Quantitative Description Of River Sand Bodies And Microfacies Based On Seismic Inversion

Daqing Changyuan Oilfield has experienced many years of development and has now entered the extra-high water cut stage.It is becoming increasingly difficult to tap the remaining oil.The development of the oilfield has put forward higher requirements for the accuracy of reservoir description.The well-seismic combination,as an important method to improve the accuracy of reservoir description in recent years,has gradually developed into an indispensable technology for predicting sand bodies between river channels and assisting oilfield development.The research area is located in the south of an oil field in Changyuan,Daqing.The area of the research area is 5.04km2.The target horizon is the PTH reservoir of the Yaojia Formation,which mainly develops river facies and delta facies.Among them,the PI group includes 18 sedimentary units,which mainly develop delta plain subfacies and delta front subfacies.The study area is affected by factors such as early seismic data collection and imperfect reservoir prediction technology.The accuracy of reservoir description has been low.How to improve the accuracy of reservoir description is a problem that needs to be solved at present.This study used seismic processing and interpretation,seismic inversion,and other methods to quantitatively describe the sand bodies in the river channel in the study area.First of all,due to the existence of unfavorable factors such as noise and errors in the currently available seismic data.Therefore,the application of diffusion filtering directional smoothing technology can suppress the noise interference and improve the parameters and section quality.Secondly,through comparative analysis,the geostatistical method is preferred for predicting sandstone from seismic inversion,and through post-log calibration,it is confirmed that the inversion prediction sandstone has a high coincidence rate,which improves the resolution of the inversion results and comprehensive geology.Explain a more refined purpose.Thirdly,by using inversion-constrained geological modeling method to extract the thickness of the sandstone plane,using the three-dimensional velocity model for time-depth conversion,using seismic interpretation results and well data to establish a structural model,and using the inversion body as a conditional constraint Class and effective sandstone are simulated and the thickness of each unit is extracted to achieve high prediction accuracy of sandstone after extraction.Finally,using the probability trend constraint well-controlled seismic waveform identification and prediction method,through evaluation,the grey correlation coefficient factor,distance factor,and sandstone thickness of the sedimentary facies occurrence probability factor weights were determined to be 0.3,0.2,and 0.5,respectively.The comprehensive evaluation coefficients of a point between the wells and the surrounding 4 adjacent wells are calculated separately.The sedimentary microfacies at this point are the types of sedimentary microfacies of the well with the highest evaluation coefficient.The above method not only realizes the quantitative description of sedimentary microfacies,but also improves the accuracy of river sand description.At the same time,the sand bodies of the 7 sedimentary units in the PI21a~PI33b layer were finely characterized and the sedimentary facies bands were drawn.Utilizing the above technologies,the accuracy of river sand description was improved from 72.9% to 81.1%,an increase of 8.2 percentage points.The application of this result has good guiding significance for oilfield development.