正演技术在地震解释中的应用

Application of Forward Modeling to Seismic Interpretation

地震解释中,标定、地震解释属性提取时时窗的选取、断裂解释都存在一些主观的不确定性。针对这些问题,模拟实际地震资料的视主频和频宽,采用雷克正子波,进行了正演研究。研究表明:剖面上厚层泥岩/厚层砂岩组合方式、砂层的顶界正对着波峰,这时要获得更多砂岩的信息,提取属性选择时窗应该在波峰下取时窗;大套泥岩中的5 m砂和10m砂提取属性选择时窗应该在波峰以下取时窗;大套泥中的15 m砂岩、20 m砂岩和25 m砂岩应以波峰对称来开时窗;剖面上厚层砂岩/厚层泥岩组合方式,泥层的顶界将会正对波谷,此可作为标定时的第二标志层;大断面下往往会出现近断面相位上提、远断面下拉,从而造成断裂假象;煤层(低速)横向相变或突变,将会在相变处或突变处造成断裂解释误区。这些认识应用效果良好。

During seismic interpretation, great subjective uncertainty exists in seismic calibration, time window selecting during extract of seismic attributes and fault interpretation. In order to solve these problems, forward modeling has been finished through simulation of the apparent dominant frequency and bandwidth with the practical seismic data by the Ricker wave. The study results indicate that in thick-mud/thick-sand combination, the top of sand layer is correlated to the wave peak. If more information about the sand is needed, it is necessary to extract the seismic attributes under wave peak by the time window. To the sand layers with thickness of 5 m and 10 m between the large set of mudstones, it is necessary to extract the seismic attributes under wave peak by the time win- dow. To the sand layers with thickness of 15 m, 20 m and 25 m between the large set of mud, it is necessary to open the time window symmetrically along the wave peaks. In the thick-sand/thick-mud combination, the top of mud layer is correlated to the wave trough, which can be used as the second markers for calibration. Under big fault, there are some phase rising near the faults and phase pulling down at the places far from the faults, which leaded to the false appearance during fault interpretation. The lateral fccies change of coal seam （low velocity） or suddenly fccies change might result in the false in fault interpretation. Good application results have been obtained in the practice study area with these conclusions.