Pore Evolution Of Wendong Oilfield In Dongpu Depression

At present,the predecessors have conducted a lot of research on the reservoirs in Wendong oilfield.However,there have been few studies on the diagenesis and pore evolution of deep reservoirs in the past work,and the characteristics of pore evolution are mainly qualitative descriptions and lack of quantitative calculations.In order to study the pore evolution characteristics and processes of deep reservoirs in detail,this paper takes the middle section of 3^rdmember Shahejie Formation,Wendong Oilfield,as the research object.Firstly,sedimentary microfacies and sandbody distribution were studied based on regional geological characteristics to analyze the type of diagenesis and the diagenetic stage.Secondly,by analyzing the effective pore composition and characteristics of the reservoir,a model of porosity evolution was established to determine the favorable area of the reservoir.The results of the study indicate that the delta frontal subfacies of the reservoir in the middle section of third member of Wendong reservoir is developed,including underwater distributary channels,estuary dams,and mat sands,etc.In all kinds of diagenesis,compaction,carbonate cementation,secondary enlargement of cementation and metasomatism of quartz,cementation and exchange of hard gypsum are the main reasons for the compactness and low permeability of reservoirs,and the dissolution of particles and carbonate minerals improves the physical properties of the reservoir.The evolution analysis of porosity parameters shows that the initial porosity of the reservoir is 34.71%,the residual inter-particle porosity is 20.65%after compaction,and the porosity decreases by 7.72%after cementation and metasomatism,and the dissolved porosity is 13.93%.The porosity error rate is 0.87%.The main factor affecting the calculation error is the particle sorting coefficient.The reservoir evaluation shows that the type I reservoirs are mainly distributed around the uplift areas and are the main areas for oil and gas exploration and development;the type II reservoirs are widely distributed and are oil and gas potential zone.By carrying out the pore evolution of deep reservoirs,it provides certain theoretical support for finding relatively high-quality reservoirs.