Multicomponent Test for Assessing Anisotropy and Imaging in a Deep Carbonate Reservoir in the Caspian Sea

Kashagan is a giant carbonate reef reservoir located in the Kazakh sector of the North Caspian Sea at a depth of approximately 4000 m TVDSS. A multicomponent 2D test was designed to evaluate the detection of horizontal anisotropy and fractures in the reservoir using shear-wave splitting. In addition, the mode-converted (PS) data was tested for imaging the intra-reservoir characteristics in an area with limited shear velocity information. The multicomponent data were processed through prestack time migration, with particular emphasis on coherent noise and multiple attenuation. VSP data were used to calibrate the processing sequence. PS waves were able to provide clear indications of anisotropy, which were consistent with other independent measurements (VSP, geological and structural studies), and they also imaged the intra-reservoir architecture. This successful result, in a difficult area with complex geology, will be used to design further multicomponent surveys in the Kashagan field.