Active Monitoring Using Tube Waves

Tube-wave monitoring is new fit-for-purpose downhole imaging and monitoring technique. It aims to characterize time-lapse changes in a cross-well space. In contrast to conventional cross-well seismic it does not require well intervention or reduce it to a minimum. Monitoring relies on a tube waves in a fluid column to carry the reservoir signals to and from the surface. We present simple modeling to support the concept and validate experimental data acquired at Stratton field. Various methods are used for time-lapse reservoir monitoring. Surface seismic is the most popular approach that delivers the areal coverage. However it suffers from non-repeatable acquisition and changing near-surface conditions. Surface 4D may not have enough resolution for for stacked reservoirs and has threshold on the amount of change it can detect. Repeated VSP has better resolution, repeatability and sensitivity but requires frequent well interventions or permanent sensors with substantial shooting effort. Conventional cross-well seismic has even better characteristics but requires intervention in two producing wells or drilling dedicated observation wells and thus rarely used in practice. Time-lapse logging can characterize detailed changes in the immediate near-wellbore, but also requires well intervention. We propose new real-time method for permanent cross-well monitoring that does not require well intervention and utilizes existing production and injection wells.