塔河油田奥陶系一间房组礁滩相溶蚀孔隙型储层特征与成因

Characteristics and genesis of reef-bank facies reservoirs with dissolution pores in Ordovician Yijianfang Formation in Tahe oilfield

塔河油田中奥陶统一间房组广泛发育的生物礁滩相具有台地内部的点礁、点滩性质,储层的储集空间主要是微裂缝一次生溶蚀孔隙。储层纵向上分布层位不稳定;平面上总体显示出西强东弱的特点;储层段内储渗空间的发育也具有较强的非均质性。次生溶蚀孔隙的形成受控于加里东期或海西早期大气水岩溶作用、后期构造破裂作用和深埋溶蚀作用的叠加改造,以晚期深埋溶蚀作用为主。烃源岩的热降解和储层中的烃类热催化裂解,生成有机酸和二氧化碳,引起深层碳酸盐岩发生溶解作用。温度差所产生的热对流循环系统是驱动流体流动的主要动力。

The organic reef and bank facies, widely developed in Middle Ordovician Yijianfang Formation in Tahe oilfield , are characterized by point reefs and banks within the caronate platforms, and the reservoir spaces are mainly of microfissures and secondary dissolution pores. Vertically, characterized by their uneven distribution in various horizons , while laterally, as a whole, they appear to be well developed in the west and poor in the east. In addition, the permeable-storage spaces are heterogeneous in the reservoir intervals. The formation of secondary dissolution pores had been controlled by karstification of meteoric water during Caledonian or Early Hercynian, and then had been superimposed by late structural fracturing and deep-lying dissolution, of which late deep-lying dissolution to be the main a-gent. Organic acid and CO2, generated from thermal degradation of source rocks and thermo-catalytic cracking of hydrocarbons in reservoirs, destabilized and dissolved the carbonates at depth. Thermal convection and circulation system, caused by temperature difference, would be the main dynamic force driving the fluid flow.