Characteristics Of Fluid Inclusions And Accumulation Period Of The 8th Segment Of The Sulige Area

Ordos basin is an important petroliferous basin with abundant reservoirs in China.Based on the project No.039 of PetroChina Changqing Oilfield-the Feature of Fluid Inclusions in Upper Paleozoic Section 8 of Ordos Basin and its Application in Diagenesis of Reservoir Stratum,regarding the reservoir of Upper Paleozoic Section 8 of Shihezi of Sulige area as the study object,the facieology,homogenization temperature and compositions of the fluid inclusion were studied with the analytic and testing data from core observation,casting thin sections,regular slices,SEM,cathode luminescence,Cold&Hot stage and Laser Raman microprobe.Combined with the history of basin geothermal evolution and burial,the forming time of petroleum reservoir and reservoir formation period as well as the coupling relationship between diagenetic evolution and hydrocarbon accumulation were studied and illustrated.The study shows that there was a series of diagenesis in reservoir,which experienced a long history of diagenetic evolution before arriving at the mesogenetic stage B,and of which the parameters of sandstone particles including grain size,sorting and grinding had particular attribution.Four types of fluid inclusions,such as brine fluid inclusion,brine fluid inclusion include hydrocarbon,gaseous hydrocarbon fluid inclusion and CO2 fluid inclusion were restored in four kinds of minerals and occurrence respectively including the micro fractures of cutting through the quartz grains and its enlarged edge&the quartz grains and its enlarged edge,the micro fractures of cutting through the quartz enlarged edge&the quartz enlarged edge,the micro fractures of cutting the quartz grains&the quartz grains,and the calcite cement&its micro fractures.The homogenization temperature of fluid inclusions was 60 ??230 ?,with the peak ranging from 100 ? to 130 ?.Three-time fluid inclusions capture events were confirmed in study area,namely,during compaction for the first time,then quartz overgrowth and last calcite cementation.Through the diagenesis-porosity evolution,we can find that the reservoir has been compacted after quartz overgrowth.Acoording to the homogenization temperature,we can infer the time of reservoir compaction was 175-165Ma,Middle Jurassic.Similarly,the time of oil and gas injection can be found by the homogenization temperature of fluid inclusion,which was 175-135Ma,from Middle Jurassic to Early Cretaceous.The model of hydrocarbon accumulation was established that during 175-165Ma accumulation was carried out as compaction,while 165-135Ma,compaction was done before accumulation.