title: Experiments on stress dependent borehole acoustic waves.
abstract: In the laboratory setup, a borehole traverses a dry sandstone formation, which is subjected to a controlled uniaxial stress in the direction perpendicular to the borehole axis. Measurements are made in a single loading-unloading stress cycle from zero to 10 MPa and then back down to zero stress. The applied stress and the presence of the borehole induce anisotropy in the bulk of the material and stress concentration around the borehole, both azimuthally and radially. Acoustic waves are generated and detected in the water-filled borehole, including compressional and shear headwaves, as well as modes of monopole, dipole, quadrupole, and higher order azimuthal symmetries. The linear and non-linear elastic parameters of the formation material are independently quantified, and utilized in conjunction with elastic theories to predict the characteristics of various borehole waves at zero and finite stress conditions. For example, an analytic theory is developed which is successfully used to estimate the changes of monopole tube mode at low frequency resulted from uniaxial stress, utilizing the measured material third order elasticity parameters. Comparisons between various measurements as well as that between experiments and theories are also presented.
authors.affiliation: Schlumberger-Doll Research, One Hampshire Street, Cambridge, Massachusetts 02139, USA.
authors.forename: Chaur-Jian
authors.initials: CJ
authors.lastname: Hsu
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kane
authors.forename: Kenneth
authors.initials: K
authors.lastname: Winkler
authors.forename: Canyun
authors.initials: C
authors.lastname: Wang
authors.forename: David Linton
authors.initials: DL
authors.lastname: Johnson
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D016880:Anisotropy; D003198:Computer Simulation; D004548:Elasticity; D004867:Equipment Design; D005844:Geology / Q000295:instrumentation / Q000379:methods*; D016014:Linear Models; D009038:Motion; D017711:Nonlinear Dynamics; D009716:Numerical Analysis, Computer-Assisted; D061329:Oil and Gas Fields; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013314:Stress, Mechanical; D013997:Time Factors; D014159:Transducers