Local Structural Discontinuity Estimation for 3D Seismic Data to Identify Subtle Faults of Khangiran Gas Field

In this paper two methods are used to estimate local discontinuity for 3-D seismic data of Khangiran gas field from NE of Iran to identify subtle faults. These methods operates on a 3-D cube of seismic data and reveal structural features like faults and stratigraphic features such as channels which are not easily seen in amplitude seismic slices. Since these methods don't require picking horizons, they are more reliable, because picking horizons might affect the results by the interpreter. Like coherency they calculate the local similarity in In-line, X-line and time direction and estimates lateral and vertical seismic discontinuity. Variations in structure, stratigraphy, lithology, porosity, and the presence of hydrocarbons cause seismic discontinuity. These methods calculate local discontinuity, based on the relations between sub-volumes (quadrants) of the analysis cube. The scale of the analysis cube is determined by the type of geological feature. These methods are more robust to noise than original three-trace cross-correlation-based coherency algorithm and computationally efficient because they avoid the computation of large covariance matrices and Eigen-values, associated with the Eigen-structure-based and semblance-based coherency estimates.