Introduction to this special section: Time-lapse measurements

The idea of monitoring our reservoirs spatially in three dimensions with discrete snapshots (time-lapse measurements) along the production (or injection) time axis is extremely compelling but of course, as we have found, it is not as straightforward as one might initially anticipate. However, by persevering we have noted a long list of direct and indirect benefits too numerous to elaborate. The methods tell us how wells perform (particularly long-reach horizontals), how the field itself is responding to production and efforts to boost recovery, and greatly improve our understanding of the field in general.