Extending Gas Well Velocity Limits: Problems and Solutions

Abstract

Production from North Rankin A platform (NRA) aims to meet the objective of supplying contract gas/LNG whilst maximising the condensate yield. This paper describes current efforts to increase production of selected wells through an extension of tubing flow velocity limits. By doing so, condensate rich wells can be produced preferentially at higher rates and overall flexibility between wells with regards to maintaining contractual gas production can be improved. Arguments used to define a new limit to tubing flow velocity are presented together with the agreed basis for allowable sand production. Also discussed are the monitoring practices undertaken to ensure a long term field trial is completed safely. Here, particular emphasis was placed on proving the reliability of sand monitoring by performing field comparison trials of available systems prior to the commencement of the high rate trial.

Openhole Gravel Packing in the Roaring Forties

“…Should any significant amount of the screen or the openhole section not contribute to the inflow, then this velocity would quickly increase to a rate that might be considered unacceptable. 6 In order to help avoid this situation, it was decided to place a delayed release acid/oxidizer filtercake removal and breaker-fluid system in the openhole after the gravel pack in order to degrade the water based drilling fluid filter cake, including the sized CaCO 3 solids and polymers, in place. This was achieved by converting the gravel-pack service tool back to wash down system and then circulating down the work-string and through the wash-pipe to the end of the wash-pipe positioned close to the end of the screen / open hole.…”

“…6 To minimize the risk of plugging the screens before the start of gravel-pack placement operations, the DIF was conditioned to reduce the size of the particles, mainly sized CaCO 3 , but the load was to be maintained to ensure that fluid density remained constant. Tailor-made quality-control devices consisting of a "mud bucket" and a "re-circulation loop," both fitted with a coupon of the premium screen filter media, was designed to confirm the treated DIF would not plug the screens.…”