Thickened oil injection and production pipe column

Abstract

The invention belongs to the field of equipment for exploiting thickened oil from a well, and particularly relates to a thickened oil injection and production pipe column. In order to prolong the low-temperature oil production period and avoid the situation that an insertion pipe needs to be pulled out after soaking and blowout every time, the thick oil injection and production pipe column comprises an eccentric oil well pump with liquid entering from the bottom, the insertion pipe and a bridge plug used for packing an oil sleeve annulus, and a flow limiting valve is further arranged between the eccentric oil well pump and the insertion pipe. The flow limiting valve comprises a first axial flow passing channel and a radial one-way flow passing channel used for allowing diluted liquid in the casing annulus to flow into the first axial flow passing channel. In the low-temperature oil production period, the diluted liquid can be added into the casing annulus, and the diluted liquid enters the first axial overflowing channel through the radial one-way overflowing channel and is mixed with crude oil, so that the viscosity of the crude oil is reduced, and the low-temperature oil production period is prolonged. Meanwhile, liquid enters from the bottom of the eccentric oil well pump, namely crude oil in the oil pipe directly enters the eccentric oil well pump, so that the insertion pipe does not need to be pulled out after soaking and blowout every time, operation is simplified, and cost is reduced.

Description

Technical Field

[0001] The invention belongs to the field of equipment for producing heavy oil from wells, and in particular relates to a heavy oil injection and production string. Background Art

[0002] Global reserves of heavy oil are vast, accounting for approximately 70% of the world's remaining crude oil resources. Steam stimulation technology is used to extract this heavy oil. First, steam is injected into the oil pipeline and the wellhead is shut down for a soak operation. This allows steam to heat the oil layer and reduce the viscosity of the heavy oil. Next, the wellhead is opened for a blowdown operation, reducing the pressure within the well. Once the blowdown is complete, crude oil can be extracted. During the extraction process, the temperature of the oil layer continues to drop, necessitating the use of steam to heat the layer again after a period of time.

[0003] In the existing technology, the main development history of using steam stimulation technology to extract heavy oil is as follows: Phase 1: Referring to the Chinese utility model patent for "A Thermal Recovery Eccentric Thickening Pump," with authorization announcement number CN201507428U and announcement date June 16, 2010, and the patentee includes the Petroleum Engineering Technology Research Institute of the Henan Oilfield Branch of Sinopec, the eccentric thickening pump, located at the bottom of the production tubing, directly feeds the crude oil in the tubing. After the well is shut down and released for blowout, the polished rod of the oil production unit drives the eccentric thickening pump, directly extracting the crude oil from the tubing.

[0004] However, when using the above-mentioned production tubing string, the polished rod must overcome the resistance of the heavy oil in the tubing as it drives the plunger downward, due to the bottom feed of the eccentric thickening pump. If the reservoir temperature falls below the set value A, the polished rod is lowered more slowly, necessitating another soaking and blowout cycle. This results in a shorter oil recovery period after each soaking and blowout cycle.

[0005] The second stage: In order to overcome the above problems, with reference to the Chinese utility model patent with authorization announcement number CN212536022U and authorization announcement date of 2021.02.12, the patent holders include the Petroleum Engineering Technology Research Institute of Henan Oilfield Branch of China Petrochemical Corporation, and the name of "Eccentric Oil Pump", the eccentric pumping pump of the production tubing string is filled with liquid from the side, and the crude oil in the casing directly enters the eccentric pumping pump. After the well is shut down and blowout is completed, the light rod of the oil production machine drives the eccentric pumping pump to work and directly extracts the crude oil in the casing. At this time, the light rod does not need to overcome the resistance of the heavy oil to the plunger when driving the plunger of the eccentric pumping pump to move downward. When the oil layer temperature is the set value A, the light rod can also be lowered at a sufficient speed, thereby effectively extending the low-temperature oil production period, and then extending the oil production period after a well is shut down and blowout.

[0006] In addition, in order to further extend the low-temperature oil production period, a dilution pipe can be set in the casing annulus, and the dilution liquid can be sent into the heavy oil layer through the dilution pipe to reduce the viscosity of the crude oil, thereby further extending the low-temperature oil production period and extending the oil production period after a soaking and blowing.

[0007] Phase 3: Currently, oil fields that are easy to develop have been largely developed. To increase crude oil production, new oil fields must be developed. For oil fields with a highly mineralized water layer above the oil layer, as shown in the Chinese invention patent application with publication number CN116717223A, published on September 8, 2023, and filed by the Henan Oilfield Branch of Sinopec, titled "A Fluid-Displacement Steam Injection Cannula for a Horizontal Well Insulated Injection and Production String," a cannula and a bridge plug for sealing the annulus of the oil casing must be installed in the production string to prevent water accumulation in the casing corresponding to the water layer, which could lead to corrosion of the casing.

[0008] In a production tubing string with a cannula and a bridge plug, either a bottom-inlet eccentric pump or a side-inlet eccentric pump can be used. However, the bottom-inlet eccentric pump still presents the problem of a short low-temperature production period (i.e., a short production period after a single well-simmering blowout). For vertical wells, if the eccentric pump is placed below the bridge plug, the polished rod becomes too long, making it impossible for the production machine to lift the rod. For horizontal wells with a vertical section (non-oil-bearing section) and a horizontal section (oil-bearing section), the eccentric pump must be placed in the vertical section because the polished rod cannot bend. Therefore, when using an eccentric oil pump with side liquid inlet, the eccentric oil pump cannot be directly set in the oil layer. After each soaking and blowout, the cannula needs to be pulled out from the socket of the bridge plug, so that the crude oil enters the casing above the bridge plug from the bottom of the bridge plug through the socket. After a period of oil production, since the temperature of the oil layer is low and cannot meet the production requirements, it is necessary to reinsert the cannula into the bridge plug and inject steam again. The operation is cumbersome and costly. Summary of the Invention

[0009] The object of the present invention is to provide a heavy oil injection and production string to solve the technical problems that, when operating in an oil field with a water layer above the oil layer and the water layer is highly mineralized, the low-temperature oil production period of the production string using an eccentric oil pump with bottom liquid inlet is short, and the production string using an eccentric oil pump with side liquid inlet needs to be pulled out of the cannula after each well soaking and blowout, and needs to be reinserted into the bridge plug for steam injection after a period of oil production, which is cumbersome and costly.

[0010] To achieve the above-mentioned purpose, the technical solution of the heavy oil injection and production string provided by the present invention is: A heavy oil injection and production string comprises an eccentric oil well pump with bottom inlet, a cannula and a bridge plug for sealing the annulus of the oil casing. A flow limiting valve is also provided between the eccentric oil well pump and the cannula. The flow limiting valve comprises a first axial flow passage and a radial one-way flow passage for allowing dilute liquid in the casing annulus to flow into the first axial flow passage.

[0011] Furthermore, the first axial flow passage is a first axial one-way flow passage for controlling the flow of crude oil from the cannula to the eccentric oil well pump. The flow limiting valve is also provided with a second axial one-way flow passage for controlling the flow of steam from the eccentric oil well pump to the cannula. The radial one-way flow passage is connected to the inlet of the first axial one-way flow passage, so as to enable the diluent to assist the crude oil in opening the first axial one-way flow passage during the low-temperature oil production period.

[0012] Furthermore, the opening pressure of the radial one-way flow passage is used to be greater than the pressure difference between the gas pressure in the oil casing annulus during oil production and the crude oil pressure in the first axial one-way flow passage.

[0013] Furthermore, the opening pressure of the radial one-way flow channel is 1~5 MPa.

[0014] Furthermore, a mixing oil pipe is provided between the eccentric oil well pump and the flow limiting valve for fully mixing the diluent with the crude oil.

[0015] Furthermore, there are at least two radial one-way flow channels evenly spaced around the same circumference.

[0016] Furthermore, the first axial one-way flow passage is arranged at the center of the flow limiting valve, and the second axial one-way flow passage is arranged beside the first axial one-way flow passage.

[0017] Furthermore, the number of the second axial one-way flow channels is at least two, all the second axial one-way flow channels are evenly spaced on the same circumference, and the center of the circumference is located on the axis of the first axial one-way flow channel.

[0018] Furthermore, on the side of the bridge plug close to the eccentric oil well pump, the oil pipes of the heavy oil injection and production string are all heat-insulated oil pipes.

[0019] Furthermore, the heavy oil injection and production string further comprises a dilution pipe for being arranged in the annulus of the oil casing, and the outlet of the dilution pipe is located on a side of the radial one-way flow channel inlet close to the insert pipe.

[0020] The beneficial effects of the heavy oil injection and production string provided by the present invention are as follows: the present invention is an improved invention. The portion of the casing corresponding to the oil layer and the portion of the casing corresponding to the water layer can be sealed by inserting a pipe and a bridge plug. During oil production, since the radial one-way flow channel only allows the liquid in the casing annulus to flow into the first axial flow channel, steam can be prevented from entering the casing annulus during well shut-in and blowout, and steam can be prevented from excessively heating the water layer and causing rapid corrosion of the casing; at the same time, during oil production, crude oil can be prevented from entering the casing, maintaining sufficient oil pressure in the first axial flow channel. During the low-temperature oil production period, a diluent can be added to the casing annulus, and the diluent enters the first axial flow channel through the radial one-way flow channel and mixes with the crude oil, thereby reducing the viscosity of the crude oil and extending the low-temperature oil production period. At the same time, since the eccentric oil pump is fed with liquid from the bottom, that is, the crude oil in the oil pipe directly enters the eccentric oil pump, there is no need to pull out the cannula after each well soaking and blowout, and there is no need to insert the cannula into the bridge plug during the next steam injection, which simplifies operation and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a structural schematic diagram of a specific embodiment 1 of the heavy oil injection and production string of the present invention.

[0022] Description of reference numerals: 1. Casing; 2. Insulated oil pipe; 3. Eccentric oil pump; 4. Flow limiting valve; 41. First axial one-way flow channel; 411. Ball seat; 412. Ball head; 413. Spring; 42. Second axial one-way flow channel; 43. Radial one-way flow channel; 5. Cannula; 6. Bridge plug; 7. Oil layer; 8. Water layer. DETAILED DESCRIPTION

[0023] In order to solve the problems in the background technology, the core inventive concept of the present invention is: by arranging a flow limiting valve with a radial one-way flow channel between the eccentric oil pump and the cannula, the diluent in the casing annulus can enter the oil pipe and mix with the crude oil, thereby extending the low-temperature oil production period.

[0024] The present invention is described in further detail below with reference to the examples.

[0025] Specific embodiment 1 of the heavy oil injection and production string provided by the present invention: like Figure 1 As shown, the heavy oil injection and production string includes an eccentric oil well pump 3 with bottom inlet, a cannula 5, and a bridge plug 6 for sealing the casing annulus. A flow limiting valve 4 is also provided between the eccentric oil well pump 3 and the cannula 5. The flow limiting valve 4 includes a first axial flow passage and a radial one-way flow passage 43 for allowing diluent in the casing annulus to flow into the first axial flow passage. The diluent can be produced diluent or a liquid such as a viscosity reducer that can reduce the viscosity of crude oil.

[0026] To simplify the structure, Figure 1 As shown, the flow limiting valve 4 also serves as a safety valve, mainly used to control the flow rate and flow rate of crude oil and steam. The first axial flow passage is a first axial one-way flow passage 41 for controlling the flow of crude oil from the cannula 5 to the eccentric wellbore pump 3. The flow limiting valve 4 is also provided with a second axial one-way flow passage 42 for controlling the flow of steam from the eccentric wellbore pump 3 to the cannula 5. The radial one-way flow passage 43 is connected to the inlet of the first axial one-way flow passage 41 to allow the diluent to assist the crude oil in opening the first axial one-way flow passage 41 during low-temperature oil production.

[0027] like Figure 1 As shown, when using the heavy oil injection and production string of the present invention to produce an oil field with a water layer 8 above the oil layer 7, and the water layer 8 is highly mineralized, the following steps can be followed: Step S1: First, the bridge plug 6 is set below the position corresponding to the water layer 8 in the casing 1 to isolate the portion of the casing 1 corresponding to the water layer 8 and the portion of the casing 1 corresponding to the oil layer 7. Then, the rest of the heavy oil injection and production string is lowered into the casing 1, and the cannula 5 is inserted into the bridge plug 6. Step S2: Steam is injected into the oil layer 7 through the tubing of the heavy oil injection and production string. The steam passes through the eccentric oil well pump 3, the second axial one-way flow passage 42, and the cannula 5 in sequence to reach the oil layer 7 and heat the oil layer 7. After the steam injection, the wellhead is closed and the well is kept dry for a period of time to allow the steam to fully heat the oil layer 7. During this process, some liquid in the annulus of the casing above the bridge plug 6 will evaporate due to the heat, causing the casing pressure to rise. The high-pressure steam in the casing 1 can enter the first axial one-way flow passage 41 through the radial one-way flow passage 43 and then enter the oil layer 7 to balance the casing pressure. Step S3: Open the wellhead and perform blowdown operation; Step S4: The polished rod of the pumping unit drives the eccentric oil pump 3 to produce oil. The crude oil passes through the cannula 5, the first axial one-way flow passage 41 and the eccentric oil pump 3 in sequence to reach the wellhead. Step S5: Since the temperature of the oil layer 7 is continuously decreasing during oil production, it enters a low-temperature oil production period after a period of time. At this time, a diluent can be added to the oil casing annulus. The diluent flows from the oil casing annulus through the radial one-way flow passage 43 into the first axial one-way flow passage 41, and assists the crude oil in opening the first axial one-way flow passage 41, thereby extending the low-temperature oil production period. Specifically, Figure 1 As shown, the diluted liquid assists the crude oil in lifting the ball head 412 on the ball head seat 411, and the spring 413 is used to control the opening pressure of the ball head 412. In this field, the structure for controlling the opening pressure of a one-way channel is a mature existing technology and will not be described in detail in the present invention. Step S6: After oil production continues for a period of time, even if the diluent is added, the polished rod still moves downward slowly. At this time, steam injection and well soaking are required again.

[0028] At the same time, since the eccentric oil pump 3 is fed with liquid from the bottom, that is, the crude oil in the oil pipe directly enters the eccentric oil pump 3, there is no need to insert the cannula 5 each time steam is injected and to pull out the cannula 5 after the well is soaked and blowout occurs. There is also no need to insert the cannula 5 into the bridge plug 6 during the next steam injection, which can simplify the operation and reduce costs.

[0029] In order to reduce the heat exchange between the steam and the corresponding parts of the casing 1 and the water layer 8 in step S2, as a specific embodiment, the oil pipes of the heavy oil injection and production string on the side of the bridge plug 6 close to the eccentric oil pump 3 are all insulated oil pipes 2. On the one hand, the use of the insulated oil pipes 2 can reduce the temperature rise of the water layer 8 caused by steam heating, slowing down the corrosion rate of the casing 1; on the other hand, the use of the insulated oil pipes 2 can reduce the heat loss of the steam, allowing more heat to enter the oil layer 7, thereby improving production efficiency.

[0030] During the low-temperature oil production period, in order to prevent the eccentric oil pump 3 from gas locking, as a specific embodiment, the opening pressure of the radial one-way flow passage 43 is designed to be greater than the pressure difference between the gas pressure in the oil casing annulus during oil production and the crude oil pressure in the first axial one-way flow passage 41. During the low-temperature oil production period, by setting the opening pressure of the radial one-way flow passage 43 to be greater than the pressure difference between the gas pressure in the oil casing annulus during oil production and the crude oil pressure in the first axial one-way flow passage 41, it is ensured that the radial one-way flow passage 43 can only be opened after the diluent submerges the radial one-way flow passage 43, thereby preventing a large amount of gas from flowing sequentially through the first axial one-way flow passage 41 and the first axial one-way flow passage 41 to the eccentric oil pump 3, thus preventing the eccentric oil pump 3 from gas locking and extending the low-temperature oil production period.

[0031] The higher the opening pressure of the radial one-way flow passage 43, the more diluent needs to be injected before the passage 43 opens. Furthermore, the more diluent remains unused after the passage 43 closes. Therefore, the opening pressure of the radial one-way flow passage 43 should not be too high. The lower the opening pressure of the radial one-way flow passage 43, the greater the likelihood that gas within the casing annulus will enter the passage 43. Preferably, the opening pressure of the radial one-way flow passage 43 is between 1 and 5 MPa, specifically 1 MPa, 2 MPa, 3 MPa, 4.5 MPa, or 5 MPa. Alternatively, the opening pressure of the radial one-way flow passage 43 can be 0.5 MPa or 6 MPa.

[0032] To further extend the low-temperature oil production period, as a specific embodiment, a mixing oil pipe is provided between the eccentric oil pump 3 and the flow-limiting valve 4 to thoroughly mix the diluent with the crude oil. The specific structure of the mixing oil pipe is the same as that of the insulated oil pipe 2. As the diluent and crude oil move along the mixing oil pipe, they continuously mix, thereby lowering the viscosity of the crude oil reaching the eccentric thickening pump, reducing the resistance of the polished rod downward and extending the low-temperature oil production period.

[0033] However, in other specific implementations, the flow limiting valve 4 may also be installed directly below the eccentric oil well pump 3 .

[0034] In order to further extend the low-temperature oil production period, as a specific embodiment, at least two radial one-way flow channels 43 are evenly spaced around the same circumference. In this case, the diluent will enter the first axial one-way flow channel 41 from at least two points in the circumference of the first axial one-way flow channel 41 and mix with the corresponding portion of crude oil, thereby improving the mixing degree of the diluent and crude oil, better reducing the viscosity of the crude oil, and extending the low-temperature oil production period.

[0035] In different embodiments, the number of radial one-way flow passages 43 may be two, three, four, or more. Of course, the number of radial one-way flow passages 43 may also be one. The greater the number of radial one-way flow passages 43, the better the mixing of the diluent and crude oil.

[0036] To reduce the outer diameter of the flow limiting valve 4 and adapt the heavy oil injection and production string to smaller wellbores, in one embodiment, the first axial one-way flow passage 41 is arranged at the center of the flow limiting valve 4, and the second axial one-way flow passage 42 is arranged to the side of the first axial one-way flow passage. Of course, in other embodiments, the first axial one-way flow passage 41 and the second axial one-way flow passage 42 can also be arranged on either side of the flow limiting valve 4.

[0037] When the flow areas of the first axial one-way flow passage 41 and the second axial one-way flow passage 42 are constant, compared with the technical solution in which the first axial one-way flow passage 41 and the second axial one-way flow passage 42 are respectively arranged on both sides of the flow limiting valve 4, arranging the first axial one-way flow passage 41 in the center of the flow limiting valve 4 can improve the space utilization of the flow limiting valve 4 and reduce the outer diameter of the flow limiting valve 4, thereby making the heavy oil injection and production string suitable for wells with smaller wellbores.

[0038] To further reduce the outer diameter of the flow limiting valve 4, as a specific embodiment, the number of second axial one-way flow passages 42 is at least two, and all second axial one-way flow passages 42 are evenly spaced and distributed on the same circumference, with the center of the circumference located on the axis of the first axial one-way flow passage 41. Of course, in other specific embodiments, only one second axial one-way flow passage 42 may be provided.

[0039] When the required steam flow area is constant, by increasing the number of the second axial one-way flow passages 42 and reducing the inner diameter of a single second axial one-way flow passage 42, the space utilization rate of the flow limiting valve 4 can be improved and the outer diameter of the flow limiting valve 4 can be reduced, thereby making the heavy oil injection and production string suitable for wells with smaller wellbores.

[0040] To prevent the diluent from contaminating the inner wall of the casing, in one embodiment, the heavy oil injection and production string further includes a diluent pipe disposed within the annulus of the casing. The outlet of the diluent pipe is located on the side of the radial one-way flow passage 43 inlet near the insert 5. Diluting through the diluent pipe effectively prevents the diluent from contaminating the inner wall of the casing. However, in other embodiments, the diluent can also be added directly to the casing 1.

[0041] Specific embodiment 2 of the heavy oil injection and production string provided by the present invention: The purpose of this embodiment is to provide a heavy oil injection and production string with different flow limiting valves.

[0042] Reference Figure 1 As shown, the main difference between this embodiment and specific embodiment 1 is that: in specific embodiment 1, the flow limiting valve 4 also serves as a safety valve, while in this embodiment, the first axial flow passage is a two-way flow passage. According to on-site needs, an additional safety valve can be installed on the heavy oil injection and production string. The safety valve has a first axial one-way flow passage 41 for controlling the flow of crude oil from the cannula 5 to the eccentric wellbore pump 3 and a second axial one-way flow passage 42 for controlling the flow of steam from the eccentric wellbore pump 3 to the cannula 5.

[0043] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments without inventive effort, or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A heavy oil injection and production string, comprising an eccentric oil well pump with bottom inlet, a cannula, and a bridge plug for sealing the annulus of the oil casing, characterized in that: A flow limiting valve is provided between the eccentric oil well pump and the cannula. The flow limiting valve comprises a first axial flow passage and a radial one-way flow passage for allowing the diluted liquid in the casing annulus to flow into the first axial flow passage.

2. The heavy oil injection and production string according to claim 1, characterized in that: The first axial flow passage is a first axial one-way flow passage for controlling the flow of crude oil from the cannula to the eccentric wellbore pump. The flow limiting valve is also provided with a second axial one-way flow passage for controlling the flow of steam from the eccentric wellbore pump to the cannula. The radial one-way flow passage is connected to the inlet of the first axial one-way flow passage so as to allow the diluent to assist the crude oil in opening the first axial one-way flow passage during the low-temperature oil production period.

3. The heavy oil injection and production string according to claim 2, characterized in that: The opening pressure of the radial one-way flow passage is used to be greater than the pressure difference between the air pressure in the oil casing annulus during oil production and the crude oil pressure in the first axial one-way flow passage.

4. The heavy oil injection and production string according to claim 3, characterized in that: The opening pressure of the radial one-way flow channel is 1~5 MPa.

5. The heavy oil injection and production string according to any one of claims 1 to 4, characterized in that: A mixing oil pipe is provided between the eccentric oil well pump and the flow limiting valve to fully mix the diluent with the crude oil.

6. The heavy oil injection and production string according to any one of claims 1 to 4, characterized in that: There are at least two radial one-way flow channels evenly spaced around the same circumference.

7. The heavy oil injection and production string according to any one of claims 2 to 4, characterized in that: The first axial one-way flow passage is arranged at the center of the flow limiting valve, and the second axial one-way flow passage is arranged beside the first axial one-way flow passage.

8. The heavy oil injection and production string according to claim 7, characterized in that: The number of the second axial one-way flow passages is at least two, and all the second axial one-way flow passages are evenly spaced on the same circumference, and the center of the circumference is located on the axis of the first axial one-way flow passage.

9. The heavy oil injection and production string according to any one of claims 1 to 4, characterized in that: On the side of the bridge plug close to the eccentric oil well pump, the oil pipes of the heavy oil injection and production string are all heat-insulated oil pipes.

10. The heavy oil injection and production string according to any one of claims 1 to 4, characterized in that: The heavy oil injection and production string also includes a dilution pipe for being arranged in the annulus of the oil casing, and the outlet of the dilution pipe is located on a side of the radial one-way flow channel inlet close to the inserting pipe.

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