Diagenesis And Pore Evolution Of The Carbonate Rocks Of The Kalatar Formation In The Kekeya Paleogene

Kalataer Formation of Kekeya area is selected as the research object in this paper,based on sedimentary petrology,carbonate sediments,carbonate reservoir geology,carbonate rock diagenesis and other disciplines,comprehensively using thin section identification,cathodoluminescence,electron microprobe,scanning electron microscopy and other technical means,research the characteristics of the carbonate rocks,sedimentary facies,reservoir physical property,diagenetic environment and diagenesis of the study area.Furtherly,rock and sedimentary facies types are classified,diagenetic types are identified,diagenetic environment and sequence are divided and pore evolution model is established.Kalataer Formation in the study area is divided into lower limestone sections,dolanite sections and upper limestone sections;The rock types is various and can be divided into limestone,dolomite,limestone and dolomite transitional rock,clastic rock and carbonate transition and gypsum,and on this basis subdivided into 8 subclasses of particle limestone,mudstone limestone,granular dolomite,calcitic dolomite,dolomite limestone,terrestrial carbonate rocks,carbonate rock fine sandstone,mudstone,gypsum;and the main types are limestone and dolomite.The sedimentary facies type is the restricted platform facies and can be further divided into four subfacies types:granule beach,tidal flat,lagoon and confined bay.The reservoir space is dominated by secondary pores and fractures,and the primary pores are rare.The main type of secondary pores are intergranular pores,intercrystalline hole and intragranular dissolved pore;The physical properties are of the low porosity and low permeability,and porosity correlation is not good.Physical property becomes better,only in the 5th and 7th small layer of dolomite section,and physical property of lower limestone section is better than that of upper limestone section.Diagenesis in Kalataer Formatin including mud crystallization,compaction,pressure dissolving,calcite cementation,dolomitization,recrystallization,rupture,and dissolution.The diagenesis shows different characteristics in different diagenetic stage and diagenetic environments.It is found that the study area has experienced seabed diagenetic environment,atmospheric diagenetic environment and buried diagenetic environment.In the early-middle burial stage,the compaction and cementation of the overlying strata rapidly accumulated and furherly reduce the porosity.Dissolution in condition of tectonic activity and hydrocarbon injection in deep burial stage is principle factor of effective reservoir which is dominated by fractured reservoir and fracture-cavern reservior.