蜀南地区茅口组断溶模式及储层地震预测

Fault-karst model and prediction based on seismic data of Maokou Formation in southern Sichuan Basin

四川盆地蜀南地区茅口组向斜—斜坡带是重要的勘探开发领域,优质储层对天然气富集具有控制作用,其分布主要受台内滩亚相颗粒灰岩后期岩溶改造程度的影响,沿断层发生的岩溶作用起着非常重要的控制作用。为了明确断裂控制的岩溶储层发育模式及地震反射特征,根据录井、测井、地震等资料综合分析,建立由两类岩溶带组成的茅口组断溶体系:①顺断层岩溶带,受断层伴生裂缝发育程度控制,主要在断面附近块状发育,厚度较大,表现为顶部相对弱波峰、底部较强波峰、内部杂乱或空白的反射特征;②顺地层岩溶带,受断层附近颗粒滩展布范围控制,距离断层较远,层状发育,单层厚度较小,表现为顶部较强波谷、底部较强波峰的“亮点”反射特征。

The Maokou Formation in syncline and slope areas in the southern Sichuan Basin are important fields for exploration and development.The highquality reservoirs can control the enrichment of natural gas,and their distributions are mainly affected by the late karst transformation degree of grainstones deposited in intra-platform shoal subfacies.In addition,karstification that occurs along faults plays an important controlling role.In order to clarify the development model and seismic reflection characteristics of fault-controlled karst reservoirs,a fault-karst system of the Maokou Formation composed of two different karst zones is established based on the comprehensive analysis of the well logging,mud logging,and seismic data.Specifically,the system is reflected by①The karst zone along faults,which is controlled by the development degree of the fault-associated fractures,and the zone is blocky and mainly developed near the faults,with a large thickness.The seismic facies are represented by reflection characteristics including weak peaks on top,strong peaks at the bottom,and clutter or blank inside.②The karst zone along formations,which is controlled by the distribution range of grain shoals near the faults,and the zone is layered and far from the faults,with its single layer having a small thickness.The seismic facies are represented by bright spot reflection characteristics including a strong wave trough on top and a strong wave peak at the bottom.