海底节点地震波场模拟与转换波成像方法研究

Due to the complexity of geological conditions of offshore continental sedimentary basins in China, it is difficult to obtain reliable reservoir evaluation and fluid detection results only by the conventional streamer seismic data. The multi-component seismic exploration with Ocean Bottom Nodes(OBN) is a key technology to solve this problem，owing to its abundant information of the primary and converted shear waves. This project intends to study the seismic numerical modeling and migration imaging for the OBN data. Based on the research of hybrid mesh generation, traveling time computation by bilinear interpolation LTI, and improved vacuum formulation to finite difference, we will develop an seismic wavefield simulation tool for three-dimensional irregular submarine interface and complex medium. Besides of wave propagation within the media, the Scholte surface wave along sea floor will also be studied. A migration velocity modeling strategy with Angle Domain Common Image Gathers(ADCIG) will be set up by jointly combing surface wave inversion and the conventional velocity analysis. In view of the OBN geometry, we will pay much attention to the global wavefield continuation datuming, continuation with DSR operator, P- and P-S migration operators as well as imaging conditions. To achieve imaging of the complex structures below rugged marine topography，this project will focus on the study of the pre stack depth migration by ADCIG，develp the software for P-wave and converted S-wave prestack depth migration with OBN data, and try to put the imaging of OBN converted waves into practical use in marine oil and gas explortion of China.

我国近海陆相沉积盆地地质条件的复杂性，常导致由拖缆地震资料难以获得可靠的储层评价及流体检测结果。海底节点(OBN)多分量地震勘探，由于能获取丰富的纵波及转换横波，是解决上述问题的有效技术。本项目拟研究OBN地震波场数值模拟与成像方法，在研究混合网格剖分、旅行时双线性插值LTI计算、及改进真空介质层法有限差分技术的基础上，研发适应3D起伏海底复杂介质的地震波数值模拟工具；研究地震波及海底Scholte型面波的传播、频散反演及其与常规速度分析联合的角度域共成像点道集(ADCIG)偏移速度建模方法；重点研究OBN数据整体波场延拓法基准面校正及双平方根(DSR)算子波场延拓技术，研究纵横波偏移成像算子及成像条件，开展基于ADCIG的转换波叠前深度偏移方法研究，形成海上OBN纵波与转换波叠前深度偏移软件，实现起伏海底复杂构造成像，使OBN转换波成像技术在我国海洋油气资源勘探中达到实用。

海底节点(OBN)地震采集数据，由于包含纵波及转换横波，在海上油气储层评价中具有十分重要的作用。本项目针对OBN料处理等问题，开展OBN地震波场数值模拟与纵横波偏移成像方法研究。.项目提出了基于海底折射波及海底Scholte面波偏振分析的OBN检波器定向方法；引入双动态惩罚函数，提出一种浅海OBN直达波与折射波初至联合的二次定位方法；开展基于振幅、相位及频率匹配的OBN双检数据鬼波压制技术研究，改进相似系数准则用于匹配双检数据相位，引入时变谱白化技术补偿陆检数据的高频成分，采用非线性小波变换阈值法压制OBN双检数据匹配噪声和残余鬼波，改善了鬼波压制效果。开展3D OBN地震波场数值模拟研究，提出基于矩形和不规则四边形网格剖分的混合网格线性插值（LTI）地震波旅行时计算方法，研发出三维起伏海底VTI介质OBN地震波模拟软件。研究角度域共成像点道集去噪、OBN偏移速度分析以及VTI介质角度域叠前深度偏移方法，形成OBN数据逐层速度建模方法，提高了基于角度域共成像点道集的纵波与转换波叠前偏移成像精度。研究横波速度预测与OBN多波联合反演，提出一种基于注意力机制和双向长短时记忆网络的横波速度预测方法，综合旅行时线性插值射线追踪正演与粒子群非线性反演算法，实现了OBN数据纵横波速度逐层联合反演。.项目研究成果及研发的针对海底节点地震资料特殊处理、波场模拟、叠前深度偏移成像与参数反演软件，已用于我国东海某探区OBN地震资料的处理与解释，获得了良好的储层成像与评价效果，为继续自主深入研究我国海上油气资源多分量地震勘探技术提供了新的理论与方法支持。