Hydrocarbon reservoir development in reef and shoal complexes of the Lower Ordovician carbonate successions in the Tazho
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ORIGINAL PAPER-- EXPLORATION GEOLOGY
Hydrocarbon reservoir development in reef and shoal complexes of the Lower Ordovician carbonate successions in the Tazhong Uplift in central Tarim basin, NW China: constraints from microfacies characteristics and sequence stratigraphy Ngong Roger Ngia1,2,3,4 · Mingyi Hu1,3,4 · Da Gao1,4 Received: 13 January 2020 / Accepted: 12 June 2020 © The Author(s) 2020
Abstract The analyses of hydrocarbon reservoirs in the high-frequency reef and shoal facies of the Lower Ordovician carbonate successions in the Penglaiba Formation (O1P) and Yingshan Formation ( O1–2Y) in the Tazhong (Katake) Uplift in central Tarim basin showed three types of hydrocarbon reservoirs: type 1 associated with synsedimentary facies, type 2 developed by hot active basinal dissolution fluids [mesogenetic fluids, geothermal/hydrothermal fluids and thermochemical sulfate reduction-related fluids] and tectonic activity, and type 3 are hypogenic–epigenetic karst reservoirs formed by meteoric and mesogenetic dissolution fluids. Porosity and permeability development in the reef and shoal facies in the highstand system tracts (HST) of the third-order sequence cycles (SQ1–SQ3) correlates well with regression peaks in O1P and O1–2Y, mostly related to multiphase tectonic activity, long-term exposure, denudation and dissolution in near-surface to shallow burial settings. The carbonate successions in the O 1P and O 1–2Y are composed of seventeen microfacies (MF-1 to MF-17) deposited on a shallow marine platform. Six main groups of microfacies associations (MFA-1 to MFA-6) were recognized, with each microfacies association corresponding to the transgressive system tracts and HST of SQ1–SQ4 in O1P and O 1–2Y. The microfacies represent specific sedimentary environment including platform interior and platform margin deposited under particular hydrodynamic conditions. Tectonics and frequent relative sea-level fluctuation associated with rapid transgression and slow regression favored the deposition of the large-scale vertical stacking, high-frequency reef and shoal facies across the carbonate platforms in this uplift. The hydrocarbon reservoirs in this study have relatively moderate porosity and low permeability, and are somewhat potential reservoirs for hydrocarbon exploration in the Tazhong Uplift. Keywords Microfacies · Tazhong Uplift · Tarim basin · Lower Ordovician · Vug-fractured karstic reservoirs
Introduction * Ngong Roger Ngia [email protected] * Mingyi Hu [email protected] 1
Sedimentary Basin Research Center, Yangtze University, Wuhan 430100, China
2
Department of Geology, University of Buea, P.O. Box 63, Buea, Southwest, Cameroon
3
Hubei Cooperative Innovation Center for Unconventional Oil and Gas, Wuhan 430100, China
4
Key Laboratory of Exploration Technologies for Oil and Gas Resources of the Ministry of Education, Yangtze University, Wuhan 430100, China
The Tarim basin in Northwest China is the largest oil-bearing basin in China (Fig. 1), where a number of oil and gas fields we
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