Quantifying Anisotropy for the Next Generation of Geomechanical Solutions
Bratton, Tom R.*1
(1) Schlumberger, Greenwood Village, CO.
Geomechanics can make a significant economic impact in tight gas reservoirs both in drilling and stimulation operations. The current generation of geomechanical solutions models the formation assuming it is homogeneous and isotropic (HI). Most formations, especially at the scale of the geomechanical problem, are heterogeneous and anisotropic. While HI models can be calibrated, changes in pore pressure or fracture gradient are interpreted when, in reality, it is only the anisotropy that is changing. Because of the number of unknowns, no single source of data is sufficient to solve the problem. Data must be integrated from multiple wells and across multiple scales (e.g., core, log, and seismic scales). Acoustical logging data provide a natural starting point to solve these multidisciplinary and multivariate geomechanical problems. A workflow is presented that first diagnoses the type of acoustical anisotropy at the log scale. Core data, representative of the unfractured background matrix, is then integrated with the log data to quantify static elastic properties. Fracture compliances can then be determined in the fractured intervals. Upscaling is then applied for integration with the seismic data. An anisotropic mechanical earth model is constructed after the acoustical velocities have been integrated with core and seismic data. The anisotropic earth model is then used to address a number of drilling and completion problems. A variety of technologies were applied in different case studies, and these case studies illustrate how an understanding of anisotropic geomechanics translates into both drilling and completion optimization.
AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain