Research On Rockphysical Modeling Of Tight Clastic Rock Fractured Reservoirs

With the deepening of unconventional oil and gas exploration and development,tight clastic oil and gas reservoirs have become one of the current research hotspots due to their huge reserves and development potential.Tight clastic rock reservoirs have generally experienced deep burial,strong compaction and complex diagenesis in the process of geological evolution.Compared with conventional reservoirs,they have stronger heterogeneity.Fractures can significantly increase the matrix permeability of low-permeability tight reservoirs,provide seepage channels and storage space for oil and gas migration,and are the key to high and stable production of tight clastic reservoirs.Therefore,comprehensive petrophysical analysis,geology,logging,and seismic data are used to predict underground fractures,and to achieve effective description of reservoir fracture characteristics,play a particularly important role in the exploration and development of tight clastic fractured reservoirs.The fractured rock physical model is the link that connects the elastic characteristics of the fractured rock with the fracture parameters,and is an important bridge for the inversion of anisotropic parameters and the description of the fracture characteristics from seismic data.This paper takes the Xujiahe Formation reservoir in the western Sichuan Basin as the main research object.Through detailed research on the rock minerals,pore structure,and reservoir space types of the tight clastic rocks in the study area,based on the development characteristics of fractures,Horizontal fracture development(VTI)hypothesis and vertical fracture development(HTI)hypothesis construct an anisotropic petrophysical equivalent model of tight clastic rock.On this basis,the impact of the changes of different fracture parameters on elastic parameters was analyzed,and accurate estimation of shear wave velocity and quantitative characterization of anisotropy parameters were realized,which provided basic data for the development of fractured reservoir inversion.The paper also constructed a petrophysical template of compact clastic rock that calculates anisotropy parameters from bulk modulus and shear modulus,which is used for quantitative interpretation of fracture density parameters in different directions.Finally,based on the constructed fracture petrophysical model,combined with drilling productivity and other research work area information,a set of classification criteria for tight clastic rock sweet spots based on fracture development characteristics are proposed: a type of sweet reservoir with both horizontal and vertical fractures;vertical The second type of sweet reservoir with well developed fractures and underdeveloped horizontal fractures;the third type of sweet reservoir with well developed horizontal fractures and underdeveloped vertical fractures.The classification standard is applied to the prediction of seismic sweet spots,which realizes the identification of reservoir locations and high-quality sweet spots.The sweet spot classification results are in good agreement with geological logging data.