Sedimentary Facies And Reservoir Characteristics Of The Middle Permian Qixia Formation, Northern Guizhou

The exploration degree of Qixia formation is low in oil and gas.With the success of well Anye-1 and wells in DaoZhen DaTang,indicated that Qixia formation has certain exploration potential in this area.In this article,used a series of methods by core description and geological profile measurement at wild combined microscopically thin sections,geochemistry,reservoir physical properties and logging data.Made a systemic research on petrological characteristics,sedimentary facies types,source rock characteristics,reservoir characteristics and controlling factors of Qixia formation.The sedimentary facie is open sea platform,and the subfacies transition from the beach to subtidal to depression of Qixian Stage.Sedimentary environment changes From shallow to deep water,from rich oxygen to hypoxia,which sometimes is intermittent.It deposited a set of deep color,fine granularity,high organic matter and local with argillaceous and flint mass or augen.Sedimentary environment changes From shallow to deep water,from rich oxygen to hypoxia,which sometimes is intermittent.It deposited a set of rocks which have deep color,fine granularity,high organic matter and local with argillaceous,flint mass or augen,augen limestone structures.They can be as hydrocarbon source rocks and can be used as reservoir rock formation at the same time.Qixia formation as good source rocks with a characteristic of large thickness,wide distribution,high organic carbon,moderate organic matter maturity,good organic type,show a good hydrocarbon generation ability.The reservoir rock can be divided into two kinds,one kind as a regular porosity rock,another kind is can be used as tight gas in source rock and reservoir of unconventional reservoir rock.The regular porosity rocks are cr?mbs limestone,calcarenite,containing raw cr?mbs micritic limestone,micritic limestone,dolomite,etc,with in diagenesis and tectonic rupture.The unconventional reservoir rocks are carbonaceous shale micrite,carbonaceous shale raw cr?mbs limestone and carbonaceous shale.These two types of rocks are very low density of distributed-infiltration unconventional reservoir rocks,which have the characteristic of relatively dense,well cementation action,nanoscale gap.At the same time,carbonate under the influence of diagenesis and tectonic fracture,solution pores and cracks more development.Because it has the characteristics of good brittleness and dissolution.Integration of source rocks and reservoir can be used as the tight gas in source rock and reservoir of unconventional gas reservoir.The calcite vein in cracks contains a lot of methane inclusions and a small amount of oil inclusions.Qixia formation indicate there have good gas and well exploitable value.Above all,the reservoir type of fracture or fracture-hole.The main control factors of Qixia formation of are sedimentary facies,diagenesis and structural fracture.The sedimentary facies is the material basis for the reservoir formation.The conventional reservoir development in particles of limestone laye which deposition in high energy environment inside the station of shoal subfacies.Unconventional reservoirs are in source rocks which deposition in subtidal with low energy environment.Cementation filling,compaction and pressure solution function are the most important factors to reduce and damage reservoir porosity of Qixia formation.Dissolution and tectonic disruption are favorable factors to form seam-hole reservoir.