an electro-hydraulic valve.

[0015] In a second aspect, the present invention provides a high-pressure and low-flow balanced gas injection control method using the above system, comprising the following steps:

[0016] At the beginning of the gas injection process, the compressor starts, and the flow control valve on the injection pipeline of the single well with the highest wellhead pressure is opened to 0%; the flow control valves on the injection pipelines of the other single wells are opened to 100%;

[0017] When the gas injection manifold pressure rises to the same level as the lowest wellhead pressure, the flow control valve opening for regulating the lowest wellhead pressure starts to decrease from 100%; when the gas injection manifold pressure rises to the same level as the second lowest wellhead pressure, the flow control valve opening for regulating the second lowest wellhead pressure starts to decrease from 100%;

[0018] As the pressure of the gas injection manifold continues to increase, the flow control valve opening corresponding to the wellhead pressure is reduced in sequence; finally, when the pressure of the gas injection manifold reaches the same as the highest wellhead pressure, the flow control valve opening with the highest wellhead pressure is slowly opened from the previous 0%;

[0019] When a gas injection well reaches its daily injection volume at any point in time, the electro-hydraulic valve is shut off and injection is stopped, while the remaining wells continue to inject gas.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention discloses a high-pressure, low-flow balanced gas injection control system and method. A flow regulating valve, an electric shut-off valve, a pressure transmitter and a flow meter are arranged at the wellhead of each injection well. By implementing flow limiting control on the well with lower pressure and pressure control on the well with the highest pressure, dynamic balanced gas injection control of each injection well in an injection well field is achieved. The problem that the gas injection speed of the well with lower pressure in the gas injection well field is too fast, resulting in gas blowby, while the injection speed of the well with higher pressure is too slow is solved. The defect that the gas injection pressure and speed of the wellhead cannot be adjusted in real time after the throttling device is manually set is overcome. In addition, the present invention saves labor costs, is safe and reliable, and has good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 It is a schematic diagram of the overall structure of the system of the present invention;

[0024] Figure 2 This is a schematic diagram of the oil field gas injection system structure.

[0025] Among them: 1-first pressure transmitter; 2-switch valve; 3-second pressure transmitter; 4-flow meter; 5-flow regulating valve; 6-check valve; 7-electro-hydraulic valve; 8-third pressure transmitter; 9-gas wellhead device. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0029] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0030] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0033] See also Figure 1 The embodiment of the present invention discloses a high-pressure, small-flow balanced gas injection control system, including a gas injection manifold; the gas injection manifold is respectively connected to a plurality of single-well injection pipelines, and the plurality of single-well injection pipelines are arranged in parallel; the outlets of the single-well injection pipelines are all connected to a gas production wellhead device 9; the single-well injection pipelines are sequentially provided with a flow meter 4, a flow regulating valve 5 and a third pressure transmitter 8 along the gas injection transmission direction.

[0034] In a feasible implementation manner of the present invention, a first pressure transmitter 1 is provided on the gas injection manifold.

[0035] In a feasible implementation manner of the present invention, a switch valve 2 is further provided on the single well injection pipeline; the inlet of the switch valve 2 is connected to the gas injection manifold through a pipeline.

[0036] In a feasible implementation manner of the present invention, a second pressure transmitter 3 is further provided on the single well injection pipeline; the second pressure transmitter 3 is located on the pipeline between the switch valve 2 and the flow meter 4 .

[0037] In a feasible implementation manner of the present invention, a check valve 6 is further provided on the single well injection pipeline; the check valve 6 is located on the pipeline between the flow regulating valve 5 and the third pressure transmitter 8 .

[0038] In a feasible implementation manner of the present invention, an electric shut-off valve is further provided on the single well injection pipeline; the electric shut-off valve is located on the pipeline between the check valve 6 and the third pressure transmitter 8 .

[0039] In a feasible implementation manner of the present invention, the electric shut-off valve is an electro-hydraulic valve 7 .

[0040] The present invention sets a flow regulating valve 5, an electric shut-off valve, a pressure transmitter and a flow meter 4 at the wellhead of each injection well, implements flow limiting control on the well with lower pressure and pressure control on the well with the highest pressure, so as to realize dynamic balanced gas injection control of each injection well in the injection well field.

[0041] The embodiment of the present invention discloses a high-pressure and low-flow balanced gas injection control method using the above system, comprising the following steps:

[0042] S1, the gas injection process begins, the compressor starts, the flow control valve (5) on the injection pipeline of the single well with the highest wellhead pressure is opened to 0%; the flow control valves (5) on the injection pipelines of the other single wells are opened to 100%;

[0043] S2, when the pressure of the gas injection manifold rises to the same as the lowest wellhead pressure, the opening of the flow control valve (5) for regulating the lowest wellhead pressure starts to decrease from the previous 100%; when the pressure of the gas injection manifold rises to the same as the second lowest wellhead pressure, the opening of the flow control valve (5) for regulating the second lowest wellhead pressure starts to decrease from the previous 100%;

[0044] S3, as the pressure of the gas injection manifold continues to increase, the opening of the flow control valve (5) corresponding to the wellhead pressure is reduced in sequence; finally, when the pressure of the gas injection manifold reaches the same as the highest wellhead pressure, the opening of the flow control valve (5) with the highest wellhead pressure is slowly opened from the previous 0%;

[0045] S4, at any time point, when a gas injection well reaches the daily injection volume, the electro-hydraulic valve (7) is closed and the injection is stopped, while the other wells continue to inject gas.

[0046] Example:

[0047] This embodiment takes a 3-well injection well field with different wellhead pressures of the 3 injection wells as an example (well fields with more than 3 wells are analogous). In a 3-well gas injection well field, before gas injection is started, the wellhead pressure PT-111 of well 1 is 12Mpa, the wellhead pressure PT-121 of well 2 is 18Mpa, and the wellhead pressure PT-131 of well 3 is 24Mpa.

[0048] In the first stage, the gas injection process begins, the compressor starts, and the gas injection manifold pressure PT-101 begins to rise (it has not reached 12MPa at this time). The regulating valve FV-113 of well 1# with the lowest wellhead pressure is opened 100%, the regulating valve FV-123 of well 2# with the second highest wellhead pressure is opened 100%, and the regulating valve FV-133 of well 3# with the highest wellhead pressure is opened 0%.

[0049] After a period of gas injection, when the manifold pressure rises to 12MPa, at this time, since the wellhead pressure PT-111 of Well 1# is the lowest (12MPa) compared with Wells 2# and 3#, according to the principle of least resistance, the gas in the manifold is injected into Well 1#, while there is basically no gas injection into Wells 2# and 3#. At this time, Well 1# performs flow regulation, and the opening of the regulating valve FV-113 begins to decrease from the previous 100% (the reduction range is calculated in the control system according to the set injection volume), controls the gas volume injected into Well 1#, and avoids gas being injected into Well 1# at the same speed as the compressor outlet. In addition, the regulating valve FV-113 of Well 1# holds part of the incoming gas in the manifold while controlling the gas injection volume, so that Well 1# The pressure before the well regulating valve (i.e., the manifold pressure PT-101) rises. At this time, the regulating valve of the 2# well with the lower pressure among the 2# and 3# wells (the 2# well has no gas injection, and the wellhead pressure PT-121 is still 18Mpa) is 100% open (because it is regulating the flow, and the manifold pressure has not risen to the level that can be injected into the 2# well, so the program controls the opening of the 2# well regulating valve FV-123 to 100%), and the regulating valve FV-133 of the 3# well with the highest pressure is 0% open (because it is regulating the pressure, and the manifold pressure has not risen to the stage that can be injected into the 3# well, so the program controls the 3# well regulating valve FV-133 to close to the minimum to achieve the increase of the manifold pressure). At this stage, the regulating valve FV-113 of the 1# well also performs cascade PID control according to the injection flow FT-113 of the 1# well and in combination with the aforementioned PT-101. The amount of gas injected into well 1# is neither too fast to cause a decrease in the manifold pressure, nor is the gas injection rate into well 1# uniform according to the allocated injection volume.

[0050] In the second stage, as the gas injection process continues, when the manifold pressure PT-101 rises to 18MPa, the 2# well begins to inject gas. Similarly, the regulating valve FV-123 of the 2# well performs flow regulation. At this time, the opening of FV-123 begins to decrease from the previous 100% (the reduction is calculated in the control system according to the set injection volume). By controlling the opening of the regulating valve of the 2# well, the injection into the 2# well is achieved at a predetermined speed. At this time, the opening of the regulating valve of the 3# well with the highest pressure is still 0% (because it is performing pressure regulation, and the manifold pressure PT-101 has not risen to the stage where it can be injected into the 3# well, so the program will control the regulating valve FV-133 to close to the minimum to achieve the increase of the manifold pressure). At this stage, the regulating valve FV-123 of the 2# well also performs cascade PID control based on the injection flow FT-123 of the 2# well and in combination with the aforementioned PT-101. The amount of gas injected into well 2# is neither too fast to cause a decrease in the manifold pressure, nor is the gas injection rate into well 2# uniform according to the allocated injection volume.

[0051] In the third stage, as the manifold pressure PT-101 continues to rise, when the manifold pressure rises to meet the injection conditions of Well 3# (PT-101 reaches 24MPa), the regulating valve FV-133 of Well 3# slowly opens from the previous 0% opening (the opening rate is calculated in the control system according to the set pressure change rate), and gas is injected into Well 3#. At this time, the regulating valve FV-133 of Well 3# performs pressure adjustment to ensure that its opening is not too large, resulting in too fast gas injection, which will cause the manifold pressure PT-101 to drop, and stop injection when it is lower than the wellhead pressure PT-131 of Well 3#. At this stage, the regulating valve FV-133 of Well 3# also performs cascade PID control based on the injection flow rate FT-133 of Well 3# and in combination with the aforementioned PT-101. The amount of gas injected into Well 3# is neither too fast to cause the manifold pressure to drop, nor the gas injection rate into Well 2# is uniformly injected according to the injection amount.

[0052] At this time, the injection of 1#~3# gas injection wells reaches dynamic balance, and the three wells are injected at the set flow rate. If the pressure of the three wells changes during the injection process, the control system continues to adjust according to the same control strategy as above. At the same time, during the gas injection process, if a gas injection well reaches the daily injection volume at any time point, the program controls the electro-hydraulic valve HY-1x2 of the well to shut off and stop injection, and the other wells continue to inject gas.

[0053] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-pressure, low-flow balanced gas injection control system, characterized in that: It comprises a gas injection manifold; the gas injection manifold is respectively connected to a plurality of single well injection pipelines, and the plurality of single well injection pipelines are arranged in parallel; the outlets of the single well injection pipelines are all connected to a gas production wellhead device (9); a flow meter (4), a flow regulating valve (5) and a third pressure transmitter (8) are sequentially arranged on the single well injection pipelines along the gas injection transmission direction.

2. A high-pressure, low-flow balanced gas injection control system according to claim 1, characterized in that: The gas injection manifold is provided with a first pressure transmitter (1).

3. A high-pressure, low-flow balanced gas injection control system according to claim 2, characterized in that: The single well injection pipeline is also provided with an on-off valve (2); the inlet of the on-off valve (2) is connected to the gas injection manifold through a pipeline.

4. A high-pressure, low-flow balanced gas injection control system according to claim 3, characterized in that: A second pressure transmitter (3) is also provided on the single well injection pipeline; the second pressure transmitter (3) is located on the pipeline between the switch valve (2) and the flow meter (4).

5. A high-pressure, low-flow balanced gas injection control system according to claim 4, characterized in that: A check valve (6) is also provided on the single well injection pipeline; the check valve (6) is located on the pipeline between the flow regulating valve (5) and the third pressure transmitter (8).

6. A high-pressure, low-flow balanced gas injection control system according to claim 5, characterized in that: The single well injection pipeline is also provided with an electric shut-off valve; the electric shut-off valve is located on the pipeline between the check valve (6) and the third pressure transmitter (8).

7. A high-pressure, low-flow balanced gas injection control system according to claim 5, characterized in that: The electric shut-off valve is an electro-hydraulic valve (7).

8. A high-pressure and low-flow balanced gas injection control method using the system according to any one of claims 1 to 7, characterized in that: The following steps are involved: The gas injection process begins, the compressor starts, and the flow control valve (5) on the injection pipeline of the single well with the highest wellhead pressure is opened to 0%; The flow control valves (5) on the injection pipelines of the other single wells are opened to 100%; When the gas injection manifold pressure rises to the same level as the lowest wellhead pressure, the opening of the flow control valve (5) for regulating the lowest wellhead pressure begins to decrease from 100%; When the gas injection manifold pressure rises to the same level as the second lowest wellhead pressure, the opening of the flow control valve (5) for regulating the second lowest wellhead pressure begins to decrease from 100%; As the pressure of the gas injection manifold continues to increase, the opening of the flow control valve (5) corresponding to the wellhead pressure is reduced in sequence; finally, when the pressure of the gas injection manifold reaches the same as the highest wellhead pressure, the opening of the flow control valve (5) with the highest wellhead pressure is slowly opened from the previous 0%; When a gas injection well reaches the daily injection volume at any time point, the electro-hydraulic valve (7) is closed and the injection is stopped, while the other wells continue to inject gas.

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