陆域冻土区天然气水合物多波地震数值模拟研究

多波地震勘探技术能够同时获得纵波和转换波资料,与常规的纵波勘探相比,能够提供更多的地下介质信息。且转换波对于埋深较浅的小断层、小幅度构造有更高的分辨率,充分利用多分量地震资料可以有效的提高地震勘探的精度。本文将多波地震技术引入到陆域冻土区天然气水合物勘探中,对陆域冻土区水合物进行多波地震数值模拟研究。采用弹性波有限差分方法进行多分量正演模拟,利用仿射坐标转换法将原始的多分量地震数据进行纵横波叠前分离,并通过多波高斯束偏移方法分别对波场分离后的PP波和转换PS波进行叠前深度偏移成像。根据我国祁连山冻土区水合物实际地震地质资料,建立逼近真实地质情况的天然气水合物数值模型。对上述水合物模型进行多波地震数值试算表明,多波地震勘探技术是一种有效的陆域冻土区水合物探测方法,充分利用多波地震资料有利于查明陆域冻土区水合物精细的地质构造,取得更好的勘探效果。

Multiwave Seismic Numerical Simulation Study on Terrestrial Gas Hydrate in Permafrost Area

For multi component seismic exploration, both PP and PS wave data can provide more subsurface information compared with conventional PP wave exploration alone. PS wave has a higher resolution for some minor faults and small structures, so making full use of multi component seismic data can effectively improve the accuracy of seismic exploration. In this paper, multiwave seismic technology was introduced into the exploration of terrestrial gas hydrate in permafrost area, where multiwave seismic numerical simulation study is performed for terrestrial gas hydrate in permafrost area. The elastic finite difference method was used for multi component forward modeling, and PP and PS waves were separated from multi component seismic data with a wave vector rotation transformation method in the affine coordinate system. Then, the multiwave Gaussian beam prestack depth migration imaging algorithms for PP and PS waves were applied. In this paper, gas hydrate numerical models are built, which are close to the real geological conditions, according to the actual seismic and geological data of gas hydrate in Qilian mountain permafrost area. Multiwave seismic numerical simulation tests of these gas hydrate models show that multiwave seismic exploration technique is an effective detection method for terrestrial gas hydrate in permafrost area. It is helpful to find out the fine geological structures of terrestrial gas hydrate in permafrost area and obtain better exploration effects using multiwave seismic data.