Oriente盆地D-F油田泥岩墙成因及其对油藏分布的影响

Genesis of mudstone dikes and their impact on oil accumulations in D-F oilfield of Oriente Basin,Ecuador

以Oriente盆地D-F油田M1-SS层发育的泥岩墙为研究对象,利用钻测井和地震资料,精细刻画泥岩墙在平面和垂向上的分布特征,从沉积环境和差异压实作用两个方面探讨了泥岩墙形成的控制因素,并分析了泥岩墙对油田油藏分布的影响。两条泥岩墙均为北西-南东向延伸,在测井和地震上分别表现为较高的泥质含量和弱振幅反射。研究认为,泥岩墙对应潮控河口湾环境的混合坪相带,与周围砂坪、砂坝环境相比泥质含量高,因此在M1-SS经历压实作用时,会发生差异压实作用,造成M1-SS层厚度在混合坪相带变薄,甚至在泥岩墙边缘出现微小断裂。另外,泥岩墙的存在影响了储层的非均质性,使M1-SS层的砂体连续性变差,对油气横向运移起到了隔挡作用,将油源断层东侧的油藏分隔成了5个油藏。

Two mudstone dikes formed in the M1-SS layer of D-F oilfield,Oriente Basin,Ecuador,were studied to characterize their vertical and planar distribution based on drilling,logging and seismic data,and to analyze the factors that controlled their formation in respects of sedimentary setting and differential compaction process. Their impact upon the distribution of oil accumulations in the oilfield was also discussed in the paper. Both NW-SE-trending dikes are characterized by higher clay content in well logging and low amplitudes in seismic data. The study suggests that the dikes correspond to hybrid sand-mud flat microfacies in a tide-dominated estuarine environment and have higher clay content than surrounding sand flat and sand bar microfaices. Therefore,after differential compaction,the sand-mud flat ended up with a thinner thickness of M1-SS and even formed tiny faults at the edge of dikes. Besides,the presence of the dikes affected the reservoir heterogeneity and decreased the continuity of the sandbodies in M1-SS,thus blocked lateral migration of hydrocarbons. As a result,the oil accumulation to the east of the source rock-rooted fault was compartmentalized into five small reservoirs.