Abstract
Pulse echo measurements are used to investigate the conditions on the outside of an oil or gas pipe by sending ultrasound pulses onto the pipe wall from inside the pipe that reverberate within the pipe wall. A range of different algorithms are used today to analyse this data and derive pipe-wall thickness and impedance of the material behind the pipe, with the aim of determining the bonding of the material. To be able to develop current algorithms further it is crucial to understand currently used algorithms and their advantages and disadvantages. The downside with using logging data from real boreholes is that no ground truth exists, making it difficult to evaluate the accuracy of the different algorithms. Therefore, we built a database of numerically generated data. This database allows us to investigate the effects of variations like casing diameter, thickness, bonding, and eccentering on the derived casing thickness and outer- material impedance using different analysis algorithms. Here, we use three of the most used algorithms and discuss comparisons of results gained from the analysis of the simulated data in the case of tool eccentering and existence of a fluid-filled annulus gap between pipe and cement on the outside showing the value of simulated data to improve and understand estimates of pipe thickness and outer-material impedance.
