Sichuan Basin In Central And Western Upper Triassic Reservoir Diagenesis

Based of the theory and method of sedimentology and diagensis of reservoir,and guided by the geology of reservoir,after referring and reading many references, combinated the field data and indoor analysis and test result and outcrops observation and measure,studied the diagensis character of Xujiahe Formation in Upper Triassic in central-west of Sichuan,discussed the main type and character and effect on the reservoir. Then set up the model of the form and evolvement of raservoir,divided the diagenetic facies,studied the regulartion of distribution and the relation to reservoir.Finally,on the foundation of make clear the controlling factors on development of reservoir,forecast the avail area for reservoir upgrowth.According to manoeuvre-research and exploration of the research section, the regularities of distribution and the characteristic of sedimentary facies unfolding are concluding in the research about the strata sedimentary characteristic. Basically,the sediment of second to sixth numbers of Xujiahe Formation are continental deposit,and could be dividde into alluvial fan,fan-delta,delta and lakes facies.The second formation give priority to delta front intrafacies,the fourth and sixth formation abroadly distribute delta plain intrafacies.In central-west of Sichuan, the lithology of Xujiahe Formation reservoir is mainly on feldspathic litharenite and lithic sandstone,and a small quantity of lithic quartz sandstone and arkose quartzite and quartz sandstone with high textural maturity and low compositional maturity. The physical property of reservoir is bad because it is low-porosity,low-permeability and special low-porosity,special low-permeability. The pore of reservoir are intergranular pore, intragranular pore,basis pore and fracture, and most of them are intergranular pore and intragranular pore.The throat of reservoir are neck throat, lamellar throat and bundled tubes throat,and most are lamellar throat. The pore configuration of reservoir is less as a whole.The diagenesis of Xujiahe reservoir is complicated. Compaction, pressure solution and cementation of siliceous and carbonate reduce pore, dissolution and tectonic disruption increase pore.Diagenetic stage of Xujiahe Formation reservoir presently is at late diagenesis A to B substage,part area is on expidiagensis' effect.Because the form and evolvement of reservoir are controlled by diagensis in the mass, the diagenetic facies are named by the diagensis according to the diagenetic environment.After lots of core observation and thin section analysis, combining the result of scanning electron microscope,x-ray diffraction and cathodeluminescence, we divided the diagenetic facies of Xujiahe reservoir into strong-compacted facies in shallow-burial,calcitic cementing in shallow to middle-burial, chlorite cementing in middle-burial,silicic cementing in middle to deep-burial,dissolution in deep-burial and kaolinite cementing near-surface. The best reservoir physical property is chlorite cementing facies, better are dissolution and kaolinite cementing facies, the worse are silicic cementing facies, calcitic cementing facies and the strong-compacted facies. The plane unfolding rule of diagenetic facies of the main reservoir members is researched, and, and the "four history" evolutionary mode of reservoir is educed for the first time.The physical property of reservoir is multiple influenced by originality component of sediment,deposition, diagensis and tectonism. According to deposition, diagenesis and tectonism and combining the log quantitative interpretation and core physical property analysis, the regularities of distribution of reservoir of each members is reliably forecasted. From basin brim to center, the reservoir physical property has improving tendency, the best area is center and intermediate belt, there should give priority to finding pore gas reservoir, and should look for fracture and pore reservoir in basin brim area.