Method for exploiting heavy oil reservoir

Abstract

The invention provides a method for exploiting a heavy oil reservoir. The heavy oil reservoir exploitation method comprises the steps that the heavy oil reservoir meeting exploitation conditions is determined; measuring fracture pressure of an oil layer; the horizontal well is drilled, the horizontal section of the horizontal well is completed through a screen pipe, a short pipe and a long pipe are put into the horizontal well, the length of the short pipe is smaller than that of the long pipe, the tail end of the short pipe is connected with oil extraction equipment, a continuous pipe is put into the long pipe, and a heating piece is arranged in the continuous pipe; a production process and production parameters are determined; cleaning and preheating the shaft; a solvent plunger and a steam plunger are sequentially injected from a long pipe annulus, a heating piece is opened, and oil extraction equipment is started for production after soaking; and after a plurality of cycles of solvent-steam slug alternate huff and puff cavity expansion, a solvent and steam are injected from the annulus of the long pipe at the same time, and the heating piece is kept to heat the solvent and the steam, so that the solvent and the steam enter an oil layer, and crude oil is driven to enter a shaft and be extracted to the ground from the short pipe. The problem that the heavy oil reservoir cannot be effectively developed in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production, and in particular to a method for producing heavy oil reservoirs. Background Art

[0002] At present, heavy oil and super-heavy oil reservoirs with a 50°C ground degassed crude oil viscosity of less than 20,000 mPa.s can be developed profitably by conventional thermal recovery methods such as steam stimulation, steam drive, hot water drive, and fire burning. Super-heavy oil reservoirs with a continuous oil layer thickness of more than 10 m can be developed profitably by using SAGD. Super-heavy oil reservoirs with a continuous oil layer of 7 to 10 m and a 50°C ground degassed crude oil viscosity of more than 50,000 mPa.s have poor lateral continuity of the oil layer, strong reservoir heterogeneity, rapid changes in physical properties, and small single-well EUR, and cannot yet achieve profitable development. This type of oil reservoir has a large reserve, generally accounting for 30% to 40% of the total heavy oil resources. The final recovery rate of conventional thermal recovery methods is generally less than 20%, the oil-gas ratio is generally less than 0.08, and the unit carbon emission reaches more than 2.0 tons of carbon / ton of oil.

[0003] As can be seen from the above, there is a problem in the prior art that heavy oil reservoirs cannot be effectively developed. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for exploiting a heavy oil reservoir, so as to solve the problem that the heavy oil reservoir cannot be effectively developed in the prior art.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a method for exploiting a heavy oil reservoir, comprising: determining a heavy oil reservoir that meets the exploitation conditions; determining the oil layer fracture pressure; drilling a horizontal well, completing the horizontal section of the horizontal well with a screen pipe, lowering a short pipe and a long pipe into the horizontal well, the length of the short pipe is less than the length of the long pipe, the tail end of the short pipe is connected to an oil production device, and a continuous pipe is lowered into the long pipe, wherein a heating element is arranged in the continuous pipe; determining a production process and production parameters; cleaning and preheating the wellbore; successively injecting a solvent plunger and a steam plunger from the annulus of the long pipe, turning on the heating element and controlling the bottom hole temperature to a first preset temperature, and turning on the oil production device for production after the well is shut down for a first preset time; after multiple cycles of alternating intake and output of the solvent-steam segment plug to expand the cavity, simultaneously injecting a solvent and steam from the annulus of the long pipe, keeping the heating element to heat the solvent and steam at a constant temperature, so that the solvent and steam enter the oil layer, drive the crude oil into the wellbore and be produced from the short pipe to the ground through the oil production device.

[0006] Furthermore, the production method also includes: transporting the produced fluid from the short tube to a solvent recovery device, and then injecting the recovered solvent into the oil layer again through the annulus of the long tube.

[0007] Furthermore, the mining method also includes: when the recovery rate reaches 35% to 40%, non-condensable gas is periodically or continuously injected from the long tube annulus, and the injection amount of steam is gradually reduced until the production is completed.

[0008] Furthermore, the non-condensable gas is at least one of nitrogen and carbon dioxide.

[0009] Furthermore, the conditions for heavy oil reservoirs to meet the exploitation requirements include: the permeability difference within the reservoir layer is less than 20; the thickness of the continuous oil layer reaches 7m to 15m; the reservoir has no edge water or bottom water; the horizontal permeability is greater than 500mD, and the vertical permeability is greater than 300mD; the viscosity of the ground degassed crude oil at 50°C is 20000Pa.s to 500000mPa.s.

[0010] Furthermore, the horizontal well is a five-section system including a straight well section, a first inclination increasing section, a first inclination stabilizing section, a second inclination increasing section and a second inclination stabilizing section connected in sequence.

[0011] Further, the oil production equipment is located at the first stabilizing section; and / or the tail end of the coiled tubing is located at the toe end of the horizontal well; and / or the heating element is located at 50% to 75% of the length of the rear section of the horizontal section of the coiled tubing.

[0012] Furthermore, when drilling a horizontal well, drilling is carried out along a structural line perpendicular to the bottom of the oil layer or in a direction oblique to the structural line at a distance of 1m to 1.5m from the bottom of the oil layer. The horizontal section is drilled at an angle of 90° to 100°, and the toe end of the horizontal well is 10m to 50m higher than the heel end of the horizontal well.

[0013] Furthermore, a sealing protection head is provided at the tail end of the continuous tube for sealing the tail end of the continuous tube.

[0014] Furthermore, a temperature measuring device is provided in the coiled tubing, and a plurality of temperature measuring points are arranged at intervals along the horizontal section of the temperature measuring device for measuring the bottom hole temperature.

[0015] Furthermore, the production process and production parameters are determined by numerical simulation methods using a detailed three-dimensional geological model. The production process includes the number of cycles of alternating solvent-steam segment plug throughput and cavity expansion, and the production parameters include at least one of solvent type, periodic solvent injection amount, steam injection amount, solvent injection rate, steam injection rate, injection pressure, production-injection ratio and maximum oil production rate.

[0016] Furthermore, cleaning and preheating the wellbore includes: injecting water from the annulus of the long tube, discharging liquid through the short tube, and continuing cleaning until the wellbore is clean; injecting steam from the annulus of the long tube, discharging liquid through the short tube, turning on the heating element, controlling the bottom hole temperature at a second preset temperature, and completing the preheating start after continuing for a second preset time.

[0017] Further, the first preset temperature is 200°C to 380°C; and / or the first preset time is 2 days to 5 days; and / or the second preset temperature is 200°C to 380°C; and / or the second preset time is 180 days to 300 days.

[0018] Furthermore, during the process of injecting the solvent slug and the steam slug, when the bottom hole pressure is lower than the oil layer fracture pressure of 0.5 MPa, the injection is stopped, and the injection is continued after the bottom hole pressure drops, until the designed injection volume is reached.

[0019] By applying the technical scheme of the present invention, the exploitation method of the heavy oil reservoir comprises: determining a heavy oil reservoir that meets the exploitation conditions, determining the oil layer fracture pressure, drilling a horizontal well, completing the horizontal section of the horizontal well with a screen tube, lowering a short pipe and a long pipe into the horizontal well, wherein the length of the short pipe is less than that of the long pipe, and the tail end of the short pipe is connected to an oil production device, lowering a continuous pipe into the long pipe, wherein a heating element is arranged in the continuous pipe, determining a production process and production parameters, cleaning and preheating the wellbore, successively injecting a solvent plunger and a steam plunger from the annulus of the long pipe, turning on the heating element and controlling the bottom hole temperature at a first preset temperature, turning on the oil production device for production after the well is shut down for a first preset time, and after multiple cycles of alternating intake and output expansion of the solvent-steam segment plug, simultaneously injecting a solvent and steam from the annulus of the long pipe, and keeping the heating element to heat the solvent and steam at a constant temperature so that the solvent and steam enter the oil layer, The crude oil is driven into the wellbore and is produced from the short pipe to the ground through the oil production equipment. In this way, a double-tube production string is lowered. After multiple cycles of alternate injection of solvent slugs and steam slugs, production is performed by cooperating with the downhole heating element to form a large steam chamber with the solvent at the front edge. Then, the solvent and steam are injected simultaneously. The large-proportion miscibility of the solvent in the crude oil reduces the seepage resistance. The high crude oil stripping ability of the solvent is utilized to greatly reduce the residual oil saturation and improve the recovery rate of heavy oil development. Furthermore, the solvent is completely vaporized by the downhole heating element, and the steam is heated at the same time to increase the steam dryness and carry more latent heat into the deep oil layer, thereby improving the solvent and steam washing efficiency and greatly improving the recovery rate. In addition, the whole process can greatly reduce the steam consumption and reduce the carbon emission of steam generated by the boiler, thus solving the problem that heavy oil reservoirs cannot be effectively developed in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 A flow chart showing a method for producing a heavy oil reservoir in a specific embodiment of the present invention is shown;

[0022] Figure 2A schematic structural diagram of the exploitation of a heavy oil reservoir in a specific embodiment of the present invention is shown;

[0023] Figure 3 The figure shows a schematic structural diagram of a long tube in a specific embodiment of the present invention.

[0024] The above drawings include the following reference numerals:

[0025] 10. Oil layer; 20. Screen tube; 30. Short tube; 40. Long tube; 50. Oil production equipment; 60. Continuous tube; 70. Heating element; 80. Long tube annulus; 90. Sealing protection head; 100. Temperature measuring device; 110. Casing. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0027] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0028] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0029] Obviously, the above-described embodiments are only a part of the embodiments of the present invention, rather than all 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.

[0030] In order to solve the problem that heavy oil reservoirs cannot be effectively developed in the prior art, the present invention provides a method for exploiting heavy oil reservoirs.

[0031] like Figure 1As shown, the method for exploiting a heavy oil reservoir includes: determining a heavy oil reservoir that meets the exploitation conditions. Determining the fracture pressure of the oil layer 10. Drilling a horizontal well, completing the horizontal section of the horizontal well with a screen pipe 20, lowering a short pipe 30 and a long pipe 40 into the horizontal well, the length of the short pipe 30 is less than the length of the long pipe 40, the tail end of the short pipe 30 is connected to an oil production device 50, and lowering a continuous pipe 60 into the long pipe 40, wherein a heating element 70 is arranged in the continuous pipe 60. Determining the production process and production parameters. Cleaning and preheating the wellbore. Injecting a solvent plunger and a steam plunger from the long pipe annulus 80 in turn, turning on the heating element 70 and controlling the bottom hole temperature at a first preset temperature, and turning on the oil production device 50 for production after the well is shut down for a first preset time. After multiple cycles of alternating solvent-steam plug expansion, solvent and steam are injected simultaneously from the long pipe annulus 80, and the heating element 70 is kept to heat the solvent and steam at a constant temperature so that the solvent and steam enter the oil layer 10, drive the crude oil into the wellbore and are produced from the short pipe 30 to the ground through the oil production equipment 50.

[0032] By adopting the above-mentioned mining method, a double-tube production string is lowered, and after multiple cycles of alternate injection of solvent slugs and steam slugs, production is carried out, and after a large steam chamber with a solvent at the front edge is formed in cooperation with the downhole heating element 70, the solvent and steam are injected simultaneously. The large-proportion miscibility of the solvent in crude oil reduces the seepage resistance, and the high crude oil stripping ability of the solvent is utilized to greatly reduce the residual oil saturation and improve the recovery rate of heavy oil development. Furthermore, the solvent is completely vaporized by the downhole heating element 70, and the steam is heated at the same time to improve the steam dryness, carry more latent heat into the deep oil layer, improve the solvent and steam oil washing efficiency, and greatly improve the recovery rate. In addition, the whole process can greatly reduce the steam consumption and reduce the carbon emission of steam generated by the boiler.

[0033] In this embodiment, if Figure 2 As shown, the vertical section of the horizontal well is completed using casing 110.

[0034] In this embodiment, the production method further includes: transporting the produced liquid from the short pipe 30 to a solvent recovery device, and then injecting the recovered solvent into the oil layer 10 again through the long pipe annulus 80 .

[0035] In this embodiment, the production method further includes: when the recovery rate reaches 35% to 40%, non-condensable gas is periodically or continuously injected from the long tube annulus 80, and the injection amount of steam is gradually reduced until the production is completed.

[0036] In this embodiment, the non-condensable gas is at least one of nitrogen and carbon dioxide.

[0037] Specifically, when the recovery degree reaches 35% to 40% and enters the mid-to-late stage of production, non-condensable gases such as nitrogen and / or CO2 are injected from the long tube annulus for 80 cycles or continuously, and the steam injection volume is gradually reduced until the end of production, thereby improving the recovery factor and solvent recovery rate of the heavy oil reservoir.

[0038] In this embodiment, the conditions for the heavy oil reservoir to meet the mining conditions include: the permeability difference within the reservoir layer is less than 20. The thickness of the continuous oil layer 10 reaches 7m to 15m. The reservoir has no edge water or bottom water. The horizontal permeability is greater than 500mD, and the vertical permeability is greater than 300mD. The viscosity of the ground degassed crude oil at 50°C is 20000Pa.s to 500000mPa.s.

[0039] In this embodiment, the horizontal well is a five-section system including a straight well section, a first inclination increasing section, a first inclination stabilizing section, a second inclination increasing section and a second inclination stabilizing section connected in sequence.

[0040] In this embodiment, the oil production equipment 50 is located at the first stable inclination section, the tail end of the coiled tubing 60 is located at the toe end of the horizontal well, and the heating element 70 is located at 50% to 75% of the length of the rear section of the horizontal section of the coiled tubing 60.

[0041] In this embodiment, when drilling a horizontal well, drilling is carried out along a structural line perpendicular to the bottom of the oil layer 10 or in a direction oblique to the structural line at a distance of 1m to 1.5m from the bottom of the oil layer 10, the horizontal section is drilled at an angle of 90° to 100°, and the toe end of the horizontal well is 10m to 50m higher than the heel end of the horizontal well.

[0042] like Figure 2 As shown, a sealing protection head 90 is provided at the tail end of the continuous tube 60 for sealing the tail end of the continuous tube 60 .

[0043] like Figure 2 As shown, a temperature measuring device 100 is also provided in the coiled tubing 60. The temperature measuring device 100 has a plurality of temperature measuring points arranged at intervals along the horizontal section for measuring the bottom hole temperature.

[0044] In this embodiment, a fine three-dimensional geological model is used to determine the production process and production parameters through numerical simulation methods. The production process includes the number of cycles of alternating solvent-steam segment plug throughput and cavity expansion, and the production parameters include at least one of solvent type, periodic solvent injection amount, steam injection amount, solvent injection rate, steam injection rate, injection pressure, production-injection ratio and maximum oil production rate.

[0045] In this embodiment, cleaning and preheating the wellbore includes: injecting water from the long tube annulus 80, draining the liquid through the short tube 30, and continuously cleaning until the wellbore is clean. Injecting steam from the long tube annulus 80, draining the liquid through the short tube 30, turning on the heating element 70, controlling the bottom hole temperature at the second preset temperature, and continuing for the second preset time to complete the preheating start.

[0046] In this embodiment, the first preset temperature is 200° C. to 380° C., the first preset time is 2 days to 5 days, the second preset temperature is 200° C. to 380° C., and the second preset time is 180 days to 300 days.

[0047] In this embodiment, during the process of injecting the solvent slug and the steam slug, when the bottom hole pressure is lower than the fracture pressure of the oil layer 10 by 0.5 MPa, the injection is stopped, and the injection is continued after the bottom hole pressure drops, until the designed injection volume is reached.

[0048] The above-mentioned method for exploiting heavy oil reservoirs is described in detail below through specific embodiments.

[0049] Embodiment 1

[0050] This embodiment adopts a method for exploiting a heavy oil reservoir, which includes the following specific steps:

[0051] Select a suitable heavy oil reservoir, the middle of the target oil layer of the reservoir is buried at a depth of 280m, and implement a horizontal well. The oil layers 10 between the horizontal sections of the well are all sand layers, the permeability difference within the layer is 7, the thickness of the continuous oil layer reaches 10m, and the reservoir has no edge water or bottom water. The horizontal permeability is 1000mD, the vertical permeability is 650mD, the viscosity of the degassed crude oil at 50℃ is 20000mPa.s, the reservoir is undeveloped, there are no faults around the horizontal well, and it is a monocline of 3° to 8° as a whole, which meets the mining conditions.

[0052] To determine the oil layer fracture pressure, four typical samples were selected from the closed coring of the reservoir and indoor rock stress experiments were carried out. The experimental analysis showed that the minimum fracture pressure was 6.8MPa.

[0053] Well layout and drilling design were optimized, and there were no faults in the horizontal well deployment area, with a horizontal section length of 400m. The five-section trajectory of "straight well section, first inclination increase section, first stable inclination section, second inclination increase section, and second stable inclination section" was adopted. The well was drilled along the oblique direction of the structural line at a distance of 1m to 1.5m from the bottom of the oil layer 10. The horizontal section was drilled at 93°, and the toe end of the horizontal well was 21m higher than the heel end of the horizontal well.

[0054] The well completion and pipe string structure design are optimized. The horizontal section is completed with a screen pipe 20. A short pipe 30 with an oil production equipment 50 is lowered into the horizontal well. The oil production equipment 50 is lowered to the bottom of the first stable inclination section, and a long pipe 40 is lowered 10m away from the toe section of the horizontal section. A continuous pipe 60 with a diameter of 30mm is lowered into the long pipe 40. A fully sealed sealing protection head 90 is connected to the tail end of the continuous pipe 60. A heating element 70 is lowered 300m after the horizontal section of the continuous pipe 60. The power density of the heating element 70 is 2kW / m. The heating element 70 is bundled with a temperature measuring device 100 and prefabricated in the continuous pipe 60. The continuous pipe 60 is fully sealed, and the temperature measuring device 100 has 8 temperature measuring points evenly spaced along the horizontal section.

[0055] The production process and production parameters are determined. By using a fine three-dimensional geological model and numerical simulation methods, it is determined that the production cycle of solvent slugs and steam slugs in the thermal power solvent cogeneration production is 5 rounds. C3+C4 is preferably used as the solvent, and the solvent components C3 and C4 are 50% respectively. The solvent injection amount in the first round is 110 tons, and it increases by 20% in each subsequent round. The solvent injection rate is 55t / d. The steam injection amount in the first round is 2000 tons, and it increases by 10% in each subsequent round. The steam injection rate is 200t / d, the maximum bottom hole injection pressure is 6.3MPa, the optimized production-injection ratio is about 0.95, and the maximum oil production rate is 0.2t / d.

[0056] To clean the wellbore and preheat, clean water or softened water is injected from the long tube annulus 80, and the short tube 30 is drained. This process lasts for 3 to 5 days until the wellbore is clean. Steam is injected from the long tube annulus 80, and the short tube 30 is drained. The heating element 70 is turned on, and the bottom hole temperature is controlled at 200°C to 380°C. The steam injection rate is 80t / d, and the liquid production rate is 70t / d. This process lasts for 180 days to complete the preheating start-up.

[0057] The solvent-steam segment plug is alternately swallowed and expanded. Turn off the heating element 70 and the short pipe 30, and according to the above-mentioned optimized production parameters, inject the designed solvent segment plug from the long pipe annulus 80, and then inject the steam segment plug. The upper limit of the bottom hole injection pressure is 6.3MPa. When the designed injection volume is reached, stop the injection. Turn on the heating element 70, control the bottom hole temperature at 250℃, stew the well for 2 days, and then start the oil production device production. Appropriately control the displacement of the oil production device to avoid self-flow and wellbore flashing. When the oil production rate drops to 0.2t / d, stop production and restart the next cycle of solvent-steam segment plug alternately swallow and expand the cavity.

[0058] In the horizontal well thermal power solvent cogeneration, after 5 cycles of alternating solvent-steam plug swallowing and cavity expansion, a solvent-steam cavity is formed in the oil layer, and solvent and steam are injected simultaneously from the long pipe annulus 80, with a steam injection rate of 60 t / d and a solvent concentration of 10% (mass). The heating element 70 is kept at a designed constant temperature of 250°C to continuously heat the solvent and steam. The solvent and steam enter the oil layer, and the condensed hot water and crude oil seep into the wellbore under the action of gravity, and are produced from the short pipe 30 to the ground through the oil production equipment 50, and the liquid production rate is controlled at 50 t / d.

[0059] The solvent is recovered and reused, and the produced liquid is transported to the solvent recovery device in a closed manner through the short pipe 30 for purification, compression, and liquefaction. The produced solvent is recovered and then injected into the oil layer 10 together with steam through the long pipe annulus 80.

[0060] Inject non-condensate gas to assist production. Through measurement and calculation, when the recovery rate reaches 40%, it enters the middle and late stages of production. In the first two years, a periodic nitrogen injection mode is adopted. In the first week of each quarter, 30,000 Nm 3 Nitrogen: 2000Nm3 / day starting from the third year 3 During the nitrogen injection period, close the short pipe 30 and gradually reduce the steam injection amount until the production is completed.

[0061] By adopting the method for producing heavy oil reservoirs in this embodiment, the recovery rate increases from 25% in conventional steam huff-and-puff production to 53.8%, and the daily oil production during the peak production period increases from 8 t / d to 20.6 t / d. The total solvent recovery rate is 90%.

[0062] Embodiment 2

[0063] This embodiment adopts a method for exploiting a heavy oil reservoir, which includes the following specific steps:

[0064] Select a suitable heavy oil reservoir, the middle of the target oil layer of the reservoir is buried at a depth of 450m, and implement a horizontal well. The oil layers between the horizontal sections of the well are all sand layers, the permeability difference within the layer is 10, the continuous oil layer thickness reaches 8m, and the reservoir has no edge water or bottom water. The horizontal permeability is 800mD, the vertical permeability is 500mD, the viscosity of the degassed crude oil at 50℃ is 80000mPa.s, the reservoir is undeveloped, there are no faults around the horizontal well, and it is a monocline of 3° to 8° as a whole, which meets the conditions of thermal power and solvent co-production.

[0065] To determine the oil layer fracture pressure, three typical samples were selected from the closed coring of the reservoir and indoor rock stress experiments were carried out. The experimental analysis showed that the minimum fracture pressure was 9.7 MPa.

[0066] Well layout and drilling design were optimized, with no faults in the horizontal well deployment area and a horizontal section length of 500m. The five-section trajectory of "straight well section, first inclination increase section, first stable inclination section, second inclination increase section, and second stable inclination section" was adopted. The well was drilled along the oblique direction of the structural line at a distance of 1m to 1.5m from the bottom of the oil layer 10. The horizontal well section was drilled at 94°, and the toe of the horizontal well was 28m higher than the heel of the horizontal well.

[0067] The well completion and pipe string structure design are optimized. The horizontal section is completed with a screen pipe 20. A short pipe 30 with an oil production equipment 50 is lowered into the horizontal well. The oil production equipment 50 is lowered to the bottom of the first stable inclination section, and a long pipe 40 is lowered 10m away from the toe section of the horizontal section. A continuous pipe 60 with a diameter of 33.2mm is lowered into the long pipe 40. A fully sealed sealing protection head 90 is connected to the tail end of the continuous pipe 60. A heating element 70 is lowered 400m after the horizontal section of the continuous pipe 60. The power density of the heating element 70 is 4kW / m. The heating element 70 is bundled with a temperature measuring device 100 and prefabricated in the continuous pipe 60. The continuous pipe 60 is fully sealed, and the temperature measuring device 100 has 12 temperature measuring points evenly spaced along the horizontal section.

[0068] The production process and production parameters are determined. The fine three-dimensional geological model is used to determine the eight production cycles of solvent slug and steam slug throughput in the thermal power solvent cogeneration production through numerical simulation. C5+C7 is preferably used as the solvent, and the solvent components C5 and C7 are 60% and 40% respectively. The solvent injection volume in the first round is 132 tons, which increases by 20% in each subsequent round and will not increase after the fifth round. The solvent injection rate is 55t / d. The steam injection volume in the first round is 2,600 tons, which increases by 10% in each subsequent round. The steam injection rate is 250t / d and will not increase after the fifth round. The upper limit of the bottom hole injection pressure is 9.2MPa, the optimized production-injection ratio is about 0.95, and the maximum oil production rate is 0.2t / d.

[0069] To clean the wellbore and preheat, clean water or softened water is injected from the long pipe annulus 80, and the short pipe 30 is drained. This process lasts for 3 to 5 days until the wellbore is clean. Steam is injected from the long pipe annulus 80, and the short pipe 30 is drained. The heating element 70 is turned on, and the bottom hole temperature is controlled at 200 to 380°C. The steam injection rate is 100t / d, and the liquid production rate is 90t / d. This process lasts for 180 days to complete the preheating start-up.

[0070] The solvent-steam segment plug is alternately swallowed and expanded. Turn off the heating element 70 and the short pipe 30, and according to the above-mentioned optimized production parameters, inject the designed solvent segment plug from the long pipe annulus 80, and then inject the steam segment plug. The maximum bottom hole pressure is 6.3MPa. When the designed injection volume is reached, stop the injection. Turn on the heating element 70, control the bottom hole temperature at 250℃, stew the well for 4 days, and then start the oil production device for production. Appropriately control the displacement of the oil production device to avoid self-flow and wellbore flashing. When the oil production rate drops to 0.2t / d, stop production and restart the next cycle of solvent-steam segment plug alternately swallow and expand the cavity.

[0071] In the horizontal well thermal power solvent cogeneration, after 8 cycles of alternating solvent-steam plug swallowing and cavity expansion, a solvent-steam cavity is formed in the oil layer 10, and the solvent and steam are injected simultaneously from the long pipe annulus 80, the steam injection rate is 70t / d, the solvent concentration is 10% (mass), and the heating element 70 is kept at a designed constant temperature of 280°C to continuously heat the solvent and steam. The solvent and steam enter the oil layer 10, and the condensed hot water and crude oil seep into the wellbore under the action of gravity, and are produced from the short pipe 30 to the ground through the oil production equipment 50, and the liquid production rate is controlled at 65t / d.

[0072] The solvent is recovered and reused, and the produced liquid is transported to the solvent recovery device in a closed manner through the short pipe 30 for purification, compression, and liquefaction. The produced solvent is recovered and then injected into the oil layer 10 together with steam through the long pipe annulus 80.

[0073] Inject non-condensate gas to assist production. Through measurement and calculation, when the recovery rate reaches 32%, it enters the middle and late stages of production. In the first two years, a periodic nitrogen injection mode is adopted. In the first week of each quarter, 35,000 Nm 3 Nitrogen: 2500Nm3 / day starting from the third year 3 During the nitrogen injection period, close the short pipe 30 and gradually reduce the steam injection amount until the production is completed.

[0074] By using the cogeneration method and system for thermal power and solvent production of horizontal wells in heavy oil reservoirs of this embodiment, the recovery rate is increased from 21.5% in conventional steam huff-and-puff production to 47.2%, the daily oil production during the peak production period is increased from 6.3t / d to 13.8t / d, and the total solvent recovery rate is 80%.

[0075] From the above description, it can be seen that the above-mentioned embodiment of the present invention achieves the following technical effects: adopting the above-mentioned mining method, a double-tube production string is lowered, and after multiple cycles of alternate injection of solvent slugs and steam slugs, production is carried out, and after a large steam chamber with a solvent at the front edge is formed in cooperation with the downhole heating element 70, the solvent and steam are injected simultaneously, and the seepage resistance is reduced by the large-proportion miscibility of the solvent with crude oil, and the high crude oil stripping ability of the solvent is utilized to greatly reduce the residual oil saturation and improve the recovery rate of heavy oil development. Furthermore, the solvent is completely vaporized by the downhole heating element 70, and the steam is heated at the same time to improve the steam dryness, carry more latent heat into the deep oil layer, improve the solvent and steam oil washing efficiency, and greatly improve the recovery rate. In addition, the whole process can greatly reduce the steam consumption and reduce the carbon emission of steam generated by the boiler.

[0076] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0077] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application 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 numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0078] The above description is only a preferred embodiment of the present invention and is 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 method for exploiting a heavy oil reservoir, characterized in that: include: Identify heavy oil reservoirs that meet production conditions; Determine the reservoir breakdown pressure; Drilling a horizontal well, the horizontal section of the horizontal well is completed using a screen pipe (20), a short pipe (30) and a long pipe (40) are lowered into the horizontal well, the length of the short pipe (30) is shorter than the length of the long pipe (40), the tail end of the short pipe (30) is connected to an oil production device (50), a continuous pipe (60) is lowered into the long pipe (40), and a heating element (70) is provided in the continuous pipe (60); Determine the production process and production parameters; Clean and preheat the wellbore; Injecting a solvent plunger and a steam plunger from the long tube annulus (80) in sequence, turning on the heating element (70) and controlling the bottom hole temperature at a first preset temperature, and turning on the oil production equipment (50) for production after the well is shut down for a first preset time; After multiple cycles of alternating solvent-steam plug expansion, solvent and steam are simultaneously injected from the long tube annulus (80), and the heating element (70) is kept to heat the solvent and the steam at a constant temperature, so that the solvent and the steam enter the oil layer (10), drive the crude oil into the wellbore and are produced from the short tube (30) to the ground through the oil production equipment (50).

2. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: The mining method further comprises: The produced fluid from the short pipe (30) is transported to a solvent recovery device, and then the recovered solvent is injected into the oil layer (10) again through the long pipe annulus (80).

3. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: The mining method further comprises: When the recovery rate reaches 35% to 40%, non-condensable gas is periodically or continuously injected from the long tube annulus (80), and the injection amount of the steam is gradually reduced until the production is completed.

4. The method for exploiting heavy oil reservoirs according to claim 3, characterized in that: The non-condensable gas is at least one of nitrogen and carbon dioxide.

5. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: The heavy oil reservoir meets the exploitation conditions as follows: the permeability difference within the reservoir layer is less than 20; the continuous oil layer thickness reaches 7m to 15m; the reservoir has no edge water or bottom water; the horizontal permeability is greater than 500mD, and the vertical permeability is greater than 300mD; the viscosity of the ground degassed crude oil at 50°C is 20000Pa.s to 500000mPa.s.

6. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: The horizontal well is a five-section system including a straight well section, a first inclination increasing section, a first inclination stabilizing section, a second inclination increasing section and a second inclination stabilizing section connected in sequence.

7. The method for exploiting heavy oil reservoirs according to claim 6, characterized in that: The oil production equipment (50) is located at the first stabilizing section; and / or The tail end of the coiled tubing (60) is located at the toe end of the horizontal well; and / or The heating element (70) is located at 50% to 75% of the length of the rear section of the horizontal section of the continuous tube (60).

8. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: When drilling the horizontal well, the well is drilled at a distance of 1m to 1.5m from the bottom of the oil layer (10) along a construction line perpendicular to the bottom of the oil layer (10) or in a direction oblique to the construction line. The horizontal section is drilled at an angle of 90° to 100°, and the toe end of the horizontal well is 10m to 50m higher than the heel end of the horizontal well.

9. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: The tail end of the continuous tube (60) is provided with a sealing protection head (90) for sealing the tail end of the continuous tube (60).

10. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: A temperature measuring device (100) is also provided in the coiled tube (60), and the temperature measuring device (100) has a plurality of temperature measuring points arranged at intervals along the horizontal section, for measuring the bottom hole temperature.

11. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: The production process and the production parameters are determined by numerical simulation method using a fine three-dimensional geological model. The production process includes the number of cycles of the solvent-steam segment plug alternating intake and output expansion cavity, and the production parameters include at least one of solvent type, periodic solvent injection amount, steam injection amount, solvent injection rate, steam injection rate, injection pressure, production-injection ratio and maximum oil production rate.

12. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: The cleaning and preheating of the wellbore comprises: Inject water from the long tube annulus (80), drain the liquid through the short tube (30), and continue cleaning until the wellbore is cleaned; Steam is injected from the long tube annulus (80), liquid is discharged through the short tube (30), the heating element (70) is turned on, and the bottom hole temperature is controlled at a second preset temperature. After the temperature continues for a second preset time, the preheating start is completed.

13. The method for exploiting heavy oil reservoirs according to claim 12, characterized in that: The first preset temperature is 200° C. to 380° C.; and / or The first preset time is 2 days to 5 days; and / or The second preset temperature is 200° C. to 380° C.; and / or The second preset time is 180 days to 300 days.

14. The method for exploiting heavy oil reservoirs according to claim 1, characterized in that: During the process of injecting the solvent slug and the steam slug, when the bottom hole pressure is lower than the oil layer fracture pressure of 0.5 MPa, the injection is stopped, and the injection is continued after the bottom hole pressure drops, until the designed injection volume is reached.

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