鄂尔多斯盆地东部奥陶系盐下天然气成藏条件  

Gas pooling conditions in the Ordovician subsalt layers,eastern Ordos Basin

作　　者：苗忠英[1] 陈践发[1] 张晨[1] 史基安[2] 邵毅[2] 战沙[3] 

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室 [2]中国科学院油气资源研究重点实验室 [3]中国石油长庆油田公司勘探开发研究院

出　　处：《天然气工业》2011年第2期39-42,123-124,共4页Natural Gas Industry

基　　金：国家自然科学基金"原油中含氮化合物分布特征与油藏储层连通性研究"(编号:40773039)

摘　　要：鄂尔多斯盆地东部下奥陶统发育优质膏盐岩区域盖层,分析其下的烃源岩特征和储集条件,对于选择有利勘探区带和降低勘探风险都具有重要意义。通过对盐下烃源岩特征、生烃潜力、储层特征及分布规律的分析,得出以下认识:垂向上下奥陶统马家沟组五段、一段烃源岩质量最好;平面上膏盐湖沉积微相有机质丰度最高(0.26%)、局限海次之(0.24%)、开阔海第三(0.235%)、含膏云坪最低(0.2%);相同沉积微相在不同层段有机质丰度有差别,其原因可能与烃源岩泥质含量有关;有机质类型以腐泥型和偏腐泥混合型为主,成熟度较高(VRo>2%),主体已进入过成熟阶段;白云岩为主要储集体,储层物性较差,储集空间以晶间孔和晶间溶孔为主,也有溶解缝和构造缝。结论认为:奥陶系膏盐岩发育层段,天然气成藏潜力以马五段最高、马一段次之、马三段最低;无膏盐岩发育层段,马二段成藏潜力好于马四段。Quality halite gypsum regional caprocks are developed in the Lower Ordovician of the eastern Ordos Basin.An analysis of the subsalt source rocks and reservoir conditions is of great significance to the recognition of favorable plays,the enlargement of exploration domain,and the mitigation of exploration risk.The following conclusions are obtained based on the studies of the features and the hydrocarbon generation potential of subsalt source rocks as well as the characteristics and distribution of the subsalt reservoirs.Vertically,the source rocks in the 5th and the 1st members of the Lower Ordovician Majiagou Formation are the highest in quality.Laterally,salt lake maicrofacies is the highest in organic matter abundance(0.26%),followed by restricted sea(0.24%),the third is open sea(0.235%),while the last is salt-bearing dolomite flat(0.2%).The organic matter abundance for the same sedimentary mcirofacies is not the same at different intervals,possibly due to the variation of shale content of source rocks.The organic matters are dominated by type-Ⅰand-Ⅲ kerogen with high maturity(VRo>2%)and most of them are over-mature.The reservoirs are dominated by dolomite with poor poroperm characteristics.The reservoir space is dominated by intercrystalline pores and intercrystalline dissolution pores,to a lesser extent,dissolution fractures and structural fractures.At the intervals with salt layers,gas potential is the highest in the 5th member of the Majiagou Formation,followed by the 1st member,and the last is in the 3rd member.In contrast,at the intervals without salt layers,gas potential of the 2nd member is higher than that of the 4th member.

关 键 词：鄂尔多斯盆地 早奥陶世 盐膏层 烃源岩 储集层 成藏潜力 有机质丰度 沉积微相 

分 类 号：P618.13[天文地球—矿床学]