Diagenetic Evolution Of Deep High-quality Reservoirs And Geological Prediction Technology: An Example From Xihu Sag,East China Sea Shelf Basin

Hydrocarbon exploration has been increasingly concentrated in deep(3500?4500m)and ultra-deep(>4500m)tight sandstone reservoirs(DUDTSR)for its large quantities.DUDTSR are always heavily cemented,while high quality reservoirs(“sweet spots”)have large numbers of pores created by dissolution and/or dolomitization.Thus,one of the major challenges for characterization of DUDTSR are to understand the distribution of diagenesis,associated products and controlling factors responsible for determining the quality and overall heterogeneity of the reservoirs.This study takes the Paleogene Huagang(E₃H)Formation in Xihu Sag,East China Sea Shelf Basin as an example to study the diagenetic evolution of middle deep and deep ultra deep reservoirs.Through comprehensive core analysis and diagenetic physical simulation,1)the control factors of reservoirs development under different burial depths were identified,2)the differential genesis of DUDTSR was revealed,3)the geological theory of DUDTSR was deepened,4)the geological model and computer algorithm of the diagenetic processes were constructed,and software was written to numerically simulate diagenetic evolution;5)finally,based on the specific geological conditions of the E₃H Formation,a prototype geological model was established to reproduce its diageneitic processes and predict the distribution of the high quality reservoirs in Xihu Sag.