东沙岛西南泥火山区的地震烃类检测

近年来通过多道地震、浅剖及海底采样调查在东沙岛西南海域发现了大量喷溢甲烷的泥火山,通过研究泥火山可能会发现含气层,具有重大的油气资源指示意义.一条多道地震剖面显示,在该海域一泥火山MV3附近存在一个具有极性反转的埋藏背斜构造,其振幅绝对值随偏移距增大而增大.为探究该背斜是否含有烃类气体,开展了速度分析、AVO反演和频率...

Seismic Detection for Hydrocarbon in Mud Volcano-Rich Area Southwest to the Dongsha Island

In recent years,a number of methane-venting mud volcanoes have been found in the southwest area of the Dongsha waters from multi-channel seismic,sub-bottom profiling and dredging survey.Studying mud volcanoes has great significance for oil and gas reserves.In this paper,a buried anticline was found near a mud volcano,MV3,with reversed polarity on a multichannel seismic profile,where the absolute amplitude increases with offset.To detect whether it contains natural gas,velocity analysis,AVO inversion and frequency absorption attenuation analysis were carried out.There is a low P-wave velocity layer under the reflector of reversed polarity.AVO inversion shows that the polarity reversal zone features negative values in intercept and gradient sections,and falls in the third quadrant in P and G cross-plot.The polarity reversal zone features positive in S-wave reflectivity section,and is highly negative in Poisson ratio change rate section.Frequency absorption and attenuation analysis shows rapid energy loss of high frequency and relative increase of low frequency.Multiple attributes point to gas accumulation there,likely associated with the methane seepage from deep.