Study on the Coalbed Methane Development under High In Situ Stress, Large Buried Depth, and Low Permeability Reservoir in the Libi Block, Qinshui Basin, China

Abstract

Coalbed methane (CBM) has been exploited in the deep area of the coal reservoir (>1000 m). The production of CBM vertical wells is low because of the high in situ stress, large buried depth, and low permeability of the coal reservoir. In this paper, efficient and advanced CBM development technology has been applied in the Libi Block of the Qinshui Basin. According to the characteristics of the coal reservoir in the Libi Block, the coiled tubing fracturing technology has been implemented in four cluster horizontal wells. Staged fracturing of horizontal wells can link more natural fracture networks. It could also expand the pressure drop range and control area of the single well. This fracturing technology has achieved good economic results in the Libi Block, with the maximum production of a single horizontal well being 25313 m3/d and the average single well production having increased by more than 60% from 5000 m3/d to 8000 m3/d. Based on the data regarding the bottom hole pressure, water production, and gas production, the production curves of four wells, namely, Z5P-01L, Z5P-02L, Z5P-03L, and Z5P-04L, were investigated. Furthermore, a production system with slow and stable depressurization was obtained. The bottom hole pressure drops too fast, which results in decreasing permeability and productivity. In this work, a special jet pump and an intelligent remote production control system for the CBM wells were developed; hence, a CBM production technology suitable for the Libi Block was established. The maximum release for the CBM well productivity was obtained, thus providing theoretical and technical support for CBM development with geological and engineering challenges.

Life Cycle Analysis of the Coalbed Methane Industry Based on Technology Paradigm and Data Analysis System Method

“…Due to the low gas content in high buried depth areas, the marginal profit of mining is reduced [22]. In the meanwhile, the geological environment of CBM in China is special, and a large number of CBM resources are located in the high buried depth area [23]. In this situation, it is very difficult to develop resources efficiently, which restricts the rapid development of the CBM industry.…”