川东北元坝地区长兴组生物礁白云岩成因机理

上二叠统长兴组白云岩为川东北元坝气田生物礁气藏主要储层岩石类型。长兴组生物礁白云岩储层形成主要由白云石化作用和溶蚀作用影响控制。为了揭示生物礁白云岩成因机理，通过长兴组岩心观察、白云岩岩相学特征分析与地球化学特征分析多方法结合，对白云岩的不同白云石类型及特征进行了深入研究，明确了白云岩储层的白云石化作用类型和期次。长兴组生物礁白云岩储层白云石化类型可划分为4类，主要为同生期高盐度条件蒸发白云石化作用及回流渗透白云石化作用、浅埋藏白云石化作用、早成岩期热液白云石化作用，这3期白云化作用控制了元坝地区长兴组生物礁白云岩储层质量和分布。

Genetic mechanism of reefal dolostones of the Changxing Formation in Yuanba area,northeastern Sichuan Basin

Dolostones of the Upper Permian Changxing Formation are the major reservoir rock type of the bioherm gas pool in Yuanba area,Northeastern Sichuan Basin.The formation of the reefal dolostone reservoir in the Changxing Formation is principally influenced by both dolomitization and dissolution.In order to reveal the genetic mechanism of bioherm dolostone,core observation,petrographic and geochemical analyses were integrated to study different types of dolomites and their characteristics of the Changxing Formation dolostone and determine the types and stages of dolomitization of the dolostone reservoir.Four types of dolomitization were identified,including syngenetic evaporative dolomitization and seepage-reflux dolomitization under high salinity,shallow burial dolomitisation and hydrothermal dolomitization of early diagenesis.The three stages of dolomitization control the quality and distribution of the reefal dolostone reservoirs of the Changxing Formation in Yuanba area.