Research On 3D Seismic Data Fault Detection And Modeling

3D seismic survey is now the primary method in oil and gas exploration. The signal collected from the survey is the reflection of artificial seismic waves. The interpreters speculate the geological structures by the rolling shapes of the underground horizons, so the horizon picking is the foundation of seismic data interpretation. The fault identification is the difficulty in the seismic interpretation work. The fault is the breaking and misplacement of horizon underground, so it is the boundary of the oilfields and it is also the channel for oil to transport and gather. The fault identification is the most important work in oil exploration. The most effective method to detect faults is 3D coherence technique. The 3D coherence cube is the discontinuity attribute of the seismic data cube. The faults can not be found in the seismic data will display in the slices of coherence cube clearly.This thesis studies some problems about the 3D seismic data the fault detection and modeling. The main results obtained in the thesis are as follows:1. The current seismic coherence cube is for the seismic amplitude data, so the computational cost is high, and the stability is poor. This thesis proposed a coherence cube algorithm based on gradient orientation. This algorithm estimates the orientation field first, defines the coherence value by the local difference of the orientation vectors. It is sensitive to the local discontinuity of the seismic data. The result can be used to assist fault detection. This thesis uses this algorithm for horizon tracking and automatic interpretation of the faults.2. Attention goes to the reconstruction of scattered points from horizon picking. This thesis proposed a surface fitting algorithm based on kernel regression. This algorithm utilizes the characteristics of horizon points. The computational cost is low, and the result number of the reconstruction surface is small. The user can set the filter parameters to control smoothing degree and fitting precision. The experiments show that the method has far less complexity than traditional reconstruction algorithm, and the result surface can satisfy the horizon rendering requirement.3. The problem of reconstructing horizons which were torn by faults is addressed. This thesis proposed a iterative subdivision and approximation method to construct a continuous surface to fit the scattered points, then delete the fault area triangles. This method handles the broken horizons well, and the experiments show that the reconstruction result is precise and the rendering result of fault area is good.4. The fault surface reconstruction by multi-slice contours is studied. We proposed a algorithm based on the shortest contours on multi-slices. The method is like the process of artificial splicing, which processes a single slice first. The method gets the shortest path on every slice, constructs a fitting surface by multi-slice contours. The experiments show that the algorithm can get a smooth surface with the fault details.