Time-Dependent Behaviour of Oil Reservoir Chalk : A Multiphase Approach

On the collapse behaviour of oil reservoir chalk

“…This variation of the void ratio corresponds to a compressive volumetric strain of about 1.5%. Some creep may also have affected this volume decrease (Ruddy et al, 10 1989;De Gennaro et al, 2003). It is worth noting that the induced volumetric strain due to wetting results from a natural infiltration process, developing from the bottom to the top of the sample.…”

“…Samples of about 50 mm diameter and 15 mm high were used for the oedometer tests (Table 1). For the retention tests, samples had a diameter of about 20 mm and their height ranged between 20 to 25 mm (De Gennaro et al, 2003). All the samples were oven dried at 105°C, put under vacuum (approximately -94 kPa for 24 hours) and oil saturated under vacuum.…”

“…It was proposed to adopt a coupled hydro-mechanical framework taken from the mechanics of unsaturated soils (containing water and air as a non wetting fluid) and to adapt it to reservoir chalks (containing water and oil as a non wetting fluid) Collin et al, 2002;De Gennaro et al, 2003). In this framework, it was demonstrated that the compaction induced by waterflooding bore strong similarities with the collapse of unsaturated soils when wetted under a constant load.…”

Water-Rock Interaction Mechanisms and Ageing Processes in Chalk

“…Considering that conditions of relative humidity, h r , of around 80% can occur in the mine, and that for this situation S rw at equilibrium is as low as 5%, the significance of the chalk behaviour in unsaturated conditions is confirmed. Similarly to what has been shown in oil reservoir chalks (De Gennaro et al, 2003, 2004, the methods and concepts of unsaturated soils have been successfully adapted to Estreux chalk. Controlled suction oedometer tests provided more details on the water-weakening effects in chalk, showing increasing compaction during water injection (pore collapse).…”

An elasto-viscoplastic model for chalk including suction effects

“…Ekofisk oilfield). Another important component of subsidence was then related to the creep behaviour of the multiphase chalk (De Gennaro et al, 2003). A modified Pasachalk model was proposed to account for time effects using the framework of Perzyna's viscoplasticity (1964) but without considering suction effects.…”