Classifying tight sandstone gas reservoirs,Shengbei depression,Tuha Basin
Gas reservoirs of the Middle Jurassic Sanjianfang Formation in Shengbei depression are characterized by dense lithology,low porosity and permeability,complex pore structure,strong vertical heterogeneity,and simultaneous oil,gas and water production.All these characteristics make reservoir classification challenging.An appropriate classification method is required to support the optimization of sweet spots in horizontal wells.So,reservoir properties were investigated through rock physics experiments.And the porosity,permeability,median grain size,displacement pressure,NMR T2 geometric mean,resistivity,and acoustic time were selected for this classification by using K-means clustering.Results show that(ⅰ)Sanjianfang reservoir rocks have moderate maturity,whose pore space is filled with clay and carbonate minerals.The reservoirs become tight due to strong compaction,with deteriorated pore structure;(ⅱ)the hydrocarbon potential in Sanjianfang gas reservoirs is controlled by lithology,physical properties,pore structure and heterogeneity.Based on the clustering analysis with parameters of median grain size,porosity,permeability,maximum pore-throat ra-dius,displacement pressure,median pressure and resistivity,the reservoirs can be classified into Ⅰ,Ⅱ and Ⅲ types;(ⅲ)type Ⅰ,as qual-ity reservoirs,is composed of medium to coarse sandstone,and exhibits good sorting,low displacement pressure and median pressure,high interval transit time and NMR T2 geometric mean,and good pore structure;and(ⅳ)Sanjianfang reservoirs present continuous extension laterally but strong heterogeneity in vertical.They belong to type Ⅱ for the most part,and type I locally.Certain zones de-veloped with type I reservoirs can be efficiently exploited by volume fracturing in horizontal wells.
Tight sandstoneClustering analysisReservoir classification and evaluationT2 geometric meanShengbei depression
万方数据
维普
