Study On Reservoir Quality Difference Of Shahejie Formation In Fan 154 Block Of Dongying Hollow

The middle section of the third member of Shahejie Formation(Es3)of Daluhu oilfield in Dongying sag is a tight sandstone reservoir of gravity flow deposition.It has the characteristics of complex microscopic pore structure and strong reservoir heterogeneity.The distribution characteristics and laws of reservoir quality difference are not clear,which seriously restricts the efficient development of the reservoir.This paper takes the middle section of Es3 in Fan 154 block as the research object,analyzes the reservoir quality characteristics,clarifies the mechanism of reservoir quality difference,reveals the spatial distribution law of different types of reservoirs based on drilling coring,laboratory analysis and logging data.The study shows that the middle section of Es3 is dominated by lithic feldspar sandstone,and the kaolinite content in clay minerals is high,which is in the mixed level of illite and smectite.The relative content of cement is high,mainly calcium.The median distribution range of grain size is 0.2mm-0.4mm,the contact relationship between particles is mainly point-line contact,the sorting is medium,and the maturity of reservoir structure is low.The pore types are mainly secondary pores,and the main body develops sheet and tubular throats.According to the pore structure and pore throat fractal characteristics of the reservoir,three types of pore structure are divided.The difference distribution of reservoir quality in the middle section of Es3 is controlled by sedimentation and diagenesis.The fabric characteristics of sediments can reflect the original reservoir space and have an impact on diagenesis.Based on the characteristics of lithology and sedimentary structure,seven types of lithofacies are divided,among which the reservoir quality of massive bedding pebbly sandstone facies and massive sandstone facies is the best.In diagenesis,medium-intensity compaction caused rapid porosity reduction and poor reservoir quality.Strong dissolution increases pore space and improves reservoir quality.The main body of moderate-intensity cementation is mainly to reduce pores and block throats.A small amount of early calcite cementation and chlorite lining cementation have a constructive effect on reservoir quality.However,due to the low development content,cementation still plays a destructive role in reservoir quality as a whole.Based on the principle of hierarchical division of pore structure-lithofaciessedimentary microfacies,the reservoir quality of the middle section of Es3 in the study area is divided into five types.On the plane,type Ⅰ reservoirs are mostly developed in the core of gravity flow channel and debris flow tongue,which are lenticular.Type Ⅱ and Ⅲ reservoirs are distributed in strips in the tongue body and lobe body of debris flow,with a wide distribution range.Type Ⅳ and Ⅴ reservoirs are distributed in the outer edge of the lobe,the outer edge of the turbidity sheet sand and the slump microfacies.