Geologic Factors of Formation of Tight Oil and Its Resource Potential in China

Huang, Fuxi; Yang, Tao; Guo, Bincheng; Li, Xin; Yan, Weipeng; Ma, Hong

Tight oil is one of the important unconventional resources, and it is abundant in China. The preliminary exploration reveals five geologic features for its formation and indicates its good prospect. Currently, it has been preliminarily estimated that the geologic resources of tight oil in China totals 8 to 10 billion tons, mainly distributed in some exploration areas like Erdos Basin, Songliao Basin, Bohai Bay Basin, Sichuan Basin and Junggar Basin. Since 2010, through the exploration principle of Vertical Shaft Controlling the Scale and Horizontal Shaft Increasing the Single Well Production, some favorable exploration results have been obtained in Erdos, Songliao, Bohai Bay and Junggar basins, e.g. by fracturing, the daily oil productions of YangP well #1, YuanP well #1, HeiP well #1, Tang well #29-26, etc. have all reached above 100 cubic meters in the initial stage.

It is indicated by the exploration that the formation of tight oil is characterized by five geologic factors, including stable and gentle structure background, the tight contact between large areas of high abundance hydrocarbon source rocks and heterogeneous tight reservoirs, sandwich-type source-reservoir-caprock association, special short distance migration, and bedded generation-transport mechanism.

As shown in the formation of tight oil in Lucaogou Formation of Permian in Jimusar sag in Junggar Basin of Western China, firstly, the weak structural deformation, undeveloped faults and well-developed direct regional cap rocks in Jimusar sag provide a favorable background for the formation of tight oil area. Secondarily, the high abundance hydrocarbon source rocks of mud shale of Lucaogou Formation (with an average TOC of 3.96%) in the whole depression establish the sufficient resource foundation. Thirdly, large areas of tight reservoirs of dolomitic siltstone and dolarenite provide a reservoir space for crude oils. Finally, the integrated configuration relation between source rock and reservoir rock of Lucaogou Formation, together with two sets of upper and lower dessert bodies with stable thickness, create superior geologic conditions for short distance transport and bedded aggregation of oil and the formation of continuous tight oil areas.

Consequently, it can be indicated from geologic researches and exploration practices that the tight oil of China has abundant resource basis and favorable formation conditions, which is expected to become an important replace resource for oil.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013