| Xinchang gas field is located in the north of Deyang City20km, Sichuan Province. The regional tectonic position of Xinchang gas field in western Sichuan depression is in the Mianzhu-Yanting NEE direction of the central large bulge with being, The Xinshengchang anticline and Fenggu anticline are in the eastern part of this large-scale uplift belt, the west is the Yazihe anticline and Xiaoquan anticline, Zitong syncline developed in the northern part of the large-scale uplift belt, Southern direction developed Pengxian syncline,tectonic background is relatively complex. The Xinchang field structure is a flat nose uplift which located in the Sichuan basin formed in Himalaya period of the Western Xiaoquan uplift-Xinchang uplift-Qing Gangzui uplift combination of the uplift belt,and extends along the north east direction Xiaoquan structure, the formation of the Xinchang structure caused by the control and the role of various factors in the formative years. Encountered problems in the research and development process,Xinchang area Shaximiao gas reservoir JS21and JS23gas vertical composed by2-3stacked sand bodies,the core average porosity is8.99%-9.64%,core average permeability rate is only0.113-0.136×10-3μm2,effective permeability is about0.015×10-3μm2,the gas reservoir is typical of tight gas reservoirs. Facing the two reservoir producing degree of reserves is low, the degree of recovery of only13.75%. The gas reservoirs stable situation is grim.Caused this status quo, in addition to the low porosity and permeability of tight sandstone gas reservoirs unique, complex the low abundance traps causes and other reasons,the relevant work area sedimentary microfacies, reservoir characterization and tight gas reservoirs in the control factors for reservoir analysis relatively The deficiency may be a deeper reason.Therefore,the systematic analysis of sedimentary microfacies and sedimentary microfacies the plane distribution law Xinchang gas field in the process of production and development of tight gas reservoirs focus, has a very important significance.This thesis based on the full collection of seismic,drilling, well logging,mud logging,localization,and work area deposition background and deposition characteristics of the environment,deposition theory guiding the work area destination layers of sedimentary microfaciesprediction research,and summarizes the Xinchang Gas Field Formation gas reservoirs Shaximiao JS21and JS23gas delta system fine sedimentary facies model.The study process of observation of the core11wells,used analysis of routine physical properties of a number of tests of the cast thin section,scanning electron microscopy analysis results that the area of the reservoir rock is mainly fine-medium-grained lithic arkose and in-fine-grained lithic sandstone with high compositional maturity and textural maturity.By observing the core logging data, logging data analysis means,in the calculation of the sandstone thickness sand than the characteristics of the heavy minerals and paleocurrent analysis based on points, combined with typical single well analysis,the the sedimentary microfacies profile contrast as well as the plan of analysisand logging, seismic facies research, comprehensive analysis of the changes and sedimentary facies characteristics and sedimentary evolution of the provenance.On the research results of the Xinchang gas field Shaximiao gas reservoir JS21and JS23gas reservoir sedimentary microfacies:Xinchang gas field Shaximiao generally the case the weak oxidation under the conditions of the arid climate of the delta depositional system. Two provenance in the on Shaximiao group in the study area during the main development, where the main source area north of meters Cangshan, the ancient Longmen Mountains of the western region, although the source material is also provided to the basin, but not much, belongs to a minor provenance. The study area Shaximiao JS21and JS23gas meandering river delta front phase, the development of micro-phase delta front underwater distributary channel, mouth bar, subaqueous distributary bay and underwater Vietnam shore sand sedimentary microfacies, underwater distributary channel microfacies can also be subdivided into the river the themes and river flank two two microfacies which underwater distributary channel microfacies the mouth bar facies sand body development phase with. In many cases, the leading edge of the study area meandering river delta underwater distributary channel deposits and mouth bar deposition stacked composite, which is mainly formed in the delta delta front subaqueous distributary channel advance and continue to migrate to the lake basin. Mouth bar formed in the early Shaximiao been the late underwater distributary channel is not completely scoured formed "dam river" This unique phenomenon.On Shaximiao the deposition early-mid shore line is not in the study area, research area by the northern margin Micangshan-Daba Mountain area overthrusting activities.Western Sichuan Depression original lake basin range gradually reduced, the water is shallow, rapid deposition of sand bodies. The latter part of the main river channel migration to the right, gradually increased hydrodynamic sediment coarse-grained sedimentary entire river system to move to the direction of the basin. The total trend of Sichuan Basin is the period of the North East, southwest low,the ancient water has nearly NS-trending characteristics, but has the characteristics of East West High low in the study area. Multiple source supply makes the development of different regions within the area of inconsistent thickness. The overall performance of delta sedimentary systems to strongly promote basin, Because of the lake area is small, shallow water, the basal growth is relatively stable, with the control of fault on the structure is not found, the delta fast forward, formed a vertical sequence development is not complete, distribution of a wide range of shallow water delta. |
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