Thirty thousand barrels of slurried drill cuttings waste, generated during the Wytch Farm Extended Reach Drilling programme, have been successfully injected into a producing sandstone formation as an environmentally acceptable means of disposal. Injection was through an existing water injection well into the producing formation because alternative shallow disposal horizons contain fresh water aquifers used to supply local drinking water. The disposal well continued to inject water in die periods between injection of the individual cuttings slurry batches, thus minimising the impact on the field management strategy.

Detailed monitoring data indicated that there was a significant increase in local formation stress at the injection well dining the operation, raising injection pressures, but that these had fully relaxed within five months of die end of the operation. Fracture growth was seen to be contained by die stress contrasts induced (thermoelastically) in the disposal formation by the long period of water injection prior to die cuttings injection operation. This provided confirmation that there had been no risk of contamination of die shallow fresh water aquifers by the slurry through vertical fracture growth.

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