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比德-三塘盆地含煤地层的储层压力普遍较高,压力梯度较大,异常高压发育.通过研究该盆地现今煤储层压力分布特点,对煤层异常高压影响因素进行了综合分析,阐明了其形成机制.结果表明:构造作用是本区异常高压形成的最主要因素,煤储层生烃作用和顶板泥岩的封闭性次之.盆地内部断裂较少,具有良好的圈闭条件,储层流体富集,压力增大,易出现超压地层.研究区煤层生烃能力强,含气量高,但渗透率普遍较低,生成的烃类气体使得储层内部流体孔隙体积膨胀产生高压.同时,超厚的顶板泥岩封闭性较好,在沉积过程中极易产生欠压实作用,进一步促进了异常高压的形成.
The reservoir pressure of the coal-bearing formation in the Bide-Santang Basin is generally high, with a large pressure gradient and abnormally high pressure.Based on the study of the present coal reservoir pressure distribution characteristics in this basin, the influencing factors of abnormal coal seam pressure are comprehensively analyzed and clarified The results show that the tectonism is the most important factor for the formation of anomalous high pressure in the area, followed by the hydrocarbon generation in the coal reservoir and the sealing of the top mudstone.The interior faults in the basin are less fractured and have good trapping conditions In the study area, the coal seam has strong hydrocarbon generation capacity and high gas content, but the permeability is generally low, and the generated hydrocarbon gas causes the pore volume expansion of the fluid in the reservoir to generate high pressure. At the same time, the ultra-thick roof mudstone has a good sealing property and can easily produce under-compaction in the deposition process, further promoting the formation of abnormal high pressure.