Research On Rock Fabric Characteristics And Logging Evaluation Methods Of Shale Oil And Gas Reservoirs

As unconventional oil and gas exploration advances,mud shale oil and gas are increasingly becoming an important resort in order to augment the reserve and stimulate the output of oil and gas.Mud shale oil and gas,one of the major types of unconventional oil and gas,is expected to become a major alternative energy source in the future.Z sag,one of the zones in Jiyang depression that are most developed in mud shale oil and gas,offers a great value of exploration and exploitation,with several exploratory wells having till now recovered industrial oil stream from Sha-3 lower sub-section mud shale reservoir strata.Mud shale reservoir strata are typically associated with poor properties of matter.The rocks there look simple in type and do not vary much longitudinally;however,the actual situation may be far from this case.Extensive researches have indicated that mud shale is diversified in lithology combination,complicated in structure,and highly heterogeneous in mineral composition,organic matter abundance,and pore type and development degree.Due to complicated Formation Rock fabric characteristics and parameters,the logging response characteristics produced by a mud shale reservoir stratum is not quite manifest,making it hard to classify different strata along the logging profile,which affect substantially subsequent production capacity assessment,reserve calculation,and development way design,etc.So far little study has addressed the rock fabric properties,identification by logging,and Logging-geological comprehensive assessment of mud shale reservoir strata.This paper studies the mud shale strata in Z sag A well Sha-3 lower sub-section and,based on the geology,rock core,logging,slice,electron microscope,and diffraction data,analyzes the characteristics of mud shale reservoir strata,including mineral ingredients,stratum properties of matter,geochemical characteristics,oil-gas possibility,fracturability,and logging attributes of the reservoir strata in the study zone as well as their relationship.Firstly,the analysis integrating lithology,physical property and multiple logging responses helped determine the logging response characteristics in mud shale reservoir strata,which were characterized by low acoustic time(AC),low neutron porosity(CNL),high densit(DEN),and relatively low natural gamma ray(GR).The second.Correlation analysis and multiple regression analysis were then conducted on mineral ingredients,geochemical parameters,properties of matter parameters,degree of saturation,oil-gas possibility parameters,and various logging response data in order to study about sensitive logging response variables and computation methods of these parameters.Thirdly,the characteristics of fractures in response to logging were summarized from rock core properties of matter,lithology analysis,gas log data(during drilling,total hydrocarbon content),and logging curves(natural gamma ray,etc.).Finally,supported by logging response characteristics analysis,rock core data,calibration logging information,and rock-electro parameters analysis,a optimization calculation model was constructed that was adapted to Z sag Sha-3 lower sub-section mud shale reservoir strata and to the geochemical parameters,and associated processing and interpretation modules were developed;the model and the modules can be used to calculate mineral contents(sandy,marly,and clayey minerals,and pyrite),geochemical parameters(TOC,S1,S2,Ro,Tmax&HI,and kerogen),properties of matter parameters(porosity,permeability),degree of saturation,and oil-gas content(Sw,Go).The work done in this article led to the creation of a set of logging assessment methods for mud shale reservoir strata,which are useful for identifying mud shale reservoir strata,stratum parameter calculation,and stratum assessment from the wellbore profile,thereby having positive significance to exploration and exploitation of mud shale oil and gas.