Prediction of low-maturity shale oil produced by in situ conversion: a case study of the first and second members of Nenjiang Formation in the Central Depression, southern Songliao Basin, Northeast China

Abstract

The Nenjiang Formation in the Centrel Depression of the Songliao Basin consists of organic-rich low-maturity shale with a wide distribution and large thickness. In this study, the spatial heterogeneity of organic matter (OM) abundance and types was studied based on core measurements and log data. A geological model was used to predict the potential of in situ electric heating using hydrocarbon generation kinetics and heat conduction models. All members of the Nenjiang Formation are in the immature to low-maturity stage and oil-prone. The first and second members of the Nenjiang Formation (K2n1+2) contain mainly types Ⅱ1 and Ⅱ2 kerogen with alginite the dominant maceral. The shale of K2n1 has the best generation quality, and the high-quality source rocks within this member are mainly distributed in the Xinbei-Daan area of the Changling Sag. It can be inferred from the in situ electric heating simulation that the temperature rises rapidly, and reaches above 600 ℃ after 4 years of heating at 2 kW heating power. At 1 kW of heating power, it would take about 8 years. As the organic matter conversion rate approached 100% by the fifth year of heating, the maximum resource abundance was achieved. At the 2 kW heating power, the resource of the K2n1 reaches 24.5×109 t at the end of the fifth year, and 6.6×109 t of the K2n2.

Keywords

• oil shale
• low-maturity shale oil
• organic heterogeneity
• heat conduction
• thermal field
• hydrocarbon generation kinetics