Effect of water occurrence in coal reservoirs on the production capacity of coalbed methane by using NMR simulation technology and production capacity simulation

• Published in: Geoenergy Science and Engineering Vol. 243; p. 213353
• Main Authors: Yao, Peng, Zhang, Junjian, Lv, Dawei, Vandeginste, Veerle, Chang, Xiangchun, Zhang, Xiaoyang, Wang, Dongdong, Han, Shuangbiao, Liu, Yu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2024
• Subjects: Gas and water; Nuclear magnetic resonance; Occurrence; Productivity simulation; Water distribution; Productivity simulation; Gas and water; Water distribution; Nuclear magnetic resonance; Occurrence
• ISSN: 2949-8910; 2949-8910
• DOI: 10.1016/j.geoen.2024.213353

The occurrence of gas and water is a critical factor affecting the production capacity of coalbed methane. Therefore, occurrence and dynamic interaction between gas and water in coal reservoirs need to be studied. T2 spectrum of all the samples were studied by NMR technique at 0, 5, 9, and 28 h of natural evaporation. Then, multifractal model was used to characterize water distribution heterogeneity, and a novel evaluation coefficient was proposed to characterize distribution heterogeneity of water content, the correlation among evaluation coefficient, water distribution heterogeneity and pore structure parameters was analyzed. The results are as follows. In the saturated state, the moisture distribution of three types is heterogeneous. Type A of adsorption pore-developed exhibits strong moisture variation heterogeneity of small pores, in contrast to the uniform moisture variation in large pores. Type B of fracture-developed has the highest coefficient of variation in moisture distribution. The coefficient of variation A1 for moisture content can determine the speed of moisture transport and evaporation in the pore structure. A lower A1 indicates a greater moisture transport volume and faster moisture transport rate over the same time. The coefficient of variation A2 for moisture distribution represents the heterogeneity of moisture content variation in the pore structure. That is, a smaller A2 indicates better heterogeneity in the distribution of moisture content in the pore structure. Numerical simulation indicates the average gas production and the peak gas production time increase and decrease with the initial moisture content (Sgrw) increases, respectively. These findings provide practical guidance for coalbed methane development, especially in optimizing coalbed methane production capacity prediction and improving recovery efficiency. •Water intrusion process by using NMR technology are studied.•Heterogeneity changes in moisture content and distribution by using formula fitting and fractal theory are studied.•Effect of water occurrence on the production capacity by using production capacity simulation are studied.