Influencing Factors And Evaluation Of Reservoir And Seepage Capacity Of Chang 7 Tight Reservoir In Ordos Basin

Carrying out research on influencing factors and comprehensive evaluation of tight reservoir accumulation and seepage capacity has great significance for sweet reservoir selection,oil and gas development,and resource potential evaluation of tight reservoirs.Therefore,based on data analysis,core observation,experimental testing,theoretical analysis,and model establishment,based on the study of the sedimentary microfacies of the Chang 7 tight reservoir in the Gucheng area,the petrological characteristics,physical properties,and pore structure characteristics,In this way,the influencing factors of tight reservoir accumulation and seepage ability were further clarified,the reservoir evaluation parameters were optimized,and finally a comprehensive evaluation model of tight reservoir was established.The study shows that the depositional environment of the Chang 7 tight reservoir in Gucheng area are semi-deep lake and deep lake reducing environment,and gravity flow deposition is widely developed;the average porosity of the reservoir is 8.9%,and the average permeability is 0.029 m D,which is a typical tight reservoir.Reservoir storage capacity is affected by a variety of factors.In terms of sedimentation,gravity flow channels and turbidite microfacies have the best storage capacity.Overflow sediments and turbidite mat sand microfacies have poor storage capacity and mud microfacies are the worst.Rigid particles increase the rock's compaction resistance,which reduces the impact of compaction on storage capacity.As for diagenesis,compaction and cementation significantly reduced the storage capacity of the reservoir,reducing the average pores by19.70% and 12.68%,respectively.Dissolution is vital to improve the storage capacity of the reservoir,with an average pore increase of 8.63%,which generates plenty of space for oil and gas charging.The seepage ability is mainly affected by the structure of the pore throat.The larger the average throat radius,the stronger the seepage ability.Among them,the pore throat in the range of 0.1 to 0.5?m contributes the most to the permeability,with an average of 69.6%.Clay minerals also affect the seepage,which attached on the surface of the pore throat,so that the radius of the pore throat is reduced or even the pore throat is blocked,resulting in poor connectivity of the pore throat,and reducing the fluid seepage ability.Based on the analysis of the factors affecting the reservoir accumulation and seepage ability,and selecting the parameters,a comprehensive evaluation model of tight reservoir accumulation and seepage ability is finally established,and the tight reservoir is classified into three types.From Type I to Type III,the reservoir's storage and seepage capacity gradually weakened,and oiliness gradually decreased.Among them,Type I reservoirs have a small distribution area,high development value,Type II reservoirs have a large distribution area,and the reservoir quality is slightly worse.Type III reservoirs have no exploration and development value.