构造坡折带对白云岩储层的控制作用

ANALYSIS OF DOLOMITE RESERVOIR CONTROLED BY STRUCTURAL SLOPE BREAK

构造坡折带.在陆相断陷湖盆的研究中已得到广泛应用,它对油气聚集具有重要的控制作用,但在海相盆地研究中还知之甚少.天1井和天2井同处于鄂尔多斯盆地西缘天环坳陷的天池构造上,两井相隔不远,天1井获高产气流,而天2井却未见油气显示.从高产气层段的岩性上来看,两井并未发生较大的变化.从孔隙类型来看,天1井以溶洞、溶缝发育;而天2井以晶间孔为主,次为裂隙和压溶缝,少量溶孔,多被充填.造成储集性能差异的根本原因在于两井分处于断裂坡折的不同位置,天1井位于坡折带之上,天2井位于坡折带之下,从而在沉积演化过程中受到孔隙流体的改造作用存在明显的差异.天1井的储集性能明显优于天2井,为后期油气运聚提供了有利的场所.

The structural slope break zone refers to the abrupt change of the depositional slope which is resulted by the long term activity of sedimentary structure. It has been applied widely in the research of continental faceis rift lake basins and controls petroleum accumulation, however, it is not be researched very deeply in the sea facies basins. Well Tian1 and Well Tian2 are located in Tianchi structure of western Tianhuan in Ordos basin, they are close at a distance. But well Tian1 got high capacity gas flow, well Tian2 has no show of oil and gas. They are very similar on the lithology of producing gas formation, but their pore types are different. Pore types of Well Tian1 are karst caves and karst apertures, while pore types of well Tian2 are mainly intercrystaline pores, secondary fractures and pressolutional fractures and a few karst caves which mostly are filled. On the basis of structural slope break in the paper, we think that it is because Well Tian1 and Well Tian2 are in different positions on the structure slope break that cause their different reservoir performance. Well Tian1 is located over the slope break, while well Tian2 is located below the slope break. So the influences of pore fluid on Well Tian1 and Tian2 are different during the sedimentary development process. The reservoir performance of well Tian1 is better than that of well Tian2, which provide the favorable place for oil and gas migration and accumulation.