CN-121995014-A - Characterization method for quantifying contribution degree of different mechanisms to improvement of gas reservoir recovery ratio

CN121995014ACN 121995014 ACN121995014 ACN 121995014ACN-121995014-A

Abstract

The invention relates to the technical field of oil and gas field development, in particular to a characterization method for quantifying contribution degree of different mechanisms to improving gas reservoir recovery ratio, which comprises the steps of constructing an equivalent long core through permeability blending average value, reducing real reservoir seepage characteristics, adopting three groups of experiments of natural failure, static pressurization and then failure and continuous gas injection displacement to realize physical decoupling of pressurization energy supplementing and physical displacement mechanisms, combining with a homologous rock powder adsorption experiment, accurately measuring competitive adsorption contribution, and establishing a quantitative calculation model based on experimental data to respectively obtain independent increment and comprehensive contribution degree of three mechanisms. The invention can solve the problem that the technology of improving the natural gas recovery ratio by carbon dioxide displacement in the prior art cannot objectively and accurately quantify the independent contribution degree of each single mechanism to extraction.

Inventors

CAO CHENG
ZHANG DEPING
TANG HUIYING
TIAN YE
ZHANG TAO
XIONG WEI
Hou Junpu
ZHAO YULONG
ZHANG LIEHUI
ZHONG JUNJIE
WEN SHAOMU
LI JINBU
LIU LILI
ZHAO ZIHAN

Assignees

西南石油大学

Dates

Publication Date: 20260508
Application Date: 20260407

Claims (9)

1. A characterization method for quantifying contribution degree of different mechanisms to improving gas reservoir recovery ratio is characterized by comprising the following steps: S1, acquiring a core sample of a plunger sample, drying the core sample, and measuring the permeability and the length dimension of the core sample; S2, calculating the permeability blending average value of each core sample by calling a preset permeability blending average value calculation mode based on the permeability and the length size of the core sample, and sequencing the core samples and sequentially placing the core samples into a rubber sleeve of a long core holder based on the permeability blending average value to obtain an equivalent long core; s3, establishing water saturation of the equivalent long core in the long core holder, carrying out saturation treatment on the equivalent long core through methane, and raising the temperature and pressure of the experimental environment of the equivalent long core to the reservoir temperature and the reservoir pressure; S4, carrying out pressure failure treatment of gradually reducing the pressure of the equivalent long rock core after saturation treatment until the pressure reaches the preset waste pressure after the pressure reduction, and recording the volume data of the produced methane to obtain the methane yield without gas injection intervention ; S5, injecting gas to the equivalent long rock core to preset pressure on the basis of failure to waste pressure, stabilizing the preset time until internal fluid reaches static balance, gradually reducing the pressure to waste pressure again, recording the volume multiple of methane in the produced gas, and obtaining the methane yield under the stripping physical pushing action ; S6, repeating the steps S3-S4 of the equivalent long core of S5, injecting the step S5 into the equivalent long core at a constant speed and carrying out gas injection and extraction experiments with gas, detecting a gas component by a chromatograph when the flow rate in the equivalent long core is detected to be steadily increased according to a preset flow rate, and stopping the gas injection and extraction experiments when the methane component in the gas component is lower than a preset methane content threshold value to obtain the methane yield of pure gas displacement ; S7 based on methane yield Methane production And methane production Calculating the methane increment of the supercharging energy supplementing effect contribution and the methane increment of the displacement effect contribution, and calling a preset gas injection supercharging contribution degree calculation mode and a preset gas injection displacement contribution degree calculation formula to calculate the supercharging energy supplementing effect contribution degree and the displacement effect contribution degree respectively; s8, acquiring rock powder homologous to the equivalent long rock core, performing a gas adsorption experiment, measuring the methane analysis amount, and obtaining the methane increment of the equivalent long rock core under the competitive adsorption effect based on the equivalent conversion of the methane analysis amount; S9, calculating the comprehensive contribution degree of the competitive adsorption effect, the comprehensive contribution degree of the supercharging energy supplementing effect and the comprehensive contribution degree of the displacement effect based on the methane increment under the competitive adsorption effect, the methane increment contributed by the supercharging energy supplementing effect and the methane increment contributed by the displacement effect; and S10, integrating the supercharging energy supplementing effect contribution degree, the displacement effect contribution degree, the competitive adsorption effect comprehensive contribution degree, the supercharging energy supplementing effect comprehensive contribution degree and the displacement effect comprehensive contribution degree, and outputting a recovery ratio contribution degree evaluation result in the gas reservoir extraction process.
2. A method of quantifying the extent of contribution of different mechanisms to enhanced gas recovery according to claim 1, wherein: the step S4 comprises the following steps: S4-1, obtaining an equivalent long core after saturation treatment, and arranging a flowmeter at the outlet end of a long core holder of the equivalent long core, wherein the long core holder is communicated with a confining pressure pump; s4-2, performing pressure failure treatment on the equivalent long rock core by using a confining pressure pump according to the pressure of each 1Mpa, and further reducing the pressure again after the flow rate of the flowmeter is displayed as 0 in the treatment process until the pressure is failed to 8MPa of waste pressure; S4-3, calibrating the chromatograph correction factors by using the standard gas, and detecting methane of the produced gas by using the calibrated chromatograph to obtain the methane yield without gas injection intervention The expression is: ; Wherein, the The volume of the gas produced for the ith stage of depressurization; Methane volume fraction in the produced gas for the i-th stage depressurization; For the purpose of the dead volume of the experimental system, The number of stages to downgrade for failure.
3. A method of quantifying the contribution of different mechanisms to enhanced gas recovery according to claim 2, wherein: the step S5 comprises the following steps: S5-1, injecting carbon dioxide gas into the equivalent long core which is depleted to 8MPa through a surrounding pressure pump for pressurizing treatment, and stabilizing for 12 hours after injecting the gas to 12MPa until the fluid in the equivalent long core reaches static balance; S5-2, gradually reducing the pressure of the equivalent long core reaching the static balance to 8MPa by using a confining pressure pump according to the pressure of each 1MPa, and further reducing the pressure again when the flow rate of the flowmeter is displayed as 0 in the step-by-step pressure reducing process; s5-3, calibrating a chromatograph correction factor by using a standard gas, detecting the volume multiple of methane in the produced gas by using the calibrated chromatograph, and calculating the methane yield to obtain the yield The expression is: ; Wherein, the The volume of the gas produced for the j-th stage depressurization; The volume fraction of methane in the produced gas for the j-th stage depressurization, For the purpose of the dead volume of the experimental system, Is the number of depressurization stages.
4. A method of quantifying the extent of contribution of different mechanisms to enhanced gas recovery according to claim 3, wherein: the step S6 comprises the following steps: S6-1, carrying out saturation treatment on the equivalent long core obtained in the step S5 through the step S3, and carrying out pressure failure treatment through the step S4 to obtain the equivalent long core with pressure failure of 8 MPa; S6-2, injecting carbon dioxide gas into the equivalent long rock core at a constant speed through the confining pressure pump, and synchronously starting the flowmeter to monitor that the flow in the equivalent long rock core steadily increases according to a preset flow rate, and detecting the components of the produced gas through the chromatograph; S6-3, calibrating a chromatograph correction factor by using a standard gas, detecting methane in the produced gas by using the calibrated chromatograph, stopping gas injection if the content of methane components is lower than a preset methane content threshold value, and calculating the methane yield to obtain the yield The expression is: ; Wherein, the For the volume of produced gas in the kth metering period, The methane volume fraction in the gas is produced for the kth period, For the purpose of the dead volume of the experimental system, The number of points is measured for the gas injection extraction stage.
5. A method of quantifying the extent of contribution of different mechanisms to enhanced gas recovery according to claim 1, wherein: the step S7 includes: s7-1 extraction of methane yield Methane production And methane production ; S7-2, calculating to obtain the boosting energy supplementing effect contribution degree by calling a preset air injection boosting contribution degree calculation mode, wherein the expression is as follows: ; ; ; Wherein, the The degree of contribution to the supercharging energy supplementing effect; Is the total increment of methane; Methane increment contributing to pressurization and energy supplementing; S7-3, calling a preset gas injection displacement contribution degree calculation formula to calculate and obtain displacement contribution degree, wherein the expression is: ; ; Wherein, the In order to be able to contribute to the degree of displacement, Methane increment contributing to displacement.
6. A method of quantifying the contribution of different mechanisms to enhanced gas recovery according to claim 5, wherein: the step S8 comprises the following steps: S8-1, scraping and crushing a homologous rock core sample of an equivalent long rock core to prepare rock powder, and carrying out a gas adsorption experiment through the rock powder to measure the methane analysis amount; S8-2, equivalent conversion of methane analysis amount to obtain methane increment independently contributed by the equivalent long core under competitive adsorption 。
7. A method of quantifying the contribution of different mechanisms to enhanced gas recovery according to claim 6, wherein: the step S9 includes: S9-1, obtaining methane increment under competitive adsorption Methane increment contributed by supercharging energy supplementing effect And methane increment contributed by displacement And calculating to obtain a global total methane increment, wherein the expression is as follows: ; Wherein, the Is the global total methane increment; S9-2 based on Global Total methane delta The comprehensive contribution degree of competitive adsorption, the comprehensive contribution degree of supercharging energy supplementing and the comprehensive contribution degree of displacement are calculated respectively, and the expression is: ; ; ; Wherein, the In order to compete for the degree of the combined contribution of the adsorption, The comprehensive contribution degree for the supercharging energy supplementing effect, The extent of contribution is integrated for the displacement effect.
8. The characterization method for quantifying the contribution degree of different mechanisms to the improvement of the recovery ratio of the gas reservoir according to claim 1 is characterized in that in S2, the expression of the preset permeability and average value calculation mode is: ; Wherein, the For the permeability to be a harmonic mean value, To account for the overall length size of all core samples involved in the calculation, For the i-th core sample length dimension, Permeability value for the ith core sample; is the number of core samples.
9. A method of quantifying the extent of contribution of different mechanisms to enhanced gas recovery according to claim 1, wherein: the step S3 comprises the following steps: s3-1, applying preset confining pressure to a long core holder where the assembled equivalent long core is positioned through a confining pressure pump, removing free water in a core gap of the equivalent long core by adopting an ultracentrifugation method, and establishing water saturation matched with a real gas reservoir; S3-2, continuously injecting methane gas with purity more than or equal to 99.99% into the long core holder through the displacement pump, and monitoring the inlet and outlet pressure and gas components of the long core holder in real time until the equivalent long core reaches a methane full saturated state; And S3-3, in the experimental environment of the equivalent long rock core, the temperature is increased to 100 ℃, the pressure is increased to 27MPa, and the constant temperature and the constant pressure are maintained.

Description

Characterization method for quantifying contribution degree of different mechanisms to improvement of gas reservoir recovery ratio Technical Field The invention relates to the technical field of oil and gas field development, in particular to a characterization method for quantifying contribution degree of different mechanisms to improving gas reservoir recovery ratio. Background Currently, under the background of a 'double carbon' target and an energy safety strategy, carbon dioxide displacement improves natural gas recovery efficiency) The technology has the advantages of both natural gas yield increase and natural gas yield increaseThe geological storage dual benefits become the core direction of the development of oil gas development and carbon emission reduction. Existing research and field practice show that injection into gas reservoirsOr contain impuritiesThe mixed gas can effectively improve the recovery ratio of the gas reservoir and realize carbon sequestration through the combined action of multiple mechanisms such as pressurization energy supplementing, physical displacement, competitive adsorption and the like. In recent years, in the prior art, a gas injection parameter pair is researched through a long core displacement experiment and a numerical simulation methodThe system analyzes the key parameters such as gas injection time, gas injection speed, irreducible water saturation, development mode and the like on the gas reservoir recovery ratio and the buried rateThe effect of the storage rate is clearAnd contain、Impurity such as impurityIn the displacement process, the change rule of the gas breakthrough characteristics, the recovery ratio and the buried ratio proves the technical feasibility of improving the natural gas recovery ratio by the displacement of the non-pure carbon dioxide, and provides theoretical reference for optimization of gas injection parameters. The research reveals the macroscopic development effect of the technology for improving the natural gas recovery ratio by carbon dioxide displacement under different working conditions through the integral displacement experiment and numerical fitting, and promotes the mechanism cognition and field application of the gas injection extraction technology. However, the existing carbon dioxide displacement and natural gas recovery mechanism improvement research and experimental method still has significant technical limitations that the existing long core displacement and numerical simulation method can only obtain integral effect indexes such as macroscopic recovery, breakthrough opportunity, burial rate and the like, and can not perform object understanding coupling and quantitative splitting on three major core extraction mechanisms of pressurization energy supplementing, physical displacement and competitive adsorption. In the conventional displacement process, the pressurization and the displacement can be highly coupled and synchronously occur, the respective contributions are difficult to separate in a physical layer, and meanwhile, the real contribution of microcosmic competitive adsorption cannot be accurately measured through a conventional plunger-type experiment under the influence of the rock pore seepage hysteresis effect. The prior art excessively relies on a numerical simulation 'black box' algorithm, has the problems of more artificial assumptions, large fitting errors, incomplete mechanism coverage and the like, and cannot objectively and accurately quantify the independent contribution degree of each single mechanism to extraction, so that a gas reservoir gas injection scheme is optimized, a gas source medium is optimized, and CCUS benefit evaluation lacks strict quantitative support. Disclosure of Invention The invention solves the technical problem of providing a characterization method for quantifying the contribution degree of different mechanisms to the improvement of the recovery ratio of a gas reservoir, so as to solve the problem that the technology for improving the recovery ratio of natural gas by carbon dioxide displacement in the prior art cannot objectively and accurately quantify the independent contribution degree of each single mechanism to the extraction. The basic scheme provided by the invention is a characterization method for quantifying contribution degree of different mechanisms to improving the recovery ratio of a gas reservoir, which comprises the following steps: S1, acquiring a core sample of a plunger sample, drying the core sample, and measuring the permeability and the length dimension of the core sample; S2, calculating the permeability blending average value of each core sample by calling a preset permeability blending average value calculation mode based on the permeability and the length size of the core sample, and sequencing the core samples and sequentially placing the core samples into a rubber sleeve of a long core holder based on the permeability blending average value to obt