Evaluation of Shale Oil Reservoir Capacity and Mobility Based on Rock Facies: A Case Study of Shahejie Formation in Dongying Sag

Abstract

AbstractDongying Sag of Bohai bay basin is one of the most important oil-rich hydrocarbon Depressions in the east of China. The lower Es3-upper Es4 in Dongying sag have great potential for shale oil exploration and development. In this paper, according to the favorable intervals of the Chunshang submember of upper Es4 in Dongying Sag, the rock facies and their compositions were classified and designated comprehensively using laboratory tests and analysis methods such as core, X-diffraction, conventional thin section, SEM and rock paralysis and fully considering mineral composition, organic matter abundance and bedding structures; the evaluation of the reservoir capacity and mobility of continental shale oil with different rock facies was studied taking mineral composition, bedding structures, reservoir space type and mechanism and movable oil saturation etc. into account. The result shows that the reservoir of the Upper Sub-member 4 in Paleogene Shahejie Formation has a relatively high content of carbonate and low content of clay; medium-rich organic laminated limy (dolomitic) mudstone is the major rock facies, which is strongly heterogonous vertically and displays varied oiliness index. The reservoir space types of different rock facies are classified as pores and fractures, mainly including clay slice pore, mineral intercrystalline pore and micro-fractures.The Chunshang submember of upper Es4 in Dongying Sag has a high oil saturation (averagely over 100), a well developed reservoir space and a shale oil reservoir with strong mobility. These findings provide a strong theoretical support for the effective development.KeywordsDongying SagShale oilRock faciesReservoir capacityMobility evaluation