Study The Fluid Inclusion Of The Ordovician Reservoir Of The 83 Wellblock Of Tazhong

Tazhong paleaohigh in central Tarim Basin is a long-term developed inheriting one, which is close to the oil sources depression and has excellent conditions of hydrocarbon accumulation. It's important oil and gas enriched area, and a major trend of exploring large oil gas field in Tarim Basin. The No.83 wellblock of Tazhong lies in a broad gentle structure region, which is between No.1 faulted slope break and the central uplift area. The reef-flat complex of the Lianglitage Formation in upper Ordovician and weathering crust reservoir in Lower Ordovician are major exploration targets in this study area.Based on core observation, core sampling and microsection of Ordovician of the No.83 wellblock, through the rock thin section analyzation by petrography analysis, fluorescence analysis and temperature-salinity analysis of fluid inclusion, it can be concluded that there are four stages of organic inclusions in the Ordovician reservoir of the No.83 wellblock of Tazhong area, whose characteristics are as follows: 1) The first stage organic inclusion: black liquid hydrocarbon inclusions, with no fluorescence; 2) The second stage organic inclusion: This stage is divided into two small sub-stages. The first one is comprised of brown liquid hydrocarbon inclusions and gas-liquid hydrocarbon inclusions, with strong yellow or yellow-green fluorescence, and the second one contains brown gas-liquid hydrocarbon inclusions, with moderate-strong brown fluorescence; 3)The third stage: light brown gas-liquid hydrocarbon inclusion + gray black gaseous hydrocarbon inclusions, with strong blue fluorescence of gas-liquid hydrocarbon inclusion; 4)The fourth stage: gray black gaseous hydrocarbon inclusions, with no fluorescence.According to components analysis and fluorescence analysis of fluid inclusions, and combined with temperature and pressure analysis of fluid inclusion, we can know that: The first stage hydrocarbon inclusions is the oil from Cambrian—Lower Ordovician source rock accumulated during the Caledonian, with a pressure of 15 ~ 23 MPa,which is comprised of heavy oil. The second stage hydrocarbon inclusions is the oil from Cambrian—Lower Ordovician source rock accumulated during the Late Hercynian, with a pressure of 30 ~ 35 MPa, which is made up of medium-heavy oil. The oil of the third and fourth stage hydrocarbon inclusions is from Cambrian—Lower Ordovician source rock accumulated during the Himalayan, and the pressure is about 40 ~ 60 MPa, with condensate oil or condensate gas in the oil of the inclusions.The crude oil of Lianglitage Formation reservoir of Upper Ordovician is mainly condensate oil and some condensate gas, and the Lower Ordovician reservoir is mainly condensate gas.The above conclusions indicate that the oil and gas reservoir of Ordovician in No.83 wellblock comes from the third and fourth stage hydrocarbon inclusions which are from Cambrian—Lower Ordovician source rocks and accumulated in the Himalayan until now.Above all, fluid inclusion technology is one of effective methods to solve the problems of formative period and the origin of oil and gas reservoirs.