CN-122022110-A - Low permeability reservoir CO2Method for identifying channel for dispelling gas and channeling

CN122022110ACN 122022110 ACN122022110 ACN 122022110ACN-122022110-A

Abstract

The invention relates to a method for identifying a CO 2 gas channeling passage of a low-permeability reservoir, which comprises the steps of S1 collecting geological data and production dynamic data of a target block well group, calculating gas channeling passage identification indexes, S2 calculating weights occupied by all the gas channeling passage identification indexes, S3 calculating a plunge coefficient and correcting boundaries, S4 calculating membership degree, realizing standardization of all the gas channeling passage identification indexes according to the membership degree, meeting the numerical value between 0 and 1, S5 calculating comprehensive identification coefficients of static and dynamic indexes of all injection wells and production wells, S6 calculating comprehensive weights of the static and dynamic indexes of all the injection wells and the production wells, S7 calculating the total identification coefficients, S8 determining three-level classification standards of the gas channeling passage and judging the development direction of the gas channeling passage. The method solves the problem that the accuracy rate of identifying the gas channeling is low because the existing gas channeling identification method lacks the study on the hypotonic conglomerate oil reservoir and does not fully utilize dynamic and static data.

Inventors

ZHANG WEN
Lian Guihui
ZHANG JINGCHEN
LI JIE
SHENG GUORONG
CHEN CHAO
Dong Haihai
ZHENG SHENG
GU HONGJUN
REN XU

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260512
Application Date: 20250321
Priority Date: 20241111

Claims (10)

1. A method for identifying a CO 2 gas-expelling channel of a hypotonic oil reservoir, comprising the steps of: S1, data collection and index optimization Collecting geological data and production dynamic data of a target block well group, and calculating a gas channeling identification index according to the geological data and the production dynamic data; s2, weight calculation Calculating the weight of each gas channeling identification index; s3, calculating a plunging coefficient and correcting boundary Calculating a plunging coefficient of each gas channeling channel discrimination index, and correcting the semi-trapezoid mathematical model according to the plunging coefficient; S4, membership calculation According to different relations between the sizes of the distinguishing indexes of each gas channeling and the development degree of the gas channeling, respectively establishing a ascending half trapezoid mathematical model and a descending half trapezoid mathematical model, calculating to obtain membership degrees, and according to the membership degrees, standardizing the distinguishing indexes of each gas channeling, so that the numerical value is 0-1; s5, calculating comprehensive discrimination coefficients of dynamic and static indexes Based on the weights and membership degrees of the discrimination indexes of each gas channeling channel, calculating to obtain the comprehensive discrimination coefficients of the static indexes and the comprehensive discrimination coefficients of the dynamic indexes of each injection well and each production well of the block; s6, calculating comprehensive weights of dynamic and static indexes Calculating the static index comprehensive weight and the dynamic index comprehensive weight of each injection well and each production well of the block; S7, calculating total discrimination coefficients Combining the static index comprehensive discrimination coefficient calculated in the step S5, the dynamic index comprehensive discrimination coefficient and the static index comprehensive weight and the dynamic index comprehensive weight calculated in the step S6 to calculate the total discrimination coefficient of each injection well and each production well gas channeling channel of the block; S8, grading and directing gas channeling channels According to field feedback of the development condition of the gas channeling channels of the block well group, the geological data and the production dynamic data collected in the step S1 are combined, three-level classification standards of the gas channeling channels are determined, and the development direction of the gas channeling channels is judged.
2. The method for identifying the CO 2 gas-expelling channel of the low-permeability reservoir according to claim 1, wherein in S1, the geological data comprise the porosity, permeability and effective thickness of an oil layer, and the production dynamic data comprise daily gas injection amount, cumulative gas injection amount, injection pressure of an injection well, maximum CO 2 content of a wellhead of a production well, daily gas production amount, daily oil production amount, wellhead oil pressure and cumulative gas production amount of the production well; The gas channeling channel distinguishing indexes comprise static distinguishing indexes and dynamic distinguishing indexes, wherein the static distinguishing indexes comprise stratum coefficients, average porosity, average permeability, permeability variation coefficients and permeability burst coefficients, the dynamic distinguishing indexes comprise injection wells and production wells, the injection wells comprise an apparent air suction index, average daily air injection quantity, unit thickness accumulated injection quantity, air injection intensity and average injection pressure, the production wells comprise wellhead maximum CO 2 content, average daily air production quantity, gas-oil ratio, wellhead oil pressure burst coefficients, unit thickness accumulated air production quantity and oil extraction intensity.
3. The method for identifying the CO 2 gas-channeling-dispelling channel of the hypotonic oil reservoir according to claim 1, wherein in S2, the calculation formula of the weight occupied by each index in the gas-channeling-distinguishing index is: wherein A i is the variation coefficient of each index; a i is the standard deviation of the i-th index; is the average value of the ith index; Omega i is the weight occupied by each index; i. n is a natural number.
4. The method for identifying a CO 2 gas-expelling channel of a hypotonic oil reservoir according to claim 1, wherein in S3, the calculation formula of the kick-in coefficient is as follows: wherein D i is the plunging coefficient of the ith index, X i,max is the maximum value of the i-th index, Is the average value of the ith index.
5. The method for identifying the CO 2 gas-expelling channel of the hypotonic oil reservoir according to claim 1, wherein the calculation formula of the ascending half trapezoid mathematical model is as follows: the calculation formula of the halfpace-down mathematical model is as follows: wherein B (x) is the membership degree of each index, A 1 is the boundary minimum value of each index, A 2 is the boundary maximum value of each index, X is the distinguishing index of the channel of the gas channeling.
6. The method for identifying a CO 2 gas-expelling channel of a hypotonic oil reservoir according to claim 1, wherein in S5, the calculation formula of the static index comprehensive discrimination coefficient is: the calculation formula of the dynamic index comprehensive discrimination coefficient is as follows: wherein C j is the comprehensive discrimination coefficient of the static index; C d is a dynamic index comprehensive discrimination coefficient; b i is the membership degree of the i-th dynamic or static index; Omega i is the weight occupied by the dynamic or static index of the i th item; i. n is a natural number.
7. The method for identifying a CO 2 gas-expelling channel of a hypotonic oil reservoir according to claim 1, wherein in S6, the calculation formula of the static index comprehensive weight is: wherein omega j is the static index comprehensive weight of each injection well or production well, Omega m is the mth static index weight of each injection well or production well; m and n are natural numbers, and m is more than or equal to 2; the calculation formula of the dynamic index comprehensive weight is as follows: Wherein omega d is the dynamic index comprehensive weight of each injection well or production well, Omega l is the first dynamic index weight for each injection well or production well, L and n are natural numbers, and l is more than or equal to 2.
8. The method for identifying a CO 2 gas-expelling channel of a hypotonic oil reservoir according to claim 1, wherein in S7, the calculation formula of the total discrimination coefficient is: C t ＝C j *ω j +C d *ω d Wherein C t is the total discrimination coefficient of the gas channeling passage of each injection well or production well, C j is the static index comprehensive discrimination coefficient of each injection well or production well, C d is the dynamic index comprehensive discrimination coefficient of each injection well or production well, Omega j is the static index comprehensive weight of each injection well or production well, Omega d is the dynamic index comprehensive weight of each injection well or production well.
9. The method for identifying the gas channeling of the low permeability reservoir CO 2 according to claim 1, wherein in S8, the three-level classification standard of the gas channeling is specifically: When the total discrimination coefficient C t of the gas channeling is more than or equal to 0.5, judging that the development degree of the gas channeling is strong; when the total discrimination coefficient of the gas channeling is more than or equal to 0.4 and less than or equal to C t and less than 0.5, judging that the development degree of the gas channeling is weak; when the total discrimination coefficient C t of the gas channeling is less than 0.4, judging that the gas channeling does not develop.
10. The method for identifying a gas channeling identification channel of a low permeability reservoir CO 2 according to claim 1, wherein in S8, the method for determining the development direction of the gas channeling identification channel is that if the sum of the total discrimination coefficients of the gas channeling identification channels of a pair of injection well and production well in the same well group is the largest and equal to or greater than 0.4, the development direction of the gas channeling identification channel is the connection direction of the injection well and the production well.

Description

Identification method for CO 2 gas-expelling channel of low-permeability oil reservoir Technical Field The invention belongs to the technical field of oil and gas field development, and particularly relates to a method for identifying a CO 2 gas-expelling channel of a low-permeability oil reservoir. Background The gas injection development can effectively improve the oil displacement efficiency and the crude oil recovery ratio. However, due to the influence of the heterogeneity of the reservoir, and the significant difference of the flowing capacities of the gas and the crude oil, the gas channeling is easy to form in the gas injection process, so that the production gas-oil ratio of the oil production well is rapidly increased, and the oil reservoir development effect is poor. Therefore, it is highly desirable to identify the gas channeling channels that are easily formed during the gas injection development process, so as to provide guidance for the design of subsequent regulation and control schemes. The invention patent of application number CN202010960492.4 discloses a method and a device for predicting gas channeling time of a CO 2 miscible flooding effective oil well of a low-permeability oil reservoir, wherein the method only aims at gas channeling time and lacks identification of a gas channeling channel. The invention patent of application number CN201710231158.3 discloses a method for carrying out dynamic inversion on a CO 2 flooding oil reservoir gas channeling channel according to the corresponding relation between characteristic parameters of a gas-oil ratio curve and an inversion index system, and the method only considers the change characteristics of the gas-oil ratio curve, ignores the application to other production dynamic data and has larger error. The invention patent of application number CN201710786398.X discloses a method for representing the gas channeling degree by utilizing the comprehensive index of CO 2 gas channeling, and data input in the method during application are the relation between the injection amount of CO 2 obtained through experiments and the gas content of CO 2, so that the relation is more ideal and the actual combination of on-site production is lacked. The invention patent of application number CN201910360031.0 discloses a method and a device for quickly inverting a gas channeling channel of a carbon dioxide flooding oil reservoir, but the method uses simple arithmetic average to split the gas injection quantity of a gas injection well into the directions of different production wells, and does not consider the influence of geological factors and development factors in an actual oil reservoir on the gas flowing process, so that a larger deviation exists in a calculation result. Disclosure of Invention The invention aims to provide a method for identifying a CO 2 gas channeling of a hypotonic oil reservoir, which aims to solve the problem that the accuracy rate of identifying the gas channeling is low because dynamic and static data are not fully utilized due to lack of research on the hypotonic conglomerate oil reservoir in the existing gas channeling identification method. In order to achieve the above purpose, the present invention adopts the following technical scheme: A method for identifying a CO 2 gas-expelling channel of a hypotonic oil reservoir, comprising: S1, data collection and index optimization Collecting geological data and production dynamic data of a target block well group, and calculating a gas channeling identification index; s2, weight calculation Calculating the weight of each index in the gas channeling identification indexes; s3, calculating a plunging coefficient and correcting boundary Calculating a plunging coefficient of each index in the gas channeling identification indexes, and correcting the semi-trapezoid mathematical model according to the plunging coefficient; S4, membership calculation According to different relations between the sizes of the distinguishing indexes of each gas channeling and the development degree of the gas channeling, respectively establishing a ascending half trapezoid mathematical model and a descending half trapezoid mathematical model, calculating to obtain membership degrees, and according to the membership degrees, standardizing the distinguishing indexes of each gas channeling, so that the numerical value is 0-1; s5, calculating comprehensive discrimination coefficients of dynamic and static indexes Based on the weights and membership degrees of the discrimination indexes of each gas channeling channel, calculating to obtain the comprehensive discrimination coefficients of the static indexes and the comprehensive discrimination coefficients of the dynamic indexes of each injection well and each production well of the block; s6, calculating comprehensive weights of dynamic and static indexes Calculating the static index comprehensive weight and the dynamic index comprehensive weight of each injection