Producing hydrocarbons in a deepwater environment is quite challenging and the goal is always to sustain production for as long as possible. Any shutdown, whether intended or unintended, can prove costly. Such was the case on Oyo-8 when the down-hole safety valve failed to open after a planned production curtailment. The several attempts to open the valve were unsuccessful due to suspected loss of hydraulic communication to the operating mechanism or the malfunction of the mechanism. A well intervention was therefore deemed necessary to re-enter the well. Well intervention in a deepwater environment is particularly expensive, risky and complex, whether it is rig based or rigless. A vessel based riserless light well intervention (RLWI) operation was determined as the optimal solution for Oyo-8. This entails a through-tubing operation to install a retrofit sub-surface controlled safety valve (velocity valve) assembly across the tubing-retrievable safety valve (TRSV) to permanently hold open its flapper and serve as a sub-surface controlled safety valve.
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