Characteristics of Ordovician reservoirs in Shunbei 1 and 5 fault zones, Tarim Basin

The Ordovician reservoir characteristics in two major fault zones (Shunbei 1 and 5) in the Shunbei area of the Tarim Basin were studied by integrated petroleum geochemical analysis techniques.The reservoir characteristics in the two fault zones are finely described and compared based on petroleum physical properties and hydrocarbon facies attributes, with a view to obtaining the origin of differential characteristics for reservoirs in different fault zones.The results show that the two fault zones share similar oil-gas sources of sapropelic hydrocarbon-generating parent materials with strong reducibility and of high thermal maturity.However, the Shunbei 1 fault zone has unsaturated volatile oil reservoirs, whereas the Shunbei 5 fault zone has unsaturated light oil reservoirs; and the maturity of oil and gas from the Shunbei 1 fault zone is significantly higher than that from the Shunbei 5 fault zone.These differences could be attributed to the multi-stage oil and gas charge and later reformation in the Shunbei area, which may have undergone three stages of hydrocarbon charge.The reservoirs in the Shunbei 5 fault zone were formed by both the first and second stages of hydrocarbon charge (mainly by the second stage as the hydrocarbon from the first stage of charge was mostly dissipated due to some damage) and those in the Shunbei 1 fault zone were largely the result of the third stage of hydrocarbon charge.Neither fault zones have undergone obvious thermal cracking, except for a slight thermochemical sulfate reduction (TSR) to the crude in the Shungbei 1 fault zone, and BSR to the early charged crude in the Shunbei 5 fault zone.Different charging processes are the main factors leading to different reservoir characteristics of different fault zones in the Shunbei area. © 2020, OIL & GAS GEOLOGY Editorial Board. All right reserved.