Pore distribution characteristics and evolution history of Tertiary sand bodies of different genetic types in Jiyang depression——taking Gudong oilfield,Shengtuo oilfield,and Dongxin oilfield as an examples

On the basis of slices,SEM,X-diffraction and physi- cal properties of sandstones from the sand bodies of Gudong, Shengtuo and Dongxin oilfields,analyses were performed on the pore distribution characteristics of sand body of different epochs,burial depths and diagenetie stages.The results in- dicate that the fluvial facies sand body of earlier epoch,shal- lower burial depth and weak diagenesis history is of the pri- mary porosity oil storage,and the delta sand body reservoir of medium geologic epoch,burial depth and diagenesis histo- ry is of the primary porosity oil storage with the secondary porosity oil storage.The turbidite reservoir of later epoch, deeper burial depth and higher diagenesis history is of the secondary porosity and micropore oil storage.The pore dis- tribution characteristics of different microfacies are of obvi- ous difference.Based on the above understanding,an evolu- tionary pattern of pores in the deep turbitc reservoir is estab- lished:with the increase of the burial depth (geotherm),the pore type evolves from the primary pore,the composite one, to the secondary one,and/or the micropore to the residual one.