Comprehensive Evaluation Of The Chang 6 Reservior Characteristics In Yanhewan Area,Ansai Oilfield

Although some oil production points have been discovered,there still has no significant progress in Yanhewan area of Ansai Oilfield.For the Chang 6 reservoir,the systematic understanding has not been formed,the resources for reservoir increase have not been implemented and the favorable direction for oil production is unclear.Gudied by the geological theory and the comprehensive analysis methods,combined with previous understandings and on the basis of the existing yeild data,By means of core,thin section and mercury injection test analysis method,the characteristics of Chang 6 reservoir are comprehensively evaluated.Then,the favorable areas for production are predicted in order to scientifically guide the futher production and construction for Ansai Oilfield.The following are the main conclusions.1.The Chang 6 formation in the Yanhewan area is a delta front subfacies,and its underwater distributary channels can be subdivided intosuperimposed channels and single channels.The sand body in Chang 6₁^1-2,Chang 6₁²,Chang 6₃¹and Chang 6₃² layer is thick and widely spread.2.The Chang 6 formation in the Yanhewan area mainly consists of medium and fine grained feldspar sandstone and lithic feldspar sandstone,which have good sorting and subangular grains.Residual intergranular pores are widely developed,followed by secondary are the dissolution pores of zeolite,feldspar and lithic debris.3.The Chang 6 reservoir in the Yanhewan area can be divided into two types,which are destructive and constructive diagenetic facies.The feldspar dissolution diagenetic facies is the most widespread in this area,then followed by chlorite thin film cementation and intergranular pore diagenetic facies.The sandstone in Chang 6 reservoir belongs to the Asubstage of the middle diagenesis stage.4.The evalution standard of Chang 6 reservoir in the study area is established and comprehensive evaluation are carried out.Underwater distributary superposed channel microfacies and chlorite thin film cementation and intergranular pore diagenetic facies are the best sedimentary and diagenetic facies.The macroscopic and microscopic factors of oil production are the difference between sedimentary microfacies and diagenetic facies and heterogeneous reservoir characteristics.5.The favorable plays of Chang 6 formation are selected.Among those areas,the 6₁^1-2layer is the best for its big area.