Effects of Igneous Intrusion on Low-rank Coalbed Methane Reservoir Formation in Fuxin Basin, China

Researches of igneous intrusion in Fuxin basin on more complex formation mechanism of low-rank coalbed methane(CBM)reservoir are not only the focus and critical problem of basic geology, but also contribute to improvement of the exploration effectiveness of the same type of reservoirs, serving as one of rare achievement examples of low-rank CBM development. This paper presents a comprehensive research of the reservoir characteristics of the Wangying-Liujia CBM formation, such as the intense control action of the dolerite dike invasion so as to further confirm the effects of igneous intrusion on low rank CBM reservoir formation. The result shows that the dolerite dike invasion not only facilitates large hydrocarbon regeneration, but also obviously improves the Ro of the thick bituminite at the bottom of Fuxin formation. It also greatly improves the coal reservoir property, which helps the groundwater double replenishment along the coal seams outcrop and dolerite dike and the closed pressure water condition formation. Moreover, the research shows that there exists much free gas clearly for the closed fault-preventing gas diffusion. So the cokeite growing area is the most advantageous where the high production CBM wells will distribute in the girdle band along the dike. In summary, concerning low-rank CBM exploration, this paper proposes gas evaluation by using CBM and conventional means.