Abstract: Under the effect of epigenic karstification, the fourth member of the Sinian Dengying Formation in Sichuan Basin (hereinafter referred to as Deng 4 Member) is obviously characterized with vertical karst zoning, and the development degree of reservoirs in different karst zones varies greatly. Thus, it is necessary to precisely describe the internal structure of paleokarst zone and further clarify the distribution of high-quality reservoirs. Based on the data of core, seismic, and imaging logging, as well as the groundwater movement pattern and development characteristics of pores, vugs and fractures, the paper divides the paleokarst zones of Deng 4 Member in Gaoshiti block, establishes a relationship between the thickness of paleokarst zone and the relative elevation of paleokarst landform, subdivides horizontal underflow subzones, analyzes the development characteristics of high-quality reservoirs in each underflow subzone in different periods, and optimizes favorable paleokarst zones in each zone. Research shows that the higher the paleokarst landforms in Deng 4 Member of Gaoshiti block, the thicker the longitudinal vadose zones and the thinner the horizontal underflow zones. Affected by periodic decline of paleokarst water table, three stages of underflow subzones were developed in the horizontal underflow zone, of which the development degree of high-quality reservoirs in the upper underflow subzones 1 and 2 is better than that in the subzone 3. According to the sedimentary facies, paleokarst landforms and distribution characteristics of high-quality reservoirs, Gaoshiti block was divided into 3 zones. Karst zones and subzones on the west side of the block (Zone 1) has well-developed high-quality reservoirs with a cumulative thickness of over 50 m, as being the most favorable area. The high-quality reservoirs on the east side of the block (Zone 2) are only developed in the longitudinal vadose zone, with a cumulative thickness of 15-20 m. The high-quality reservoirs on the south side of the block (Zone 3) are mainly developed in the longitudinal vadose zone and the horizontal underflow subzone 1, with a cumulative thickness of 30-40 m. In conclusion, there are differences in karst zones and subzones of high-quality reservoirs developed in different areas, so that it is necessary to adopt different development technologies and policies.

Key words: Sichuan Basin, Gaoshiti block, Sinian System, Dengying Formation, paleokarst zone, high-quality reservoir

摘要： 四川盆地震旦系灯影组四段（灯四段）在表生期岩溶作用影响下纵向岩溶分带特征明显，不同岩溶带储层发育程度差异较大，有必要精细刻画古岩溶带内部结构，进一步明确优质储层的分布。综合岩心、地震、成像测井等资料，基于地下水运动方式及孔、洞、缝发育特征，开展了高石梯区块灯四段古岩溶带划分，建立了古岩溶带厚度与古岩溶地貌相对高程的关系，并细分水平潜流亚带，分析不同期水平潜流亚带优质储层的发育特征，分区优选了有利古岩溶亚带。研究表明，高石梯区块灯四段古岩溶地貌越高，垂直渗流带厚度越大、水平潜流带厚度越小。受古岩溶潜水面周期下降影响，水平潜流带内发育3期水平潜流亚带，上部水平潜流亚带1、亚带2优质储层发育程度优于亚带3。根据沉积相、古岩溶地貌及优质储层展布特征，将高石梯区块划分为3个区域。区块西侧（1区）各岩溶带和亚带优质储层均较发育，优质储层累计厚度超50 m，为最有利区域；区块东侧（2区）优质储层仅发育于垂直渗流带，优质储层累计厚度为15~20 m；区块南侧（3区）优质储层主要发育于垂直渗流带和水平潜流亚带1，优质储层累计厚度为30~40 m。不同区域优质储层发育的岩溶带、亚带存在差异，应采用不同的开发技术政策。

关键词: 四川盆地, 高石梯区块, 震旦系, 灯影组, 古岩溶带, 优质储层