CN117905426A - Method for improving crude oil recovery ratio and application - Google Patents
Method for improving crude oil recovery ratio and application Download PDFInfo
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- CN117905426A CN117905426A CN202211233657.3A CN202211233657A CN117905426A CN 117905426 A CN117905426 A CN 117905426A CN 202211233657 A CN202211233657 A CN 202211233657A CN 117905426 A CN117905426 A CN 117905426A
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- 238000011084 recovery Methods 0.000 title claims abstract description 59
- 238000000034 method Methods 0.000 title claims abstract description 56
- 239000010779 crude oil Substances 0.000 title claims abstract description 40
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 claims abstract description 224
- 239000003921 oil Substances 0.000 claims abstract description 132
- 235000019198 oils Nutrition 0.000 claims abstract description 131
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 87
- 238000004519 manufacturing process Methods 0.000 claims abstract description 74
- 238000002347 injection Methods 0.000 claims abstract description 66
- 239000007924 injection Substances 0.000 claims abstract description 66
- 239000007864 aqueous solution Substances 0.000 claims abstract description 48
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 32
- 235000019476 oil-water mixture Nutrition 0.000 claims abstract description 29
- 239000007788 liquid Substances 0.000 claims description 25
- 239000000243 solution Substances 0.000 claims description 24
- 239000011435 rock Substances 0.000 claims description 18
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 16
- 239000011148 porous material Substances 0.000 claims description 15
- 239000012752 auxiliary agent Substances 0.000 claims description 11
- 239000002904 solvent Substances 0.000 claims description 11
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- 150000001768 cations Chemical class 0.000 claims description 5
- 230000001965 increasing effect Effects 0.000 claims description 5
- 230000000149 penetrating effect Effects 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 4
- 238000011065 in-situ storage Methods 0.000 claims description 3
- BZLVMXJERCGZMT-UHFFFAOYSA-N Methyl tert-butyl ether Chemical compound COC(C)(C)C BZLVMXJERCGZMT-UHFFFAOYSA-N 0.000 claims description 2
- 150000002576 ketones Chemical class 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 238000004064 recycling Methods 0.000 claims description 2
- NUMQCACRALPSHD-UHFFFAOYSA-N tert-butyl ethyl ether Chemical compound CCOC(C)(C)C NUMQCACRALPSHD-UHFFFAOYSA-N 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 12
- 238000006073 displacement reaction Methods 0.000 abstract description 8
- 238000005755 formation reaction Methods 0.000 description 26
- 238000000605 extraction Methods 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 8
- 239000007789 gas Substances 0.000 description 7
- 239000004094 surface-active agent Substances 0.000 description 5
- 239000008398 formation water Substances 0.000 description 4
- 239000003027 oil sand Substances 0.000 description 4
- 230000035699 permeability Effects 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 3
- 239000013505 freshwater Substances 0.000 description 3
- 239000003208 petroleum Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 239000012267 brine Substances 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000012466 permeate Substances 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- DQYBDCGIPTYXML-UHFFFAOYSA-N ethoxyethane;hydrate Chemical compound O.CCOCC DQYBDCGIPTYXML-UHFFFAOYSA-N 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- -1 heat Substances 0.000 description 1
- 230000009545 invasion Effects 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
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- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
Abstract
The invention discloses a method for improving crude oil recovery efficiency and application thereof. The method of the invention comprises the following steps: injecting the dimethyl ether aqueous solution into the oil-bearing stratum above the water-bearing stratum through an injection well; raising the oil-water interface in the formation; lifting the oil-water mixture in the formation to the surface through the production well; the injection well is arranged at the lower part of the production well; crude oil is produced from the oil-water mixture. According to the invention, the dimethyl ether aqueous solution is continuously injected into the oil-bearing stratum through the injection well, the dissolved crude oil can be continuously lifted through the water quantity continuously injected while the crude oil is dissolved, so that a bottom-up displacement effect is formed, finally, the oil-water mixture is lifted to the ground through the production well, and then, the crude oil is extracted from the oil-water mixture and the dimethyl ether is recovered. The method can effectively enlarge the swept volume and improve the recovery ratio of crude oil.
Description
Technical Field
The invention relates to the technical field of oilfield development, in particular to a method for improving crude oil recovery efficiency and application thereof.
Background
As oil production continues, many oil fields have entered a high water cut in the later stages of development. The remaining oil is trapped in the reservoir rock pores under viscous and capillary forces as a discontinuous oil film. In order to increase the recovery ratio of old oil fields, the recoverable reserves are increased, and after secondary oil recovery, chemical agents, heat, mixed solvents and other substances are injected to improve the mutual performance of oil, gas, water and rock so as to recover more petroleum. If proper surfactant is used, interfacial tension between oil and water is reduced, and resistance caused by deformation of oil droplets when residual oil moves is reduced, so that oil displacement efficiency is improved. But the production process and the production process of each surfactant are comprehensively considered, and the production cost of the surfactant is high. The surfactant has sometimes insignificant effect on the enhancement of oil recovery due to the influence of factors such as crude oil properties in the reservoir, reservoir temperature, porosity, permeability and wetting characteristics, and is unstable and liable to fail especially at high temperatures (above 70 ℃).
The invention patent CN113431540A, named as a method for exploiting crude oil by utilizing liquid dimethyl ether to permeate and dissolve in a stratum, discloses a method for exploiting crude oil by utilizing liquid dimethyl ether to permeate and dissolve in the stratum, which utilizes the property that dimethyl ether has good extraction efficiency on oil, adopts a exploiting mode of two transverse wells, pressurizes and injects liquid dimethyl ether from an upper transverse well to produce the effects of displacement, dissolution and viscosity reduction on oil sand oil, applies suction force in a lower transverse well to extract a mixture of oil and oil sand oil, releases pressure in a separating tank to separate gaseous dimethyl ether after extraction, leaves oil sand oil extract, and carries out cyclic utilization treatment such as pressurization on gaseous dimethyl ether. However, the cost of the method for preparing the pure liquid dimethyl ether is too high, and the method needs a large amount of injection, so that the investment cost is high. The method is suitable for deep oil sand in-situ exploitation and is not suitable for secondary oil exploitation.
Therefore, there is a need to develop a method with better recovery of crude oil, especially after secondary recovery.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for improving the recovery ratio of crude oil and application thereof. According to the invention, the dimethyl ether aqueous solution is continuously injected into the oil-bearing stratum through the injection well, the dissolved crude oil can be continuously lifted through the water quantity continuously injected while the crude oil is dissolved, so that a bottom-up displacement effect is formed, finally, the oil-water mixture is lifted to the ground through the production well, and then, the crude oil is extracted from the oil-water mixture and the dimethyl ether is recovered. The invention effectively expands the swept volume and improves the recovery ratio of crude oil by injecting the dimethyl ether aqueous solution into the lower part and producing and recovering the petroleum from the upper part. The invention can also be matched with a flow-regulating water flow-controlling pipe column in the production well to realize balanced liquid discharge and improve the oil extraction effect. The method can be matched with a well group mode for development, the swept area is larger, and the oil extraction effect is better.
It is an object of the present invention to provide a method for enhanced oil recovery comprising the steps of:
Injecting the dimethyl ether aqueous solution into an oil-containing stratum above an aquifer through an injection well, and raising an oil-water interface in the stratum; lifting the oil-water mixture in the formation to the surface through the production well; the injection well is arranged at the lower part of the production well; crude oil is produced from the oil-water mixture.
In the enhanced oil recovery method of the present invention, preferably,
In the step (1), the content of the dimethyl ether in the dimethyl ether aqueous solution is 1 to 25mol percent, preferably 3 to 12mol percent at the temperature of 25 to 60 ℃; in the dimethyl ether aqueous solution, the concentration of cations in the solvent water is less than or equal to 10ppm; this is because dimethyl ether is less soluble in high salinity brine; in actual production, stratum water can be extracted from the water layer produced by an adjacent well, and the salinity is measured. If the salinity is high, taking measures to reduce the content of divalent cations so as to meet the requirements.
Preferably, the method comprises the steps of,
The invention can be used to provide water or brine solution from river, lake, fresh water area, aquifer, formation water, sea water, brackish water or water source for treating water supply; the total dissolved solids content of the water in the solvent water used ranges from 100ppm to 50000ppm.
It is further preferred that the first and second regions,
The solvent water is selected from fresh water; the Total Dissolved Solids (TDS) content of the solvent water ranges from 100ppm to 2000ppm, preferably from 250ppm to 450ppm.
The solvent water is selected from saline water; the Total Dissolved Solids (TDS) content of the solvent water is less than or equal to 50000ppm, preferably 2000ppm to 45000ppm.
If injected water is not matched with formation water, chemical reaction may occur to generate precipitation, and damage the reservoir. The dimethyl ether aqueous solution considers the influence of the salt content in the formation water, has certain compatibility with the formation water, and is easier to realize injection and oil displacement. The solvent water used may also be heated hot water. Because dimethyl ether is less soluble in high salinity brines than fresh water or low salinity brines.
In the enhanced oil recovery method of the present invention, preferably,
The dimethyl ether aqueous solution also comprises an auxiliary agent; preferably, the auxiliary agent is selected from at least one of ether, alcohol and ketone; and/or the number of the groups of groups,
The content of the auxiliary agent in the dimethyl ether aqueous solution is 2-4mol%;
Further preferably, the auxiliary agent is at least one selected from diethyl ether, methyl tertiary butyl ether, ethyl tertiary butyl ether, methanol, ethanol and acetone.
Adding an auxiliary agent into the dimethyl ether aqueous solution to achieve the optimal viscosity reduction effect; the invention not only maintains the viscosity reduction effect of the dimethyl ether on the crude oil, but also adapts to the well bore fluid environment, and can recycle and save the cost of injection (dimethyl ether aqueous solution).
In the enhanced oil recovery method of the present invention, preferably,
Preparing dimethyl ether water solution in situ; and/or the number of the groups of groups,
Separating and recovering dimethyl ether after crude oil is extracted from the oil-water mixture, and recycling the recovered dimethyl ether; the oil-water mixture circulated out of the production well shaft in the invention can recycle dimethyl ether on the ground through the treatment means of depressurization, drying, impurity removal and the like, and simultaneously, the produced crude oil is conveyed.
Preferably, the method comprises the steps of,
When the dimethyl ether aqueous solution is prepared, preparing dimethyl ether into the dimethyl ether aqueous solution with water when the dimethyl ether is in a liquid state;
further preferably, the gaseous dimethyl ether is pressurized to bring the dimethyl ether into a liquid state;
Still more preferably, the dimethyl ether is in a liquid state at a pressure of 0.5MPa or more. In the present invention, dimethyl ether is preferably liquid when mixed with feed water, and dimethyl ether can be kept in a liquid state in an environment of more than 0.5MPa so as to facilitate mixing, and the mixed aqueous solution is kept as a single phase.
In the enhanced oil recovery method of the present invention, preferably,
The injection well is a horizontal well; and/or the number of the groups of groups,
The production well is selected from a horizontal well and a vertical well.
In the enhanced oil recovery method of the present invention, preferably,
Injecting a dimethyl ether aqueous solution into an oil-bearing formation at a horizontal section of the injection well; and/or the number of the groups of groups,
When the production well is selected from a horizontal well, the horizontal section of the production well is located above, preferably directly above, the horizontal section of the injection well; or alternatively
When the production well is selected from a vertical well, the bottom of the vertical well is located above, preferably directly above, the horizontal section of the injection well.
In the enhanced oil recovery method of the present invention, preferably,
When the production well is selected from a horizontal well, collecting the oil-water mixed liquid in the horizontal section of the production well; or alternatively
When the production well is selected from a vertical well, collecting the oil-water mixed solution at the bottom of the vertical well;
Preferably, a water-regulating sieve tube is arranged in the horizontal section of the production well. And a flow control element such as water control elements is added on the horizontal section of the horizontal well, so that water phase burst is delayed, and oil phase is promoted to enter the shaft.
In the enhanced oil recovery method of the present invention, preferably,
The horizontal section of the injection well is arranged at the lower part of the oil-bearing stratum;
the oil-water mixed liquid collecting section of the production well is arranged at the upper part of the oil-bearing stratum in a penetrating way;
Preferably, when the production well is selected from a horizontal well, the vertical distance between the horizontal section of the injection well and the horizontal section of the production well is less than or equal to 4/5 of the thickness of the oil-bearing formation; or alternatively
When the production well is selected from a vertical well, the vertical distance between the horizontal section of the injection well and the bottom of the production well is less than or equal to 4/5 of the thickness of the oil-bearing stratum;
further preferably, the oil-water mixed liquid collecting section of the production well is arranged on a fracture zone of the stratum in a penetrating manner; still more preferably, the fracture zone is subterranean. The fractures in the fracture zones in the formations of the present invention may be naturally formed within the formations or may be formed by conventional formation fracturing processes (e.g., hydraulic fracturing). Particularly, the water injection well is preferably a horizontal well, and more reservoirs or fracture zones can be penetrated at the time, so that the collection of the oil-water mixture is facilitated.
In the enhanced oil recovery method of the present invention, preferably,
The injection well is an injection well group; preferably, the number of horizontal wells in the injection well group is greater than or equal to 2;
the production well is a production well group; preferably, the number of horizontal wells in the production well group is equal to or greater than 2 or the number of vertical wells in the production well group is equal to or greater than 2. Such as the mode of underground double-horizontal well groups or multi-horizontal well groups matched with injection and production, or the mode of upper straight well groups of lower multi-horizontal wells,
In the enhanced oil recovery method of the present invention, preferably,
Step (2) the injection amount of the aqueous dimethyl ether solution is 0.1 to 5 times, preferably 0.5 to 1 times the pore volume of the oil-bearing formation between the injection well and the production well.
In the enhanced oil recovery method of the present invention, preferably,
The formation is a bottom water reservoir formation. The bottom water oil reservoir stratum is an aquifer, and the aquifer is an oil reservoir of the oil-bearing stratum.
It is a second object of the present invention to provide a method for enhanced oil recovery according to one of the objects of the present invention for use in oil recovery, preferably in residual oil recovery from a bottom water reservoir formation after secondary oil recovery; it is further preferred that after secondary oil recovery, the method is applied to residual oil exploitation of a bottom water reservoir stratum of fractured, sandstone and clastic rock.
The remaining oil in the formation may be held in the pores within the rock porous matrix by capillary forces, surface forces of the oil and the pore surfaces, interfacial tension between the oil and water in the formation, and the like. In the present invention, after injection of the aqueous dimethyl ether solution into the formation, the aqueous solution may be imbibed into the porous rock matrix. In the porous matrix of the rock, dimethyl ether may be mixed with oil in the pores of the rock, so that the oil is expanded, the wettability of the oil on the surfaces of the pores is reduced, or the capillary force holding the oil in the pores is reduced, so that at least a part of the oil escapes from the pores to mobilize the oil, the residual oil in the stratum is dissolved out, and after the water solution of the flooding dimethyl ether is moved through the porous matrix of the rock and mixed with the dissolved crude oil in the stratum, an oil-water interface is formed, and due to the difference of the oil-water density, the dimethyl ether oil solution is accumulated at the upper part of the oil-water interface, and meanwhile, the water amount in the stratum is increased by continuously injecting the dimethyl ether water solution through an injection well, so that the oil-water interface in the stratum is raised, and the crude oil is pushed to continuously move upwards. As the oil is pushed and moved up through the porous rock matrix, the dimethyl ether in the aqueous solution or in the flowing oil may be further transferred to the oil still retained in the pores of the porous rock to mobilize more oil. As the mobilized dissolved oil and the dimethyl ether-containing aqueous solution move in the formation, dimethyl ether may be further absorbed into the rock pores through the fractures as it passes through the fractures in the formation to mobilize the oil further, thereby enhancing recovery of the remaining oil. Finally, the oil-water mixture can be collected by the production well through gaps among stratum rocks such as fractured, sandstone and clastic rocks, and the collected oil-water mixture is lifted to the ground.
In summary, the invention forms upward displacement pressure of bottom water by injecting dimethyl ether water solution into the lower part of the reservoir, lifts the oil-water mixture to the ground by the pumping action of the upper production well through the gravity separation of oil and water and the continuously rising oil-water interface. The stereoscopic development effect of the oil extraction water mixed solution of the upper horizontal well or the vertical well of the dimethyl ether water solution at the lower part of the stratum is realized.
The endpoints of the ranges and any values disclosed in the present invention are not limited to the precise range or value, and the range or value should be understood to include values close to the range or value. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein. In the following, the individual technical solutions can in principle be combined with one another to give new technical solutions, which should also be regarded as specifically disclosed herein.
Compared with the prior art, the invention has at least the following advantages:
According to the invention, the development mode of the upper production and recovery of petroleum by injecting the dimethyl ether aqueous solution into the lower part of the oil-containing stratum is adopted, so that the swept volume is effectively enlarged, and the crude oil recovery ratio is improved.
The dimethyl ether aqueous solution adopted by the invention has high oil displacement efficiency, the dimethyl ether can be recovered from the oil-water mixture on the produced ground by means of depressurization and the like, so that the cyclic utilization is realized, and compared with the direct injection of pure liquid dimethyl ether, the dimethyl ether is less in quantity and lower in cost.
Drawings
FIG. 1 is a schematic diagram of recovery of crude oil by injection of an aqueous dimethyl ether solution in the process of the present invention;
FIG. 2 is a schematic diagram of a well pattern for the stereoscopic exploitation and recovery of crude oil by injecting an aqueous solution of dimethyl ether in the method of the present invention;
Reference numerals illustrate:
In FIG. 1, 101-an injection well; 102-an aquifer; 103-a production well; 105-oil-bearing formation; 106-ground; 107-cracking; 108-dimethyl ether aqueous solution; 109-an oil-water mixture;
in FIG. 2, injection well group-201; production well group-202.
Detailed Description
The present invention is described in detail below with reference to the specific drawings and examples, and it is necessary to point out that the following examples are given for further illustration of the present invention only and are not to be construed as limiting the scope of the present invention, since numerous insubstantial modifications and adaptations of the invention to those skilled in the art will still fall within the scope of the present invention.
In addition, the specific features described in the following embodiments may be combined in any suitable manner without contradiction. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention can be made, so long as the concept of the present invention is not deviated, and the technical solution formed thereby is a part of the original disclosure of the present specification, and also falls within the protection scope of the present invention.
The raw materials used in examples and comparative examples, if not particularly limited, are all as disclosed in the prior art, and are, for example, available directly or prepared according to the preparation methods disclosed in the prior art.
Example 1
The oil reservoir of this embodiment is a side bottom water low permeability oil reservoir, and after secondary oil recovery, the remaining crude oil in the oil-bearing formation is recovered, and the height of the oil-bearing formation is 50 meters.
(1) Preparing a dimethyl ether aqueous solution;
And (5) extracting stratum water from the water layer produced by the adjacent well, and measuring the salinity. If the salinity is high, measures are taken to reduce the divalent cation content to the desired level, the multivalent cation content of the solvent water used in this example is 6ppm, and the Total Dissolved Solids (TDS) content of the solvent water used is in the range of 2000ppm.
The dimethyl ether gas storage tank or gas source is pressurized to 0.6MPa and 35 deg.c to convert dimethyl ether from gaseous state to liquid state. The liquid dimethyl ether is mixed with water in a convection pipeline, a stirring tank and other devices to form a homogeneous single-phase dimethyl ether aqueous solution. The mole fraction of dimethyl ether in the aqueous solution was 6mol%.
(2) Injecting the dimethyl ether aqueous solution into an oil-containing stratum above an aquifer through an injection well, and raising an oil-water interface in the stratum; lifting the oil-water mixture in the formation to the surface through the production well; the injection well is disposed in a lower portion of the production well, as shown in FIG. 1; in particular, the method comprises the steps of,
The prepared dimethyl ether aqueous solution 108 is injected into a shaft through an injection well 101, and the injection well 101 is a horizontal well. Below the injection well 101 is an aquifer 102. The production well 103 is also a horizontal well, and the dimethyl ether aqueous solution is injected into the oil-bearing stratum at the horizontal section of the injection well 101, wherein the horizontal section of the injection well is arranged at the lower part of the oil-bearing stratum; the horizontal section of the production well 103 is located in a space right above the horizontal section of the injection well 101, and the horizontal section of the production well 103 is arranged on the upper portion of the oil-bearing stratum 105 in a penetrating manner, and the vertical distance between the horizontal section of the production well 103 and the horizontal section of the injection well 101 is 40 meters.
The dimethyl ether aqueous solution flows from the surface injection facility through injection well 101 into oil-bearing formation 105. The oil-bearing formation 105 is a fractured reservoir in which fractures communicating with adjacent reservoir media may be formed after completion by conventional formation fracturing processes, such as hydraulic fracturing. The fracture 107 extends through the rock porous matrix and the injection amount of the aqueous dimethyl ether solution is 0.8 times the pore volume of the oil-bearing formation between the injection well and the production well. After being injected, the dimethyl ether aqueous solution contacts with the porous rock matrix, so that the residual oil in the stratum can be dissolved out to form an oil-water mixture; because the density of the oil is lower than that of water, the dissolved oil is positioned above the oil-water interface of the oil-water mixture after the oil is contacted with the oil; as the injection well 101 continues to inject aqueous dimethyl ether, the amount of water in the aquifer 102 increases and the water level increases, thereby increasing the oil-water interface within the oil-bearing formation 105. As the oil-water mixture is pushed through the porous rock matrix and moves upward, the dimethyl ether in the aqueous solution or the dimethyl ether in the flowing oil may be further transferred to the oil still retained in the pores of the porous rock to mobilize more oil. Finally, the mobilized oil-water mixture 109 is lifted to the surface 106 through the production well 103.
(3) Crude oil is extracted from the oil-water mixture, dimethyl ether is separated and recovered, and the recovered dimethyl ether is recycled.
The oil-water mixture circulated out of the production well shaft in the invention can recycle dimethyl ether on the ground through the treatment means of depressurization, drying, impurity removal and the like, and simultaneously, the produced crude oil is conveyed.
The recovery ratio of crude oil produced by the method is 19.02%, and the recovery ratio of crude oil produced by the adjacent well by the existing injection surfactant is 13%. As can be seen from the comparison, the invention adopts the development mode of exploiting the dimethyl ether aqueous solution through the upper part of water injection at the lower part, effectively expands the swept volume, improves the recovery ratio and has better oil extraction effect.
Example 2
The oil extraction method is basically the same as that of the example 1, except that the dimethyl ether aqueous solution of the example 2 also contains an auxiliary agent diethyl ether, and the diethyl ether content of the dimethyl ether aqueous solution is 3mol%; the addition of the auxiliary agent enables the dimethyl ether aqueous solution to have better viscosity reduction effect on crude oil.
The recovery ratio of crude oil produced by the method is 20.6%.
Example 3
The oil extraction method is basically the same as that of the embodiment 1, except that a flow control water screen pipe is arranged in the horizontal section of the production well of the embodiment 3, a spiral flow passage is arranged on the screen pipe, water control and oil stabilization can be realized when oil-water mixture flows in, water phase inflow is limited in the well section with higher permeability, oil phase inflow is promoted in the well section with lower permeability, balanced oil extraction in the whole well section is realized, and water phase invasion is delayed.
The recovery ratio of crude oil produced by the method is 24.6%.
Example 4
The oil extraction method is basically the same as that of the embodiment 1, except that the number of injection wells is increased to 3 in the embodiment 4, so that a horizontal well type injection well group 201 is formed, a large-range side bottom water environment is formed at the lower part of a stratum, and the three-dimensional oil displacement effect of an oil reservoir block is realized by injecting a large amount of dimethyl ether water solution; the production wells were replaced with 3 vertical wells to form a production well group 202, and the designed production well group 202 was placed at a well depth of 40 meters above the injection well group 201, as shown in fig. 2.
The recovery ratio of crude oil produced by the method is 25.7%.
Example 5
The oil recovery process of example 1 is essentially the same, except that the dimethyl ether aqueous solution used in example 5 is: the dimethyl ether gas storage tank or gas source is pressurized to 0.5MPa and 40 deg.c to convert dimethyl ether from gaseous state to liquid state. The liquid dimethyl ether is mixed with the saline water solution in a convection pipeline, a stirring tank and other devices to form homogeneous single-phase dimethyl ether water solution. The mole fraction of dimethyl ether in the aqueous solution was 3mol%.
Example 5 the injection amount of the aqueous dimethyl ether solution was 1 time the pore volume of the oil-bearing formation between the injection well and the production well.
The recovery ratio of crude oil produced by the method is 17.8%.
Example 6
The oil recovery process of example 1 is essentially the same, except that the dimethyl ether aqueous solution used in example 5 is: the dimethyl ether gas storage tank or gas source is pressurized to 0.55MPa and 60 deg.c to convert dimethyl ether from gaseous state to liquid state. The liquid dimethyl ether is mixed with the saline water solution in a convection pipeline, a stirring tank and other devices to form homogeneous single-phase dimethyl ether water solution. The mole fraction of dimethyl ether in the aqueous solution was 12mol%.
Example 5 the injection amount of the aqueous dimethyl ether solution was 0.5 times the pore volume of the oil-bearing formation between the injection well and the production well.
The recovery ratio of crude oil produced by the method is 22.3 percent.
The invention has been described in detail in connection with the specific embodiments and exemplary examples thereof, but such description is not to be construed as limiting the invention. It will be understood by those skilled in the art that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, and these fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
Claims (11)
1. A method of increasing oil recovery comprising the steps of:
Injecting the dimethyl ether aqueous solution into an oil-containing stratum above an aquifer through an injection well, and raising an oil-water interface in the stratum; lifting the oil-water mixture in the formation to the surface through the production well; the injection well is arranged at the lower part of the production well; crude oil is produced from the oil-water mixture.
2. The method of enhanced oil recovery according to claim 1, wherein:
In the dimethyl ether aqueous solution, the content of the dimethyl ether is 1 to 25mol percent, preferably 3 to 12mol percent at the temperature of 25 to 60 ℃; in the dimethyl ether aqueous solution, the concentration of cations in the solvent water is less than or equal to 10ppm;
Preferably, the method comprises the steps of,
The total dissolved solids content of the water in the solvent water used ranges from 100ppm to 50000ppm.
3. The method of enhanced oil recovery according to claim 2, wherein:
The dimethyl ether aqueous solution also comprises an auxiliary agent; preferably, the method comprises the steps of,
The auxiliary agent is at least one selected from ether, alcohol and ketone; and/or the number of the groups of groups,
The content of the auxiliary agent in the dimethyl ether aqueous solution is 2-4mol%; it is further preferred that the composition comprises,
The auxiliary agent is at least one selected from diethyl ether, methyl tertiary butyl ether, ethyl tertiary butyl ether, methanol, ethanol and acetone.
4. The method of enhanced oil recovery according to claim 1, wherein:
Preparing dimethyl ether water solution in situ; and/or the number of the groups of groups,
Separating and recovering dimethyl ether after crude oil is extracted from the oil-water mixture, and recycling the recovered dimethyl ether;
Preferably, the method comprises the steps of,
When the dimethyl ether aqueous solution is prepared, preparing dimethyl ether into the dimethyl ether aqueous solution with water when the dimethyl ether is in a liquid state;
further preferably, the gaseous dimethyl ether is pressurized to bring the dimethyl ether into a liquid state;
still more preferably, the dimethyl ether is in a liquid state at a pressure of 0.5MPa or more.
5. The method of enhanced oil recovery according to claim 1, wherein:
the injection well is a horizontal well; and/or the number of the groups of groups,
The production well is selected from a horizontal well and a vertical well.
6. The method of enhanced oil recovery according to claim 5, wherein:
Injecting a dimethyl ether aqueous solution into an oil-bearing formation at a horizontal section of the injection well; and/or the number of the groups of groups,
When the production well is selected from a horizontal well, the horizontal section of the production well is located above, preferably directly above, the horizontal section of the injection well; or alternatively
When the production well is selected from a vertical well, the bottom of the vertical well is located above, preferably directly above, the horizontal section of the injection well.
7. The method of enhanced oil recovery according to claim 6, wherein:
When the production well is selected from a horizontal well, collecting the oil-water mixed liquid in the horizontal section of the production well; preferably, a water-regulating sieve tube is arranged in the horizontal section of the production well; or alternatively
When the production well is selected from a vertical well, collecting the oil-water mixture at the bottom of the vertical well.
8. The method of enhanced oil recovery according to claim 7, wherein:
The horizontal section of the injection well is arranged at the lower part of the oil-bearing stratum;
the oil-water mixed liquid collecting section of the production well is arranged at the upper part of the oil-bearing stratum in a penetrating way; preferably, the method comprises the steps of,
When the production well is selected from a horizontal well, the vertical distance between the horizontal section of the injection well and the horizontal section of the production well is less than or equal to 4/5 of the thickness of the oil-bearing stratum; or alternatively
When the production well is selected from a vertical well, the vertical distance between the horizontal section of the injection well and the bottom of the production well is less than or equal to 4/5 of the thickness of the oil-bearing stratum;
Further preferably, the oil-water mixture collecting section of the production well is arranged on a fracture zone of the stratum in a penetrating manner.
9. The method of enhanced oil recovery according to claim 5, wherein:
The injection well is an injection well group; preferably, the number of horizontal wells in the injection well group is greater than or equal to 2;
the production well is a production well group; preferably, the number of horizontal wells in the production well group is equal to or greater than 2 or the number of vertical wells in the production well group is equal to or greater than 2.
10. The method of enhanced oil recovery according to claim 1, wherein:
Step (2) the injection amount of the aqueous dimethyl ether solution is 0.1 to 5 times, preferably 0.5 to 1 times the pore volume of the oil-bearing formation between the injection well and the production well.
11. The use of a method of enhanced oil recovery according to any one of claims 1 to 10 in oil recovery, preferably in residual oil recovery from a bottom water reservoir formation after secondary oil recovery; it is further preferred that after secondary oil recovery, the method is applied to residual oil exploitation of a bottom water reservoir stratum of fractured, sandstone and clastic rock.
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