Petroleum system assessment of conventional-unconventional oil in the Jimusar sag, Junggar basin, Northwest China

Abstract In recent years, petroleum assessment incorporates the petroleum system concept method instead of the play concept method to estimate petroleum resources, because conventional-unconventional petroleum resources are more reliably estimated by the genetic similarities of petroleum fluids in the petroleum system. Conventional-unconventional oil resources co-exist in the Lucaogou-Permian petroleum system in the Jimusar sag of the Junggar basin, Northwest China. The mean in-place resources (IPR) of tight oil of the Lucaogou Formation (LF) were estimated at 2.0 billion tons by an integration method in the Jimusar sag. Based on the assessment of the technically recoverable coefficient by drill productivity, it is estimated that the mean technically recoverable resources (TTR) of tight oil are about 0.11 billion tons. The mean IPR and TTR of conventional oil of the Wutonggou Formation (WF) were evaluated at 0.36 billion tons and 0.06 billion tons by analogy methods, respectively. The ratio of mean IPR of unconventional oil to conventional oil in the Jimusar is about 5:1, but the ratio of mean TTR is only about 2:1. In addition, tight oil development is higher cost than conventional oil so far. Therefore, the development of tight oil in the Jimusar sag should be a careful consideration. Anyway, the integrated resource assessment of unconventional and conventional oil in the Jimusar sag could provide as a classic example for other lacustrine petroleum systems.