大港油田奥陶系岩相古地理及储层特征

ORDOVICIAN LITHOFACIES PALEOGEOGRAPHY AND RESERVOIR CHARACTERISTICS OF THE DAGANG OILFIELD

大港油田在奥陶纪时期为华北陆表海的一部分,在坳陷内发育了一套碳酸盐岩地层。下奥陶统发育冶里组和亮甲山组,中奥陶统发育马家沟组和峰峰组,上统缺失。早奥陶世的岩相古地理具有南北分区的特点,中奥陶世古地理面貌发生了改变,呈现出"海中有坪"的格局。奥陶系储集层由于后期的多次改造,并受岩性、沉积相、成岩作用、断层、裂缝等多种因素制约,其主要特点为高孔、低渗,总体上属较好—差储集岩。其中沈青庄—塘沽、孔西、王官屯、南皮—吴桥和徐黑等地区为较好储集岩分布区。

During the Ordovician period,the Dagang Oilfield was a part of the Huabei Epicontinental Sea,in which a set of carbonate deposits was formed.The Lower Ordovician contains the Yeli Formation and Liangjiashan Formation;and the Middle Ordovician consists of the Majiagou Formation and Fengfeng Formation.The Upper Ordovician is missing.The early Odovician paleogeography was characterized by the south-north differentiation.But the pattern of paleogeography was changed in the Middle Ordovician.There was a dolomitic lime flat along north-east border of the open epicontinental sea.The quality of the Ordovician reservoirs in this area changed in a range from relatively good to relatively bad,and were characterized by higher porosity but low permeability due to multiple deformation and other factors such as lithology,sedimentary facies,diagenesis,faulting and cracking.Favorable reservoirs are distributed in Shenqingzhuang-Tanggu,Kongxi,Wangguantun,Nanpi-Wuqiao and Xuhei regions.