Abstract
The objective is to present a case study on dual gas lifting methodology which resulted in revival and subsequent production optimization of a shut offshore well. This well has encountered multiple stratified oil and gas sands and is completed as cased and perforated. The shallowest gas sand is compartmentalized between two production packers and has a sliding sleeve door (SSD) for zonal isolation. The bottom oil sand is below tubing and has resin consolidation for sand control. The upper completion string has a circulation SSD. The well was shut after depletion of the oil zone. Presence of shallow gas zone gave an opportunity for utilizing as auto gas lifting to revive the shut well. Considering unavailability of gas lift mandrel across the gas zone, innovative approach was needed. The well was modelled for gas lifting and accordingly the conventional jet pump was selected as straddle gas lift valve and installed across the gas zone SSD. This achieved controlled gas rate resulting in successful well revival at rates ~ 800 bopd, 1.1 mmscfd gas and 1000 bwpd. Post revival, the well produced at stable parameters for more than a year after which it started showing cyclic behavior. This behavior was attributed to gas sand depletion hence additional external gas lift support was required to augment auto-gas lift sand. The unavailability of both permanent gas lift setup on platform and gas lift mandrels in completion restricted the conventional approach of external gas lifting from surface. A new well was drilled on same platform which produced dry gas at high pressure. Gas Lift modelling suggested successful feasibility for utilizing this gas as gas lift in subject well. Another jet pump was installed in circulation SSD for external gas lifting. This augmented auto-gas lift sand and stabilized the well resulting in doubling the production rates.
