Designing Frac Stages using Geophysics 

Geophysical data maps hot spots in a formation to position frac stages and increase effectiveness

Overview:
Resource plays by their nature have changed the challenge of defining the geometry of a trap to analyzing the properties of a laterally extensive subsurface formations. Engineering parameters such as Poisson’s Ratio and Young’s Modulus characterize formation locations where hydraulic fracturing will have the greatest effect. Seismic velocities describe conditions within the formations where pore pressures and local stress conditions vary, showing them either as targets or locations to avoid.

 

 

By combining newly-acquired shear wave data with conventional compression wave surveys these engineering parameters can be measured and development programs designed to target locations where pressure pumping can have the greatest effect. For details see shear wave results. The resulting reduction in effort and cost can upgrade an “average” property to a top-performer by improving cash-flow.

Takeway: Geoscientists contribute to resource plays by increasing engineering effectivenes

  • P-wave reflection data alone are inadequate to characterize lithology of fluid-filled formations; using combined S-wave and P-wave profiles gives a complete picture.
  • Elastic properties can be derived from seismic velocities, however the matrix velocities must be used, not the fluid values. Using S-wave velocities as a model gives matrix values and derives the “drained” Poisson’s ratio rather than the “undrained” ratio.
  • Poisson’s Ratio, Shear and Youngs Modulus provide formation attribute signatures. Pore pressure variations can be detected by velocity changes, which in turn indicate stress changes within a formation.

Svitzer’s newly-developed method uses techniques pioneered by geotechnical engineers to derive geomechanical properties of subsurface formations. Using this new information operators can harvest the reserves that offer the highest rate of return. This method is US patent pending under application 62/603,763.