Crossdipole Sonic Data Analyzed To Target Stack Pay in the Permian Basin

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 209327, “Analysis of Crossdipole Sonic Data for an Intelligent Targeting of Stack Pay in the Permian Basin,” by Bikash Sinha, Farid Mohamed, and Lili Xu, SPE, Schlumberger, et al. The paper has not been peer reviewed. The preferred placement of a producer well in unconventional reservoirs is based on available information about the presence of natural fractures and formation stresses. Identifying the depth intervals with natural fractures and the relative magnitudes of the maximum and minimum horizontal stresses enables placement of a producer well that will support effective hydraulic fractures. In the complete paper, the authors apply a work flow to crossdipole sonic data acquired in a vertical pilot well drilled in the Permian Basin. Introduction The authors describe processing, analysis, and interpretation of sonic data acquired in a vertical pilot well with the goal of identifying optimal depth intervals and azimuths for drilling a lateral producer well with a potential for enhanced hydrocarbon productivity. The preferred placement of a lateral producer well requires drilling through an oil-rich layer that exhibits higher fracturability. Theory Borehole sonic data consist of monopole headwave slownesses and borehole Stoneley dispersions together with dipole headwave slownesses and borehole flexural dispersions. While monopole data provide azimuthally averaged formation properties, crossdipole data probe the formation in two opposite quadrants and discriminate formation properties in the two orthogonal directions in the borehole cross-sectional plane. Compressional and shear headwave slownesses can be transformed into compressional and shear moduli of the formation. Borehole Stoneley and flexural dispersions can be inverted to obtain formation transversely isotropic (TI) constants. One can invert for TI constants when the fast- and slow-dipole flexural dispersions overlay, and a subset of orthorhombic constants when the fast- and slow-dipole dispersions are different. Both the borehole flexural and Stoneley dispersions exhibit frequency-dependent sensitivities to changes in the formation anisotropic constants. It is possible to invert for those formation anisotropic constants that show sufficient sensitivities to such measured flexural dispersions. This section of the complete paper is devoted to inversion of borehole Stoneley and flexural dispersions for formation anisotropic constants and associated equations and discusses determination of Young’s moduli and Poisson’s ratio for a transversely isotropic with vertical axis of symmetry (TIV) formation.