Injection device and carbon dioxide injection oil displacement under-injection well unblocking construction method based on same

Abstract

The invention discloses an injection device and a carbon dioxide injection oil displacement under-injection well unblocking construction method based on the injection device, and belongs to the technical field of oil development well repair operation. The injection device comprises a storage tank system, a self-dosing system and a high-pressure injection system; the storage tank system is connected with the self-dosing system and the high-pressure injection system; the storage tank system comprises a first storage tank and a second storage tank which are connected with each other; a first outlet and a second outlet are respectively formed in the bottoms of the first storage tank and the second storage tank; the first outlet and the second outlet are connected through a pipeline, a first branch and a second branch are arranged on the pipeline in parallel, and the self-dosing system and the high-pressure injection system are arranged on the first branch and the second branch respectively; an inlet of the self-dosing system is connected with an outlet of the feeding pipeline; an outlet of the high-pressure injection system is connected with an inlet of the injection pipeline.

Description

Technical Field

[0001] The invention belongs to the technical field of oil development and well repair operations, and in particular relates to an injection device and a construction method for unblocking an under-injected well by injecting carbon dioxide for oil recovery based on the injection device. Background Art

[0002] At present, most oil fields have entered the medium-to-high water content period, which makes development difficult and costly. With the continuous advancement of exploration and development technology, the proportion of low-permeability oil reservoirs in the total oil reserves is increasing, but due to the many characteristics of low-permeability reservoirs, such as low porosity, low permeability, severe heterogeneity, and strong reservoir sensitivity, their utilization is low. With the progress of water injection development, low-permeability oil reservoirs have production contradictions: production declines rapidly, water injection pressure continues to increase, and water injection oil recovery effect is poor.

[0003] As CO2-EOR technology gradually matures, CO2 flooding technology is an effective method to improve oil recovery. Injecting CO2 into the formation can not only improve the recovery of crude oil, but also achieve permanent storage of greenhouse gas CO2. CO2 capture, flooding and storage not only improve economic benefits, but also produce extensive social benefits. The CO2 miscible flooding has a significant oil recovery effect, but after CO2 is injected into the formation, it will contact with crude oil under certain temperature and pressure conditions, causing heavy components in the crude oil to precipitate and deposit, and crude oil asphaltene will deposit on the surface of the reservoir pores. The generated organic scale is adsorbed on the rock surface, which will block the pores and change the wettability of the rock. The organic scale accumulates near the wellbore in the near-wellbore area, which will cause the seepage channel to be blocked.

[0004] For CO2 flooding under-injection well unblocking construction, on-site construction operations are usually divided into two methods: one is conventional well workover unblocking operation with wellhead pressure relief; the other is pressurized coiled tubing unblocking operation. Conventional pressure relief well workover takes a long time to occupy the well, and due to the early injection of carbon dioxide, it is even difficult to reduce the pressure of some wellheads to zero; and pressurized operations have disadvantages such as high cost and high well control risks, so it is necessary to carry out research on new construction methods. Summary of the invention

[0005] In order to overcome the shortcomings of the conventional CO2 injection wells in the prior art, such as long decompression time, risk of backflow and gas exhalation, risk of high-pressure well control in pressurized operation and high cost, the purpose of the present invention is to provide an injection device and a construction method for unblocking under-injected wells by injecting CO2 for oil recovery based on the injection device, and to form a construction method for unmoving downhole pipe strings and pressurized operation by skidding the high-pressure injection device. The construction method of the present invention has the advantages of simple construction, low operation risk, and simultaneous unblocking of multiple under-injected wells, and convenient movement of supporting equipment without the need for large-scale lifting vehicles.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides an injection device, including a storage tank system, a self-dosing system and a high-pressure injection system;

[0008] The storage tank system is connected with the self-dosing system and the high-pressure injection system;

[0009] The storage tank system comprises a first storage tank and a second storage tank connected to each other;

[0010] The first storage tank and the second storage tank are provided with a first outlet and a second outlet at the bottom thereof, respectively; the first outlet and the second outlet are connected by a pipeline, a first branch and a second branch are provided in parallel on the pipeline, and the self-dosing system and the high-pressure injection system are provided on the first branch and the second branch, respectively;

[0011] The inlet of the self-dosing system is connected to the outlet of the feeding pipeline; the outlet of the high-pressure injection system is connected to the inlet of the injection pipeline.

[0012] In the specific implementation process, the self-dosing system and the high-pressure injection system are connected to a voltage stabilization control system; and the voltage stabilization control system is connected to a power generation system.

[0013] In the specific implementation process, a skid-mounted chassis of a trailer is arranged below the storage tank system, the self-dosing system and the high-pressure injection system, and a hydraulic support is arranged below the skid-mounted chassis of the trailer.

[0014] In the specific implementation process, a pressure gauge is provided on the injection pipeline.

[0015] In a specific implementation process, the outlet of the injection pipeline is connected to the inlets of several branches arranged in parallel, and the outlets of the branches are connected to the external input injection interface.

[0016] In a specific implementation process, a first storage tank internal reflux outlet and a second storage tank internal reflux outlet are respectively opened on the first storage tank and the second storage tank; the first storage tank internal reflux outlet is connected to the second storage tank internal reflux outlet through a pipeline.

[0017] In a specific implementation process, the bottoms of the first storage tank and the second storage tank are respectively provided with discharge outlets, and the discharge outlets are both connected to the inlet of the sewage pipe.

[0018] The present invention also provides a construction method for unblocking an under-injected well by injecting carbon dioxide for oil recovery, comprising the following steps:

[0019] S1: The injection device is connected to the CO2 injection wellhead, the valve on the second branch is closed, the valve on the first branch is opened, and the valve on the feeding pipeline is opened to suck the plugging remover and liquid preparation water to be injected into the first storage tank and the second storage tank through the self-dosing system;

[0020] S2: Close the valve on the feeding pipeline, open the valves on the first branch, the first storage tank and the second storage tank connecting pipeline, and start the self-dosing system for circulation and mixing;

[0021] S3: Open the valves on the second branch and the injection pipeline, and close other valves; start the high-pressure injection system, start injecting the plugging remover solution, and after the injection is completed, close the valves on the second branch and the injection pipeline, and then dismantle the connecting pipeline of the CO2 injection wellhead;

[0022] S4: Drain the remaining liquid in the first storage tank and the second storage tank, and end the construction.

[0023] The pressure test step is also included, and the pressure test step is as follows:

[0024] Diesel is used for pressure testing, and the test pressure is adjusted to be 2 to 5 MPa higher than the normal injection pressure at the wellhead. The pressure test lasts for 5 minutes.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention provides an injection device and a construction method for unblocking an under-injected well by injecting carbon dioxide for oil recovery based on the injection device. A skid-mounted high-pressure injection device is connected to the CO2 injection wellhead, and then a pressure-reducing and injection-increasing unblocking agent is added to the storage tank box of the skid-mounted high-pressure injection device, and finally the injection pump is started. When the injection pressure is high and the wellhead pressure is injected, the unblocking agent is injected into the wellhead along with the carbon dioxide and is injected into the formation, dissolving, dispersing, and clearing the formation blockage with organic blockages such as asphaltene in the formation, reducing the injection pressure and increasing the injection volume. The above construction method is simple in construction, low in operating risk and operating cost, and good in economy. More importantly, it reduces the risk of well control in on-site construction and is safer and more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the connection between the skid-mounted high-pressure injection device of the present invention and the CO2 injection wellhead;

[0028] Figure 2 It is a schematic diagram of the skid-mounted high-pressure injection device of the present invention;

[0029] Among them: 1-first storage tank; 2-second storage tank; 3-first valve; 4-self-priming pump; 5-second valve; 6-third valve; 7-fourth valve; 8-high-pressure injection pump; 9-fifth valve; 10-sixth valve; 11-seventh valve; 12-eighth valve; 13-ninth valve; 14-tenth valve; 15-eleventh valve; 16-twelfth valve; 17-pressure gauge; 18-generator; 19-trailer skid-mounted chassis; 20-pressure stabilizing control system; 21-reflux outlet in the first storage tank; 22-reflux outlet in the second storage tank; 23-thirteenth valve; 24-fourteenth valve; 25-drainage outlet; 26-injection device; 27-CO2 injection wellhead. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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 only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

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

[0033] See also Figure 1 as well as Figure 2 The present invention provides an injection device and a method for unblocking an under-injected well by injecting carbon dioxide for oil recovery based on the injection device. Figure 2 The injection device 26 includes a storage tank system, a self-dosing system and a high-pressure injection system, a voltage stabilization control system 20, and a power generation system; wherein the storage tank system is connected to the self-dosing system and the high-pressure injection system; the storage tank system includes a first storage tank 1 and a second storage tank 2 that are connected to each other; a first outlet and a second outlet are respectively opened at the bottom of the first storage tank 1 and the second storage tank 2; the first outlet and the second outlet are connected by a pipeline, a first branch and a second branch are arranged in parallel on the pipeline, and the self-dosing system and the high-pressure injection system are respectively arranged on the first branch and the second branch.

[0034] The inlet of the self-dosing system is connected to the outlet of the feeding pipeline; the self-dosing system is used to add the unblocking liquid to the first storage tank 1 and the second storage tank 2 through the feeding pipeline and the valve, thereby reducing the labor intensity of feeding.

[0035] The outlet of the high-pressure injection system is connected to the inlet of the injection pipeline, and a pressure gauge 17 is provided on the injection pipeline; the outlet of the injection pipeline is connected to the inlet of several branches arranged in parallel, and the outlet of the branch is connected to the external injection interface. The high-pressure injection system is connected to the external injection interface through the injection pipeline and the pressure gauge 16, and then connected to the external injection interface, so that single well or multiple wells can be continuously injected.

[0036] The self-dosing system and the high-pressure injection system are connected to the voltage stabilizing control system 20; the voltage stabilizing control system 20 is connected to the power generation system. The power generation system, i.e., the generator 18 and the voltage stabilizing control system 20, have power supply and switch control functions for the self-dosing system and the high-pressure injection system. Alternatively, if there is an external power supply, the voltage stabilizing control system 20 can be directly powered by an external power supply without the generator 18 working. The skid-mounted injection device has two working modes: self-powered and externally powered.

[0037] Furthermore, the skid-mounted chassis 19 of the trailer is arranged below the storage tank system, the self-dosing system, the high-pressure injection system, the voltage stabilization control system, and the power generation system. Through the skid-mounted chassis 19 of the trailer and the unpowered trailer connected thereto, the trailer has the ability to travel on the road under power conditions; a hydraulic support can be further arranged below the skid-mounted chassis 19, and the skid-mounted high-pressure injection device 26 can be lowered to support the unblocking construction, so as to avoid the wheels bearing the load for a long time. The side panels around the skid-mounted chassis 19 of the trailer can be connected by buckles to form a box-type trailer shape.

[0038] Furthermore, the first storage tank 1 and the second storage tank 2 are respectively provided with a first storage tank internal reflux outlet 21 and a second storage tank internal reflux outlet 22; the first storage tank internal reflux outlet 21 and the second storage tank internal reflux outlet 22 are connected by a pipeline to realize circulation and stirring of the fluid in the tank.

[0039] The first storage tank 1 and the second storage tank 2 are respectively provided with discharge ports at the bottom, and the discharge ports are connected to the inlet of the sewage pipe for discharging the residual liquid in the tank after the construction is completed.

[0040] The present invention provides a method for unblocking an under-injected well by injecting carbon dioxide for oil recovery, comprising the following steps:

[0041] S1: The injection device 26 is connected to the CO2 injection wellhead 27, the valve on the second branch is closed, the valve on the first branch is opened, and the valve on the feeding pipeline is opened to suck the plugging remover and the liquid preparation water to be injected into the first storage tank 1 and the second storage tank 2 through the self-dosing system;

[0042] S2: Close the valve on the feeding pipeline, open the valves on the connecting pipelines of the first branch, the first storage tank 1 and the second storage tank 2, and start the self-dosing system for circulation and mixing;

[0043] S3: Open the valves on the second branch and the injection pipeline, and close other valves; start the high-pressure injection system, start injecting the plugging remover solution, and after the injection is completed, close the valves on the second branch and the injection pipeline, and then dismantle the connecting pipeline of the CO2 injection wellhead 27;

[0044] S4: Drain the remaining liquid in the first storage tank 1 and the second storage tank 2, and end the construction.

[0045] Furthermore, it also includes a pressure test step, which is as follows:

[0046] Diesel is used for pressure testing, and the test pressure is adjusted to be 2 to 5 MPa higher than the normal injection pressure at the wellhead. The pressure test lasts for 5 minutes.

[0047] Example

[0048] This embodiment provides an injection device, including: a skid-mounted chassis 19, a storage tank system, a self-dosing system, a high-pressure injection system, a power generation system, and a voltage stabilization control system 20; the storage tank system, the self-dosing system, the high-pressure injection system, the power generation system, and the voltage stabilization control system 20 are installed on the skid-mounted chassis 19, wherein the four side panels can be connected by snaps to form a box-type trailer shape. The injection device 26 is a non-powered trailer, which has the ability to travel on the road under power conditions. The skid-mounted chassis 19 of the trailer is set at the bottom of the injection device 26, and four hydraulic supports are also set below the skid-mounted chassis 19 of the trailer.

[0049] The self-dosing system is a self-priming pump 4 and its related pipelines and valves thereon; the high-pressure injection system is a high-pressure injection pump 8 and its related pipelines and valves thereon; and the power generation system is a generator 18.

[0050] The storage tank system includes a first storage tank 1 and a second storage tank 2 connected to each other. The first storage tank 1 and the second storage tank 2 have a first storage tank internal reflux outlet 21 and a second storage tank internal reflux outlet 22 respectively opened on the first storage tank 1 and the second storage tank 2, which are connected to each other. A thirteenth valve 23 and a fourteenth valve 24 are arranged on the connecting pipeline.

[0051] The first storage tank 1 and the second storage tank 2 are respectively provided with a first outlet and a second outlet at the bottom; the first outlet and the second outlet are connected by a pipeline, a first branch and a second branch are provided in parallel on the pipeline, a self-priming pump 4 and a high-pressure injection pump 8 are respectively provided on the first branch and the second branch; a first valve 3 and a second valve 5 are provided on the first branch; a third valve 6 and a fourth valve 7 are provided on the second branch.

[0052] The first storage tank 1 and the second storage tank 2 are connected to the self-priming pump 4 through the first branch and the first valve 3 and the second valve 5 arranged thereon. The self-priming pump 4 is connected to add the unblocking liquid through the feeding pipeline and the fifth valve 9 arranged on the feeding pipeline to reduce the labor intensity of feeding.

[0053] The first storage tank 1 and the second storage tank 2 are connected to the high-pressure injection pump 8 through the second branch and the third valve 6 and the fourth valve 7 arranged thereon.

[0054] The first storage tank 1 and the second storage tank 2 are provided with discharge ports at their bottoms, and the discharge ports are connected to the inlet of the sewage pipe. The sewage pipes are provided with a sixth valve 10 and a seventh valve 11 respectively on the pipes connected to the discharge ports of the first storage tank 1 and the second storage tank 2. The outlet of the sewage pipe is the sewage port 25. The first storage tank 1 and the second storage tank 2 are connected to the sewage port 25 through the sewage pipe.

[0055] The first storage tank 1 and the second storage tank 2 are connected to the external injection interface through a high-pressure injection pump 8 and an injection pipeline. The outlet of the injection pipeline is connected to the inlet of several branches arranged in parallel, and the outlet of the branch is connected to the external injection interface. A pressure gauge 17 is arranged on the injection pipeline; the eighth valve 12, the ninth valve 13, the tenth valve 14, the eleventh valve 15, and the twelfth valve 16 are respectively arranged on several branches arranged in parallel, so that single-well or multi-well continuous injection can be realized.

[0056] like Figure 1 As shown, this embodiment also provides a method for unblocking an under-injected well by injecting carbon dioxide for oil recovery, which is specifically as follows: a skid-mounted high-pressure injection device 26, a connecting pipeline and a CO2 injection wellhead 27 are sequentially connected; before the squeeze injection unblocking construction, a pressure test is first performed with diesel, and the pressure test pressure is 2 to 5 MPa higher than the normal injection pressure of the CO2 injection wellhead 27, and the pressure test time is 5 minutes;

[0057] After the injection device 26 is connected to the CO2 injection wellhead 27, the third valve 6 and the fourth valve 7 are closed, and the first valve 3, the second valve 5, and the fifth valve 9 are opened, and the plugging remover and the liquid preparation water to be injected are sucked into the first storage tank 1 and the second storage tank 2 by the self-priming pump 4; then the fifth valve 9 is closed, the first valve 3, the second valve 5, the thirteenth valve 23, and the fourteenth valve 24 are opened, and the self-priming feeding pump 4 is started for circulation and mixing for 30 minutes;

[0058] Open the third valve 6 and the fourth valve 7, and close the other gates; start the high-pressure injection pump 8 and start injecting the unblocking agent solution. After the injection is completed, close the third valve 6 and the fourth valve 7, the eighth valve 12, the ninth valve 13, the tenth valve 14, the eleventh valve 15, and the twelfth valve 16 on the branch connected to the injection pipeline to dismantle the connecting pipeline of the CO2 injection wellhead 27.

[0059] The sixth valve 10 and the seventh valve 11 are opened to discharge the residual liquid in the first storage tank 1 and the second storage tank 2, and the construction is finished. If other wells need to be constructed, the high-pressure skid-mounted injection device 26 can be carried to the destination by a power vehicle without the need for truck transportation.

[0060] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An injection device, characterized in that: Including storage tank system, self-dosing system and high-pressure injection system; The storage tank system is connected with the self-dosing system and the high-pressure injection system; The storage tank system comprises a first storage tank (1) and a second storage tank (2) which are connected to each other; A first outlet and a second outlet are respectively provided at the bottom of the first storage tank (1) and the second storage tank (2); the first outlet and the second outlet are connected by a pipeline, a first branch and a second branch are arranged in parallel on the pipeline, and the self-dosing system and the high-pressure injection system are respectively arranged on the first branch and the second branch; The inlet of the self-dosing system is connected to the outlet of the feeding pipeline; the outlet of the high-pressure injection system is connected to the inlet of the injection pipeline.

2. The injection device according to claim 1, characterized in that The self-dosing system and the high-pressure injection system are connected to a voltage stabilization control system (20); and the voltage stabilization control system (20) is connected to a power generation system.

3. The injection device according to claim 1, characterized in that A trailer skid-mounted chassis (19) is arranged below the storage tank system, the self-dosing system and the high-pressure injection system, and a hydraulic support is arranged below the trailer skid-mounted chassis (19).

4. The injection device according to claim 1, characterized in that The injection pipeline is provided with a pressure gauge (17).

5. The injection device according to claim 1, characterized in that The outlet of the injection pipeline is connected to the inlets of several branches arranged in parallel, and the outlets of the branches are connected to the external input injection interface.

6. The injection device according to claim 1, characterized in that The first storage tank (1) and the second storage tank (2) are respectively provided with a first storage tank internal reflux outlet (21) and a second storage tank internal reflux outlet (22); the first storage tank internal reflux outlet (21) and the second storage tank internal reflux outlet (22) are connected via a pipeline.

7. The injection device according to claim 1, characterized in that The bottoms of the first storage tank (1) and the second storage tank (2) are respectively provided with discharge outlets, and the discharge outlets are both connected to the inlet of the sewage pipe.

8. A construction method for unblocking an under-injected well by injecting carbon dioxide for oil recovery, characterized in that: The following steps are involved: S1: The injection device (26) is connected to the CO2 injection wellhead (27), the valve on the second branch is closed, the valve on the first branch is opened, and the valve on the feeding pipeline is opened to suck the plugging remover and the liquid preparation water to be injected into the first storage tank (1) and the second storage tank (2) through the self-dosing system; S2: closing the valve on the feeding pipeline, opening the valves on the connecting pipelines of the first branch, the first storage tank (1) and the second storage tank (2), and starting the self-dosing system for circulation and mixing; S3: Open the valves on the second branch and the injection pipeline, and close other valves; start the high-pressure injection system, start injecting the plugging remover solution, and after the injection is completed, close the valves on the second branch and the injection pipeline, and then remove the connecting pipeline of the CO2 injection wellhead (27); S4: Drain the remaining liquid in the first storage tank (1) and the second storage tank (2), and end the construction.

9. The method for unblocking an under-injected well by injecting carbon dioxide for oil recovery according to claim 8, characterized in that: The pressure test step is also included, and the pressure test step is as follows: Diesel fuel is used for pressure testing, and the pressure testing pressure is adjusted to be 2 to 5 MPa higher than the normal injection pressure of the CO2 injection wellhead (27), and the pressure testing time is 5 minutes.

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