The Petrology Characteristics, Sedimentology And Reservoir Analysis Of Cambrian-ordovician Siliceous Rocks In Kalpin Fault-uplift

This thesis researched on siliceous rocks in Yuertusi Formation in Cambrian andPenglaiba Formation in Ordovician in Kalpin fault-uplift, Tarim Basin. It focused onthe field classification and combination character of the siliceous rocks, as well as thetexture, structure and the relationships of the siliceous rocks under the microscope;based on petrography, the silicite of Yuertusi Formation is formed in quiet water, whilethe silicate of Penglaiba Formation is the replacement of carbonate rocks by rich Sihydrothermal fluids; the major element, trace element, rare-earth element and isotopegeochemistry characters are studied in detail, the sedimentary environment and causalanalysis of the two types are discussed, and the application of the siliceous rocks inpetroleum exploration and production is summarized. This paper has given below mainfruits:The siliceous rocks in Cambrian-Ordovician in Kalpin are located in the bottom ofYuertusi Formation and Penglaiba Formation. In the profiles, the silicite coexistingwith black shales in Yuertusi Formation with Laminar structures, sponge spicules withastatic alignment, and fauna such as Foraminifera, Brachiopoda and testa wereobserved under polarized-light microscopy. The silicite interbedded with carbonaterock in Penglaiba Formation, with a sharp margin from the neighbor, and acceded to thecolor and granulated texture of the protolith, which is consisted of residualpsammosilicite. It showed the characteristics of different shape and different size ofcryptocrystalline quartz, chalcedony, microcrystal quartz and giant crystal quartzclearly under polarized-light microscopy. The siliceous rocks in Kalpin are hydrothermal silicite formed by metasomatism,with the characteristics of the thermal water in the diagram of Al/(Al+Fe+Mn)-Al/Fe,the sedimentary deposit by thermal spring limits in the diagram of [(Cu+Ni+Co)×10]-Fe-Mn, and obviously Ce negative anomalies, enrichment in LREE, depleted inHREE, right inclination of the REE distribution curves, δEu normal anomalies, δ30Siranging from1.1‰-2.9‰, δ18O ranging from15.6‰-21.9‰. The depositional silicatein Xiaoerbulak are affected by the hydrothermal activities and the environment offormation is the edge of continental, faring from ocean basin.The siliceous rocks in this region have very significant for the oil and gasexploration on the Cambrian-Ordovician sedimentary rocks. The anoxygenousenvironment from great Si-rich hydrothermal fluids is beneficial to bury and preserveorganic matter. Meanwhile, Si-rich fluids can make carbonate rock corroded andimprove the ability of the carbonate reservoir. So, a modest silicification in thefavorable positions not only can improve the carbonate reservoir, but also can form thefractured or hydrothermal reservoir, according to the brittle character of siliceous rocksand subsequent tectonic movement.