川东北地区长兴组生物礁成礁类型及分布

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

目前在川东北地区发现了龙岗、普光、黄龙、五百梯等多个生物礁气藏,它们具有储层较厚、面积较大、储量丰度高等特点,展示出了广阔的滚动勘探开发前景。本文根据野外露头与钻井资料,结合前人研究成果,通过对生物礁的造礁生物古生态特征研究,按照生物礁所处的古地理位置、礁体的形态和礁岩的特征,归纳总结出川东北地区长兴组生物礁主要分为台地边缘礁和台内点礁,其特征差异明显。台地边缘礁主要表现为规模较大,礁组合相带完整,礁体旋回较少,水体能量强,其分布受古地理位置、古地貌环境控制,主要沿海槽两侧呈串珠状分布;台内点礁主要表现为规模较小,水体能量较弱,造礁生物个体较小,无礁前礁后沉积,礁体旋回较多,发育有凝块石,主要发育在长兴组中下部,分布规律性不强,主要受古地貌影响,沿台内局部高地随机分布。

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.