Eeffective oil expulsion threshold of argillaceous source rocks and geological significance of shale oil

Key words:  source rocks  simulation of hydrocarbon generation and expulsion  hydrocarbon expulsion threshold  shale oil

Abstract:

A method of determining the effective hydrocarbon expulsion threshold was carried out by a series of simulation experiments on immature-low mature source rocks of different types and organic carbon content, and the geological significance to shale oil exploration were discussed. The results show that the minimum oil production is 5-8 mg/g (oil/rock) when the effective oil expulsion occurrs. Effective hydrocarbon expulsion threshold is controlled by the match of type, abundance and evolution of organic matter. Source rocks with original organic matter content less than 1.5% of type I, 2.0% of type Ⅱ₁, 2.5% of type Ⅱ₂, respectively, can not reach the effective oil expulsion threshold in the whole oil generation stage. The remaining oil in the source rock strata would be as a favorable target for shale oil exploration. The poor exploitation prospect is due to the low degree of evolution and low quality, so the in-situ heating conversion mining technology could be a good way to develop this part of shale oil resources. The exploration and development of shale oil should focus on source rock strata where effective oil expulsion has occurred and evolution degree (R_o) is between 1.0%-1.3%. In these locations, there are more light oil and natural gas in detained hydrocarbon, and the high gas oil ratio and good fluidity imply optimistic mining prospect.