A pressure decrease in a reservoir will inevitably cause compaction and an associated subsidence pattern at the surface/seafloor. In many cases this has been considered insignificant or impossible to measure. Compaction can be an important drive mechanism in oil production and is then a key process to model in flow simulations. Rock stiffness in aquifer zones is a key parameter in these models, as water is rather incompressible. There is usually little, if any, data available from the aquifers outside the hydrocarbon field itself.
In cases of large compaction (several meters), the production infrastructure — well casings and pipelines — can be at risk. In such cases it is important to get early warnings and good predictions – as history has shown.
The measurement of gravity and height at stations above the reservoir provide important information which can constrain geomechanical reservoir and overburden models and can help optimize production.