Gas Well Deliquification Workshop Adams Mark Hotel, February 25-27, 28 Modelling Gas Well Liquid (Un)Loading Kees Veeken (NAM, Assen) Murat Kerem (Shell, Rijswijk)
Objectives of Modelling Liquid loading Improve capacity forecast to maximise nomination Determine proven and expectation reserves Predict end of field life i.e. abandonment date Predict date that deliquification should be installed Liquid unloading (a.k.a. deliquification) Determine SFR and reserves at stake Generate incremental forecast to justify investment Select best (sequence of) deliquification measures Optimise deliquification techniques and implementation 2
Contents Objectives Well & reservoir model Abandonment pressure & ultimate recovery Production forecast for deliquification Minimum gas rate & metastable production Gas well unloading Future modelling 3
Well Model Cullender-Smith FBHP = FTHP + HH + FF: FBHP 2 = B.FTHP 2 + C.Q 2 Forcheimer Pres = FBHP + DD: P res2 FBHP 2 = A.Q + F.Q 2 Turner Q min = TC.FTHP.5.ID 2 /[(FTHT+273).Z] Abandonment Q = Q min : P ab2 = B.FTHP 2 + A.Q min + (C+F).Q 2 min B & C, Q min FBHP FTHP Hydrostatic Head, Fluid Friction & Minimum Rate A & F Pres Drawdown 4
Turner 2 7/8" 3 1/2" 5" 7" 3 25 Q min (e 3 m 3 /d) 2 15 1 5 2 4 6 8 1 FTHP (bar) 5
Abandonment Pressure & Reserves P i UR = GIIP x (P i P ab ) / P i P res P ab G p UR GIIP 6
Wellhead Pressure & Tubing Size P ab (bar) 16 12 8 4 Compression benefit for all A Velocity string benefit increases with A Compression 5", 5 bar FTHP 3-1/2", 5 bar FTHP 5", 1 bar FTHP 3-1/2", 1 bar FTHP Velocity String 5 1 15 2 Prolific A (bar 2 /1 3 m 3 /d) Tight 7
Stim., Foam, Gas Lift, Plunger & Pump TC= TC=1 TC=2 TC=285 16 12 Stimulation increases reserves Foam lift benefit increases with A P ab (bar) 8 Stimulation Gas Lift Pump Plunger Foam 4 5 1 15 2 A (bar 2 /1 3 m 3 /d) 8
Prolific Gas Well (Low A) GIIP = 1 9 m 3, A = 4 bar 2 /(1 3 m 3 /d), 5" tubing Base Case Compression Foamer Gas Lift Base Case Compression Foamer Gas Lift 4 77% 22% 1% 1% 1 Gas Rate (1 3 m 3 /d) 3 2 1 75 5 25 Gas Volume (1 6 m 3 ) 1 2 3 4 5 Time (yrs) 9
Prolific Gas Well (Low A) GIIP = 1 9 m 3, A = 4 bar 2 /(1 3 m 3 /d), 5" tubing Base Case Compression Foamer Gas Lift Gas Rate (1 3 m 3 /d) 4 3 2 1 77% 22% 1% 1% Compression/eductor most useful Reduced scope for other measures 2 4 6 8 1 Gas Volume (1 6 m 3 ) 1
Tight Gas Well (High A) GIIP = 1 6 m 3, A = 4 bar 2 /(1 3 m 3 /d), 5" tubing Base Case Compression Foamer Gas Lift Base Case Compression Foamer Gas Lift 4 37% 32% 21% 1% 1 Gas Rate (1 3 m 3 /d) 3 2 1 75 5 25 Gas Volume (1 6 m 3 ) 4 8 12 16 2 Time (yrs) 11
Tight Gas Well (High A) GIIP = 1 6 m 3, A = 4 bar 2 /(1 3 m 3 /d), 5" tubing Base Case Compression Foamer Gas Lift Gas Rate (1 3 m 3 /d) 4 3 2 1 37% 32% 21% 1% Deliquification critical for recovery Scope for wide range of measures Sharing the same cake Selection is key 2 4 6 8 1 Gas Volume (1 6 m 3 ) 12
Tight Gas Outflow Challenge RF (%) 1% 8% 6% 4% Outflow as challenging as inflow! 2-7/8 tubing THP 5 bar H 1m, 1x RF=% if K < 1 µd 2% % Gas well deliquification essential to maximise recovery for tight gas wells.1 1 1 1 1 KH (md.m) 13
Minimum Rate Actual & Turner 25 Number of Wells (-) 2 15 1 5 <1. 1.-1.5 1.5-2. 2.-2.5 >2.5 Actual minimum rate / Turner criterion (-) 14
Modified Turner Actual/Turner (-) 4. 3.5 3. 2.5 2. 1.5 1..5. Well more sensitive to pressure fluctuations at low pressure y = 3.4441x -.1717 R 2 =.285 2 4 6 8 1 A.5 x FTHP 15
Turner Literature Data 12 Unloaded Loaded Questionable 1:1 1:1.5 Success Failure 1 Actual Gas Rate (Mscf/d) 8 6 4 2 1 2 3 4 5 6 7 Calculated Loading Rate (Mscf/d) 16
Dependency on A in Simulator Qmin increases as A decreases FTHP Poor Prolific Well more sensitive to pressure fluctuations at low pressure Q gas 17
Model Limitations Underestimates hydrostatic head Calculated abandonment pressure too low Uplift when injecting foam just above critical rate (?) No recharging due to tight or slow gas Connected volume increases with time Intermittent production Monobore only i.e. no wet foot across larger liner Extra back pressure No metastable flow 18
Metastable Gas Production Gas Rate (m3/d) 8 6 4 2 Gas Rate THP BHP Gas bubbles through liquid column (SPE 95282) Stable rate 4, m3/d Metastable rate 12, m3/d 4 3 2 1 THP, BHP (bar) 29-Dec 18-Jan 7-Feb 27-Feb 19-Mar 8-Apr 19
Metastable Gas Production Offshore wellhead temperature provides indication of liquid loading & metastable production.8.7 7 8 MILJ.NM3/D BARG DEG.CELC..6.5.4.3.2.1 Q min = 18, m 3 /d -1-12 24/4/26 8:3:12 9. Day(s) 23/7/26 8:3:12 2
Unloading Gas Well Gas well unloads far below Turner criterion Initial unloading via piston like displacement Critical velocity of Taylor gas bubble 1x lower than Turner critical velocity Piston model OLGA multiphase dynamic flow simulator 21
Unloading Well with 7 Tubing Q min,water ~4E5 m 3 /d, Q min,condensate ~2E5 m 3 /d FTHP Model vs Actual FTHP Actual FTHP Piston FTHP OLGA Choke Gas Rate 25 5E+5 FTHP (bar), Choke (1/64") 2 15 1 5 Gas @ surface Liq @ surface 4E+5 3E+5 2E+5 1E+5 Gas Rate (m 3 /d) 6 12 18 24 3 36 42 48 E+ Time (min) 22
Volume Fraction @ 24 min (OLGA) Oil Based Mud Completion Brine Base Oil 1. Q gas ~4E4 m 3 /d.8 Fraction (-).6.4.2. 5 1 15 2 25 3 35 Along Hole Distance from Toe (m) 23
Volume Fraction @ 48 min (OLGA) Oil Based Mud Completion Brine Base Oil 1. Q gas ~4E5 m 3 /d.8 Fraction (-).6.4.2. 5 1 15 2 25 3 35 Along Hole Distance from Toe (m) 24
Future Modelling Liquid loading Update & upgrade modified Turner Resolve abandonment pressure discrepancy Support multiphase dynamic modelling of liquid loading Liquid unloading (a.k.a. deliquification) Model interaction between reservoir and well in liquid loading domain to produce better deliquification forecasts & to optimise deliquification techniques 25
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