渤海湾盆地济阳坳陷孤岛下古生界碳酸盐岩潜山油气成藏特征

Characteristics of petroleum accumulation of the Gudao Lower Paleozoic carbonate rock buried hill in the Jiyang depression,Bohai Bay basin,China

位于沾化凹陷的孤岛下古生界碳酸盐岩潜山为菱形断块山,边界断裂为多条断层构成的断裂带,潜山主体构造呈短轴穹隆构造,潜山为多期构造叠合的继承性隆起构造。潜山下古生界碳酸盐岩储层储集空间有晶间孔和晶间溶孔、粒间孔和粒间溶孔、铸模孔、砾内-砾间孔和砾内-砾间溶孔、溶洞、溶蚀缝和构造缝、方解石晶簇间孔等。储层基质孔隙度大部分低于2%,孔隙度随深度变化不大;渗透率从几十个10-3μm2到0.0001×10-3μm2,渗透率随孔隙度的增大而增大。潜山的生储盖组合为下生上储顶盖型,但油源侧向运移。油气成藏特征有南北逢源、复式立体输导、高凸指向、混源充注、断层控制、缝洞发育、逸顶"天窗"和局部成藏等。由于孤岛潜山长期隆起,潜山顶部位缺失1.84 km2东营组,直接与馆下段砂砾岩体相接,形成一个油气向上逸散的"天窗"。这是导致潜山不能大规模聚集油气的重要原因。

The Gudao Lower Paleozoic carbonate rock buried hill is located in Zhanhua sag. It is a prismatic fault block hill and dome fold structure. Its Lower Paleozoic carbonate rock reservoir spaces are intercrystal pores and intercrystal solution pores, interparticle pores and interparticle solution pores, moldic pores, inter-intra gravel pores and inter-intra gravel solution pores, cavities, solution fractures and structural fractures etc. The main part of matrix porosity is lower than 2%, which doesn＇t change too much with the variation of depth. The permeability varies from 10^-3 μm^2 to 0.0001 × 10^-3 μm^2, and increases with the augment of the porosity. The source-reservoir-caprock assemblage of the buried hill consists of the source rock in the lower part, reservoir rock in the middle, and caprock in the upper. However, the petroleum migration is lateral. The characteristics of petroleum accumulation in the Gudao Lower Paleozoic carbonate rock buried hill are as follow： the petroleum from the source rocks in the southern and northern sags, the multiple petroleum conduit system, petroleum migration to paleo-uplift, fault controlling, well development of the fractures and cavities, petroleum escaping through the eroded holes of Dongying Formation, and local petroleum accumulation. Because of long-time uplifting, the top of the buried hill has been lost 1. 84 km^2 Dongying Formation and is in touch with the lower section of Guantao Formation. This makes the gathering of oil and gas in large scale impossible.