Differential Genetic Mechanism And Property Evaluation Of Tight Sandstone Reservoir Of The Shaximiao Formation In Jinhua Area

The continental tight sandstone reservoirs often experienced complex diagenesis transformations.The interrelationship and differential combination of different diagenesis directly affect the differential evolution of reservoir pores,lead to the complexity and difference of the reservoir genetic evolution process.However,the current research mainly focuses on the influence of single diagenesis on reservoirs,and lacks detailed research on the differential evolution mechanism of different reservoirs,which seriously restricts the distribution prediction of high-quality tight sandstone reservoirs.Therefore,this paper takes the Shaximiao Formation in Jinhua area as the research object,uses thin section identification,scanning electron microscopy(SEM),X-ray diffraction(XRD),Cathodolumines-cence(CL),electron probe analysis,fluid inclusions and isotopic analysis to identify the different types and characteristics of reservoirs,comprehensively analyze the different genetic mechanisms of the reservoirs,and explore the response characteristics of reservoirs under different genetics,so as to provide a basis for tight sandstone reservoir evaluation and high-quality reservoir prediction.The results of this study are:(1)The diagenesis of the Shaximiao Formation sandstone in Jinhua area is mainly compaction,cementation and dissolution,and the authigenic minerals mainly include calcite,laumontite and chlorite.Mainly are primary pores and secondary dissolved pores,the former is slightly higher than the latter;(2)The main controlling factor of the heterogeneity of tight sandstone reservoirs is the diagenetic evolution process,followed by the depositional environment;based on the basic characteristics of the reservoir and the diagenetic relationship in the study area,according to the cementation type,grain contact relationship and primary pore porosity,the reservoir is divided into 5 types;(3)Favorable microfacies determine the material basis for reservoir development,differences in diagenesis types,strengths,and interrelationships lead to differential evolution of reservoir pores,resulting in strong reservoir heterogeneity;(4)In favorable sedimentary microfacies sand bodies of branch channel and underwater distributary channel,moderate compaction-moderately weak cementation-with chlorite coating-strong dissolution,moderate compaction-strong laumontite cementation-with chlorite coating-strong dissolution combination is type I reservoir,which is conducive to high quality Reservoir development;moderate compaction-strong calcite cementation-with chlorite coating-moderate dissolution assemblage is type II reservoir,which is more favorable for reservoir development;The pore space geometry of the combination of strong compaction-weak cementation-achlorite coating-weak dissolution and weak compaction-strong calcite cementation-achlorite coating-weak dissolution combination is destroyed,and it is a type III reservoir,not conducive to high quality reservoir development.