Planning, Acquiring and Processing a Walkaround VSP for Fracture Induced Anisotropy

B-28 PLANNING ACQUIRING AND PROCESSING A WALKAROUND VSP FOR FRACTURE INDUCED ANISOTROPY 1 Introduction The Rangely field Western Colorado is a large monoclinal structure with gentle dips of less than 4 degrees at the reservoir depth of approximately 1.7km. The principal reservoir rock is the lower Pennsylvanian Weber formation which is a massive fine-grained aeolian sandstone exhibiting cross-bedding. The Weber formation is mostly overlain by shales with some sandstones. Rangely is a mature field discovered in 1933. Since initial production in the 1940s the field has undergone pressure depletion followed by water injection and now CO2 miscible flood. Injector-producer pattern