US 12,093,343 B1
Analysis method for determining gas-bearing situation of unknown shale reservoir
Kun Zhang, Chengdu (CN); Shu Jiang, Wuhan (CN); Pei Liu, Chengdu (CN); Xuri Huang, Chengdu (CN); Xiangyu Fan, Chengdu (CN); Hong Liu, Chengdu (CN); Hu Zhao, Chengdu (CN); Jun Peng, Chengdu (CN); Xiong Ding, Chengdu (CN); Lei Chen, Chengdu (CN); Xuefei Yang, Chengdu (CN); Bin Li, Chengdu (CN); Binsong Zheng, Chengdu (CN); Jinhua Liu, Chengdu (CN); Fengli Han, Chengdu (CN); Xueying Wang, Chengdu (CN); Xinyang He, Chengdu (CN); Xuejiao Yuan, Chengdu (CN); Jingru Ruan, Chengdu (CN); Hengfeng Gou, Chengdu (CN); and Yipeng Liu, Chengdu (CN)
Assigned to Southwest Petroleum University, Chengdu (CN); China University of Geosciences, Wuhan, Wuhan (CN); and University of Electronic Science and Technology of China, Chengdu (CN)
Filed by Southwest Petroleum University, Chengdu (CN); China University of Geosciences, Wuhan, Wuhan (CN); and University of Electronic Science and Technology of China, Chengdu (CN)
Filed on Mar. 1, 2024, as Appl. No. 18/592,581.
Claims priority of application No. 2023101916847 (CN), filed on Mar. 2, 2023.
Int. Cl. G06F 17/18 (2006.01); E21B 49/00 (2006.01)
CPC G06F 17/18 (2013.01) [E21B 49/00 (2013.01); E21B 2200/20 (2020.05)] 4 Claims
OG exemplary drawing
 
1. An analysis method for determining gas-bearing situation of an unknown shale reservoir, comprising the following steps:
S1, selecting a shale reservoir of a target interval of a place; collecting cores of each of a known gas-bearing shale reservoir A and a known water-bearing shale reservoir B of the shale reservoir, wherein a total number of the collected cores of the known gas-bearing shale reservoir A is na, and a total number of the collected cores of the known water-bearing shale reservoir B is nb; and obtaining values of parameters of each of the collected cores of each of the known gas-bearing shale reservoir A and the known water-bearing shale reservoir B, wherein the parameters comprise: a core porosity Φ, a core permeability K, and a gas saturation Sg;
S2, calculating average values of the parameters of the collected cores of the known gas-bearing shale reservoir A and average values of the parameters of the collected cores of the known water-bearing shale reservoir B respectively according to formulas (1) and (2), expressed as follows:

OG Complex Work Unit Math
where xn(A) represents an average value of an n-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir A; xn(B) represents an average value of an n-th typed parameter of the parameters of the collected cores of the known water-bearing shale reservoir B; m represents a type number of the parameters of each of the collected cores of each of the known gas-bearing shale reservoir A and the known water-bearing shale reservoir B, the parameters of each of the collected cores of each of the known gas-bearing shale reservoir A and the known water-bearing shale reservoir B are numbered as 1, 2, . . . , m in turn, and a value of n depends on the type number of the parameters; xnj(A) represents a value of an n-th typed parameter of a j-th core of the collected cores of the known gas-bearing shale reservoir A; and xnj(B) represents a value of an n-th typed parameter of a j-th core of the collected cores of the known water-bearing shale reservoir B;
S3, calculating average differences between the parameters of the collected cores of the known gas-bearing shale reservoir A and the parameters of the collected cores of the known water-bearing shale reservoir B according to a formula (3) as follows:
dn=xn(A)−xn(B)(n=1,2, . . . ,m)  (3);
S4, calculating covariance values between the parameters of the collected cores of the known gas-bearing shale reservoir A and the parameters of the collected cores of the known water-bearing shale reservoir B according to a formula (4) as follows:

OG Complex Work Unit Math
where sik represents a covariance value between one parameter of the parameters of the collected cores of the known gas-bearing shale reservoir A and one parameter of the parameters of the collected cores of the known water-bearing shale reservoir B; xij(A) represents a j-th value of an i-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir A; xkj(A) represents a j-th value of a k-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir A; xi(A) and xk(A) respectively represent an average value of the i-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir A and an average value of the k-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir A; xij(B) represents a j-th value of an i-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir B; xkj(B) represents a j-th value of a k-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir B; xi(B) and xk(B) respectively represent an average value of the i-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir B and an average value of the k-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir B;
S5, establishing, according to the covariance value sik obtained in the S4, the following equation group (5), and resolving discriminant coefficients c1, c1, . . . , cm based on the equation group (5):

OG Complex Work Unit Math
S6, establishing a discriminant equation according to the obtained discriminant coefficients, the discriminant equation is expressed as follows in a formula (6);
Y=c1x1+c2x2+ . . . +cmxm  (6),
where x1, x2, . . . , xm represent values of parameters of a corresponding core, and Y represents a discriminant value of the corresponding core; and
solving, according to the following formula (7), a discriminant index Yc for discriminating a reservoir to which the unknown shale reservoir belongs:

OG Complex Work Unit Math
where Y(A) and Y(B) represent an average discriminant value of the known gas-bearing shale reservoir A and an average discriminant value of the known water-bearing shale reservoir B, respectively, which are calculated according to the formula (6); and formulas for calculating Y(A) and Y(B) are as follows:
Y(A)=c1x1(A)+c2x2(A)+c3x3(A)+ . . . +cmxm  (A)
Y(B)=c1x1(B)+c2x2(B)+c3x3(B)+ . . . +cmxm  (B),
where xm(A) represents an average value of an m-th typed parameter of the parameters of the collected cores of the known gas-bearing shale reservoir A, and xm(B) represents an average value of an m-th typed parameter of the parameter of the collected cores of the known water-bearing shale reservoir B, which are calculated in the S2; and
S7, obtaining values of relevant parameters of cores of a sample X of the unknown shale reservoir, wherein the relevant parameters comprise a core porosity Φ, a core permeability K and a gas saturation Sg; substituting the values of the relevant parameters into the formula (6) to calculate a discriminant value Y of a corresponding core of the cores of the sample X of the unknown shale reservoir; and in a situation of Y≥Yc, determining that the unknown reservoir belongs to a gas-bearing shale reservoir, or in a situation of Y<Yc, determining that the unknown reservoir belongs to a water-bearing shale reservoir.