<< Click to Display Table of Contents >> Navigation:  Input Panels > Artificial Lift Options > Gas Lift Design > Detailed Gas Lift Design Parameters

The panels that refer to these items are on the Gas Lift Design panel.

For a tutorial on this subject, visit Gas Lift Valve Design Tutorial.

 

The following items may be edited on the Gas Lift Design General Properties Panel, Gas Lift Parameters section:

 

KICKOFF GL CSG WELLHEAD PRESSURE (psia): The gas lift injection pressure at the surface available during the unloading sequence.  This pressure must be 30-50 psig less than the maximum wellhead casing pressure that can be maintained when lift gas is flowing at the desired operating rate (a larger difference is better, but do not compromise the pressure available down hole to lift the well at the deepest possible point).  The gas lift valve calibration pressures are calculated using a force “balance” equation.  The result is that although the valve may technically be open, it may not be open enough to flow significant quantities of gas.  Therefore, a pressure greater than the casing pressure used to calculate the calibration pressure value must be available to make the valves flow the desired amount of gas during the unloading process.  If this 30-50 psig of extra pressure is not available, it may be very difficult or even impossible to unload the well.

 

KICKOFF WELLHEAD TEMPERATURE (deg F): This is the surface temperature in the tubing during the unloading process.  This can normally be set equal to the flowing wellhead temperature.  If the well unloads at lower than the normal flowing temperature, the valves will operate at lower pressures until the well warms up.  Setting the kickoff temperatures of the top one or two unloading valves lower than the flowing temperature can be utilized to help “lock out” upper those valves, thus saving some casing pressure to gain a deeper gas lift injection depth.  This technique should be used with extreme caution as it could cause those upper valves to be difficult or impossible to re-open after a brief shut in period.

 

UNLOADING GRADIENT (psi/ft): This is the gradient of the heaviest fluids that may be present in the well.  The unloading gradient must be equal to or heavier than the unlifted flowing gradient of the well bore hydraulics.  A good default value is 0.45 psi/ft.

 

INJECTION GAS GRAVITY (sg): The specific gravity of the lift gas.

 

OBJECTIVE LIQUID RATE: The desired liquid production rate to be calculated for this case.  The adjacent “import” button allows you to import the calculated solution rate generated by the hydraulics and IPR information after a successful run has been made.

 

Injection gas target options:

TGLR TARGET: The objective total gas liquid ratio (includes both formation and gas lift gas) for the case to be calculated.  This field is linked to the INJECTION GAS RATE TARGET field so that a change to one automatically updates the other.  Selecting the TGLR Target will allow TGLR sensitivity cases to be run.  Sensitivities are selected on a later panel.

 

INJECTION GAS RATE TARGET (mscfpd): The objective gas lift gas injection rate.  This field is linked to the TGLR TARGET field so that a change to one automatically updates the other.  Selecting this field will allow Injection Gas Rate sensitivity cases to be run. Sensitivities are selected on a later panel.

 

GLR or CALC GLR Options: ENTER GLR for each Valve as the Well Kicks Off:

This option uses the values entered in the GLR column of the VALVE DESIGN panel to calculate the required lift gas rate at each unloading station.  This is the recommended setting for this option.  The Gas Lift Simulator Utility can be used to aid in GLR selection.

 

CALC GLR from Predicted Hydraulic Curves: Do not use this selection in this program version.  This option has not been fully and could yield inaccurate results.

 

SURFACE CASING PRESSURE Options: Drop Psc at Orifice to match requested Qg: The Surface Casing Pressure will be decreased until a match is obtained between the calculated gas flow through the operating valve and the required lift gas flow rate.  If a match is obtained, an operating casing pressure line will be drawn on the gas lift graph.

 

Do not drop Orifice PSC to match requested Qg: The Surface Casing Pressure will be decreased only enough to close the unloading valves (the surface closing pressure of the top valve plus the DELTA PRESSURES are summed and subtracted from the KICKOFF CASING PRESSURE).  This option calculates the maximum gas passage through the operating valve that would be possible without opening the upper unloading valves.  An operating casing pressure line is not drawn on the gas lift graph.

 

GAS PASSAGE METHOD Options:  For easy comparison, results from all methods are displayed on the gas lift report that is displayed when the gas lift design is calculated.  Plots of performance curves are available from the valve detail panel.

 

VALVE PERFORMANCE CLEARINGHOUSE:  This is the recommended method for those that are current members of this consortium.  It models flow rates when the valve is performing in either the throttling or orifice regime and includes a full set of performance curves for essentially all valves in use today.  When using this method, you can inspect the flow rate performance of each selected calve on the valve detail page.

 

TUALP:  This is the recommended method.  It models flow rates when the valve is performing in either the throttling or orifice regime. Tulsa University Artificial Lift Program dynamically flow tested valves of different manufacturers and sizes at their flow lab, but not all of the valves that are currently available on the market were tested.  Be sure to verify that the valves you are using were tested by TUALP before relying on the results of this method.

 

McBRIDE:  For use only with 1-1/2” OD valves.  McBride made field observations and developed this model.

 

THORNHILL CRAVER:  The standard model for gas flow through a square edged orifice plate in a meter run.  This method is the default when none of the more rigorous methods is available.

 

CASING GRADIENT Options:  Three methods for calculating the gradient of the lift gas in the annulus due to gravity and true vertical depth.  Either the STANDARD or RIGOROUS method may be used depending on your desire to conserve computing power.  The rigorous method is recommended.  The PRUDHOE method was developed for it’s namesake oilfield because of the unique composition of their lift gas, and should not be used for any other areas.

 

GENERATE SETUP REPORT:  If this box is selected, the program will generate a “rich text” formatted document with the basic information required by a shop technician to calibrate the gas lift valves.

 

IMPORT PRIOR DATA button:  Clicking this button will update the input fields with information from previous panels.  You may also edit directly into any of the cells.

 

FLOWING WELLHEAD TEMPERATURE (deg F):

The temperature in the tubing at surface when the well has unloaded and is operating at objective conditions.

 

STATIC BOTTOM HOLE TEMPERATURE (deg F):

The temperature in the well at the mid-perforation depth.

 

STATIC BOTTOM HOLE PRESSURE (psia):

The average reservoir pressure measured at the mid-perforation depth.

 

SNAP IPR or FIXED PI:  Check the SNAP IPR box if you wish to use the inflow information developed from previous input panels.  Do not check the SNAP IPR box if you wish to use a fixed PI (productivity index, bpd/psi) that can be typed into the available filed.

 

WATER CUT (decimal fraction):  The producing water cut for the case to be calculated.

 

FORMATION GOR (scf/stb):  Produced formation gas only.  This does not include lift gas.

 

PERFORATION DEPTH (ft):  This is the mid-perforation depth.  This value should be equal to or less than the last depth in the Well Bore Geometry panel .  The MD (measured depth) and TVD (true vertical depth) cells are linked.  Changing either one will automatically update the other.  The corresponding MD or TVD is calculated using the deviation information in the previous Well Bore Geometry panel .

 

LIFT DEPTH (ft):  Depth of lift gas injection for this calculation.  The MD and TVD cells are linked to each other so that changing one automatically updates the other.  The lift depth cells are also linked to the MD and TVD of the individual valves on the GAS LIFTDESIGN, VALVE DESIGN panel so that pushing the + or the – button will scroll you to the next available gas lift valve depth.  The dummy valve depth are skipped when using the + or – buttons.

 

Create Set-Up Report:  This selection is used to create a report used for field procedures and documentation.   It can be retrieved using the Open Setup Report.  A sample report follows this page.

 

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   Engineer : Engineer1

    Dataset : 8b GasLiftDesign.snp

      Title : new GLD for Leak Detect

-------------------------------------------------------------------------

Engineer1              Solution Rate   204 blpd    Pvc Bottom Bellows:  1261

Kick Off Prss:  1350   Solution fbhp   1777 psi    Operating Pressure:  1189

Suggested KOP:         Flwg Wh Temp (Twh):   60    Casing DP:           1584

SNAP IPR function      Top Valve Flwg Temp:  97    Orifice DP:            58

Static BHP(Pws):2250   Static BH Temp:      160    KO Gas Gradient:   0.0409

2.068.497 8/28/2008    Tubing Size:       2.992    Flwg Gas Gradient: 0.0424

08/28/08    21:17:10   Dsgn Liquid Rate:    444    Watercut:          25.0 %

Model:DunsRos          Unloading Gradient:0.450    Formation GOR:        500

Oil Rate:   153 bopd   Water Rate:      51 bwpd    FM Gas Rate:    76 mscfpd  

 

Sta Depth  Depth  Valve  Valve          Valve   Port    Valve   Valve GLD Flwg

 #   TVD    MD     OD     Type          Model   Size    Ap/Ab    Ppef  TV   TV

 1  2320   2516  1.00 Bellows       Camco_BK  0.1250  0.0430  0.0449  110   97

 2  3906   5085  1.00 Bellows       Camco_BK  0.2500  0.1650  0.1976  130  123

 3  4864   6643  1.00 Bellows       Camco_BK  0.1875  0.0940  0.1038  143  139

 4  5398   7512  1.00 Bellows       Camco_BK  0.1875  0.0940  0.1038  150  147

 5  5721   8037  1.00 Orifice    Camco_BKO-3  0.1563  0.0000  0.0000  154  152

 6  6063   8593  1.00   Dummy       Camco_BK                          158  158

 

Sta   Ppd    Pwf     Ql*  Rgl Qgi(req) Qgi(TU) Qgi(VPC) Qgi(ThH) Qgi(Wnk) Pvo60    Pvo

 #    Prs    psig  stbpd scf/b   mm/d    mm/d     mm/d     mm/d    mm/d    psi  installed

  1   603    2513    200   375  0.000   0.422    0.000    0.372    0.000   1319    1327

  2   929    1903    154 14493  2.176   0.943    0.000    1.450    0.000   1484    1499

  3  1142    1738    218  2227  0.405   0.464    0.126    0.630    0.081   1352    1371

  4  1265    1632    257  1760  0.355   0.372    0.208    0.504    0.238   1334    1355

  5  1339    1777    204  1803  0.291   0.179    0.219    0.291    0.323

  6  1415   Dummy

 

Sta   Pgd   GLD   GLD   GLD   Flwg  Flwg  Flwg   GLD   GLD   GLD   Pvc Ppd-Pmin

 #    Prs  Piod  Pvcd PpTran    Ct  Piod  Pvc     Ct   Pio   Pvc    DP     psig

  1  1445  1445  1416   767  0.917  1411  1285 0.891  1350  1321    20      165

  2  1510  1538  1461  1069  0.862  1537  1283 0.848  1378  1301    20      139

  3  1549  1503  1480  1262  0.835  1500  1275 0.828  1304  1281    20      119

  4  1571  1496  1482  1350  0.820  1495  1261 0.816  1275  1261    20       84

  5  1584  1397                                                              58

  6  1598 Dummy

 

 

 

 

 

 

Slick Line Procedure:

 

                                 Surf.        Surf.        TRO

 MD        Valve        Valve        Port        Open        Close        Press

GLM        (RKB)        Size        Name        Size        Press        Press        60° F

 

1        2516        1"        Camco_BK        1/8"         1350        1321        1319

2        5085        1"        Camco_BK        1/4"         1378        1301        1484

3        6643        1"        Camco_BK        3/16"         1304        1281        1352

4        7512        1"        Camco_BK        3/16"         1275        1261        1334

5        8037        1"        Camco_BKO-3        5/32"         ------ Orifice ------

6        8593        1"        Camco_BK                 ------ Dummy ------

 

 

Recommended Unloading Procedure