To meet winter peak delivery obligations, a depleted gas field in the North Netherlands was converted to a storage reservoir. The 7 5/8″ mono-bore wells were designed for high production and injection rates, up to 280 MMscf/d (8 MMsm3/d) per well from the fully charged reservoir. To produce at such high rates any damage to the formation has to be avoided. A particular concern in this respect was killing the wells e.g. prior to a work-over or in case of an emergency. Inclusion of a side pocket mandrel to land a down-hole circulation device, a potential leak path, was considered undesirable in the design for the high-pressure wells. Hence the wells were to be killed by bullheading. This technique however bears the risk of damaging the productive formations when plugging material is forced into the rock. Therefore it was investigated how the bullheading process could be controlled so that all the gas is pushed back into the reservoir, while avoiding the invasion of foreign material in the productive formations. A dedicated field test to demonstrate the feasibility of the technique was carried out. This test, results and analysis will be discussed.

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