大港千米桥潜山储层形成对油气分布的控制

位于黄骅坳陷北大港构造带之下的千米桥潜山是一个深埋的奥陶系碳酸盐岩潜山油气藏。潜山形成经历了中—新生代褶皱抬升—埋藏改造等复杂的地质过程,碳酸盐岩储层成因复杂,有效孔隙分布具有极强的非均质性,严重影响了晚期油气的充注。对碳酸盐岩储层成岩过程的解析表明,中生代强烈构造变形事件之后的大气水岩溶作用形成了潜山储层基本格架,而第三纪埋藏过程中发生的选择性溶蚀与胶结作用则使储层结构复杂化,储集空间分割性进一步加强。在潜山油气充注过程中,缝洞系统与供烃窗口的对接关系决定着油气主疏导网络分布,而疏导网络与储集空间的连通与否则控制潜山油气分布。千米桥潜山油气藏应属于成岩封闭的裂缝性油气藏,而非块状油气藏。

Controls of Carbonate Reservoir Diagenesis on Hydrocarbon Distribution in Qianmiqiao Buried-hill Reservoirs, Bohaiwan Basin

Qianmiqiao Oil Field consists of Ordovician carbonate buried-hill reservoirs that lie under Beidagang Belt in Huanghua Depression. The buried hill experienced a complex uplifted and buried history due to multiple faulting and/or folding deformations during Mesozoic to Cenozoic eras so that the reservoirs,in which different kind of anisotropy pore spaces formed by fracturing, karstification and cementation, was in control of late hydrocarbon migration and emplacement. By analysis of diagenesis process of carbonate reservoirs,it is suggested that effective pore spaces in the buried hill are fractures that formed by deformation and meteoric karstification during Mesozoic intensive deformation stage and then complicated by selective solution and cementation during Tertiary buried stage, which strongly reshaped reservoir textures and dismembered seepage flow units so as to cause disconnected spaces for fluid flow. Fracture-pore system and hydrocarbon-supplying "windows" may co-affect the hydrocarbon migration and accumulation net, and further predominate distribution of hydrocarbon in the buried hill reservoirs. It is proposed that Qianmiqiao Field is of the fractured reservoirs controlled by carbonate diagenesis but not of block reservoirs controlled by connective karst pores.