Production characteristics of deep coalbed methane wells in the Linxing block and associated their influencing factors

Objective The production characteristics of deep coalbed methane (CBM) are significantly distinguished from those of middle-shallow CBM, and even the production wells of deep CBM within the same block exhibit different characteristics. Given that relevant research remains in its exploratory stage, gaining a deeper understanding of the factors influencing the differences in production characteristics of deep CBM is significant for the production capacity prediction and production management of the subsequent large-scale production stage.

Methods  To determine the production characteristics of deep CBM in the Linxing block and their influencing factors, this study examined geological engineering factors including gas content, coal thickness, burial depth, hydrochemical characteristics, and fracturing technology.

Results and Conclusions The results are as follows: (1) Deep CBM wells in the Linxing block can be categorized into three types: flowing wells of supersaturated CBM reservoirs, production wells of supersaturated CBM reservoirs, and production wells of undersaturated CBM reservoirs. (2) Gas-bearing properties are identified as a dominant factor controlling the production characteristics of three types of wells. CBM wells in coal seams with burial depths ranging from 1800 to 2000 m exhibit relatively high gas content and stable gas production. (3) Production wells of undersaturated CBM reservoirs reveal inferior preservation conditions and hydrochemical characteristics that are significantly different from those of the other two types of wells, resulting in relatively poor production performance. Additionally, the fouling and corrosion of strings, caused by high total dissolved solids (TDS) and \mathrmHCO_3^- concentration, lead to discontinuous production. (4) Large-scale fracturing serves as an effective reservoir stimulation measure to increase the production of gas wells, and the effective propping of proppants for fractures proves critical in guaranteeing high and stable gas production of deep CBM wells. The results of this study present the factors influencing the differences in the production characteristics of deep CBM in the Linxing block, acting as a reference for the production of deep CBM in the Linxing block and its adjacent areas.