四川盆地中三叠统雷口坡组天然气勘探的关键地质问题

The key geological problems of natural gas exploration in the Middle Triassic Leikoupo Formation in Sichuan Basin

基于四川盆地中三叠统雷口坡组的深入研究和油气勘探过程分析,总结了目前有关雷口坡组的基本认识:①烃源复杂且主力烃源层不明确,混源气占多数;②储集层类型多样,既有滩相储层、风化壳岩溶储层,又有微生物岩储层;③储集层层位多,雷一段、雷三段、雷四段均有优质储层发育,但各段优质储层发育的主控因素和形成机理不清楚;④油气成藏机理复杂,过程不明。据此,提出四川盆地中三叠统雷口坡组天然气勘探的关键地质问题有:①气藏主力烃源岩和输导系统问题;②储层类型、成因和分布问题;③气藏成藏过程和机制问题。只有这些关键地质问题的研究取得较大进展,雷口坡组的勘探才有望发现成片成带的规模性天然气藏。

Based on the oil and gas exploration process of the Middle Triassic Leikoupo Formation in Sichuan Basin and the understanding of the basic research on oil and gas carbonate reservoirs,the following key geological problems of the natural gas exploration in the Leikoupo Formation in the Sichuan basin are systematically analyzed.(1)The hydrocarbon source rocks are diverse and the main hydrocarbon source layer is not clear.(2)There are various types of reservoir rocks,but their main controlling factors and formation mechanism are not known.The Leikoupo Formation consists of both beach facies reservoir rocks,karst reservoir rocks and microbial reservoir rocks,all of which are dolomite.There are high-quality reservoir rocks in the 1st,3rd and 4th members of Leikoupo Formation,but the main controlling factors and formation mechanism of the development of all kinds of reservoir rocks are not clear,resulting in little guiding effect on petroleum exploration.(3)Hydrocarbon migration and accumulation mechanism is complicated and the processes are unknown.There are no bitumen in the Leikoupo Formation gas reservoir rocks,which is different from the other carbonate reservoir rocks(Upper Sinian,Lower Cambrian,Carboniferous,Permian and Lower Triassic carbonate rocks,etc.)in the Sichuan basin.Therefore,the Leikoupo Formation gas reservoirs may be secondary gas reservoirs.More Leikoupo Formation gas reservoirs in the Sichuan Basin can be found when the key problems mentioned above are deeply studied and understood.