Comprehensive Depositional System and Reservoir Characterization Study of Chang 4+5 Reservoir of Yanchang Group, Infill Well Region in Baiyushan Area, Ordos Basin

LIU Yuyang1,2, PAN Mao1,2, LIU Shiqi1,2, SHI Yongmin1,2,†, DONG Yue3, ZHANG Zhiqiang1,2, WANG Ziyuan1,2

ACTA Scientiarum Naturalium Universitatis Pekinensis - - Contents -

1. The Key Laboratory of Orogenic Belts and Crustal Evolution (MOE), School of Earth and Space Sciences, Peking University, Beijing 100871; 2. Institute of Oil & Gas, Peking University, Beijing 100871; 3. Energy School, China Geological University, Beijing 100083; † Corresponding author, E-mail:

Abstract The authors focus on the ultra-low permeability reservoirs of Chang 4+5 reservoir period of Yanchang Group, Jing’an oil field, Ordos Basin. Cores, thin sections, wireline logs, and imaging logs were used to understand depositional systems, reservoirs and to furtherly characterize vertical and horizontal distribution patterns of sandstones. The results show that main reservoirs of Chang 4+5 of Yanchang Group are composed of medium-tofine grained arkose. Parallel beddings and cross beddings are common. Interpartical pores and a few fractures are main reservoir spaces and reservoir quality is poor. Sand bodies are uniformly distributed in the horizontal direction with brand shape and thickness between 2 to 5 meters. Front delta is the main sedimentary subfacies. Distributary main channel, distributary shallow channel, distributary shoal, and inner distributary bay are four main sedimentary microfacies. In the vertical direction, distributary main channels and distributary shallow channels are distributed reciprocally related to the variation of hydrodynamic power. The research result is a guidance on the hydrocarbon exploration in this region. Key words Ordos Basin; infill well region in Baiyushan area; sedimentary characteristic; reservoir distribution

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