A New Type of Tight-oil and Its Feature in Zhahaquan Area of Qaidam Basin

ZHOU Bin1, GUAN Ping1,†, WEI Hengfei1, ZHANG Yongshu2, FU Ling1, YU Chuanqi1

ACTA Scientiarum Naturalium Universitatis Pekinensis - - Contents -

1. The Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871; 2. Exploration and Development Research Institute of Qinghai Oil Field, CNPC, Dunhuang 736202; † Corresponding author, E- mail: pguanl@pku.edu.cn

Abstract Sedimentology, reservoir geology and organic geochemistry are applied to the research of tight-oil found in Zhahaquan area of Qaidam Basin. The sedimentary facies in Zhahaquan area are mainly beach-bar sand, which becomes a good sedimentary background for tight-oil forming. The occurrence of tight-oil in this area is thin oil layer and source rocks interbed, so the tight- oil is a self- generating and self- preserving reservoir near source. Which provides a favorable condition of reservoir and source paragenesis for tight-oil forming. The reservoir is very tight which has pore of micron and nanometer, and has an average porosity of 5.8% and an average permeability of 0.45 md, so it is a typical tight-oil reservoir. Type of organic matter in Eocene source rocks is mainlyⅠ and Ⅱ 1. Tmax value is 311  461º C, which illustrates that the source rocks are between immaturate and maturation stages. Content of organic carbon falls 0.29%  4.42%, mainly less than 1.0%, which is much less than the source rock indicator for tight- oil. The tight- oil in the area should be a new type. It is believed that the conversion efficiency of the organic matter is higher in the lake environment with high salinization in this area, although the abundance of organic matter in source rock of tight-oil in Zhahaquan area of Qaidam Basin is much less than that in other basins. Therefore, the environment here can also support formation of much liquid

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