Pore pressure is an important parameter in coalbed methane (CBM) exploration and development; however, the distribution pattern and mechanism for pore pressure differences in the Upper Permian CBM reservoirs are poorly understood in the western Guizhou region of South China. In this study, lateral and vertical variations and mechanisms for pore pressure differences are analyzed based on 126 injection-falloff and in-situ stress well test data measured in Permian coal reservoirs. Generally, based on the pore pressure gradient and coefficient in coal reservoirs of the western Guizhou region, five zones can be delineated laterally: the mining areas of Zhina, northern Liupanshui, northern Guizhou, northwestern Guizhou and southern Liupanshui. Vertically, there are two main typical patterns: i) the pore pressure gradient (or coefficient) is nearly unchanged in different coal reservoirs, and ii) the pore pressure gradient (or coefficient) has cyclic variations in a borehole profile with multiple coal seams, which suggests the existence of a “superimposed CBM system”. The mechanism analysis indicates that coal permeability, thermal evolution stage and hydrocarbon generation contribute little to pore pressure differences in coal reservoirs in the western Guizhou region. The present-day in-situ stress field, basement structure and tectonic activity may be the dominant factors affecting lateral pore pressure differences. The sealing capacity of caprocks and the present-day in-situ stress field are significant parameters causing vertical pore pressure differences in coal reservoirs. These results are expected to provide new geological references for CBM exploration and development in the western Guizhou region.

孔隙压力是煤层气勘探开发的重要参数；然而，在华南黔西地区，对上二叠统煤层气储层孔隙压力差异的分布格局和机制知之甚少。在本研究中，基于 126 注入衰减和原位分析，分析了孔隙压力差的横向和纵向变化及其机制。在二叠纪煤层中测得的压力试井数据。一般根据黔西地区煤层孔隙压力梯度和孔隙压力系数，可以横向圈定五个矿区：直纳矿区、六盘水北部、黔北、黔西北和六盘水南部。纵向上，主要有两种典型的模式：i）不同煤层的孔隙压力梯度（或系数）几乎不变；ii）多煤层钻孔剖面中的孔隙压力梯度（或系数）具有周期性变化，这表明存在“叠加的煤层气系统”。机理分析表明，煤渗透率、热演化阶段和生烃对黔西地区煤储层孔隙压力差异的影响不大。地应力场、基底结构和构造活动可能是影响侧向孔隙压力差异的主要因素。盖层的封闭能力和现今地应力场是导致煤储层垂直孔隙压力差异的重要参数。这些成果有望为黔西地区煤层气勘探开发提供新的地质参考。