桑塔木地区三叠系层序地层特征及有利区带预测

Sequence stratigraphic characteristics and favorable hydrocarbon accumulation prediction of Triassic in Sangtamu area

为了预测桑塔木地区三叠系有利勘探区带,利用地震、钻测井、岩心等资料,通过合成记录标定达到井震统一,将桑塔木地区三叠系划分为1个构造层序、5个三级层序(SQ1-SQ5)和9个体系域,建立高精度的层序地层格架.研究表明,区内除了发育普遍认识的辫状河三角洲-湖泊沉积体系外,还存在曲流河三角洲沉积体系.通过探讨目标层序(SQ3-SQ5)内的沉积特征及演化规律,结合储盖组合分布、反演特征及成藏条件综合分析认为:层序SQ3和SQ5内部低位水进体系域辫状河三角洲储层发育,厚度大、连续性好,但是不易形成岩性油气藏,应以加强断垒带两侧的滚动勘探,寻找新的低幅度构造油气藏为主;而层序SQ4低位水进体系域曲流河三角洲前缘砂体薄,横向连续性较差,易尖灭,有利于形成岩性圈闭,在平面上断垒带东北部斜坡带上为有利的油气聚集相带,可作为下一步油气勘探的重点.

In order to forecast the favorable hydrocarbon exploration zones of the Triassic in Sangtamu area,Tarim Basin,well seismic calibration is finished using seismic,drilling,logging and core data,the Triassic is divided into one structure sequence,five third-order sequences and nine system tracts,and a high-resolution sequence stratigraphic framework is established. The results show that besides braid delta and lacustrine sedimentary systems which have been recognized before,there also developed meandering river delta sedimentary systems. By studying the sedimentary characteristics and evolution law of key sequences( SQ3 - SQ5) ,and combining it with the comprehensive research of the reservoir-cap combination distribution and the hydrocarbon accumulation conditions,it is held that the braided delta reservoirs are developed in the LTST in SQ3 and SQ5,they are of large thickness and good continuity,but they are not favorable to form lithologic traps. Therefore,rolling exploration should be strengthened in the two sides of fault horst zone to find low amplitude structural traps. The meandering river delta front sand bodies in the LTST of SQ4 were thin and easily pinched out,and they are favorable to the formation of lithologic traps. In the plane,the slope zone in northeast of the fault horst zone is favorable hydrocarbon accumulation zone,and it will be a significant oil and gas exploration target area.