Hydraulic fracturing (fracking) of shale resources has become a trend in the oil and gas industry that is associated with exorbitant costs. This calls for certainty in the productivity and success of every fracture stimulation program. Current fracking practices rely mostly on a geometric design and evaluation of vertical well sections and pilot holes to predict properties along wellbore laterals. Consequently, there is a reduction in the efficiency of fracture stimulation programs and productivity of shale reservoirs. This problem is associated with the fact that shale reservoirs are anisotropic, possessing directional properties that cannot be accurately predicted as such. In order to increase the efficiency of fracture stimulation, considerations have to be given to the anisotropic tendencies of shale petrophysical and geomechanical properties along wellbore laterals where fractures are hydraulically induced. In this study, an approach for the accurate quantification of vertical transverse isotropy (VTI) and resultant anisotropic properties along shale wellbore laterals using an LWD azimuthal sonic log was investigated. Using the case study of a Marcellus shale well in Northeastern Pennsylvania having azimuthal sonic data, a work flow for obtaining anisotropic properties, critical to fracture stimulation design was developed. An algorithm for the characterization of wellbore geomechanical quality based on estimated VTI anisotropy, anisotropic closure stress and brittleness was also developed.
OLUYEMI, G.F. and AFOLABI, T.S. 2018. Optimisation of hydraulic fracture placement design in anisotropic shale reservoirs using azimuthal LWD sonic and spectral gamma ray analysis. International journal of petroleum engineering [online], 3(2), pages 83-94. Available from: https://doi.org/10.1504/IJPE.2018.093154