Selection of suitable engineering modes for CBM development in zones with multiple coalbeds: A case study in western Guizhou Province, Southwest China

Recently, many types of coalbed methane (CBM) engineering practices have been applied in western Guizhou. However, most of these CBM practices (e.g., vertical well, horizontal well, cluster well.) have failed due to the complex geological conditions. To improve the success rate of CBM development projects, this paper proposes a CBM engineering mode selection method based on the geological conditions of the CBM resources found in western Guizhou. By analyzing the geology and considering the Upper Permian coal seams in western Guizhou as a case study, the geological conditions associated with CBM development were examined using measured data. In addition, the selective matching of existing CBM engineering methods to the geological conditions was examined and preliminarily demonstrated. The results indicated that the evolution of the geological conditions was primarily controlled by the vertical distribution of the coal strata, the hydrogeological conditions, and the tectonic stresses. The classification of the geological conditions into different types of CBM development geology was conducted according to the regional configuration of the geological parameters. A basic relationship exists between the type of geology and the engineering method for CBM development. To optimize the development engineering method and obtain high CBM production, the engineering methods of thin-layer staged fracturing of multiple coal seams, supplementary fracturing of sandstone reservoirs in coal deposits, and reservoir stimulation via protected coal seams during mining were preliminarily established. These methods represent a new direction for the CBM development of thin to moderate coal seams in western Guizhou. The technical feasibilities of the selected CBM development methods were verified by engineering practices, and certain CBM wells reported good production. This study describes the engineering effectiveness and adaptability of CBM engineering practices from the perspective of the development methods in the study area. In addition, this study emphasizes that the relationships between the geological conditions and the engineering methods might be broadly applicable when choosing the best CBM development engineering method for zones with multiple coalbeds in China.