Influencing Factors of Reservoir Physical Properties of Qianjiang Formation in Qianjiang Salt Lake Depression
The reservoir types of Qianjiang Salt Lake Depression are different from other Eastern Basins.Tak-ing the Paleogene Qianjiang Formation reservoir as the research object,this article analyzes the reservoir prop-erties of a large number of samples,observes thinsection under microscope,and studies diagenesis to define the unique reservoir types and their influencing factors in the Qianjiang Salt Lake Basin combining with ex-ploration practice results.Sandstones,carbonate bearing sandstones and carbonate sandstones are considered as favorable conventional oil and gas reservoirs.Sandstone reservoirs are mainly distributed in sandstone and mudstone facies areas,while carbonatebearing sandstones and carbonate sandstones are mainly distributed in transitional lithofacies areas.And the physical properties of the three types reservoirs are mainly affected by sedimentary microfacies,cementation,dissolution besides compaction..Sedimentary microfacies sandstones such as underwater branching channels,estuarine dams,and sheet sand exhibit medium porosity and good permeability,while carbonate bearing sandstone and carbonate sandstone in the transitional zone are of main-ly low porosity and poor permeability.The development of dolomite,calcite,anhydrite and other cements se-riously damaged the original intergranular pores of sandstone reservoirs,resulting in poor porosity and perme-ability of reservoirs.The organic acids formed during the hydrocarbon generation stage can dissolve early car-bonate cements,forming secondary dissolution pores,and to some extent improving reservoir porosity and permeability.Under this dissolution mechanism,combined with hydrocarbon generation and pressure boost-ing,it is believed that carbonate bearing sandstone and carbonate sandstone have certain reservoir capacity and can serve as effective and subtle oil reservoirs in the study area.
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