--> Integrated Sedimentary Characterization and Reservoir Architecture Analysis of Coastal Sandstone in the Hadeson Area, Tarim Basin, NW China

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Integrated Sedimentary Characterization and Reservoir Architecture Analysis of Coastal Sandstone in the Hadeson Area, Tarim Basin, NW China

Abstract

Remaining oils in conventional sandstone reservoirs is presently becoming the main extraction target using new and innovative reservoir development technologies. The internal structures of reservoir sandstones have an important bearing on the distribution of the remaining oil and its extraction. The Lower Carboniferous coastal Donghe Sandstone is an excellent reservoir and one of the main oil-producing intervals in the Tarim Basin, NW China. An integrated stratigraphic, sedimentological and reservoir architecture analysis was carried out on the Donghe Sandstone outcrops and drill cores. The findings were used to predict the reservoir architectures of the Donghe Sandstone in the subsurface. By using dipmeter logs and horizontal welling drilling data, six hierarchies of boundary layers and eight main types of lithofacies were delineated in the Donghe Sandstone. The characteristics and spatial distribution of 3rd to 6th boundaries were investigated in great details to construct a reservoir architecture model. The remaining oil distribution in the coastal reservoirs was simulated using sand-packed model based on the reservoir architectural patterns. The simulation provides some useful insight on the remaining oil distribution patterns and the effect of reservoir architecture on the remaining oil distribution. The Donghe Sandstone consists mainly of coastal dunes, backshore subfacies, foreshore subfacies and shore subfacies. We constructed six facies architectural models using quartz sand with different grain-sizes, including (1) connected accretion model, (2) partially connected accretion model, (3) connected prograding model, (4) partially connected prograding model, (5) connected retrograding model and (6) Partial connected retrograding model. The remaining oil in these six models were simulated experimentally. Three interlayer models were also constructed to simulate the remaining oil distribution, including an oblique-shaped interlayer, a staged-interlayer and parallel-shaped interlayer. The experimental results show that connected prograding model has the best oil displacement/extraction effect, whereas the partially connected retrograding model has the least favorable one for oil displacement among the six types of reservoir architectures. The oblique-shaped interlayer model has the largest influence on the remaining oil and the displacement effect, followed by the cross-shaped interlayer and the parallel-shaped interlayer.