Acoustic Amplitude Ratio Logging

Abstract

A,calibra:fon systetn is obtained that permits correlation of amplhude data from borehole to borehole regardless oj composition of hole fluid, hole diameter, or other hole~derived parameters, Two-receiver attenuation logging provides better interpretation of acoustic cement bond logs because o# this calibration system. Recent advances in acoustic amplitude logging have left undone the requisite of all physical nzeasurements, that is, calibration: toa known acceptable and consistently repeatable standard unit, In our study of two-receiver amplitude ratios we show that theratio scale tnay be precisely stated in a common term of atteituation rate-decibels per foot. Results of amplitude ratio logging in'various representative areas including both cased and open ho~es are given. Curves are presented showing ratio relations for various spacings. A nomograph for deiernthting hole factor kf rom the ratio and one single-receiver amplitude (recorded sitnultaneoasly) has been developed. This indicates tile possibility that new information concerning acoustic energy translation at the weilbore-fortnation interfaces maybe obtahted, She~r wave and compressive wave attenuatiori rates are discussed as a means to assess fluid mobility. .:. ,