Patent ID: 10481289

Abstract:
A downhole installation comprises: a first pipe layer 8, a second pipe layer 10 about the first pipe layer 8, an annulus 12 between the first pipe layer 8 and the second pipe layer, and a geological formation outside of the second pipe layer 10. A logging system for evaluation of the downhole installation comprises: a logging tool 4 including an angled acoustic transmitter 20 for exciting a flexural wave in the first pipe layer 8, and three or more 10 angled acoustic receivers 14, 16, 38, 40, 42 spaced apart along the tool 4 such that, in use, the receivers are at different locations along the length of the pipe layers 8, 10, the receivers 4, 16, 38, 40, 42 each being for obtaining third interface echo data from the second pipe layer 10; and a processor arranged to process acoustic data from the receivers in order to: identify trends in the amplitude of the third interface echo as it propagates along the length of 1 the pipes, calculate an estimated exponential decay for the third interface echo when reinforcement from other acoustic energy is disregarded, use this estimation to predict if the material behind the second pipe layer 10 is fluid or solid, and analyze the third interface echo data in light of the determined material state in order to thereby evaluate material conditions in the annulus 12 outside the second pipe layer 10.