Numerical Simulation of the Influence of Aquifer Leakage Recharge on CBM Productivity:A Case Study from Shizhuan South Block

doi:10.19657/j.geoscience.1000-8527.2024.130

Abstract

Abstract:

Aquifer leakage recharge is a common issue in coalbed methane (CBM) development in China, significantly hindering efficient production. Taking a vertical CBM well in the Shizhuang South Block of the Qinshui Basin as a case study, this research comprehensively evaluates the impact of aquifer leakage recharge parameters on CBM well productivity through numerical simulation and sensitivity analysis.The results indicate that classifying aquifers into finite and infinite recharge types based on their water supply capacity is the fundamental reason for the varying effects of leakage recharge. The location, morphology, and spatial distribution of water-conducting fractures relative to hydraulic fractures exhibit high sensitivity to productivity characteristics: in infinite recharge aquifers, they primarily affect gas production volume, while in finite recharge aquifers, they influence the shape of gas production curves.The sensitivity of aquifer leakage recharge parameters to coalbed methane productivity, from strongest to weakest, is aquifer type, properties of leakage channels, aquifer physical properties, and formation water properties.Based on these findings, a production discrimination flowchart is developed, categorizing CBM well productivity characteristics under the influence of aquifer leakage recharge into six types, and further delineating the distribution of wells with different productivity characteristics in the study area. This flowchart provides scientific guidance for analyzing CBM productivity characteristics and evaluating productivity potential under the influence of aquifer leakage recharge.

Key words: coalbed methane, aquifer, leakage recharge, numerical simulation, sensitivity analysis of productivity characteristics

CLC Number:

P618.13

YAN Xinlu, TANG Shuheng, FU Xiaokang, DONG Xianshu, LI Zhongcheng, DENG Zhiyu, MENG Yanjun. Numerical Simulation of the Influence of Aquifer Leakage Recharge on CBM Productivity:A Case Study from Shizhuan South Block[J]. Geoscience, 2025, 39(04): 1143-1155.

Figures/Tables 13

Fig.1 Elevation of 3# coal seam (a) and stratigraphic histogram (b) in Shizhuang South Block

Fig.2 Chart showing aquifer leakage recharge mode in Shizhuang South Block (See Fig.1 for profile’s location)

Fig.3 Numerical simulation modeling method (a) and setting of fracture distribution (b)

Table 1 Numerical simulation parameters of coal reservoir

模拟数值参数	数值	模拟数值参数	数值
埋深(m)	714.7	兰氏体积(m³∙t^-1)	24
煤厚(m)	5.8	兰氏压力(MPa)	2.8
储层压力(MPa)	3.9	含气量(m³∙t^-1)	10
临界解吸压力(MPa)	2.0	人工压裂缝范围(m²)	110 $×$ 20
渗透率(mD)	0.8	压裂缝渗透率(mD)	20
裂缝孔隙度(%)	4.0	煤岩密度(g∙cm^-3)	1.3

Table 1 Numerical simulation parameters of coal reservoir

模拟数值参数	数值	模拟数值参数	数值
埋深(m)	714.7	兰氏体积(m³∙t^-1)	24
煤厚(m)	5.8	兰氏压力(MPa)	2.8
储层压力(MPa)	3.9	含气量(m³∙t^-1)	10
临界解吸压力(MPa)	2.0	人工压裂缝范围(m²)	110 $×$ 20
渗透率(mD)	0.8	压裂缝渗透率(mD)	20
裂缝孔隙度(%)	4.0	煤岩密度(g∙cm^-3)	1.3

Table 2 Numerical simulation parameters of aquifer

越流补给性质	影响参数	参数取值
含水层物性	渗透率(mD)	无限补给含水层 50/100/200	有限补给含水层 10/20/40
	孔隙度(%)	10/20/30
	厚度(m)	5/10/15
	大小(m $×$ m)	200 $×$ 100/200 $×$ 200/200 $×$ 300
	综合压缩系数 ( $10 - 4$ MPa^-1)	1/2/3
地层水性质	黏度(mPas)	0.5/1/1.5
越流通道性质	越流距离(m)	0/100/200
越流通道性质	越流方向 (m $×$ m)	法向5 $×$ 80/法向80 $×$ 5/方形 20 $×$ 20/径向5 $×$ 80/径向80 $×$ 5

Table 2 Numerical simulation parameters of aquifer

越流补给性质	影响参数	参数取值
含水层物性	渗透率(mD)	无限补给含水层 50/100/200	有限补给含水层 10/20/40
	孔隙度(%)	10/20/30
	厚度(m)	5/10/15
	大小(m $×$ m)	200 $×$ 100/200 $×$ 200/200 $×$ 300
	综合压缩系数 ( $10 - 4$ MPa^-1)	1/2/3
地层水性质	黏度(mPas)	0.5/1/1.5
越流通道性质	越流距离(m)	0/100/200
越流通道性质	越流方向 (m $×$ m)	法向5 $×$ 80/法向80 $×$ 5/方形 20 $×$ 20/径向5 $×$ 80/径向80 $×$ 5

Fig.4 Sensitivity analysis of infinite recharge aquifers on CBM production

Fig.5 Pressure propagation contour map in coal reservoir affected by fracture direction sensitivity

Fig.6 Sensitivity analysis of finite recharge aquifers on CBM production

Table 3 Gas production sensitivity of aquifer leakage recharge (%)

产能敏感性	时间(d)	大小	厚度	孔隙度	综合压缩系数	渗透率	黏度	越流距离	越流方向
无限补给含水层	1000	7.6	7.6	0	0	10.2	8.9	190.5	70.0
	3000	15.3	15.3	0	0	18.2	13.1	185.4	109.1
	5000	11.7	11.7	0	0	14.0	9.3	227.7	130.0
有限补给含水层	1000	25.7	36.4	31.2	31.2	14.4	9.6	83.1	31.3
	3000	39.2	41.0	46.5	46.5	0.9	1.4	72.6	9.8
	5000	34.4	30.9	33.3	33.3	6.0	5.4	48.4	32.6

Fig.7 Flow chart of the influence of aquifer leakage recharge on CBM production

Fig.8 Productivity characteristics of TS-10 well group

Fig.9 Productivity characteristics of TS-02 well group

Fig.10 Distribution of aquifer leakage recharge types in Shizhuang South Block

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