Method Development and method description using Durham ultrasonic data

This report describes development of time-lapse monitoring method and its validation.

Our aim is to newly developed 4D crosswell tomography validate not only on synthetic but also on ultrasonic data. To obtain needed crosswell data two types of modelling experiments are considered: i) 2D finite-difference (FD) modelling and ii) 3D ultrasonic modelling of a time-lapse system.

Time-lapse tomographic method is first validated using synthetic data obtained by 2D FD modeling. Numerical modeling simulates ultrasonic experiment where ultrasonic broadband waveform data were recorded in a crosswell setting at the laboratory of University of Durham. Two data sets have been obtained from two almost identical physical models simulating pre-flood and post-flood stages during an enhanced oil recovery. We have applied a time-lapse method based on ray theory and wave scattering theory to estimate velocity differences thereby induced