Engineering geological models for efficient development of high-rank coalbed methane and their application – Taking the Qinshui Basin for example

Abstract

Low average single-well production resulting in low economic benefit has become the main bottleneck of the CBM gas development in China. So it is significant to choose suitable efficient development technologies based on CBM geological factors for high rank CBM recovery enhancement. In view of this, CBM geological factors were analyzed, different geological models were established and the corresponding models of development engineering technologies were thus put forward. It was proposed that the four main factors affecting high rank CBM recovery from a lower degree to a higher degree respectively include coal texture, rank of coal metamorphism, in-situ stress, and the ratio of critical desorption pressure to initial reservoir pressure. On this basis, four engineering geological models were classified as follows: vertical well, open-hole multilateral horizontal well, U-shaped and roof tree-like horizontal wells, and fish-bone and L-shaped wells. It is concluded that the former two models are more adaptable in such areas with better coal texture and high degree of thermal maturity, while the latter two are commonly applied in a wide range of areas. Keywords: Qinshui Basin, High-rank coalbed methane (CBM), Coal texture, Rank of coal metamorphism, In-situ stress, Ratio of critical desorption pressure to initial reservoir pressure, Engineering technology, Geological model, Optimization model, Development benefit