Wells that can only Flow under gas Lift
•WTEST can be used to revive a dead well by adding lift gas
•The WIG is calculated based on the total number of lift gas increments that would give the well the largest ratio of oil production rate to lift gas injection rate (line
O-A)
•If a well is only just able to flow (at point B), the WDG is calculated based on all the increments (line O-B)
Using the GLO Facility (1)
•Prepare the VFP Tables - VFPPROD
•ALQ = lift gas injection rate (GRAT)
•VFPTABL
•1 = Linear interpolation
•2 = Cubic Spline interpolation
•LIFTOPT keyword
•Activates the GLO facility
•Sets:
•incremental size for lift gas injection rate
•Min economic gradient
•Min interval between GLOs
•GLO during each of the 1st NUPCOL iterations?
•WLIFTOPT keyword
•Well name
•Is the well to be optimized using GLO?
•Max lift gas injection rate
•Weighting factor for preferential allocation of lift gas
•Min lift gas rate
•>0 = Min rate unless the well cannot flow
•<0 = at least enough lift gas to enable the well to flow
•allocate in decreasing order of weighting factor to group of wells
•Note: By default, no lift gas is allocated if the group’s target can be met unless the weighting factor > 1.0
•GLIFTOPT keyword (optional)
•group lift gas supply limits
•group lift gas rate = SUM well lift gas rate x efficiency factor
•maximum total (produced + lift ) gas rate for the group
• Group Production Rate Limits
•Lift gas is allocated if a group/field cannot reach its OPR
•subject to lift gas supply limits, other phase limits (unless
necessary to make the well’s Min lift requirement & the well’s
weighting factor > 1.0)
•Rates could change if GLO is only in the 1st iteration
•Use with network option
•GLO when the network is being balanced
•if the network is only balanced in the 1st iteration, GLO is only in the start of the time step
•if the network is only balanced in the 1st NUPCOL iterations, GLO will also be carried out in the 1st NUPCOL iterations
•Computing time increases with (No. wells)2
•effect of lift gas in pipe line:
•item 6 of GRUPNET
•‘FLO’ = add wells’ lift gas to the branch. The total GFR is used in VFP table
•‘ALQ’ = total ALQ = SUM of wells’ ALQs = the total ALQ is used in VFP table
•Output
•Gas lift injection rate: FGLIR, GGLIR, WGLIR
•well oil gas lift ratio: WOGLR
•FGPR & WGPR do not include injected lift gas
•Restrictions
•Do not use
•GLIFTLIM - Max(sum ALQ), Max No. wells on artificial lift
•the lift switching option in WLIFT
•Use GLIFTOPT and WLIFTOPT instead
•Flux Boundary Conditions facility should no be used
•lift gas supplied to wells outside the flux boundary is not taken into account