Application of Isotropic PP/PS-stereotomography to a Gas Cloud Context – The Snøhvit Gas Field

Gas clouds may considerably distort the energy of P-waves travelling through them. This complicates imaging, and particularly velocity estimation. When seismic data cannot be used a priori information may help to estimate a satisfying model. Stereotomography is a flexible tool, but the parameterization of the estimated model by cubic B-splines makes the introduction of a priori information difficult. Here, we use a hybrid model, consisting of a smooth layered model and some smooth variations on top of it. This model parameterization is smooth, allowing the use of paraxial ray tracing, and is at the same time connected to some layers, allowing the introduction of a priori information. By using such a model parameterization, we show that we can significantly improve the estimated results on a 2D dataset, which exhibits a low signal-to-noise ratio of the PP-data underneath a gas cloud at the Snøhvit gas field.