Chang 9 Reservoir Characteristics And Oil Reservoir Distribution Controlling Factors Of Zengcha Block,Wuqi Oil Field

Wuqi oilfield is located in the central ordos basin of wuqi county.Triassic Yanchang formation is the main oil-bearing series,In recent years the oil and gas exploration and development of Chang 9 oil bearing beds of Triassic Yanchang Formation in Zengcha block have made significant breakthrough,Wuqi oil field are the newly discovered oil bearing series of Lower Yanchang Formation,which are currently in the exploration evaluation stage and the comprehensive study of petroleum geology is still low.Guided by the theory of reservoir geology and hydrocarbon reservoir-forming,based on the analysis of various tests,oil test and producing test data,this paper systematically studies the reservoirs characteristics and oil reservoir distribution controlling factors of Chang 9 oil bearing beds,provide the basis for the following exploration deployment of this block.Under the control of the marker layer,based on the sedimentary cycle,Chang 9 oil layer group can be divided into 3 single layers,Chang 91,Chang 92 and chang93 single layers.Chang9 oil-bearing strata are mainly 91 reservoir.The superface structure of each layer represent monoclinal structure characteristic which is low-lying east to the west,and the nose-shaped uplift caused by differential compaction are developed locally.Chang 9 oil layer group primarily developed delta front deposits,underwater distributary channel deposit is the main type of reservoir bodies.The principle type of reservoir rock of Chang 9 oil layer groups is gray fine-grained feldspar sandstone which has low component maturity and low textural maturity.It has been observed that a series of diagenesis have already taken place in the reservoir rock,including compaction,presssolution,cementation,dissolution and cataclasis,which affected the pore development and physical property significantly.Various types of pore formed during the diagenesis,which are characteristic by intergranular dissolution pore and feldspar dissolution pore,the original intergranualr pore takes the second place,and the remaining is a small amount of lithic fragment dissolution pore,intercrystalline dissolution pore,micro pore and micro fracture.The intrusive mercury curve shows that the pore and throat size distribution of Chang 9 oil layer group is not concentrated,which also have poor sorting and small overall throat radius.The average porosity of Chang 9 oil layer group is 8.90%,the average permeability is 0.46×10-3?m2,most parts of the reservoirs areclass ultralow porosity and permeability reservoir.Chang 9 oil deposits are typical lithologic oil deposits,the reservoir distribution is controlled by source rock,sedimentary microfacies,diagenesis and abnormal pressure.The fine quality source rocks in the research area provided a good material basis for the formation of the Chang 9 deposits.The study area in excess pressure low pressure area at the same time,it is favorable to hydrocarbon migration area.Underwater distributary channel sand body distribution pattern and characteristics of the preservation of the primary intergranular pore and secondary pore development is the most fundamental factors that control long 9 oil-gas accumulation.This research area is located in the low pressure area,and is the favorable direction of migration.Distributary channel main sand body and property of high value area is the main oil and gas gathering area.Sedimentary micro facies,sand body thickness,reservoir physical property,oil reservoir thickness and trial production as favorable oil and gas zone classification parameters and predict the favorable zone,Including?has three areas favorable for class,? favorable area,there are two classes,?favorable area,there are two classes,explain the huge potential for development.