Research On The Characteristics And Evaluation Of Cambrian Reservoirs In Bachu Uplift, Tarim Basin

For a long time in the past,exploration targets in the Bachu uplift of the Tarim basin were mainly focused on the ordovician,and a number of medium and large oil and gas reservoirs were discovered successively.With the shortage of oil and gas resources at home and abroad,people began to pay more attention to the Cambrian system in recent years.At present,several wells in this area have been drilled into the Cambrian dolomite stratum,and good reservoir development can be seen on the core.Different levels of oil and gas show during the drilling process,indicating that the Cambrian dolomite reservoir also has good exploration potential.This paper is based on drilling,logging,well logging,core and various testing and analysis data,and guided by the theories and methods of mineralogy,sedimentary petrology and reservoir geology.The characteristics of the Cambrian dolomite reservoir in the Bachu uplift were studied,analyzed and summarized in detail with the multi-disciplinary and multi-means comprehensive research idea and the previous research results.The evaluation criteria of the carbonate reservoir in this area were formulated and the comprehensive evaluation of the reservoir was carried out.The purpose of this study is to further reveal the development pattern and distribution pattern of the Cambrian dolomite reservoirs in the Bachu uplift and to provide some reference for the exploration of Cambrian oil and gas in this area.The results show that the Cambrian dolomite in the Bachu uplift can be divided into five types:crystal dolomite,grain dolomite,micrite dolomite,carneule dolomite and transitional dolomite,the crystal dolomite can be classified into silty crystal dolomite,fine crystal dolomite,medium-coarse crystal dolomite and unequal crystal dolomite.In the lower,middle and upper Cambrian formations of Bachu uplift,Wusonggeer formation and Xiaoerbulake formation of lower Cambrian have relatively good physical properties,high porosity and permeability,and good pore connectivity.Secondly,the upper Cambrian lower Qulitage formation,the middle Cambrian Awatage formation and Shayilike formation have relatively poor reservoir properties.Various types of reservoir space combination,including intercrystal pore/intergranular dissolved pore and intragranular solution pores,intergranular dissolved pore and intracrystal solution pores,solution pores and cracks.Among them,the solution pores and cracks are Bachu uplift of Cambrian dolomite reservoir main reservoir space types.According to the conventional and imaging logging data analysis,the Cambrian reservoir in this area can be divided into solution pores,cracks and the crack and cavity composite reservoirs such as three types.The Cambrian dolomite reservoirs in this area have experienced various diagenetic processes such as micritization,compaction solution,cementation,dolomitization,dissolution,transitional dolomitization,recrystallization,silicification,filling,dolomitization and fracture.Dolomitization,dissolution and fracture play constructive roles in reservoir development.According to previous classification of carbonate reservoir levels and combined with well logging interpretation and test analysis results of reservoir,the evaluation criteria of Cambrian reservoir in the study area were established,and the Cambrian dolomite reservoir in the Bachu uplift was divided into non-fractured reservoir and fractured reservoir.Appropriate logging data and mathematical geological method are selected to further subdivide and evaluate these two types of reservoirs.The high quality reservoirs in the Bachu uplift are mainly developed in the upper part of the lower Cambrian Xiaoerbulake group and the upper Cambrian Xiaqulitage group.The Reservoir types are mainly ? reservoir,? class of reservoir optimal reservoir levels,least? kind of reservoir.