Coalbed Methane Development in Liulin Block, Ordos Basin: A Study on the Complexity of Fracture Morphology in High-Rank Coal Rock Fracturing

Complex fracture morphology may form in the hydraulic fracturing of high-rank coal rock resulting in poor coalbed methane (CBM) yield. This paper proposes a numerical simulation model which reveals the causes of poor hydraulic fracturing effect in Liulin block. Hydraulic fracturing experiments on eight coal samples collected from the target block were also conducted. Taken together, the results are used to establish three types of proppant-filling calculating models and fracturing construction curves which accurately show effective fracture lengths and yields. The results of this case study show that: (a) effective fracture length is the key factor affecting the CBM yield in the target block; (b) the CBM reservoir with high-rank coal rock readily forms complicated fractures, which does not allow for the proppant to fill into the designed position; (c) the model returns effective fracture length predictions within 9% of measured values by microseismic monitoring in the target block. This paper may provide theoretical guidance for the optimization of CBM reservoir hydraulic fracturing operations with high-rank coal rock.