Chatacteristics And Accumulation History Of Carboniferous Oils In Eastern Chepaizi Uplift Of Junggar Basin

The Chepaizi uplift is characterized by multiple sources of oil and gas and multiple stages of accumulation and the area is a complex oil and gas accumulation area with multiple oil reservoirs,and there are multiple sets of oil bearing strata.In recent years,a large number of oil and gas reservoirs have been found in the volcanic rock reservoirs at home and abroad,which make the volcanic rocks from the original"forbidden zone,to the "target area" for exploration,and the volcanic oil and gas reservoirs exploration has gradually changed into a new field of oil and gas exploration.Carboniferous volcanic reservoir in Chepaizi uplift is one of the most important exploration strata because of its great potential.It is of great significance to guide the deployment for exploration by analyzing its sources and accumulation stages and working out the migration path of oil and gas.In this paper,by geochemical analysis of crude oil,thermodynamics of inclusions and petrographic analysis,the burial history and thermal history evolution of the Carboniferous System in the east part of the uplift of the Chepaizi are analyzed,and then accumulation stages and filling process are determined.conclusions are:.Carboniferous crude oil in the east part of the Chepaizi uplift is a low sulfur heavy thickened oil,and the density of crude oil increases from east to west.Carboniferous crude oils in the east part belong to the same genre,all of which are characterized by lacustrine source rocks with high maturity.Carboniferous oil from the east part of the Chepaizi uplift are mainly derived from Permian source rocks in the Changji sag,and may be contributed by Carboniferous source rocks.The inclusions in the study area can be divided into two stages by analyzing the characteristics of fluid inclusion samples such as microscope features,petrography and polarizing fluorescence.Inclusions of the first stage developed at the stage of diagenesis and were filled in the microfissures such as quartz grains or calcite as liquid hydrocarbon inclusions in brown or dark brown without fluorescence.Inclusions of the second phase mostly developed in the calcite-zeolite ridge formation period,mostly spreading in calcite-square zeolite ridge bodies as liquid hydrocarbon inclusions in brown,dark brown,yellow or light brown,showing yellow,yellow brown,blue or yellow green fluorescence.By using hydrocarbon generation method,fluid inclusion method and structural evolution comprehensive analysis,it is found that Carboniferous crude oil in the east part of the uplift of the Chepaizi is secondary oil reservoir after latter changes,and there was two accumulation stages.The first stage was from the Cretaceous to the Paleogene period,the previously generated oil and gas moved along the fault and unconformable surface to the Carboniferous reservoir,and the second period was from the Neogene on,because of the tectonic tilt,the secondary reservoir in the southwest was reorganized again in the early stage,oil and gas move along the newly formed fault to the northeast part and finally in the northeast,the second stage of accumulation was completed.