Depletion-induced Reservoir Compaction in Shallow Overconsolidated Reservoir

Production induced reservoir depletion in unconsolidated reservoirs may result in reservoir compaction and surface subsidence. The potential for such impacts can be assessed by integrating geomechanical models with reservoir properties obtained from laboratory measurements. The response of reservoir compaction to pressure depletion depends on the burial history. This study investigates reservoir compressibility and compaction due to depletion from reservoirs of shallow overconsolidated sands caused by uplift compared to normally compacted sands from experimental mechanical compaction. Static moduli obtained from the experimental mechanical compaction show that uniaxial compressibility of the overconsolidated sands is less compared to the normally consolidated sands. The reservoir compaction due to depletion in such a reservoir is therefore less compared to the normally compacted reservoir. The mineral compositions and textural variations do not influence the compressibility in the overconsolidated case. The preconsolidation stress associated to the maximum burial depth before uplift is an important estimation to predict when the pore pressure drawdown will change the compaction behaviour from poro-elastic to plastic. The results can be applied to reservoir compaction during hydrocarbon production in uplifted basins like the Barents Sea.