地震速度在浅层气勘探中的应用

根据钻井判定的工业油气层与过井地震道制作合成记录,在地震剖面上标定.再利用地震速度谱和层速度递推公式,分别拾取和计算与油气地质体同一时域的速度值.采用美国学者莱德尔提出的差异速度叠合法,将地质体顶、底的速度值叠合,低速异常发育带可能是气层.经地震测网的追踪闭合在平面上进行圈定.将此法,用于新场气田试研究,发现1600～2200m以浅的上侏罗统蓬莱镇组气藏,沙溪庙组A、B气层与低速异常的符合率较高,达80%以上,2200m以深的沙溪庙组C气层与中侏罗统千佛崖组气层符合率较低,约20%～30%. 

APPLICATION OF SEISMIC VELOCITY TO THE EXPLORATION OF SHALLOW GAS

Commercial oil/gas reservoir determined by the well drilling and seismic channels across the well are used to prepare combined records which are plotted on the seismic profile;then using a recursion formula for the seismic velocity spectrum and interval velocity,the velocity values having the same time domain with the oil/gas geologic body are picked up and calculated.Based on the method of superposition of differential velocity proposed by Leder,an American scholar,the superposition of velocity values from the top and bottom of the geological body are made.The results show that the abnormal sounding zone with a low velocity would be a gas reservoir.The method is applied to a trial study in Xinchang gas field after a delineation in plane by means of tracing and closing in the seismic net;it is found that the gas pool of Penglai Zheng Formation,and gas reservoirs A&B of Shaximiao Formation from the upper Jurassic above 1600-2200m indicate a higher rate of coincidence with low velocity abnormaly,as high as 80%.Gas reservoir C of Shaximiao Formation of middle Jurassic below 2200m indicate a lower rate of coincidence,about 2O%-30%.