Study On The Characteristics Of Reservoir Distribtution In Chang9Formation Of Wuqi Oilfield

The production of Wuqi oilfield has exceeded2.0million tons. However, the overalldevelopment level of reservoir urgently needs to be improved due to the lag of technicalstrength and scientific research, which seriously restricts the sustainable development ofoilfield and long-term interests. Typical block of Chang9reservoir in Wuqi oilfield wasanalysed in this paper, representative core samples were collected, then cores description andconventional thin section identification were made to determine the diagenesis characteristics,Chang9reservoir property of different blocks was analysed. According to the well logginginterpretation, marker beds comparison and the study of sedimentary characteristics,sandstone and reservoir thicknesses were determined, and reservoir distributioncharacteristics was analysed, which was further confirmed through oil test and production testin typical blocks in Wuqi oilfield.On the basis of sedimentary cycle, chang9formation of Triassic is subdivided intochang91, chang92, chang93through its rock texture, sedimentary structure and electricalcharacteristics. The lithology is comprised of interbedded grayish black mudstone, dark graysilty mudstone and fine sandstone. Sonic, natural gamma, resistivity logging curves overallperform dentately. Through the typical block analysis, Chang9reservoir has good inheritance,structure generally has the character of“high in the east and low in the west”, the reservoirdistribution is mainly controlled by the development of sand body in sedimentary facies,structure does not affect obviously. The types of sedimentary face is delta face and lacustrineface, mainly contain the microfacies of lake mud, subfluvial distributary channelinterdistributary bay and front sheet sand.The provenance mainly comes from the north andnortheast. The principal types of Chang9reservoir are arkosic sandstone and lithic sandstone.The major types of porosity are remainder intergranular pore,intracrystalline pore and fillingingredient dissolution pore, but microcrack is seldom. The average porosity is8%, theaverage permeability value is0.9mD, chang9reservoir belongs to low porosity and lowpermeability formation reservoir. Oil layers distribute along the main sandstone belt, reservoirdistribution is controlled by the sand shape and physical character, differentiation between oiland water is not obvious with no uniform oil-water interface, oil and water mixed together inthe reservoir. Comprehensive research on Chang9reservoir distribution characteristics hasthe important theory significance and the guiding effect on the further oil exploration anddevelopment.