南哈Marsel探区Asa区块下石炭统岩溶储层精细刻画及分布特征

摘要

位于哈萨克斯坦Marsel探区中北部的Asa区块具有良好的天然气成藏条件,特别是下石炭统碳酸盐岩具有丰富的气测显示,成为近期勘探阶段的一个新突破,有利储层发育与岩溶作用关系密切.以成像测井资料为主,结合常规测井曲线、岩心以及测井数据交会图,对研究区内的典型单井进行了岩溶结构单元的精细划分,发现Asa区块下石炭统除杜内阶外,其余各个层段均有岩溶发育,但以谢尔普霍夫阶和维宪阶三段岩溶较为发育.利用成像测井对重点岩溶段进行了精细刻画,结果表明谢尔普霍夫阶岩溶和维宪阶三段岩溶具有明显不同的发育特征.其中,谢尔普霍夫阶发育2套岩溶,且这2套岩溶均发育在指示干旱暴露环境的膏岩层下方;通过横向连井对比,发现维宪阶三段所发育的岩溶具有表生岩溶的特征,纵向分带性明显,自上而下依次可划分为风化壳古土壤层、垂向渗流岩溶带和水平潜流岩溶带.其中,垂向渗流岩溶带以高角度溶蚀扩大缝为主,水平潜流岩溶带主要发育低角度溶蚀扩大缝和未充填洞穴.该研究成果对碳酸盐岩岩溶储层精细刻画及寻找有利的碳酸盐岩岩溶储层均具有指导作用.%The Asa block located in Marsel exploration area at the north and middle of Kazakhstan has a good condition for natural gas deposits,and the Lower Carboniferous carbonate rocks have a rich gas display,which becomes a new breakthrough in recent exploration phase. As found in the related study,the favorable reservoir development is closely related with karstification. The imaging logging data,combined with cores,conventional logging curves and logging cross plots,were used to divide karst structural units for typical single wells in the study area. The results show that except Tournaisian(C1 t),Karst developed in all the other layers of the Lower Carboniferous in Asa block,especially developed in Visean(C1 v3)and Serpukhovian(C1 sr). A fine description of the main karst section was conducted by using imaging logging and the result shows that karst in C1 sr and in C1 v3 has obvious different characteristics. Moreover,there are two sets of karsts developed in C1 sr,and they are below the gypsum rocks which can indicate arid environment. Through horizontal well-tie section contrast,C1 v3 has the features of epigenic karst and obvious vertical distribution and it can be divided into the weathering crust palaeosol,vertical vadose karst zone and horizontal underflow karst zone from the top to the bottom. The vertical vadose karst zone is dominated by high angle dissolved enlarged fractures,while horizontal underflow karst zone is dominated by low angle dissolved enlarged fractures and unfilled caverns. This study result is helpful for guiding fine description of carbonate karst reservoirs and searching for favorable carbonate karst reservoirs.