Single-well S-wave imaging using multicomponentdipole acoustic-log data

摘要

Single-well S-wave imaging has several attractive featuresbecause of its directional sensitivity and usefulness for fracturecharacterization. To provide a method for single-wellacoustic imaging, we analyzed the effects of wave radiation,reflection, and borehole acoustic response on S-wave reflectionmeasurements from a multicomponent dipole acoustictool.Astudy of S-wave radiation from a dipole source and thewave’s reflection from a formation boundary shows that theS-waves generated by a dipole source in a borehole have awide radiation pattern that allows imaging of reflectors atvarious dip angles crossing the borehole. More importantly,the azimuthal variation of the S-waves, in connection withthe multicomponent nature of a cross-dipole tool, can determinethe strike of the reflector.We used our theoretical foundationfor borehole S-wave imaging to formulate an inversionprocedure for field data processing. Application to fielddata validates the theoretical results and demonstrates the advantagesof S-wave imaging. Application to near-boreholefracture imaging clearly demonstrates S-wave azimuthalsensitivity to fracture orientation.