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4D Anisotropy Analysis on the Niobrara Formation Using P-wave Legacy Survey
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 79th EAGE Conference and Exhibition 2017, Jun 2017, Volume 2017, p.1 - 5
Abstract
In a joint effort between the Reservoir Characterization Project and FairfieldNodal we processed two legacy P-wave seismic surveys acquired in 2010 (baseline) and 2013 (monitor) in the Denver Basin Colorado, USA. We applied a common processing work flow aimed to ensure and improve the repeatability of both surveys. These common processes included: common datum, replacement velocity, refraction static model, and deconvolution, normal move-out velocity, noise attenuation parameter, migration and residual velocity. The investigation on the differences in travel time within a COCA gathers shows HTI effect. We observed sinusoidal phenomena on the post-imaging COCA gathers especially on the far offset (larger than 1200 meters). We then calculated the fast and slow velocity and measured the eccentricity (degree of the anisotropy). The azimuthal velocity analyses were done on individual surveys. The co-processing of two legacy P-wave surveys shows time-lapse changes in azimuthal anisotropy presumably related to an enhanced fracture network related to hydraulic fracturing operations in horizontal wells. This observation bodes well for using legacy P-Wave surveys to detect and delineate the stimulated reservoir volume in the Niobrara.