鄂尔多斯盆地陇东地区上古生界天然气富集规律

基于鄂尔多斯盆地陇东地区上古生界气源条件、储层特征、盖层特征等的分析，对研究区上古生界天然气富集主控因素进行了研究。研究表明，鄂尔多斯盆地陇东地区上古生界天然气气藏的形成与分布主要受气源、盖层和储层条件三元耦合关系控制。气源条件、山西组1段直接盖层条件共同控制区域上气藏的形成与分布。区域上生烃强度高，山西组1段泥岩盖层厚度大于35 m的区域为山西组1段气藏有利成藏区，山西组1段泥岩盖层厚度小于35 m的区域则主要为石盒子组8段气藏有利成藏区。储层条件控制天然气的局部富集，其中气源条件、山西组1段盖层条件相似时储层“甜点”控气，即储层质量越好天然气越富集；气源条件、山西组1段盖层条件均有利时，相对较差储层亦可成藏。值得注意的是，气源、盖层和储层条件三元耦合关系控制的天然气最佳成藏富集区并非三者均为最优的地区，而是三者最佳配置、相互补偿形成的有利区。

Accumulation patterns of natural gas in the Upper Paleozoic in Longdong area,Ordos Basin

Based on the analysis of source rocks, reservoirs and cap rocks in the Upper Paleozoic, Longdong eara, Ordos Basin, studies were performed on the controlling factors of natural gas accumulation.It's shown that the formation and distribution of gas reservoirs in the Upper Paleozoic are mainly controlled by the source rocks, reservoirs and cap rocks and the coupling relationship among them.Source rocks and cap rocks of the Shanxi Formation jointly control the formation and distribution of the gas reservior in the region.The gas play fairway of the first member of Shanxi Formation(P₂s¹) are distributed in area with high gas generation intensity and thick P₂s¹ cap rock over 35 meters.In contrast, gas play fairway of the eighth member of Shihezi Formation(P₂h⁸) occurs in area where the thickness of P₂s¹ cap rock is less than 35 meters.Local enrichment of gas is dermermined by the reservior conditions.When the source rocks and cap rocks of the first member of the Shanxi Formation are similiar, "sweet spot" controls gas distribution, that is to say the better the quality of the reservoir is, the more enrichment the natural gas is.When both the source rocks and cap rocks of the first member of Shanxi Formation are favorable, gas reservoir can also be formed in the relatively poor formations.It is worth noting that best gas enrichment area is not the one where the gas source, seal and reservoir conditions are all favorable, rather the one where the gas source, seal and reservoir conditions match and compensate best.