3D Alford Rotation Analysis for the Diamond M Field, Midland Basin, Texas
Oswaldo Davogustto Cataldo¹, Tom Thomas, and Steve Roche
2C by 2C "shear wave" surveys generated significant excitement in the mid-1980s, but then fell out of favor when the shear wave splitting initially attributed to fractures was also found to be associated with an anisotropic stress regime. In general, 2C by 2C data requires more expensive acquisition and more processing effort in order to obtain images of comparable to single component "compressional wave" data acquired with vertical component sources and receivers. Since shear waves are insensitive to fluids, and hence the water table, the effective shear wave weathering zone is greater than that for compressional waves, making statics more difficult. Shear wave splitting due to anisotropy complicates residual statics and velocity analysis as well as the final image. Shear wave frequencies and shear wave moveout are closer to those of contaminating ground roll than compressional waves.
Since Alford's introduction of shear wave rotation from survey coordinates to the principal axes in 1986, geoscientist and engineers retain their interest in fractures but are also keenly interested in the direction and magnitude of maximum horizontal stress. Simultaneous sweep and improved recording technology have reduced the acquisition cost to approximate that of single component data. Alford's work was applied to 2C by 2C post stack data. In this work we extend Alford rotation to prestack data using a modern high fold 2C by 2C survey acquired over a fractured carbonate reservoir in the Diamond M field, Texas. Through careful processing, the resulting images are comparable and in many places superior to that of the contemporaneously acquired single component data. More importantly, we find a good correlation between our derived fracture azimuth map and the fracture azimuth log data from wells present in the field.
AAPG Search and Discovery Article #90205 © AAPG Geoscience Technology Workshop, Permian and Midland Basin New Technologies, September 4-5, 2014, Houston, Texas