Research And Application Of Deepwater Marine High Precision Seismic Imaging Technology

In recent years, marine oil and gas exploration gradually became the main battlefield of energy exploration. More than half of the oil and gas are discovered from the ocean, especially from the deep ocean. In the abyssal region of South China Sea, the sea area with water depth above 300 m is more than 2 million square kilometers, and the area of deep water basin is more than 800 thousands square kilometers. As possessing abundant oil and gas resources, oil and gas exploration in deep sea has become an important research field.The grade of maturity of deep ocean oil and gas exploration in our country is relatively low and the drilling is with high costs and big risk. Now there are still many problems that to be solved, such as concave structure set, tectonic style parsing, sedimentary characteristic analysis, and so on. Accordance with the existing problems, improving the quality of seismic data and profile in deep sea, improving the success rate of reservoir and oil prediction, and reducing the risk of oil and gas exploration are important work in deep sea seismic exploration. In this paper, we aim at the characteristics of seismic data in deep sea, and conduct further research on high precision technology for seismic imaging, including ghost suppression process, high precision denoising process, high precision velocity modeling and imaging, and so on. Among these, full waveform inversion(FWI) is a high resolution and high precision velocity modeling method. FWI matches the theoretical data according to the initial model to the real acquisition data, and updates the velocity model gradually in this process. Finally, we can obtain velocity model in depth domain that can accurately describe the distribution of subsurface velocity. The seismic data in deep sea have high SNR, so after ghost suppression process, we can obtain broad-band seismic data. And in real application, we obtain good results.In the research of FWI, aiming at solving the problems and difficulty we face when using FWI for velocity modeling with seismic data acquired in deep sea, we provide corresponding solutions. In this paper, FWI is the core content, and we provide a processing workflow corresponding to conventional streamer seismic data in deep sea. It includes two parts of contents. One is broad-band seismic data processing, including ghost suppression processing, high fidelity pre-stack denoising, multiple suppression, and so on. The other part is determining FWI parameters using initial velocity model, and using FWI to reconstruct velocity model in depth domain. Finally, based on inversed velocity model, we verify in inversed model by conducting pre-stack depth migration and stacking process.In this paper, we apply this workflow to 2D streamer seismic data and inclined cable seismic data. We obtain good processing results, find the disadvantages of FWI application and industrialization and provide some solutions.