Reef-forming types and distribution of organic reefs in Changxing Formation of northeastern Sichuan area

Abstract：Organic reefs gas reservoirs such as Longgang, Puguang, Huanglong and Wubaiti were found in northeastern Sichuan area. They are characterized by thick reservoirs，larger areas and abundant reserves, thus suggesting wide exploration and development prospects. In northeastern Sichuan, reefs are mainly divided into platform marginal reef and point reef in platform, with obvious different characteristics. The platform marginal reef is characterized by large scale, intact facies belt of reef combination, strong water energy, control by paleogeographic location and paleogeomorphic environment, and cluster distribution mainly on both sides of the oceanic trough. In contrast, the point reef in platform is characterized by small scale, weak water energy, smaller reef-forming organism individual, no deposition of reef front or reef back, more cycles of the reef body, development of thrombolite, insignificant distribution regularity, control by paleogeomorphogy, and random distribution along local highland in the platform.