The Characteristic Of Pore Texture And Diagenesis Of Chang8₁ In The South Of Baima Region Of Xifeng Oil Field

Applied with Polarizing microscope, cathodoluminescence, Scanning Electron Microscope and other analytic techniques, combining with geophysical logging, the reservoir petrology, pore texture, reservoir digenesis and influences on reservoir of Chang 81, Yanchang Formation of the Triassic period in the south of Baima in XiFeng oil- field are studied.Braided delter front is the main subfacies of Chang8₁ in study area and the reservoir sandstone is fine-medium grained arkose and felspathic lithoclast sandstone. The main constituents of Clastic are feldspar, quartz and lithoclast and diagenetic authigenic mineral are chlorite, silicon and ferreous calcspar.The dominant diagenesis types in the area are compaction, cementation, replacement and dissolution. Based on the data of reservoir micro-study and fluid inclusion homogenization temperature testing, Consulting the division standard of diagenesis phase, all the formations have entered A period of late diagenesis, digenesis sequence,pore revolutionoil and gas filling time are ascertained. All sorts of digenesis influences on reservoir are discussed. and the secondary dissolution pores are important to form good reservoir in this period.Pore can be classified with original and secondary pore,besides, pore assembling can be sorted 4 types such as pore, compact,in which fissure-pore type is developed well, capability of reservoir is good. Pore texture are studied by parameter of mercury capillary pressure curves, and the curve can be classified three types.Calcite and mica of cement have negative relativity according to porosity and permeability, whereas chlorite has Positive relativity according to porosity ,and negative permeability according to permeability, Chlorite diagenetic facres are better developed in Chang 8₁²¹ and Chang 8₁²² by diagenetic facres statistical analysis.Therefore,Chang 8₁²¹ and Chang 8₁²² are favorable reservoir.According to the lithology, reservoir characteristics, pore texture, diagenesis in the south of Baima, but the variety of permeability are mainly considered,and looking the evaluation of low- pore and low- permeability reservoir in study area as evaluation target, The sandy reservoir can be classified three types,and the reservoir of individual group are sorted by the standard.