Welcome to the Rock Mechanics Group

Production-induced changes in pore pressure and temperature cause changes in the effective rock stresses in the reservoir rock, which in turn can cause rock mechanical phenomena to be triggered within and around the reservoir. Within the reservoir, these phenomena can include near wellbore effects such as sand production and wellbore collapse, while reservoir-scale phenomena include compaction drive, joint activation inducing directional controls on fluid flow, and changes in compartmentalisation by fault activation. Reservoir-scale phenomena can be seen either as threats to or opportunities for improving oil recovery.

Above the reservoir, a stress contrast is created between the reservoir and the cap rock, which, given its low permeability, will retain its original pore pressures. The cap rock will also suffer from stress and strain changes induced as the reservoir compacts, with localised extreme changes occurring around faults which have been activated. Thus wellbore stability through the cap rock can become a significant issue when re-entering partially depleted reservoirs. Furthermore subsidence in the overburden can cause wells to be lost due to casing collapse.

Application of 4D seismic to reservoir management should also allow of the impact of production induced stress changes as well as the more usually addressed saturation changes on acoustic impedence.