关于煤层气叠置成藏效应的研究通常注重煤系地层层序地层格架的时空配置，对于原位地应力制约下储层的“自封闭效应”关注不足，应力场垂向转换诱导的煤储层渗透性的非单调性变化及其对储层压力、含气性等成藏特征参数的调控作用常被忽视。系统分析了黔西地区煤储层地应力场的垂向分布规律及其构造控制效应，揭示了渗透率随埋深的非指数变化规律及其在沁水、鄂东等含煤盆地的普适性，探讨了储层压力、压力系数垂向差异性分布及其与地应力-渗透率的匹配关系。黔西地区煤储层水平主应力(200~1 300 m)是埋深和构造综合作用的结果，含煤向斜轴部是水平主应力最为集中的区域。根据应力梯度垂向演变规律可以将其划分为应力挤压区(200~500 m，水平构造应力主导)、应力释放区(500~750 m，垂直应力主导)、应力过渡区(750~1 000 m，近向斜轴部)和构造集中区(>1 000 m，向斜轴部低点部位，高应力区)。埋深中段的应力释放区有利于相对高渗储层的形成(平均0.2×10-15 m2)，在此深度区间上下(200~500 m，平均0.06×10-15 m2;>750 m，平均0.02×10-15 m2)渗透率普遍较低。渗透率随埋深的这种非单调性变化规律具有普遍性，黔西盘关—土城向斜、比德—三塘向斜埋深中段均存在渗透率相对高值区，沁南(650~800 m)、鄂东(800~950 m)、滇东(600~800 m)、准南(600~800 m)等含煤盆地内这一现象也并不鲜见。原位条件下，低渗储层(<0.1×10-15 m2)的“自封闭”作用使其可以不依赖于盖层等封堵条件，即可构成层间相对独立的流体单元。例如，黔西地区200~500 m,>750 m埋深段的低渗储层自封闭成藏作用显著，储层压力与埋深相关性较差，含气量与压力系数垂向呈“波动式”的无规律变化，常压、欠压、超压储层均有分布，流体压力系统叠置发育。500~750 m的相对高渗储层需外围形成致密的封堵盖层才能阻断层间的流体联系，相对于其他埋深区间更有利于形成统一的流体压力系统，储层压力随埋深增加或层位降低而单调递增，压力系数无明显波动，基本以常压储层为主，含气量随着埋深增大而增大。在同一煤层或气藏内部，储层相对致密部分也可能会封堵高孔渗部分的流体，导致流体压力系统横向上多段叠置。

Research on the superimposed coalbed methane system usually pays attention to the sequence stratigraphic framework of the coal-measure stratigraphy.There is insufficient attention to the “elastic self-sealing effect” of the reservoir under the restriction of in-situ in situ stress.The non-monotonic changes in coal reservoir permeability and its control on reservoir pressure,gas content are often overlooked.Here,the vertical variation in in-situ stress and its structural control factors in western Guizhou were systematically analyzed,and the non-exponential variation in permeability with increasing depth in several coal-bearing basins were revealed.Finally,the matching relationship between reservoir pressure,pressure coefficient and permeability in the vertical were further discussed.In western Guizhou,the horizontal stress gradient changes with depth is non-uniform and is overprinted by the effect of syncline,and the stress gradient is remarkably high nearing the axis.These observations within 200-500,500-750,750-1 000 and >1 000 m depths are similar with the variations in horizontal stress difference and lateral pressure coefficient,corresponding to stress extrusion (horizontal stresses dominated),stress release (vertical stress dominated),stress transition (stress concentration in syncline axis begins to appear),and stress concentration zones (the low point of the syncline axis,high stress area),respectively.The stress release zone is favorable for a relatively high permeability reservoir (mean 0.2×10-15 m2).Below (750-1 000 m，mean 0.04×10-15 m2;>1 000 m，mean 0.003×10-15 m2) and above(200-500 m，mean 0.06×10-15 m2)this zone,the reservoirs have a very low permeability.The non-monotonic change law in permeability with depth is universal,the relatively high permeability zones at the middle depths can be found in the Panguan-Tucheng and Bide-Santang synclines,as well as in the southern Qinshui Basin (650-800 m) and the eastern margin of the Ordos Basin (800-950 m).Under in-situ conditions,the “self-sealing” effect of low-permeability reservoirs (<0.1×10-15 m2) makes it possible to form relatively independent fluid units or accumulation units without relying on caprocks and other sealing conditions.For seams at 200-750 m and >750 m in depth,penetration is restricted by reduced permeability,resulting in discontinuous gas-bearing systems with irregular gas content distributions and unpredictable reservoir pressure gradient.The higher permeability reservoirs at 500-750 m depths need tight sealing cap rock to block the fluid connection between layers,and thereby is favorable to form a unified gas-bearing system,where the gas content generally increase with depth to a“peak gas”horizon under hydrostatic pressure.The relatively tight part of the reservoir may also block the high porosity and permeability part,causing multiple section of fluid pressure system in the same gas reservoir.

1 地质背景与数据处理

2 原位地应力场垂向分布规律

   2.1 含煤向斜构造水平主应力变化

   2.2 原位地应力状态垂向转换规律

3 原位地应力控渗、控藏效应

4 地应力控藏机制探讨及研究展望

5 结论