Quantification method for swept extent between gas injection wells and judgment method for treatment of gas channeling production wells

Abstract

The embodiments of the present application provide a method for quantifying the sweep extent between gas injection wells and a method for judging the treatment of gas channeling production wells. The method for quantifying the sweep extent between gas injection wells includes: determining the fractional flow derivative at the front of the gas drive in the oilfield based on unsteady relative permeability tests; establishing a core model of the production interval between injection and production wells, and determining the fractional flow derivative at the front of the gas drive in the swept area based on this model; determining the third relationship among the swept thickness between gas injection wells, the fractional flow derivative at the front of the gas drive in the swept area, the fractional flow derivative at the front of the gas drive in the oilfield, and the average thickness of the production interval between injection and production wells in the oilfield; detecting the average thickness of the production interval between injection and production wells in the oilfield, the dissolved gas-oil ratio, and the formation background concentration; determining the swept thickness between gas injection wells; judging whether the injected gas breaks through the production well; selecting a corresponding calculation formula based on the judgment result to calculate the vertical sweep coefficient of the gas drive based on the swept thickness between gas injection wells; so as to evaluate the sweep extent between gas injection wells. The quantification of the swept thickness and the vertical sweep coefficient between gas injection wells is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of development and recovery of fractured-vuggy carbonate reservoirs, and specifically relates to a method for quantifying the sweep efficiency between gas injection wells and a method for judging the treatment of gas channeling production wells in such reservoirs. Background Art

[0002] In fractured-vuggy carbonate reservoirs, a fracture-vug system is developed, and the vertical permeability is large. During gas flooding, gas override fingering is likely to occur, resulting in premature gas channeling in production wells, which limits the gas flooding development effect of fractured-vuggy carbonate reservoirs. Therefore, it is necessary to timely and accurately quantify the gas flooding sweep parameters between wells in fractured-vuggy carbonate reservoirs to provide a basis and support for understanding the effective sweep status between wells, adjusting the production system, and designing profile control and plugging measures.

[0003] Currently, the main methods for quantifying the gas flooding sweep between wells in fractured-vuggy carbonate reservoirs include numerical simulation methods, laboratory experiment methods, and reservoir engineering methods. The numerical simulation method is based on a three-dimensional numerical model that has been history matched to obtain a gas saturation distribution model at different development times, thereby realizing the quantification of the gas flooding sweep between wells. For example, Yao Jun, Hu Rongrong, Wang Chenchen, etc. (2015) established 19 numerical simulation models of four types with different fracture-vug medium structures to study the influence of the complex fracture-vug medium structure of fractured-vuggy reservoirs on gas flooding. A series of immiscible nitrogen gas flooding numerical simulation studies were carried out, and the distribution field maps of the injected gas in the fractures and vugs at different times were obtained. The simulation results show that the gas flooding recovery factor is mainly affected by factors such as gravity, vug density, vug porosity, and fracture density in the displacement direction. The accuracy of this method depends on the richness of data and the depth of understanding of simulation personnel, and there are problems such as the need for a large amount of data, long simulation time, and high price of simulation software.

[0004] The laboratory experiment method establishes a glass etched model with a similar fracture-vug structure and uses the observation system in the experimental device to visually observe the migration speed and front shape of the injected gas. The patent with the application number CN201510063864.2 provides a three-dimensional single-well gas injection displacement oil simulation experimental device for fractured-vuggy reservoirs, which includes a gas injection system, a fracture-vug simulation system connected to the gas injection system, and an image acquisition and information processing system. This experimental device can monitor the migration speed, pressure, and time of oil, gas, and water phases in the karst caves, fractures, and wellbores during the gravity segregation process in real time, accurately, and visually. However, due to scale differences and similarity differences, there are still many difficulties in directly applying the experimental results to actual field operations, and the laboratory experiment method cannot accurately depict the gas injection sweep status between actual injection and production wells.

[0005] Reservoir engineering methods are based on the physical assumptions of the reservoir seepage process and use the solutions of corresponding mathematical models to describe the sweep situation between wells. The core of existing reservoir engineering methods is the Buckley-Leverett theory, which can quickly describe the sweep situation between injection wells through the equal saturation advance equation. However, due to the neglect of the influence of gravity on seepage, this theory cannot be directly applied to the quantitative evaluation of the gas drive sweep between wells in fractured-vuggy carbonate reservoirs. The patent with the application number CN201510574202.1 discloses a method for evaluating the effect of single-well nitrogen injection in fractured-vuggy carbonate reservoirs, including: calculating the critical oil production increase value of single-well nitrogen injection according to the petroleum price information; calculating the gas storage rate according to the cumulative gas production during the production period after nitrogen injection, the average nitrogen content in the gas composition during the production period after nitrogen injection, and the cumulative nitrogen injection volume during the period; calculating the underground gas-to-oil conversion rate according to the cumulative oil production during the production period after nitrogen injection and the cumulative nitrogen injection volume during the period; and obtaining the evaluation information of the effect of single-well nitrogen injection in fractured-vuggy carbonate reservoirs by combining the critical oil production increase value of single-well nitrogen injection, the gas storage rate, and the underground gas-to-oil conversion rate with the recoverable reserve of single-well remaining oil. This patent evaluates the effect of nitrogen injection in fractured-vuggy carbonate reservoirs through parameters such as oil production increase, oil conversion rate, and remaining recoverable reserves, but fails to evaluate the sweep situation of injected nitrogen between wells, and the evaluation content of the effect of nitrogen injection is incomplete.

[0006] In fact, as shown by the results of numerical simulation and laboratory experiment methods, the influence of gravity on the migration of oil and gas in fractured-vuggy reservoirs cannot be ignored. This is because the vertical seepage capacity in fractures and vugs is large, the capillary force is small, and the injected gas is easily affected by gravity segregation and migrates to the high position.

[0007] Therefore, a method for quantitatively evaluating the gas drive sweep between wells in fractured-vuggy carbonate reservoirs that can be fast and accurate is needed. Summary of the Invention

[0008] The present invention provides a method for quantitatively characterizing the degree of gas drive sweep between wells and a method for judging the treatment of gas channeling production wells to quickly and accurately quantify the degree of gas drive sweep between wells in fractured-vuggy carbonate reservoirs.

[0009] In a first aspect, an embodiment of the present application provides a method for quantifying the gas drive inter-well sweep extent, including the following steps: Based on unsteady relative permeability testing, determine a first relationship between the fractional flow derivative at the gas drive front in the field and the gas saturation. When the gas saturation is the gas drive front saturation corresponding to the oil-gas pseudo relative permeability in the field, use the first relationship to determine the fractional flow derivative at the gas drive front in the field; establish a core model of the production layer section between injection and production wells, and based on the established core model of the production layer section between injection and production wells, determine a second relationship between the fractional flow derivative at the gas drive front in the swept area and the gas saturation. When the gas saturation is the gas drive front saturation corresponding to the oil-gas relative permeability in the swept area, use the second relationship to determine the fractional flow derivative at the gas drive front in the swept area; determine a third relationship among the gas drive inter-well sweep thickness, the fractional flow derivative at the gas drive front in the swept area, the fractional flow derivative at the gas drive front in the field, and the average thickness of the production layer section between injection and production wells in the field; detect the average thickness of the production layer section between injection and production wells in the field, the dissolved gas-oil ratio, and the formation background concentration; according to the fractional flow derivative at the gas drive front in the field, the fractional flow derivative at the gas drive front in the swept area, and the measured average thickness of the production layer section between injection and production wells in the field, use the third relationship to determine the gas drive inter-well sweep thickness; detect the production gas-oil ratio and the injected gas concentration in the produced gas of the production well. When the duration for which the production gas-oil ratio is greater than the dissolved gas-oil ratio is greater than or equal to a given time threshold, and the duration for which the injected gas concentration in the produced gas is greater than the formation background concentration is greater than or equal to a given time threshold, determine that the production well has experienced injected gas breakthrough; otherwise, determine that the production well has not experienced injected gas breakthrough; select a corresponding calculation formula based on the judgment result of whether the production well has experienced injected gas breakthrough, and calculate the gas drive vertical sweep coefficient based on the gas drive inter-well sweep thickness, where the gas drive vertical sweep coefficient is used to characterize the gas drive vertical sweep extent; use the gas drive vertical sweep coefficient to evaluate the gas drive inter-well sweep extent.

[0010] In one embodiment, based on unsteady relative permeability testing, determining a first relationship between the fractional flow derivative at the gas drive front in the field and the gas saturation includes: Based on unsteady relative permeability testing, determine a first functional relationship between the oil-phase pseudo relative permeability in the field and the gas saturation at the production end, and a second functional relationship between the gas-phase pseudo relative permeability and the gas saturation at the production end; determine a third functional relationship among the gas drive fractional flow, the oil-phase pseudo relative permeability, the gas-phase pseudo relative permeability, the oil-phase viscosity, and the gas-phase viscosity in the field; according to the first functional relationship, the second functional relationship, and the third functional relationship, determine a first relationship between the fractional flow derivative at the gas drive front in the field and the gas saturation.

[0011] In one embodiment, the first functional relationship between the oil-phase pseudo relative permeability in the field and the gas saturation at the production end is:

[0012]

[0013] where, Kro represents the pseudo relative permeability value of the oil phase in the oilfield, f G represents the volumetric fractional flow rate of the production well represents the dimensionless gas injection volume, I represents the injection capacity ratio, S ge represents the gas saturation at the production end

[0014] In one embodiment, the second functional relationship between the pseudo relative permeability of the gas phase in the oilfield and the gas saturation at the production end is:

[0015]

[0016] wherein, K rg represents the pseudo relative permeability value of the gas phase in the oilfield, K ro represents the pseudo relative permeability value of the oil phase in the oilfield, f G represents the volumetric fractional flow rate of the production well, μ g represents the gas viscosity, μ o represents the oil viscosity

[0017] In one embodiment, the third functional relationship among the gas drive fractional flow rate, the pseudo relative permeability of the oil phase, the pseudo relative permeability of the gas phase, the oil viscosity and the gas viscosity in the oilfield is:

[0018]

[0019] wherein, f gH (S g ) represents the gas drive fractional flow rate in the oilfield, S g represents the gas saturation, K ro represents the pseudo relative permeability value of the oil phase in the oilfield, K rg represents the pseudo relative permeability value of the gas phase in the oilfield, μ g represents the gas viscosity, μ o represents the oil viscosity

[0020] In one embodiment, the first relationship between the derivative of the gas drive front fractional flow rate and the gas saturation in the oilfield is:

[0021]

[0022] wherein, f’ gH (S gfH ) represents the derivative of the gas drive front fractional flow rate in the oilfield, S gfH represents the gas drive front saturation corresponding to the pseudo relative permeability of the oil and gas in the oilfield, f gH (S gfH ) represents the gas drive front fractional flow rate in the oilfield, that is, the value of the gas drive fractional flow rate curve in the oilfield at the gas drive front, S gcH represents the irreducible gas saturation corresponding to the pseudo relative permeability of the oil and gas in the oilfield

[0023] In one embodiment, a production interval model between injection and production wells is established according to the following steps: Obtain core data of the production interval between injection and production wells; establish a core model of the production interval between injection and production wells based on the core data of the production interval between injection and production wells.

[0024] In one embodiment, determining a second relationship between the fractional flow derivative at the gas drive front and the gas saturation in the swept zone based on the established core model of the production interval between injection and production wells includes: determining a fourth functional relationship between the gas drive fractional flow, the gas-phase relative permeability, the oil-phase relative permeability, the gas-phase viscosity, and the oil-phase viscosity in the swept zone based on the established core model of the production interval between injection and production wells; determining the second relationship between the fractional flow derivative at the gas drive front and the gas saturation in the swept zone according to the fourth functional relationship.

[0025] In one embodiment, the second relationship between the fractional flow derivative at the gas drive front and the gas saturation in the swept zone is:

[0026]

[0027] where f’ gh (S gfh ) represents the fractional flow derivative at the gas drive front in the swept zone, S gfh represents the gas drive front saturation corresponding to the experimental oil-gas relative permeability, f gh (S gfh ) represents the gas drive fractional flow in the swept zone, that is, the value of the gas drive fractional flow curve at the gas drive front in the swept zone, S gch represents the irreducible gas saturation corresponding to the experimental oil-gas relative permeability.

[0028] In one embodiment, the third relationship between the gas drive swept thickness between wells, the fractional flow derivative at the gas drive front in the swept zone, the fractional flow derivative at the gas drive front in the field, and the average thickness of the production interval between injection and production wells is:

[0029]

[0030] where h represents the gas drive swept thickness between wells, f’ gh (S gfh ) represents the fractional flow derivative at the gas drive front in the swept zone, f’ gH (S gfH ) represents the fractional flow derivative at the gas drive front in the field, and H represents the average thickness of the production interval between injection and production wells.

[0031] In one embodiment, select a corresponding calculation formula according to the judgment result of whether the injected gas breaks through in the production well, and calculate the gas drive vertical sweep coefficient based on the gas drive swept thickness between wells, including:

[0032] When it is determined that there is no breakthrough of the injected gas in the production well, the calculation formula selected for calculating the vertical sweep efficiency of gas flooding is as follows:

[0033]

[0034] Among them, E v represents the vertical sweep efficiency of gas flooding, t represents the gas injection time, T represents the breakthrough time of the injected gas, h represents the swept thickness between gas injection wells, and H represents the average thickness of the production interval between injection and production wells.

[0035] When it is determined that there is a breakthrough of the injected gas in the production well, the calculation formula selected for calculating the vertical sweep efficiency of gas flooding is as follows:

[0036]

[0037] Among them, E v represents the vertical sweep efficiency of gas flooding, h represents the swept thickness between gas injection wells, and H represents the average thickness of the production interval between injection and production wells.

[0038] In a second aspect, an implementation manner of the present application provides a method for judging the treatment of gas channeling production wells, including the following steps: determining the vertical sweep efficiency of gas flooding of gas channeling production wells according to the above-mentioned method for quantifying the degree of inter-well gas flooding; judging whether to treat the gas channeling production wells according to the vertical sweep efficiency of gas flooding of the gas channeling production wells.

[0039] The method for quantifying the degree of inter-well gas flooding in the present application divides the inter-well fracture-cavity unit in gas flooding into a lower unswept area and an upper swept area with a constant thickness where oil and gas two-phase seepage occurs. By using the static and dynamic data of the oil field of the target well pair, the pseudo relative permeability of oil and gas in the oil field is calculated, and a quantitative evaluation method for the inter-well gas flooding thickness and vertical sweep efficiency based on the relative permeability of oil and gas in the oil field and experiments is established, realizing the scientific quantitative evaluation of gas channeling wells. The present invention solves the problem that it is difficult to quickly and accurately quantify the inter-well swept condition caused by the gravity-controlled gas migration between wells in fractured-vuggy carbonate reservoirs, can provide a basis for the quantitative evaluation of gas injection dynamics and the design of development adjustment measures, and is beneficial to improving the development management level of fractured-vuggy carbonate reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic 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:

[0041] Figure 1 is a flowchart of the method for quantifying the degree of inter-well gas flooding according to an implementation manner of the present application;

[0042] Figure 2The pseudo relative permeability curve of oil and gas in the oilfield, the gas drive fractional flow curve in the oilfield, and the leading edge fractional flow derivative of gas drive in the oilfield according to an embodiment of the present application;

[0043] Figure 3 The experimental relative permeability curve of oil and gas, the gas drive fractional flow curve in the swept area, and the leading edge fractional flow derivative of gas drive according to an embodiment of the present application;

[0044] Figure 4 The curve of the variation of the vertical sweep coefficient of gas drive with time calculated according to an embodiment of the present application;

[0045] Figure 5 The pseudo relative permeability curve of oil and gas in the oilfield, the gas drive fractional flow curve in the oilfield, and the leading edge fractional flow derivative of gas drive in the oilfield according to another embodiment of the present application;

[0046] Figure 6 The experimental relative permeability curve of oil and gas, the gas drive fractional flow curve in the swept area, and the leading edge fractional flow derivative of gas drive according to another embodiment of the present application;

[0047] Figure 7 The curve of the variation of the vertical sweep coefficient of gas drive with time calculated according to another embodiment of the present application. Detailed implementation manners

[0048] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0049] Embodiment 1

[0050] The present application provides a method for quantifying the sweep degree between gas injection wells, including the following steps:

[0051] S110: Based on the unsteady phase permeability test, determine the first relationship between the leading edge fractional flow derivative of gas drive in the oilfield and the gas saturation. When the gas saturation is the gas drive front edge saturation corresponding to the pseudo relative permeability of oil and gas in the oilfield, use the first relationship to determine the leading edge fractional flow derivative of gas drive in the oilfield.

[0052] Before quantifying the sweep degree between gas injection wells, static data and dynamic data of the oilfield can be collected to judge the breakthrough situation of the injected gas in the production wells according to the static data and dynamic data of the oilfield, and determine the target well pairs for the implementation and application of the method of the present application.

[0053] Among them, the static data of the oilfield may include: oil phase viscosity, gas phase viscosity, ground density of the injected gas, underground density of the injected gas, oil volume coefficient, injection-production well spacing, average thickness of the production interval between the injection and production wells, porosity, average width of the fracture-cavity unit between the injection and production wells, original dissolved gas-oil ratio, etc.

[0054] The dynamic data of the oilfield can include: gas injection rate, injection-production pressure difference, gas-oil ratio of the production well, etc.

[0055] The application target well pair refers to the production well where the injected gas breaks through, that is, the gas-channeling production well, and the injection well corresponding to it, forming a well pair.

[0056] Based on the unsteady relative permeability test, determine the first relationship between the fractional flow derivative at the front of gas drive in the oilfield and the gas saturation, including: based on the unsteady relative permeability test, determine the first functional relationship between the pseudo relative permeability of the oil phase in the oilfield and the gas saturation at the production end and the second functional relationship between the pseudo relative permeability of the gas phase and the gas saturation at the production end; determine the third functional relationship between the fractional flow of gas drive, the pseudo relative permeability of the oil phase, the pseudo relative permeability of the gas phase, the viscosity of the oil phase and the viscosity of the gas phase in the oilfield; determine the first relationship between the fractional flow derivative at the front of gas drive in the oilfield and the gas saturation according to the first functional relationship, the second functional relationship and the third functional relationship.

[0057] Among them, the first functional relationship between the pseudo relative permeability of the oil phase in the oilfield and the gas saturation at the production end is:

[0058]

[0059] Among them, K ro represents the value of the pseudo relative permeability of the oil phase in the oilfield, f G represents the volumetric fractional flow of the production well, represents the dimensionless gas injection volume, I represents the injection capacity ratio, S ge represents the gas saturation at the production end.

[0060] In the calculation formula (1):

[0061] Among them, f G represents the volumetric fractional flow of the production well, B o represents the formation volume factor of crude oil, ρ g represents the underground density of the injected gas, ρ gs represents the surface density of the injected gas, R represents the gas-oil ratio of production, R s represents the original solution gas-oil ratio;

[0062] Among them, represents the dimensionless gas injection volume, Q in represents the gas injection rate, t represents the gas injection time, Φ represents the porosity, b represents the average width of the fracture-vug unit between the injection and production wells, H represents the average thickness of the production interval between the injection and production wells, L represents the distance between the injection and production wells, with the unit of m;

[0063] Among them, I represents the injection capacity ratio, Qs represents the initial gas injection rate, Δp represents the injection-production pressure difference, and Δp s represents the initial injection-production pressure difference;

[0064] where f G represents the volumetric fractional flow rate of the production well, represents the dimensionless gas injection volume, represents the average gas saturation between the injection and production wells, where ρ g represents the underground density of the injected gas, and ρ gs represents the surface density of the injected gas, R represents the production gas-oil ratio, and R s represents the original dissolved gas-oil ratio, Q in represents the gas injection rate, t represents the gas injection time, Φ represents the porosity, b represents the average width of the fracture-cavity unit between the injection and production wells, H represents the average thickness of the production interval between the injection and production wells, and L represents the distance between the injection and production wells, with the unit of m.

[0065] The second functional relationship between the apparent relative permeability of the gas phase in the field and the gas saturation at the production end is:

[0066]

[0067] where K rg represents the value of the apparent relative permeability of the gas phase in the field, and K ro represents the value of the apparent relative permeability of the oil phase in the field, f G represents the volumetric fractional flow rate of the production well, and μ g represents the viscosity of the gas phase, and μ o represents the viscosity of the oil phase.

[0068] Therefore, according to the calculation formulas (1) and (2), the apparent relative permeability curves of the oil and gas in the field can be plotted. Further, conventional models such as the Corey model can be selected to fit the apparent relative permeability curves of the oil and gas in the field to make the curves smooth.

[0069] The field dynamic data of the fracture-cavity carbonate reservoir are affected by gravity. Therefore, the apparent relative permeability of the oil and gas in the field includes the influence of gravity and can be used to calculate the prefrontal fractional flow rate of gas drive between wells in the actual reservoir.

[0070] The third functional relationship between the fractional flow rate of gas drive, the apparent relative permeability of the oil phase, the apparent relative permeability of the gas phase, the viscosity of the oil phase, and the viscosity of the gas phase in the field is:

[0071]

[0072] where f gH (S g ) represents the fractional flow rate of gas drive in the field, S g represents the gas saturation, and Kro Denote the pseudo relative permeability value of the oil phase in the oilfield as \(K\). rg Denote the pseudo relative permeability value of the gas phase in the oilfield as \(\mu\). g Denote the gas viscosity as \(\mu\). o Denote the oil phase viscosity.

[0073] Therefore, the gas drive fractional flow curve can be plotted according to Equation (3).

[0074] The first relationship between the derivative of the front fractional flow of gas drive in the oilfield and the gas saturation is as follows:

[0075]

[0076] where \(f'\) gH (\(S\) gfH ) denotes the derivative of the front fractional flow of gas drive in the oilfield, \(S\) gfH denotes the gas drive front saturation corresponding to the pseudo relative permeability of oil and gas in the oilfield, \(f\) gH (\(S\) gfH ) denotes the front fractional flow of gas drive in the oilfield, i.e., the value of the gas drive fractional flow curve in the oilfield at the gas drive front, \(S\) gcH denotes the irreducible gas saturation corresponding to the pseudo relative permeability of oil and gas in the oilfield. The values of \(S\) gfH and \(S\) gcH can be obtained in the inversion of the pseudo relative permeability curve using the unsteady relative permeability test.

[0077] S120: Establish a core model for the production interval between injection and production wells. Based on the established core model for the production interval between injection and production wells, determine the second relationship between the derivative of the front fractional flow of gas drive in the swept area and the gas saturation. When the gas saturation is the gas drive front saturation corresponding to the relative permeability of oil and gas in the swept area, use the second relationship to determine the derivative of the front fractional flow of gas drive in the swept area.

[0078] Among them, the core model for the production interval between injection and production wells is established according to the following steps: Obtain the core data of the production interval between injection and production wells; Establish a core model for the production interval between injection and production wells based on the core data of the production interval between injection and production wells.

[0079] In one embodiment, determining the second relationship between the derivative of the front fractional flow of gas drive in the swept area and the gas saturation based on the established core model for the production interval between injection and production wells includes: Determining the fourth functional relationship between the fractional flow of gas drive, the relative permeability of the gas phase, the relative permeability of the oil phase, the gas viscosity, and the oil phase viscosity in the swept area based on the established core model for the production interval between injection and production wells; Determining the second relationship between the derivative of the front fractional flow of gas drive in the swept area and the gas saturation according to the fourth functional relationship.

[0080] The second relationship between the derivative of the front fractional flow of gas drive in the swept area and the gas saturation is as follows:

[0081]

[0082] Among them, f' gh (S gfh ) represents the derivative of the fractional flow at the front of gas drive in the swept area, and S gfh represents the saturation of the gas drive front corresponding to the relative permeability of oil and gas in the experiment, and f gh (S gfh ) represents the fractional flow at the front of gas drive in the swept area, that is, the value of the fractional flow curve of gas drive in the swept area at the front of gas drive, and S gch represents the irreducible gas saturation corresponding to the relative permeability of oil and gas in the experiment.

[0083] For fractured-vuggy reservoirs, since it is difficult to extract the cores of the production intervals between injection and production wells, a conceptual model of the core can be constructed based on the core data of the production intervals between injection and production wells in fractured-vuggy reservoirs. Using this conceptual model, the relationships between the relative permeability of the oil phase and the gas saturation and between the relative permeability of the gas phase and the gas saturation can be obtained by numerical simulation, and the relative permeability curves of oil and gas can be plotted respectively. S gfh and S gch values can be obtained during the numerical simulation process.

[0084] For reservoir types other than fractured-vuggy reservoirs, the relative permeability of the oil phase and the gas phase obtained from core displacement experiment data are composed of two curves of Sg~kro and Sg~krg.

[0085] S130: Determine the third relationship among the swept thickness between gas injection wells, the derivative of the fractional flow at the front of gas drive in the swept area, the derivative of the fractional flow at the front of field gas drive, and the average thickness of the production interval between injection and production wells in the field.

[0086] The third relationship among the swept thickness between gas injection wells, the derivative of the fractional flow at the front of gas drive in the swept area, the derivative of the fractional flow at the front of field gas drive, and the average thickness of the production interval between injection and production wells is:

[0087]

[0088] Among them, h represents the swept thickness between gas injection wells, and f' gh (S gfh ) represents the derivative of the fractional flow at the front of gas drive in the swept area, and f' gH (S gfH ) represents the derivative of the fractional flow at the front of field gas drive, and H represents the average thickness of the production interval between injection and production wells.

[0089] During the gas drive process, the fracture-vug unit between wells is divided into the lower unswept area and the swept area with approximately constant thickness in the upper part where two-phase seepage of oil and gas occurs. It is assumed that the injected gas only flows in the swept area. According to the equal gas drive velocity between wells, the calculation method for the swept thickness between gas injection wells as shown in calculation formula (6) can be established.

[0090] S140: Detect the average thickness of the production interval between injection and production wells in the oilfield, the dissolved gas-oil ratio, and the formation background concentration.

[0091] S150: Determine the swept thickness between gas injection wells according to the derivative of the fractional flow at the front of gas drive in the oilfield, the derivative of the fractional flow at the front of gas drive in the swept area, and the measured average thickness of the production interval between injection and production wells in the oilfield, using the third relationship.

[0092] Substitute the derivative of the fractional flow at the front of gas drive in the oilfield obtained from Equation (4), the derivative of the fractional flow at the front of gas drive in the swept area obtained from Equation (5), and the measured average thickness of the production interval between injection and production wells in the oilfield into Equation (6), and the swept thickness between gas injection wells can be obtained.

[0093] S160: Detect the production gas-oil ratio of the production well and the concentration of the injected gas in the produced gas. When the duration for which the production gas-oil ratio is greater than the dissolved gas-oil ratio is greater than or equal to a given time threshold, and the duration for which the concentration of the injected gas in the produced gas is greater than the formation background concentration is greater than or equal to a given time threshold, it is determined that gas breakthrough has occurred in the production well; otherwise, it is determined that gas breakthrough has not occurred in the production well.

[0094] For example, when the production gas-oil ratio of the production well is greater than the dissolved gas-oil ratio and the concentration of the injected gas in the produced gas is greater than the formation background concentration for three consecutive months, it is determined that gas breakthrough has occurred in the production well.

[0095] S170: Select a corresponding calculation formula according to the judgment result on whether gas breakthrough has occurred in the production well, and calculate the vertical sweep coefficient of gas drive based on the swept thickness between gas injection wells, where the vertical sweep coefficient of gas drive is used to characterize the vertical sweep degree of gas drive.

[0096] Select a corresponding calculation formula according to the judgment result on whether gas breakthrough has occurred in the production well, and calculate the vertical sweep coefficient of gas drive based on the swept thickness between gas injection wells, including:

[0097] When it is determined that gas breakthrough has not occurred in the production well, the calculation formula selected for calculating the vertical sweep coefficient of gas drive is:

[0098]

[0099] where E v represents the vertical sweep coefficient of gas drive, t represents the gas injection time, T represents the gas breakthrough time, h represents the swept thickness between gas injection wells, and H represents the average thickness of the production interval between injection and production wells.

[0100] where where f’ gH (S gfH ) represents the derivative of the fractional flow at the front of gas drive in the oilfield, SgfH Denotes the saturation of the gas drive front corresponding to the pseudo relative permeability of oil and gas in the oilfield, ρ g Denotes the underground density of the injected gas, ρ gs Denotes the surface density of the injected gas, Q in Denotes the gas injection rate, Φ denotes the porosity, b denotes the average width of the fracture-vug unit between the injection and production wells, H denotes the average thickness of the production interval between the injection and production wells, and L denotes the distance between the injection and production wells, with the unit of m.

[0101] When it is determined that the injected gas breaks through in the production well, the calculation formula selected for calculating the vertical sweep efficiency of gas drive is:

[0102]

[0103] Among them, E v Denotes the vertical sweep efficiency of gas drive, h denotes the swept thickness between gas drive wells, and H denotes the average thickness of the production interval between the injection and production wells.

[0104] S180: Evaluate the swept degree between gas drive wells by using the vertical sweep efficiency of gas drive.

[0105] Taking a certain injection-production well group in Tahe Oilfield as an example, the swept thickness between gas drive wells and the vertical sweep efficiency are calculated by using the method of the present invention. The swept thickness between gas drive wells is 13.92 m, and the vertical sweep efficiency of gas drive corresponding to the production well seeing gas is 0.29. The implementation case shows that this method realizes the quantitative evaluation of the swept thickness between gas drive wells by using the static and dynamic data of the oilfield and the experimental relative permeability curve of the application target well pair, and solves the problem that it is difficult to quickly and accurately quantify the swept condition between wells caused by the gravity-controlled gas migration between wells in the fracture-vug type carbonate reservoir.

[0106] The method for quantifying the swept degree between gas drive wells of the present application reasonably assumes the migration and distribution characteristics of the injected gas between the injection and production wells, proposes a calculation method for the pseudo relative permeability of oil and gas in the oilfield, and establishes a quantitative evaluation equation for vertical sweep, so as to realize the quantitative evaluation of the swept thickness between gas drive wells and the vertical sweep efficiency. The implementation mode of the present application reflects the influence of gravity on seepage, combines the oilfield dynamic and experimental data, and can quickly and accurately evaluate the swept situation between gas drive wells in the fracture-vug type carbonate reservoir on the premise of considering the control effect of gravity on seepage. Among them, the obtained swept thickness between gas drive wells and the vertical sweep efficiency of gas drive can be used for the quantitative evaluation of gas injection effect and the design of development adjustment measures, which is beneficial to improving the development management level of the fracture-vug type carbonate reservoir.

[0107] Example Two

[0108] Embodiments of the present application provide a method for judging the treatment of gas-channeling production wells, including the following steps: determining the vertical gas drive sweep coefficient of a gas-channeling production well according to the gas drive sweep degree quantification method described above; judging whether it is necessary to treat the gas-channeling production well according to the vertical gas drive sweep coefficient of the gas-channeling production well.

[0109] In one example, a threshold value can be set. When the vertical gas drive sweep coefficient of a gas-channeling production well is less than or equal to the threshold value, it is determined that the gas-channeling production well needs to be treated.

[0110] In another example, the vertical gas drive sweep coefficients of multiple gas-channeling production wells can also be sorted, and it is determined that several gas-channeling production wells with the smallest vertical gas drive sweep coefficients need to be treated.

[0111] Embodiment III

[0112] Taking a certain injection-production well group in the fractured-vuggy carbonate reservoir of Tahe Oilfield as an example, the specific implementation manner of the method of the present invention is introduced.

[0113] Step 1: Collection and analysis of field data

[0114] The static field data is shown in Table 1. The dynamic field data includes: gas injection rate, injection-production pressure difference, and production gas-oil ratio of the production well.

[0115] Nitrogen is injected into injection well W1. After 218 days of gas injection, production well W2 experiences gas channeling. The production gas-oil ratio is continuously greater than the dissolved gas-oil ratio for 3 months. After gas channeling, the nitrogen content is as high as about 80%. It is judged that this production well is a gas-channeling production well. Injection well W1 and gas-channeling production well W2 are determined as the target well pairs for application.

[0116] Table 1 Static field data

[0117]

[0118]

[0119] Step 2: Calculation of pseudo relative permeability of oil and gas in the field

[0120] Based on the dynamic and static data, according to calculation formulas (1) and (2), the pseudo relative permeability curve of oil and gas in the field is inversely obtained (as shown in Figure 2 ).

[0121] Step 3: Quantitative evaluation of gas drive thickness between wells

[0122] Based on the experimental oil-gas relative permeability curve (as shown in Figure 3 ) and the pseudo relative permeability curve of oil and gas in the field (as shown in Figure 2 ), according to calculation formula (6), the gas drive thickness between wells is calculated to be 8.36 m.

[0123] Step 4: Evaluation of gas drive vertical sweep efficiency

[0124] According to calculation formula (8), the gas drive vertical sweep efficiency is calculated (as shown in Figure 4 ), and the gas drive vertical sweep efficiency after the breakthrough of the injected gas is 0.28.

[0125] Example 4

[0126] Taking a certain injection-production well group in the fracture-vuggy carbonate reservoir of Tahe Oilfield as an example, the specific implementation method of the present invention is introduced.

[0127] Step 1: Collection and analysis of field data

[0128] The static field data is shown in Table 2. The dynamic field data includes: gas injection rate, injection-production pressure difference, and production gas-oil ratio of the production well.

[0129] Nitrogen is injected into injection well W3. After 244 days of gas injection, gas channeling occurs in production well W4, and the production gas-oil ratio is greater than the dissolved gas-oil ratio for 3 consecutive months. After gas channeling, the nitrogen content is as high as about 80%. It is determined that this production well is a gas-channeling production well. Injection well W3 and gas-channeling production well W4 are determined as the target well pair for application.

[0130] Table 2 Static field data

[0131]

[0132]

[0133] Step 2: Calculation of pseudo relative permeability of oil and gas in the field

[0134] Based on the dynamic and static data, according to calculation formulas (1) and (2), the pseudo relative permeability curves of oil and gas in the field are inversely obtained (as shown in Figure 5 ).

[0135] Step 3: Quantitative evaluation of gas drive thickness between wells

[0136] Based on the experimental oil-gas relative permeability curve (as shown in Figure 6 ) and the pseudo relative permeability curve of oil and gas in the field (as shown in Figure 5 ), according to calculation formula (6), the gas drive thickness between wells is calculated to be 9.246 m.

[0137] Step 4: Evaluation of gas drive vertical sweep efficiency

[0138] According to calculation formula (8), the gas drive vertical sweep efficiency is calculated (as shown in Figure 7 ), and the gas drive vertical sweep efficiency after the breakthrough of the injected gas is 0.31.

[0139] Step 5: Well Selection Decision for Treating Gas Channeling Production Wells

[0140] If one well is to be selected from gas channeling production wells W2 and W4 for treatment, and arranged in ascending order according to the vertical sweep efficiency of gas flooding, the gas channeling production well W2 with a smaller vertical sweep efficiency of gas flooding should be treated for gas channeling production wells.

[0141] 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. When the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0142] It should be understood that the exemplary embodiments in this specification can be implemented in many different forms and should not be construed as being limited only to the embodiments set forth herein. These embodiments are provided so that the disclosure of the present application is thorough and complete, and the concept of these exemplary embodiments is fully conveyed to those of ordinary skill in the art, and should not be construed as a limitation of the present invention.

Claims

1. A method for quantifying the sweep efficiency between gas injection wells, characterized in that, It includes the following steps: Based on the unsteady relative permeability test, determine the first relationship between the fractional flow derivative at the gas drive front in the oilfield and the gas saturation. When the gas saturation is the gas drive front saturation corresponding to the pseudo relative permeability of oil and gas in the oilfield, use the first relationship to determine the fractional flow derivative at the gas drive front in the oilfield; Establish a core model for the production layer section between injection and production wells. Based on the established core model for the production layer section between injection and production wells, determine the second relationship between the fractional flow derivative at the gas drive front in the swept area and the gas saturation. When the gas saturation is the gas drive front saturation corresponding to the relative permeability of oil and gas in the swept area, use the second relationship to determine the fractional flow derivative at the gas drive front in the swept area; Determine the third relationship among the vertical swept thickness between gas drive wells, the fractional flow derivative at the gas drive front in the swept area, the fractional flow derivative at the gas drive front in the oilfield, and the average thickness of the production layer section between injection and production wells in the oilfield; Detect the average thickness of the production layer section between injection and production wells in the oilfield, the dissolved gas-oil ratio, and the formation background concentration; According to the fractional flow derivative at the gas drive front in the oilfield, the fractional flow derivative at the gas drive front in the swept area, and the measured average thickness of the production layer section between injection and production wells in the oilfield, use the third relationship to determine the vertical swept thickness between gas drive wells; Detect the production gas-oil ratio of the production well and the concentration of the injected gas in the produced gas. When the duration for which the production gas-oil ratio is greater than the dissolved gas-oil ratio is greater than or equal to a given time threshold, and the duration for which the concentration of the injected gas in the produced gas is greater than the formation background concentration is greater than or equal to a given time threshold, it is determined that the production well has experienced breakthrough of the injected gas; otherwise, it is determined that the production well has not experienced breakthrough of the injected gas; Select a corresponding calculation formula based on the judgment result of whether the production well has experienced breakthrough of the injected gas, and calculate the vertical sweep coefficient of gas drive based on the vertical swept thickness between gas drive wells, where the vertical sweep coefficient of gas drive is used to characterize the vertical sweep degree of gas drive; Evaluate the sweep degree between gas drive wells using the vertical sweep coefficient of gas drive.

2. The gas drive inter-well sweep extent quantification method according to claim 1, wherein Based on the unsteady relative permeability test, determining the first relationship between the fractional flow derivative at the gas drive front in the oilfield and the gas saturation includes: Based on the unsteady relative permeability test, determine the first functional relationship between the pseudo relative permeability of the oil phase in the oilfield and the gas saturation at the production end, and the second functional relationship between the pseudo relative permeability of the gas phase and the gas saturation at the production end; Determine the third functional relationship among the gas drive fractional flow, the pseudo relative permeability of the oil phase, the pseudo relative permeability of the gas phase, the viscosity of the oil phase, and the viscosity of the gas phase in the oilfield; According to the first functional relationship, the second functional relationship, and the third functional relationship, determine the first relationship between the fractional flow derivative at the gas drive front in the oilfield and the gas saturation.

3. The gas drive inter-well sweep degree quantification method according to claim 2, wherein The first functional relationship between the pseudo relative permeability of the oil phase in the oilfield and the gas saturation at the production end is: Among them, K ro represents the pseudo relative permeability value of the oil phase in the oilfield, f G represents the volumetric fractional flow rate of the production well, represents the dimensionless gas injection volume, I represents the injection capacity ratio, S ge represents the gas saturation at the production end.

4. The method for quantifying the sweep degree between gas injection wells according to claim 2, wherein The second functional relationship between the pseudo relative permeability of the gas phase in the oilfield and the gas saturation at the production end is: Among them, K rg represents the pseudo relative permeability value of the gas phase in the mine, K ro represents the pseudo relative permeability value of the oil phase in the mine, f G represents the volumetric fractional flow rate of the production well, μ g represents the gas phase viscosity, μ o represents the oil phase viscosity.

5. The method for quantifying the sweep degree between gas injection wells according to claim 2, wherein The third functional relationship among the gas drive fractional flow, the pseudo relative permeability of the oil phase, the pseudo relative permeability of the gas phase, the viscosity of the oil phase, and the viscosity of the gas phase in the oilfield is: Among them, f gH (S g ) represents the gas drive fractional flow rate of the oilfield, S g represents the gas saturation, K ro represents the pseudo relative permeability value of the oil phase in the oilfield, K rg represents the pseudo relative permeability value of the gas phase in the oilfield, μ g represents the gas phase viscosity, μ o represents the oil phase viscosity.

6. The method for quantifying the inter-well sweep efficiency of a gas drive according to claim 1 or 2, characterized in that The first relationship between the fractional flow derivative at the gas drive front in the oilfield and the gas saturation is: Among them, f’ gH (S gfH ) represents the derivative of the fractional flow at the gas drive front in the oilfield, and S gfH represents the saturation of the gas drive front corresponding to the pseudo relative permeability of oil and gas in the oilfield. f gH (S gfH ) represents the fractional flow at the gas drive front in the oilfield, that is, the value of the gas drive fractional flow curve in the oilfield at the gas drive front in the oilfield, and S gcH represents the irreducible gas saturation corresponding to the pseudo relative permeability of oil and gas in the oilfield.

7. The method for quantifying the sweep degree between gas injection wells according to claim 1, characterized in that, Establish a model for the production layer section between injection and production wells according to the following steps: Obtain the core data of the production layer section between injection and production wells; Establish a core model for the production layer section between injection and production wells according to the core data of the production layer section between injection and production wells.

8. The method for quantifying the sweep efficiency between gas injection wells according to claim 1 or 7, characterized in that Determine the second relationship between the gas drive front fractional flow derivative and the gas saturation in the swept area based on the established core model of the production interval between injection and production wells, including: Determine the fourth functional relationship among the gas drive fractional flow, gas phase relative permeability, oil phase relative permeability, gas phase viscosity, and oil phase viscosity in the swept area based on the established core model of the production interval between injection and production wells; Determine the second relationship between the gas drive front fractional flow derivative and the gas saturation in the swept area according to the fourth functional relationship.

9. The gas drive inter-well sweep extent quantification method according to claim 1, wherein The second relationship between the gas drive front fractional flow derivative and the gas saturation in the swept area is: Among them, f’ gh (S gfh ) represents the derivative of the fractional flow at the front of the gas drive in the swept zone, and S gfh represents the saturation of the gas drive front corresponding to the relative permeability of the experimental oil and gas, and f gh (S gfh ) represents the fractional flow at the front of the gas drive in the swept zone, that is, the value of the fractional flow curve of the gas drive in the swept zone at the gas drive front, and S gch represents the irreducible gas saturation corresponding to the relative permeability of the experimental oil and gas.

10. The method for quantifying the sweep efficiency between gas injection wells according to claim 1, characterized in that, The third relationship among the gas drive vertical swept thickness in the swept area, the gas drive front fractional flow derivative in the swept area, the field gas drive front fractional flow derivative, and the average thickness of the production interval between injection and production wells is: Among them, h represents the swept thickness between gas injection wells, f’ gh (S gfh ) represents the derivative of the fractional flow at the leading edge of the gas drive in the swept area, f’ gH (S gfH ) represents the derivative of the fractional flow at the leading edge of the field gas drive, and H represents the average thickness of the production interval between injection and production wells.

11. The method for quantifying the swept extent between gas injection wells according to claim 1, wherein, Select the corresponding calculation formula according to the judgment result of whether the injected gas breaks through in the production well, and calculate the gas drive vertical sweep coefficient based on the gas drive vertical swept thickness between injection and production wells, including: When it is determined that the injected gas does not break through in the production well, the calculation formula selected for calculating the gas drive vertical sweep coefficient is: Among them, E v represents the gas drive vertical sweep efficiency, t represents the gas injection time, T represents the breakthrough time of the injected gas, h represents the swept thickness between gas injection wells, and H represents the average thickness of the production interval between injection and production wells. When it is determined that the injected gas breaks through in the production well, the calculation formula selected for calculating the gas drive vertical sweep coefficient is: Among them, E v represents the gas drive vertical sweep efficiency, h represents the swept thickness between gas drive wells, and H represents the average thickness of the production interval between injection and production wells.

12. A method for judging the treatment of gas channeling production wells, characterized in that, Include the following steps: Determine the gas drive vertical sweep coefficient of the gas channeling production well according to the gas drive inter-well sweep degree quantification method described in any one of claims 1 to 11; Judge whether to treat the gas channeling production well according to the gas drive vertical sweep coefficient of the gas channeling production well.

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