US 12,338,732 B2
Quantitative prediction method for gas content of deep marine shale
Xinyang He, Chengdu (CN); Kun Zhang, Chengdu (CN); Hulin Niu, Chengdu (CN); Chengzao Jia, Chengdu (CN); Yan Song, Chengdu (CN); Zhenxue Jiang, Chengdu (CN); Shu Jiang, Chengdu (CN); Xueying Wang, Chengdu (CN); Nanxi Zhang, Chengdu (CN); Xiaoxia Dong, Chengdu (CN); Jun Dong, Chengdu (CN); Ruisong Li, Chengdu (CN); Tong Wang, Chengdu (CN); Pu Huang, Chengdu (CN); Jiasui Ouyang, Chengdu (CN); Xingmeng Wang, Chengdu (CN); Shoucheng Xu, Chengdu (CN); Hanbing Zhang, Hangzhou (CN); Yubing Ji, Hangzhou (CN); Lei Chen, Chengdu (CN); Xuefei Yang, Chengdu (CN); Fengli Han, Chengdu (CN); Weishi Tang, Chengdu (CN); Jingru Ruan, Chengdu (CN); Hengfeng Gou, Chengdu (CN); Lintao Li, Chengdu (CN); Yipeng Liu, Chengdu (CN); and Ping Liu, Chengdu (CN)
Assigned to Southwest Petroleum University, Chengdu (CN); Sinopec Southwest Petroleum Bureau Co., Ltd, Chengdu (CN); and PetroChina Zhejiang Oilfield Company, Hangzhou (CN)
Filed by Southwest Petroleum University, Chengdu (CN); Sinopec Southwest Petroleum Bureau Co., Ltd, Chengdu (CN); and PetroChina Zhejiang Oilfield Company, Hangzhou (CN)
Filed on Oct. 17, 2024, as Appl. No. 18/918,078.
Claims priority of application No. 202311386727.3 (CN), filed on Oct. 24, 2023.
Prior Publication US 2025/0129717 A1, Apr. 24, 2025
Int. Cl. E21B 49/00 (2006.01)
CPC E21B 49/008 (2013.01) [E21B 2200/22 (2020.05)] 5 Claims
OG exemplary drawing
 
1. A quantitative prediction method for shale gas content, comprising:
S1, obtaining raw data; wherein the raw data comprises adsorbed gas contents, a free gas contents, pore specific surface areas and pore volumes of shale samples at different sampling depths of a known well in an area; and a depth difference between two adjacent sampling depths hi-1 and hi of the different sampling depths is 10 m, i≥2, and i is a natural number;
S2, establishing, based on the raw data, relationship formulas between the pore specific surface areas and the adsorbed gas contents of the known well as an adsorbed gas content quantitative prediction model; wherein the step S2 comprises:
S21, expressing the pore specific surface areas as x, and expressing the adsorbed gas contents as y, to form a first discrete series [xi, yi]; wherein xi represents a pore specific surface area of a shale sample at an ith sampling depth hi of the known well, and yi represents an adsorbed gas content of the shale sample at the ith sampling depth hi of the known well;
S22, obtaining linear equations of straight lines passing through every two adjacent points (xi-1, yi-1) and (xi, yi) as adsorbed gas content prediction formulas corresponding to different burial depths; wherein the step S22 specifically comprises:
(1) expressing a first linear equation of a first straight line passing through two points (x1, y1) and (x2, y2) as y−y1=k1(x−x1), substituting the two points (x1, y1) and (x2, y2) into the first linear equation y−y1=k1(x−x1) to obtain a first slope k1, and obtaining the first linear equation of the first straight line passing through the two points (x1, y1) and (x2, y2) based on the first slope, expressed as a formula 1 as follows:

OG Complex Work Unit Math
 wherein the formula 1 is an adsorbed gas content prediction formula corresponding to a first burial depth range of h1 to h2;
(2) expressing a second linear equation of a second straight line passing through two points (x2, y2) and (x3, y3) as y−y2=k2(x−x2), substituting the two points (x2, y2) and (x3, y3) into the second linear equation y−y2=k2(x−x2) to obtain a second slope k2, and obtaining the second linear equation of the second straight line passing through the two points (x2, y2) and (x3, y3) based on the second slope, expressed as a formula 2 as follows:

OG Complex Work Unit Math
 wherein the formula 2 is an adsorbed gas content prediction formula corresponding to a second burial depth range of h2 to h3;
(3) expressing a third linear equation of a third straight line passing through two points (x3, y3) and (x4, y4) as y−y3=k3(x−x3), substituting the two points (x3, y3) and (x4, y4) into the third linear equation y−y3=k3(x−x3) to obtain a third slope k3, and obtaining the third linear equation of the third straight line passing through the two points (x3, y3) and (x4, y4) based on the third slope, expressed as a formula 3 as follows:

OG Complex Work Unit Math
 wherein the formula 3 is an adsorbed gas content prediction formula corresponding to a third burial depth range of h3 to h4; and
(4) expressing a (i−1)th linear equation of a (i−1)th straight line passing through every two adjacent points (xi-1, yi-1) and (x, yi) as y−yi-1=ki-1(x−xi-1), wherein i≥5, substituting the two points (xi-1, yi-1) and (xi, yi) into the (i−1)th linear equation y−yi-1=ki-1(x−xi-1) to obtain a (i−1)th slope ki-1, and obtaining the (i−1)th linear equation of the (i−1)th straight line passing through the two adjacent points (xi-1, yi-1) and (xi, yi) based on the (i−1)th slope, expressed as follows:

OG Complex Work Unit Math
 wherein the (i−1)th linear equation y=ki-1(x—xi-1)+yi-1 is an adsorbed gas content prediction formula corresponding to a (i−1)th burial depth range of hi-1 to hi;
S23, predicting, according to the adsorbed gas content prediction formulas corresponding to the different burial depths, adsorbed gas contents at the different burial depths in segment by segment; and
S24, averaging the adsorbed gas contents at the different burial depths predicted in the step S23 to obtain an adsorbed gas content Qa1 of the known well;
S3, establishing relationship formulas between the pore volumes and the free gas contents of the known well as a free gas content quantitative prediction model; wherein the step S3 comprises:
expressing the pore volumes as u, and expressing the free gas contents as v, to form a second discrete series [ui, vi]; wherein ui represents a pore volume of the shale sample at the ith sampling depth hi, and vi represents a free gas content of the shale sample at the ith sampling depth hi; and
obtaining a free gas content Qb1 of the known well according to a same method of the steps S22-S24;
S4, summing the adsorbed gas content Qa1 and the free gas content Qb1 to obtain a total gas content Qtotal 1 of the known well;
S5, performing the steps S1-S4 to determine an adsorbed gas content, a free gas content and a total gas content of each of other known wells in the area, to thereby obtain an adsorbed gas content Qai, a free gas content Qbi and a total gas content Qtotal i of each known well in the area; and
S6, drawing a contour map of predicted adsorbed gas content, a contour map of predicted free gas content and a contour map of predicted total gas content of the area according to the adsorbed gas content Qai, the free gas content Qbi and the total gas content Qtotal i of each known well in the area obtained in the step S5; reading a predicted adsorbed gas content Qax, a predicted free gas content Qbx and a predicted total gas content Qtotal x of an unknown well in the area from the contour map of predicted adsorbed gas content, the contour map of predicted free gas content and the contour map of predicted total gas content; summing the predicted adsorbed gas content Qax and the predicted free gas content Qbx of the unknown well in the area to obtain a calculated total gas content Qab of the unknown well in the area; and averaging the calculated total gas content Qab and the predicted total gas content Qtotal x as a total gas content of the unknown well in the area;
wherein the quantitative prediction method for gas content of a deep marine shale further comprises:
dividing the unknown wells in the area into three levels according to the total gas content of each unknown well in the area, comprising:
determining an unknown well with a total gas content greater than a first threshold as a first level gas-bearing area;
determining an unknown well with a total gas content greater than a second threshold and smaller than the first threshold as a second level gas-bearing area; and
determining an unknown well with a total gas content smaller than the second threshold as a third level gas-bearing area; and
developing shale gas in the unknown wells in the area in an order of the first level gas-bearing area, the second level gas-bearing area and the third level gas-bearing area, thereby eliminating various influence factors of the adsorbed gas content and the free gas content and achieving a high quantitative prediction for shale gas content in the deep marine.