Two marine seismic interference attenuation methods : Based on automatic detection of seismic interference

Marine Seismic Interference (SI) occurs when several seismic vessels operate in close proximity, and the interfering energy from one vessel is recorded as interfering noise by another. Generally, SI is removed by various SI removal methods. However, it is often difficult to remove SI if the arrival time, moveout and/or amplitude of the SI exceed certain limits. In this case, the vessels commence time sharing. Time sharing is expensive, and therefore something the industry wants to avoid. A strong motivation exists for developing robust and efficient SI removal methods. The reference method for this thesis consists of sorting/transforming series of consecutive SI contaminated shot gathers to common-p domain where the SI appears random. The SI can then be removed by applying a random noise attenuation method. However, this method breaks down if the arrival time of the SI is synchronized in the consecutive shot gathers. The aim of this thesis has been to develop a method referred to as Vector Field (VF) method. VF method works on singular shot gathers, and calculates a vector field estimate which represents the local moveout in the considered shot gather. Analysis of the vector field in three different domains allow automatic SI moveout detection. The SI moveout detection comprises two possible techniques for SI removal. First technique automatically generates tau-p mutes designed to isolate the SI in tau-p domain. This technique is the main focus of the thesis. The second technique uses the line integral convolution method and an estimate of vector fields to subtract the SI from the shot domain. Analysis of RMS plots, shot gathers, and stacks show that the VF method in combination with tau-p muting is an efficient SI removal method. Compared to the reference tau-p to common-p method, VF method in combination with tau-p muting is able to detect and remove SI regardless of a synchronized arrival time of SI in consecutive shot gathers