Heterogeneity Characterization Of Tight Sandstone Gas Reservoirs,Shan-1 Member,Southeastern Part Of Ordos Basin

Tight sandstone gas has become a key area of unconventional natural gas exploration and development in the world,due to its significant role in energy supply.At present,despite of the the achievements in the exploration and development of tight sandstone gas in China,understanding gas distribution and sweet spot are still difficult due to the strong heterogeneity of the reservoirs.In order to better understand the aforementioned problems,this thesis selected an important gas production layer,the Upper Paleozoic Shan1 Member,southeastern Ordos Basin,as the study focus.The heterogeneity of tight sandstone gas reservoir was characterized to delineate its distribution and predict swet spot.Based on the understanding of the basinal geological background,this thesis comprehensively analyzes the outcrop,core,mud log,well log,thin section,XRD,nuclear magnetic resonance,and mercury injection tests to characterize the tight sandstone gas reservoirs in detail.Rock facies are defined,their well log responses are recognized,and templates are established on the basis of heterogeneous characteristics,classification of reservoir rocks,and understanding of favorable rock type.The established templates are used to identify the rock facies of other exploration wells in the works area without detailed core information.Finally,based on the identified log responses and phased-control modeling concepts,petrel software was used to establish a three-dimensional reservoir rock-phase model using the sequential indication simulation method.Through the aforementioned work,the following conclusions have been obtained.The tight sandstone gas reservoir in the Shan-1 Member of the study area is characterized by strong heterogeneity.According to the sandstone structure,physical properties,and the differences in pore and diagenetic evolution processes,the Shan-1 Member contains plastic lithic poor sandstone,plastic lithic rich sandstone,and carbonate-cemented lithic quartz sandstone.On the basis of the analysis of different sandstone phases,plastic lithic poor sandstone is an effective reservoir rock facies.Principal component analysis can be used to effectively identify rock facies and predict their distribution in different reservoirs.Finally,with the aid of three-dimensional geological modeling methods,the understanding of effective reservoir distribution has been improved.The effective reservoirs are mainly distributed at the longitudinal direction of the Shan-1~1 Member and in the middle portion of the subaqueous distributary channel deposits in the horizontal direction.This study provides an analog for effective tight gas reservoir prediction,exploration and development for other studies,through analyzing the distribution rules,understanding main controlling factors of effective reservoirs,and comprehensively evaluating the characteristics of effective reservoirs.