Elastic anisotropy in the Haynesville Shale from dipole sonic data

Worldwide interest in shales as hydrocarbon resources has increased in recent years, driven mostly by the successful development of gas shales in North America. One of these gas shale plays is the Haynesville Shale located in Texas and Louisiana. In this paper we analyse dipole sonic log data acquired over the build section of a deviated well and show how these data can be used to estimate the elastic anisotropy of the formation. In this case the formation is relatively homogeneous over the build section and so the deviated well allows the sampling of well deviations from approximately 50° to horizontal. Using the compressional, fast-shear, and slow-shear data as a function of the well deviation angle, we estimated the anisotropy for the gas shale. These anisotropy estimates were then used to remove the anisotropy effects observed in the deviated well. Comparison of these ‘corrected’ sonic logs to sonic logs acquired in the vertical pilot well shows good agreement.