Concealed-Fault Detection in Low-Amplitude Tectonic Area—An Example of Tight Sandstone Reservoirs

Fault detection is important to seismic interpretation, especially for tight oil and gas reservoirs. Generally speaking, large-scale faults can be accurately imaged and are easy to detect by conventional methods, but the concealed ones in low-amplitude structural regions are difficult to find. In these areas, the scale and displacement of concealed faults are usually very small. Due to the good uniform and weak amplitude disturbances in the seismic events, the traditional discontinuity attributes extracted from seismic data are always not effective. This is because the discontinuous features of large faults are very significant, and the weak anomalies caused by hidden faults are very close to the continuous background. This paper takes a tight sandstone reservoir in the Ordos Basin of China as an example to explore the detection method of subtle faults in low-amplitude structural areas. With the phase congruency analysis method, we extract edge features from the post-stack coherence attributes to identify hidden faults. Practice shows that this idea has outstanding performance in mining hidden fracture features and improving the accuracy of fracture recognition. The results successfully predict a shear fault zone in the northeast of the work area, find a new fracture zone in the center of the survey and a series of hidden faults in non-target strata. It would be beneficial to extend the strata and area of oil and gas reservoirs.