Siyou Tong

High Resolution Radon Transform and its Applications in Multiple Suppression of Seismic Data in Deep-Sea

The multiple reflections develop in deep-sea. Especially in rough deep-sea bottom, the multiple is more complicated. Conventional radon transform filtering has its deficiency, and the effection is not obvious in multiple suppressing of seismic data in deep-sea. In order to achieve high resolution radon transform, this paper proposes an improved method. This method is able to build a very good model of multiple reflections, then suppress the multiples, overcome the deficiency by conventional radon transform. To verify the efficiency of this method, the rough deep seafloor model was established. By using this method, good results were obtained. At the same time, the method has been applied to process many real deep-sea seismic data, the highprecision seismic data profile was gained and obvious effects of application were achieved. KeywordsRadon Transform;high resolution; multiple suppression

The Improvement of Ant Colony Algorithm and Its Application to TSP Problem

The researches and applications on ant colony algorithm have made great progress in recent years. A number of results have proved the validity of the algorithm and its advantages in some fields. However, its basic shortcomings, which are long searching time and easily jumping into local optimal solution, have not been completely solved. This paper analyzes the reasons of stagnation and then introduces a new solution for avoiding stagnation, which includes the direct exchange of pheromone of some edges and dynamically setting evaporation rate for each edge. The simulation results demonstrate that the above approach is reasonable and efficient.

Retrieving drill bit seismic signals using surface seismometers

Seismic while drilling (SWD) is an emerging borehole seismic imaging technique that uses the downhole drill-bit vibrations as seismic source. Without interrupting drilling, SWD technique can make near-real-time images of the rock formations ahead of the bit and optimize drilling operation, with reduction of costs and the risk of drilling. However, the signal to noise ratio (SNR) of surface SWD-data is severely low for the surface acquisition of SWD data. Here, we propose a new method to retrieve the drill-bit signal from the surface data recorded by an array of broadband seismometers. Taking advantages of wavefield analysis, different types of noises are identified and removed from the surface SWD-data, resulting in the significant improvement of SNR. We also optimally synthesize seismic response of the bit source, using a statistical cross-coherence analysis to further improve the SNR and retrieve both the drill-bit direct arrivals and reflections which are then used to establish a reverse vertical seismic profile (RVSP) data set for the continuous drilling depth. The subsurface images derived from these data compare well with the corresponding images of the three-dimension surface seismic survey cross the well.

Estimation of Elastic Parameters Using Two-Term Fatti Elastic Impedance Inversion

Elastic impedance (EI) inversion has been widely used in industry to estimate kinds of elastic parameters to distinguish lithology or even fluid. However, it is found that conventional three-term elastic impedance formula is unstable even with slight random noise in seismic data, due to the ill-conditioned coefficient matrix of elastic parameters. We presented two-term Fatti elastic impedance inversion method, which is more robust and accurate than conventional three-term elastic impedance inversion. In our method, density is ignored to increase the robustness of inversion matrix. Besides, P-impedance and S-impedance, which are less sensitive to random noise, are inverted instead of VP and VS in conventional three-term elastic impedance. To make the inversion more stable, we defined the range of K value as a constraint. Synthetic tests claim that this method can obtain promising results with low SNR (signal noise ratio) seismic data. With the application of the method in a 2D line data, we achieved λρ, μρ and VP/VS sections, which matched the drilled well perfectly, indicating the potential of the method in reservoir prediction.

Shallow water body data processing based on the seismic oceanography

Physical properties of sea water, such as salinity, temperature, density and acoustic velocity, could be demarcated through degradation of energy caused by water absorption, attenuation and other factors. To overcome the challenging difficulties in the quick monitoring of these physical properties, we have explored the high resolution marine seismic survey to instantly characterize them. Based on the unique wavefield propagating in the sea water, we have developed a new approach to suppress the noise caused by the shallow sea water disturbance and obtain useful information for estimating the sea water structure. This approach improves seismic data with high signal-to-noise ratio and resolution. The seismic reflection imaging can map the sea water structure acoustically. Combined with the knowledge of local water body structure profile over years, the instant model for predicting the sea water properties could be built using the seismic data acquired from the specially designed high precision marine seismic acquisition. This model can also be updated with instant observation and the complete data processing system. The present study has the potential value to many applications, such as 3D sea water monitoring, engineering evaluation, geological disaster assessment and environmental assessment.

Using Mirror Migration of OBS Data to Image the Deepwater Area of South China Sea

Ocean bottom seismograph (OBS) is widely used in investigating deep crustal structure, which is characterized by a large amount of data information and abundant frequency components because of its multi-component acquisition. OBS is seldom used in deepwater oil and gas exploration and basin research due to the high cost. The complicated seismic wave field is caused by the complex seabed topography, basin and oil and gas structure in deepwater area, which increases the difficulty of image processing. In addition to reflection imaging, we utilize the multiple of OBS data to make accurate imaging and have achieved desirable results in a deep sea area in South China Sea in this paper. Firstly, the original P and Z components of OBS data are processed by wave field separation to obtain the upgoing wave filed and downgoing wave filed. Secondly, its image velocity filed is constructed. Finally, downgoing wave data is used to image (called mirror migration). Compared with conventional migration, the mirror migration can clearly image the seabed and provide better illumination for shallow layer below the seafloor in the case of sparse nodes, which is proved by the migration results of theoretical and real data in this paper.