河道砂体叠前地震属性的优化与应用——以哈萨克斯坦南图尔盖盆地为例

Optimization and application of prestack seismic attributes to the mapping of channel sandbodies:A case study from the South Turgay Basin in Kazakhstan

哈萨克斯坦南图尔盖盆地侏罗系岩性圈闭较为发育,河道多期次发育、砂体较为孤立且连续性差,勘探处于高成熟阶段,目前主要利用叠后地震资料进行河道识别但效果不佳。为此,对河道砂体叠前道集特征进行了分析,采用子波拉伸校正、品质因子Q补偿、特定角度叠加等措施,改善了河道的成像效果,优化出了能更清晰地反映河道特征的叠前地震属性。借助地层切片技术,结合盆地的基本地质情况,精细地刻画出了工区内河道的空间展布特征。结论认为:1研究区的物源是来自西北方向的;2J3ak组内3个四级层序中至少发育5期河道;其中SQ8-2层序内至少发育3期,代表着河道发育最广泛、发育最强烈的时期,沉积过程的继承性特征明显;3早期的SQ8-1层序充填以湖盆被河流填平补齐为特点,晚期的SQ8-3层序充填范围缩小,反映了水体范围缩小的过程。

The Jurassic lithologic traps are well developed in the South Turgay Basin,Kazakhstan.The river channels are developed in multiple stages in this basin and the sandbodies are isolated and poor in continuity.Their exploration has entered a highly-mature stage.Post-stack seismic data are mainly used to map the channel sandbodies at present,but the effects are not satisfactory.Based on the thorough analysis of the characteristics of pre-stack gathers of channel sandbodies,various approaches including wavelet stretch correction,quality factor Qcompensation and partly angle stack were used to improve the imaging quality of the channel sandbodies and optimize pre-stack seismic attributes which can better reveal the characteristics of channel sandbodies.Stratigraphic slice and the basic geologic characteristics of the basin were integrated to map the spatial distribution of the channels in the study area.The following conclusions were obtained.（1）The provenience was located to the northwest.（2）Channel sands of at least five stages occurred in the three fourth-order sequences in J3 ak.Among these five-stage channel sands,at least three stages were developed in the SQ8-2.During these stages,channel sand development was the most extensive and strongest and the inheritance feature was also very prominent.（3）The early SQ8-1sequence is characterized by the filling of channel deposits in a lake basin,while the late SQ8-3sequence is smaller in scale,revealing the shrinkage of water volume.