济阳坳陷典型岩性油气藏相—势耦合控藏作用解剖及应用

济阳坳陷岩性油气藏成功勘探表明,岩性油气藏受"相"和"界面势能"的双重控制。相控油气作用表现为高孔渗优相控藏,势控油气作用表现为低界面势能控藏,只有优相和低界面势能耦合区才能形成岩性油气藏。通过对沾化凹陷埕913、牛庄洼陷牛35-牛20-王70等典型岩性油气藏解剖表明,只有相—势耦合控藏指数(FPI)大于0.5,岩性圈闭才能聚集油气成藏,成藏临界条件呈现为"双低"或"双高"的标准,即优相指数(FI)低、界面势能指数(PIS)低,或优相指数(FI)高、界面势能指数(PIS)高。一般FPI越大,圈闭含油饱和度也越高,越有利于油气聚集成藏。根据济阳坳陷73个岩性圈闭和54个浊积砂岩透镜体岩性圈闭含油气性的统计及其相势特征的分析,分别建立了2类岩性圈闭的含油饱和度(So)与FPI定量关系模型,利用该模型预测了东营凹陷13个岩性圈闭的含油饱和度,预测偏差率小于20%的准确率达84.6%,应用效果较好,可以用于岩性圈闭含油饱和度的预测。

Anatomy and application of facies-potential coupling on hydrocarbon accumulation in typical lithologic reservoirs in Jiyang Depression

Oil and gas exploration in the Jiyang Depression showed that lithologic reservoirs were mainly controlled by facies and interfacial potential. As to the facies-controlled effect, the favorable facies with high porosity and high permeability controlled hydrocarbon accumulation. And for the potential-controlled effect, low interfacial potential controlled hydrocarbon accumulation. Only in the coupling region of favorable facies and low interfacial potential, could lithologic reservoirs form. Through typical cases studies of the lithologic reservoirs of the Cheng913 in the Zhanhua Sag and the Niu35-Niu20-Wang70 in the Niuzhuang Sag, results showed that only when the facies-potential coupling index(FPI) was larger than 0.5, could hydrocarbons accumulate in lithologic traps. Besides, the critical condition for hydrocarbon accumulation displayed the characteristics of Two Lows or Two Highs, that was, low or high facies index (FI) and interfacial potential index (PI_S). The larger the FPI was, the higher the oil saturation was, and the easier it was for hydrocarbons to accumulate. Based on the statistics of petroliferous property and the analysis of facies, the potential characteristics of 73 lithologic traps and 54 turbidite lens traps in the Jiyang Depression were concluded, and the quantitative models of the relationship between oil saturation and FPI for two categories of traps were established. Oil saturation of 13 lithologic traps in the Dongying Sag was predicted through this model, and it achieved the accuracy rate of 84.6% for the reservoirs with the deviation rate less than 20%. As a result, this model could be applicable in predicting the oil saturation of lithologic reservoirs.