Characteristics Of The Dolomite Buried Hill Reservoir Of The Ordovician,penglaiba Formation,in Southwest Of Tarim Basin

The paper takes the dolomite buried hill reservoir of Ordovician,Penglaiba Formation as the research object,which is in the southwest of Tarim Basin.In order to solve the main controlling factors of the formation of dolomite reservoirs and the unclear relationship between the different factors,the horizontal development law and the vertical evolution characteristics are not clear,the paper plan to through the core observation,thin section identification,combined with physical property analysis and log analysis,the stratigraphic and petrology characteristics,sedimentary types of the O_1p,the type of reservoir space,the physical properties of the reservoir and the diagenesis of reservoir are studied.And combined with the karst outcrops of the Aguoyi in the Aheqi area of Xinjiang,the karst zone characteristics and reservoir development factors in this area were compared and analyzed.Conclusions are drawn according to the research:1.The total thickness of the O_1p is about 450m,which has a slight thinning from west to east;2.The Penglaiba Formation in the study area is in a carbonate gentle slope sedimentary environment,with granular beaches and beach interact sea facies;3.The reservoir rock type is dominated by sand-gravel cloud rocks,which develop a variety of reservoir spaces,including induced pores,dissolution pores and fractures,where the dissolution pores are most developed,and the reservoir porosity is between 0.1%and 6.3%,the permeability is between 0.1m D and 5m D.Physical properties are characterized by low porosity and permeability in general,medium porosity and medium permeability in partial intervals,and strong reservoir heterogeneity.4.The reservoir of O_1p has undergone compaction,pressure-solution,cementation,filling,dolomitization and karstification,etc.,and the karstification has the greatest impact on reservoir physical properties;5.By comparing and analysing the karst outcrop of the reservoir,the karst reservoirs in southwest of the Tarim Basin can be divided into vertical seepage zone,horizontal subsurface flow zone and deep slow-flow zone;6.The study shows that the reservoir in the study area is mainly influenced by diagenesis and tectonic movement,wherein the strong karstification has formed a large number of dissolution holes in the study area,which greatly improves the reservoir property,and the tectonic movement forms a large number of fractures to provide channels for karstification.Based on the well-seismic data and the reservoir model of the outcrop area,the geological model of the buffered dolomite buried hill reservoir in the O_1p of the study area was comprehensively analyzed and established.