Lee Hunt1, Eric Street1, Graham Hack1, Jason Schweigert2 and Matthew Allen2




This is part 3 of a 3-paper series describing a new monitoring, measurement, and verification (MMV) method for onshore carbon capture and storage (CCS). The method is called Theseus 24D, and it focusses on reducing unnecessary seismic effort in MMV. Part 1 and 2 of the series focused on the potential capital and environmental benefits that the method might yield, along with a set of technical requirements that would need to be met for the maximum value of the method to be realized. The value is material with potentially a 57% capital savings and 96% reduction in surface disturbances. However, to achieve this a special baseline 3D design would have to be able to produce arbitrary 2D lines to act as baseline surveys to be compared to repeat native 2D lines to be shot in time-lapse fashion. These 2D lines would have to be produced at no extra cost, and the baseline 3D would need to retain sufficient quality. While part 2 of the series showed that the 3D design most likely to succeed in this role would produce the arbitrary 2D lines through wavefield reconstruction, and identified four candidate 3D geometries, it was insufficient to either prove that such an approach would work, or which design would work best. This final part in the series attempts to resolve these questions through a 3D ray tracing and processing experiment. The experiment involves a model of the Basal Cambrian Sand (BCS), a storage reservoir of current interest in Alberta and Saskatchewan, Canada.

This experiment supports the idea that arbitrary time-lapse comparable 2D lines can be produced from certain 3D geometries, and that some geometries, such as the standard orthogonal, the zigzag and reverse zigzag geometries are superior for this purpose than the parallel geometry. Evidence of this claim is both qualitative and quantitative in nature. These results are also supportive of the potential endpoint version of the Theseus 24D method, where repeat 3D surveys are completely replaced by repeat 2D seismic.