自适应时窗相干体计算技术及其应用

相干体技术是预测断层形态、河道砂体分布及碳酸盐岩裂缝发育状况等的重要技术之-。但在计算相干体时以计算点为中心选取固定长度时窗很难兼顾浅层和深层,即在分析浅层时出现跨多个同相轴,在分析深层(低频带)时因时窗长度不够,在同相轴零点附近相干值易受随机噪声影响;另外,即使时窗大小合适,但在波组起跳点和终止点附近易受邻近波组影响,也难以准确求取同相轴倾角、方位角和相干值等属性;此外,相干体还有较多沿层特征。本文通过地震数据波形自适应地确定时窗,由该时窗计算相干值作为时窗内各样点的相干值;在此基础上,通过计算各视倾角对的相干值估算波形的倾角和方位角。实际资料的处理效果表明,应用本文方法求取的相干体、倾角和方位角属性较为可靠。

Coherence calculation with adaptive windows and its application

Coherence is one of the most important attrib-utes to be used to identify fault form，channel sandbody distribution and carbonate fracture develop-ment .At present the time window is fixed at cen-ter point during coherence calculation. This cannotinvolve both the shallow and the deep layers.Itmay cross a few events when analyzing the shallowlayer，but within one event when analyzing thedeep layer(low frequency zone).The coherencenear zero point of events is influenced by randomnoise.In addition, even if the window size is ap-propriate，the first break points or the end pointsof the waveform are easily affected by the adjacentwaveform，and it is difficult to obtain accurate dip，azimuth and coherence values.In order to over-come these challenges，we propose a new ap-proach. First the window is chosen adaptively bythe seismic data waveform.The calculated coher-ence value in the window is taken as the coherencevalue of all the samples in this window.The dipand azimuth of the waveform are estimated by cal-culation of the apparent dip coherence value.Andthe dip and azimuth of the adjacent waveforms arethen merged.Field data tests indicate that this ap-proach obtains better results.