Potential Tapping Evaluation Of Penglaizhen Formation Gas Reservoir Xindu Gasfield

Xindu gas field is located in the eastern slope of the Western Sichuan depression,Pengxian Deyang Syncline in the West and northwest,and Luodai damianpu nose like structural belt in the southeast.After years of exploration and development,it has entered the stage of low pressure and low production.Affected by the early geological understanding,some potential areas are classified as difficult to produce reserves.Through further evaluation of geological potential,the use of old wells to tap the potential can effectively improve the development effect of the gas field.So it is necessary to develop the evaluation of gas reservoir.Guided by the new theories of sedimentary reservoir geology,development geology and gas reservoir description,this paper selects Penglaizhen Formation gas reservoir in Xindu gas field as the main research object.On the basis of previous studies,through core observation,thin section identification,and analysis of drilling data,well logging data and logging data in recent years,this paper has carried out small layer correlation division and sand body distribution research on characterization and reservoir characteristics description.On this basis,combined with the preliminary test and gas reservoir dynamic development data,the potential tapping target area and potential tapping well are optimized to carry out potential tapping operation.The following three understandings have been made:（1）Through the comparison of marker bed+formation lithology thickness,it is found that:The boundary between the top of Penglaizhen Formation and the lower Cretaceous is mainly a set of thick fine-grained lithic sandstone at the bottom of Cretaceous system,which is in parallel unconformity contact with the mudstone at the top of Penglaizhen formation,well logging curve shows that GR curve changes from low value block to high value tooth,and RD and RS curves change from high value cone to low value tooth.A set of light grey fine-grained lithic sandstone at the bottom of Penglaizhen formation is distinguished from the brown grey fine sandstone at the upper part of Suining Formation.Penglaizhen formation can be divided into J₃p_1-J₃p₄ layers from bottom to top according to Jingfuyuan shale,Lishuwan shale,Cangshan shale and dark mudstone of similar color as the marker layer.According to the principle of similar logging curve shape and lithologic thickness,Penglaizhen formation is further divided into 19 sublayers.To sum up,the skeleton section is established for horizontal comparison.（2）The reservoir lithology of Penglaizhen Formation gas reservoir of Xindu gas field is mainly light brown grey,light green grey medium fine grained lithic quartz sandstone,lithic sandstone and feldspathic quartz sandstone,the main reservoir spaces are:（1）residual intergranular pores;（2）intergranular corrosion pores;（3）intragranular corrosion pores;mold pores and fractures.The combination type of pore throat is mainly mesopore-small throat,followed by micropore-micro throat,in addition,there are a few macropores-microlarynx+micropores–microlarynx.The porosity of the reservoir is between 1.45%～18.43%,with an average of 10.13%;the permeability is between 0.010～16.43×10^-3μm²,with an average of 0.694×10^-3μm².Reservoir porosity and permeability have a good correlation,and it is a porous reservoir.（3）Based on the analysis of the characteristics of logging parameters and the development dynamic data of the research area,the criteria for selecting wells and evaluating layers in the potential target area are established:the energy storage coefficient shall be higher than 0.3,the daily production of potential well shall be lower than 0.1×10³m³,the weight value of comprehensive geological evaluation index shall be higher than 6.9,the thickness of reservoir interpreted by logging shall be≥5m,GR value shall be≤85API,acvalue shall be≥65us/ft,CNL value shall be≤19%,DEN value shall be≤2.5g/cm³,RD value shall be≥12ΩM.According to this standard,10 potential exploration target areas and 15 potential exploration wells such as chuandu 620-dusui 1 well area are selected.