鄂西渝东地区震旦、寒武系天然气成藏条件

NATURAL GAS RESERVOIRING CONDITIONS OF SINIAN AND CAMBRIAN IN FROM WESTERN HUBEI TO EASTERN CHONGQING AREAS

鄂西渝东地区预测震旦系、寒武系天然气资源量为1.42×1012m3,勘探前景广阔。通过系统地对天然气成藏条件的分析,认为下寒武统泥岩是主力烃源岩,具有良好的生烃潜力;指出有利的沉积相带、古岩溶作用和裂缝的沟通作用形成了震旦系灯影组、下寒武统石龙洞组两套优质储层,同时具有良好的区域盖层和保存条件,并结合烃源岩、构造和古隆起演化将鄂西渝东地区震旦系、寒武系天然气成藏过程划分为三个阶段:以岩性(古岩溶)-地层型油气藏为主的加里东期-海西期;以构造型油气藏为主的印支期-燕山早期;燕山晚期-喜马拉雅期为油气藏调整定型期。在此基础上结合已钻井资料分析,认为鄂西渝东地区成藏条件优越,石柱复向斜应为近期"下组合"天然气勘探的主战场,建南构造圈闭规模大、类型好,是钻探的最有利目标。

The predicted Sinian and Cambrian gas resource amounts to about 1.42×1012 m3 in from western Hubei to eastern Chongqing areas,the prospect for the exploration is broad.Lower Cambrian mudstone is mostly hydrocarbon source rock and has good gas generating potential.Dengying Formation of Sinian and Shilongdong Formation of Lower Cambrian are two sets of high quality reservoirs attributed to favorable sedimentary facies,paleokarst action and fractures linkage.The sealing ability of the multi-cap cocks is good,which is beneficial to the preservation condition of natural gas.According to hydrocarbon source rocks evolvement,tectonic evolvement and paleo-uplife evolvement,reservoiring course of Sinian and Cambrian natural gas in the areas is grouped into three phases:lithologic(paleokarst)-stratum reservoirs during Caledonian-Hercynian,structural reservoirs during Indo-Chinese epoch-early Yanshanian,reservoirs adjustment and finality during late Yanshanian-Himalayan.Based on these facts and combined with the analysis of drilling date,it is indicated that there are excellent gas reservoir formation conditions in the areas and that Shizhu synclinorium is an important target in from western Hubei to eastern Chongqing areas for future Sinian and Cambrian natural gas exploration.Jiannan structure is a large-scaled trap and has good trap style,so that it should be taken as the most favorable exploration target.