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Title: Characteristics of penecontemporaneous diagenesis in sequence and its control over pore distribution — A case study of reef-bank sediments of upper Ordovician in Tazhong area, Tarim basin, China
Authors: Zheng, J
Wang, Z Y
Liu, Z G
Zhang, Y W
Li, B
Keywords: ln(Th/U) curve;Parasequences;Penecontemporaneous diagenesis;Selective dissolved pores;Tazhong area Upper Ordovician
Issue Date: Dec-2020
Publisher: NISCAIR-CSIR, India
Abstract: Penecontemporaneous diagenesis of different lithologies in sequence has an uncertain correlation with pore distribution inside the reef-bank reservoir. The article divides the Lianglitage Formation into 3 third-order sequences, 5 parasequence sets, and 25 parasequences through the characteristics of ln(Th/U) ratio curve and sedimentary cycles, where the parasequence thickness has an obvious correlation with sedimentary facies. The rock, mineralogical and geochemical characteristics inside the multiple reef-bank sediments show that the penecontemporaneous diagenesis and eogenetic seawater cementation are widely developed in it. Atmospheric diagenetic lens, formed by penecontemporaneous diagenesis, are concentrated on the top of descending cycles of subsequence, and rich selective dissolved pores therein can contribute 3 to 6 % porosity to the reef-bank reservoir and also provide places and channels for the reconstruction of alien fluids and tectonic movement in the late burial. The early dissolved pores formed by the penecontemporaneous diagenesis are the main reservoir spaces and can also provide the prerequisites for the later diagenesis reconstruction, so the penecontemporaneous diagenesis is the basic reason for the development of high quality reef-bank reservoir. The high-porosity sections are concentrated on the top of the atmospheric diagenetic lens, revealing that the formation and distribution of selective dissolved pores are controlled by the descending cycles of parasequences. The comprehensive analysis indicates that the favorable development zones of selective dissolved pore as lens shape or belt shape are discontinuously distributed inside the high energy facies belt of the platform marginal facies, which are formed under the control of steep fault.
Page(s): 1819-1830
ISSN: 2582-6727 (Online); 2582-6506 (Print)
Appears in Collections:IJMS Vol.49(12) [December 2020]

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