磨溪气田嘉二段陆表海型台地内沉积微相研究

结合四川盆地下三叠统嘉陵江组区域地质背景资料,对磨溪嘉二段的岩石类型组合、沉积构造、沉积韵律、古气候及成岩演化等沉积相标志的详细分析表明,嘉二段并非普遍发育潮坪环境,而是属于陆表海型碳酸盐岩局限—蒸发海台地相沉积,并可进一步划分为台坪、粒屑滩、滩间海、局限泻湖、蒸发泻湖5种亚相及20余种微相,类潮坪相仅出现在嘉二~2B层沉积期。对重点层段沉积微相平面展布特征的研究表明,嘉二沉积期沉积微相演化受沉积古地貌特征、古气候及相对海平面变化共同控制,纵向上沉积微相展布具有一定的继承性。建立了适合本区嘉二段颗粒岩和粉晶云岩沉积时期的陆表海碳酸盐岩台地相的沉积演化模式。

Research on sedimentary microfacies of the epicontinental sea platform of Jia 2 Member in Moxi Gas Field

Based on the geologic background of Jia 2 Member in Jialingjiang Formation of the lower Triassic in Sichuan Basin, the lithology, sedimentary structures, sedimentary rhyme, palaeoclimate and diagenetic evolution were analyzed. It is indicated that the tidal flat facies are not broadly developed in Jia 2 Member of Moxi Gas Field. Jia 2 Member was restricted to the evaporate epicontinental sea carbonate platform deposits. The sedimentary facies in Jia 2 Member of Moxi Gas Field mainly include five sub-facies of platform flat, grain shoal, inter-bank sea, restricted lagoon and evaporate lagoon. The five sub-facies were divided into over 20 microfacies. The depositional characteristics of similar tidal-flat environment existed only in Jia 2 Member B bed. The analysis on the sedimentary microfacies distribution of the key formations shows that the sedimentary environment evolution is subject to palaeogeog- raphy characteristic, relative sea-level and palaeoclimate, and the sedimentary microfacies distribution characteristics are inheritable vertically. The sedimentary evolution model was given which was suitable for the epicontinental sea carbonate platform facies in the deposition of grained stone and dolomite rock of Jia 2 Member.