Large diameter gas-condensate pipelines are rarely operated below their minimum turndown rate specified during design. However there are circumstances where operations at low flow rates are necessary, such as partial shutdown of downstream facilities, which may be planned or in response to abnormal situations.
At low flow rates, large liquid volumes are likely to build up in pipelines and limited time is available before production needs to be turned up or stopped to manage liquid surges on ramp-up or restart. This paper describes three events where large diameter two-phase (gas and condensate) and three phase (gas, condensate and aqueous phase) offshore pipelines were operated for extended time periods below their notional minimum turndown rate. For each event, an operating strategy was developed to manage liquid surges in receiving facilities. This strategy is described and analyzed through comparisons between field measurements and dynamic multiphase flow simulations.