Micro-occurrence of Cretaceous tight oil in southern Songliao Basin, NE China

• Published in: Petroleum exploration and development Vol. 42; no. 3; pp. 323 - 328
• Main Authors: GONG, Yanjie, LIU, Shaobo, ZHU, Rukai, LIU, Keyu, TANG, Zhenxing, JIANG, Lin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2015; KeAi Communications Co., Ltd
• Subjects: Cretaceous; oil micro occurrence form; oil occurrence space; southern Songliao Basin; tight oil; southern Songliao Basin; oil occurrence space; tight oil; Cretaceous; oil micro occurrence form
• ISSN: 1876-3804; 1876-3804
• DOI: 10.1016/S1876-3804(15)30022-7

Combined experiment method of Environmental Scanning Electron Microscope (ESEM) and Energy Dispersive Spectroscopy (EDS) was proposed to detect tight oil occurrence in micro- and nano-pores of tight sands in Member 4 of Cretaceous Quantou Formation. Observation and analysis of 168 measurement points and seventeen samples from seven typical wells shows that the tight oil occurrences in micro- and nano-pores have two main forms: oil film and oil droplet, oil film is dominant. Intra-granular pores, inter-granular pores and micro-fractures are three kinds of micro storage space, mainly inter-granular pores. The oil films in the intra-granular pores and micro-fractures are irregular and adhesive, and the size is about (1−5 μm) × (1−5 μm), the carbon mass percentage of oil films are mainly 40%−90%. The size of oil droplets is (0.2−1.0 μm) × (0.2−1.0 μm), with relatively small occurrence space. The carbon mass percentage of oil droplets are mainly 15%−30%. Reservoir types and distribution of pores control tight oil occurrence. The carbon contents and thicknesses of oil film decrease from type I to type III reservoirs. The carbon mass percentage and thicknesses are controlled by the median pore throat radius and reservoir quality coefficient.