Development pattern and reservoir-formation mechanism of reef-bank complex in Late Ordovician Lianglitage Formation, Tazhong area, Tarim Basin, China

Abstract

Present study consists the development pattern of reef-bank complex and its reservoir formation mechanism. The earliest Ordovician coral-stromatoporoids reef-building organisms are found in Lianglitage Formation, which fills the blank of Late Ordovician organic reef in China. Type of sedimentary microfacies, combination form and scale differentiation of reef-bank complex in Lianglitage Formation are controlled by high-frequency sea-level change and multi-stage tectonic evolution. In vertical direction, four or five periods of reef-back motivated inside out of platform margin of Lianglitage Formation. Besides that, reef-bank complex is linear and clumped distributed along Tazhong NO.1 fault belt on horizontal direction. High-energy reef-bank in platform margin controlled distribution of favourable reservoir lithofacies. Karstification in syngenetic-supergene stage is the key factor for the development of high-quality vuggy reservoir. Hercynian deep fluid that migrating along the faults, fractures and previous vuggy layers greatly improve the reservoir property of reef-bank carbonates during the buried process.