MULTICANNEL SONIC TOOL (MCS)

Drilling operator: Warren George Inc.

Logging operator: LDEO-BRG

Hole: Moodus 1

Location: Moodus Township (Middlesex County, Connecticut)

Latitude: 41° 31.68' N

Longitude: 72° 26.56' W

Logging date: July, 1987

Total penetration: 1458 mbrf (4784 ftbrf)

Total core recovered: Nine 3-m cores were recovered at approximately 150 m intervals

Lithologies: 0-579 m - Granitic gneisses, schists, and granites (Hebron Formation); 579-637 m - Granitic gneisses (Canterbury Gneiss); 637-678 m - Canterbury gneisses interlayered with Tatnic Hill œschists ; 678-802 m - Biotite schists and gneisses (Tatnic Hill Formation); 802-1085 m - Granitic gneisses and schists (Waterford Group); 1085-1458 m - Biotite-amphibole gneisses (Lower Avalon Complex).

TOOL USED. The Multichannel Sonic Tool (MCS) is a single source, multi-receiver logging tool that records a set of 12 full waveforms at 2ft depth intervals in the borehole. The pricipal received phases are 1) a first arrival P-wave refracted along the borehole wall, 2) a second-arrival S-wave followed by a ringing pseudo-Raley pahse, and 3) a low frequency Stoneley wave. Compressional and shear velocities are computed from the linear moveouts across the receiver array of the P and S waves. The Poisson;s atio can be compueted from the Vp/Vs, and the elastic moduli can be computed from the velocities if the density is known. The Stonely wave velocitu and amplitued provide information about fracturing and fracture permeability.

DATA PROCESSING. The compressional and shear sonic wave velocities were calculated from the 12 received waveforms by a modified semblance technique. Semblance for a given wave mode is defined as the energy-normalized maximum coherence, and is calculated as a function of velocity, as the sum of the cross-correlations of the windowed waveforms divided by the sum of the auto correlations within each window. The time delay to each window is the product of the receiver offset from the source and the inverse velocity or slowness. The window length is selected so that several full cycles of data are included.

RESULTS. For a complete report, see Zoback M. and Moos D., In situ stress, natural fracture and sonic velocity measurements in the Moodus, Connecticut, scientific well, in Woodward-Clyde Consultants, 1988, Regional crustal stress study 3: Tectonic stress in south-central Connecticut: Empire State Elec. Ener. Res. Corp. (ESEERCO), v. 86-46, Appendix C, 90 pp.

For further information about the logs please contact:

Cristina Broglia
phone: 845-365-8343
fax: 845-365-3182
email: Crisitna Broglia