中文摘要：

在油气田勘探开发阶段,VSP（垂直地震剖面）作为一种精细勘探技术发挥着重要作用,三维VSP地震初至波走时层析成像可以直接得到地层速度模型。它结合了三维VSP地震射线追踪算法和数学反演算法,它能够实现对地下地层速度模型进行重构,速度成像结果对认识地质结构提供了直观的依据。为了测试算法的稳定性和抗干扰能力,对三维VSP正演走时加入了20%的高斯噪声,然后利用三维地震初至波走时层析成像进行速度反演,得到了三维地层速度模型、垂直切片图和水平切片图。射线方向的交叉性程度决定了反演结果的质量和可靠性,由于射线在浅部地层的交叉性比深部地层的交叉性更好,浅部地层的反演效果更加清晰;相反,深部地层的速度反演效果较差。算法对含噪声数据取得了良好的反演结果,验证了该算法具有较好的抗干扰能力。

英文摘要：

VSP （Vertical seismic profile） is a high resolution exploration technology. It plays a significant role in the exploration and development stage of oil and gas. 3D VSP first arrival traveltime tomography can invert the un- derground velocity model directly. This method combines 3D VSP seismic ray tracing algorithm and mathematical inversion algorithm. It can reconstruct the underground velocity models directly. These models can provide apparent evidence to know the underground geological structure better. In order to test the stability and anti-noise ability of the algorithm, there are 20% Gaussian noises were added into the 3D VSP forward traveltimes. Then, the 3D VSP first arrival travehime tomography is used to invert the velocity models. We have obtained 3D velocity models for the checkerboard model, and its vertical slices and horizontal slices. The more rays cross with each other, the better the reliability and effect of inversion result are. Therefore, the effect of shallow strata inversion result is better than the deep strata, because there are more rays cross with other in shallow strata than the deep strata. On the contrary, the velocity effect in deep strata is much worse. The inversion algorithm has inverted good results by use of the noise contained travehimes. This confirms that the robust algorithm has strong ability to antinoise.