塔中北斜坡走滑断裂对碳酸盐岩油气差异富集的影响

塔中北斜坡发育NE向走滑断裂体系。走滑断裂活动导致其周围一定范围内裂缝交错发育,扩大了储集层的储集空间,同时沟通深部热流体,溶蚀围岩形成大量溶蚀孔洞,促进了岩溶风化壳储集层发育,改善了储集层储集性能,增大了岩溶储层发育的深度。源-储配置关系、断裂活动期次和原油微量元素分布研究表明,走滑断裂是塔中地区重要的油气运移通道,与鹰山组不整合面组合形成了下奥陶统油气输导网络格架,对油气的再分配起到了重要作用。以大型主干走滑断裂和逆冲断裂的延伸方向作为边界,将塔中北斜坡划分为20个构造区块,每个局部构造区块内油气水正常分异,油气富集程度与距走滑断裂的远近有一定关系,离断裂近,储层物性好,油气富集程度高;不同区块之间的油气富集特征存在明显差异。

Effects of strike-slip faults on the differential enrichment of hydrocarbons in the northern slope of Tazhong area

A series of NE strike-slip faults are developed in the northern slope of Tazhong area. Activities of these strike-slip faults generated a great deal of fractures and enlarge reservoir space, form massive dissolved pores and carities by deep thermal fluid from faults, which improves reservoir property significantly and increases development depth of karst reservoirs. Studies on source rock-reservoir relationship, active stages of faults and trace element distribution of crude oils indicated that strike-slip faults are an important pathway for hydrocarbon migration in the Tazhong area, together with unconformity of the Yingshan Formation, form a Lower Ordovician hydrocarbon transportation framework that controls hydrocarbon redistribution. The northern slope of the Tazhong area can be divided into twenty structural blocks with extension direction of major strike-slip faults and thrust faults. Each block has a normal differentiation of oil, gas and water. The extent of hydrocarbon enrichment in individual blocks has a certain correlation with distance away from strike-slip faults, smaller distance away from strike-slip faults, better property of reservoirs and higher extent of hydrocarbon enrichment. In addition, different blocks show obviously different characteristics of hydrocarbon enrichment.