Study on Hydrogeological Conditions and Water Source Identification of 8+9# Coalbed Methane Reservoir in Sanjiao Block

Abstract

Purposes The productivity of 8+9# coalbed methane wells in Sanjiao Block is poor owing to the intrusion of external water. Therefore, clarifying the hydrogeological characteristics and identifying its impact on the coalbed methane (CBM) development have become the key to increasing CBM production capacity. Methods On the basis of actual geological and production data, Fisher discriminant theory is used to identify water sources, and logging interpretation is further used to identify the distribution and water content of each aquifer in the Taiyuan Formation. An advanced study is ultimately achieved on the hydrogeological conditions of the 8+9# coal reservoirs. Findings The results show that the water from the CBM wells is mainly from the limestone in the Taiyuan Formation, partially showing the mixed water from Taiyuan Formation limestone and Permian sandstone, which is induced by the tensile strike-slip faults. There are five sets of limestone layers (L1-L5) developed on the coal seam 8# roof. The limestone development is generally stable with local branching and merging phenomena, and the northern part is significantly thinner. The five sets of limestone have obvious heterogeneity both vertically and horizontally in terms of water content. Conclusions Targeted development technology should be adopted in areas with different limestone development and water content. This study is of great significance for clarifying the hydrogeological characteristics and guiding the CBM development and deployment.

Keywords

• sanjiao block
• 8+9# coal reservoirs
• cbm development
• hydrogeological conditions
• water source identification