Appalachian Basin Gas Well Deliquification Seminar Marietta College, Marietta, Ohio June 7-8, 2010 Is The Selection Of Artificial Lift Too Arbitrary? Jim Hacksma - Consultant
How Is Artificial Lift (AL) Selected? Nearly Identical Wells SHOULD Receive The Same AL When Identical Wells Are Receiving Several Types of AL, Then; Mistakes Are Being Made Some Are Failing To Select The Best AL In Nearly Identical Wells (sometimes just across lease line), We Often See Following Inconsistencies: i Different Operators Using Different AL The Same Operator Using Different AL An Operator Starts Using Different AL In A Field: Simply Because A Different Engineer Is Assigned To Field New Engineer Not Armed With Different Facts Only Different Opinions Inconsistencies Are Evidence Selection Is Too Arbitrary Is The Selection Arbitrary Because Those Selecting AL Are Being Provided Too Little Reliable Info On Merits of AL Methods? 2
A Better Selection Process If The Technical Merits Of Each AL Method Are: More Widely Disseminated Better Understood More Commonly Used In The AL Selection Process Then The AL Selection Process Will Yield More Uniform Results: Nearly Identical Wells Would More Often Receive Same AL Inconsistencies Would Largely Disappear 3
The Technical Merits I Compare Outflow Curves (or J-curves) from Nodal Analysis For Each Artificial Lift Method (when possible) A Flowing Gas Well The Benchmark Flowing Just Above The Critical Rate Just Before Liquid Loading Becomes A Problem At That Point The Very Lowest FBHP Exists (The Benchmark) Ask The Following About Each AL Method What Will The FBHP Be? Initially, Will FBHP Be Higher or Lower Than The Benchmark? As Well Declines Further, Will FBHP Increase, Decrease, Or Stay Flat? Will AL Method Remove Liquid Even When Gas Rate Approaches 0 4
Artificial Lift Methods Compared The Following Presentation Shows Outflow Curves (where possible) for Several e Artificial Lift Methods: Velocity Strings Foam Plunger Lift Beam Pumping Continuous Gas Circulation (CGC) Two Operating Modes CO Operating Mode C+R Operating Mode Compression Gas Lift 5
Velocity Strings ¾ 1 1¼ BROAD OPERATING RANGE 2⅜ NARROW OPERATING RANGE Must Change Tubing Often Very Costly Reduces Critical Rate (but not to 0 ) Not A Permanent Solution What Should Be Installed Next? 6
Foam Reduces Critical Rate (but not to 0 ) Not A Permanent Solution What Should Be Installed Next? FOAM LOADING AGAIN A PROBLEM L RATES CRITICA NATURAL FLOW 7
Plunger Lift What Happens As Well Declines? Flows Shorten & Shut-Ins Lengthen Back-Pressure (FBHP) On Formation Increases Fewer Trips Can Be Made Eventually No Trips Can No Longer Build Up To Req d Opening Pressure Not A Permanent Solution What Should Be Installed Next? No More Trips PLUNGER LIFT FBHP & Back-Pressure Increase As Well Gets Weaker NATURAL FLOW 8
Beam Pump Beam Pump Often Best Method For Oil Wells But, May Not Be Best For Gas Wells Where Liquid Rates Are Often Quite Low In Gas Wells, An Achilles Heel GAS LOCK Often No Way To Control Pump Capacity: No Pump-Off Controller 8 SPM 1¼ Pump 64 Stroke Pump Capacity = 93 BPD Way TOO MUCH PUMP For Low Rate Gas Wells Very Little Liquid id Production In Typical Gas Well: 100 MCFD 10 bbl/mmcf Only 1 BPD 8 SPM 11,500 Strokes/Day Only ½ Oz Liquid/Stroke Way TOO LITTLE LIQUID For Beam Pump 9
Beam Pump (cont d) Gas Enters Pump, Because There Is Very Little Liquid Gas Separation Can t Prevent It Pump Gas Locks Fluid Level Increases Gas Rate Falls Very High Fluid Level Needed To Break Gas Lock Personal Experience: Oil Wells Previously On Beam Pump GOR Increased Replaced Pump With Plunger Lift Increased Production CONCLUSION: Pump Not Always Best Required On Gas Wells With Beam Pump Pump-Off Controller Ability To Stop & Start Electric Motor or Gas Engine Automatically 10
Continuous Gas Circulation; CO Separator Compressor Sales Meter Formation ato Gas= Sales SaesGas Circulated Gas Formation + Circulation = High Velocity Continuously Circulates Gas Creates High Velocity In Tubing Note Compressor Position: Sales By-Pass Compressor Does Not Reduce FTP Think of CGC As Gas Lift, Except: No Gas Lift Valves No Packer No Outside Source Of Gas CO Operating Mode CO = Circulate Only No Reduction Of FTP Controls Not Shown & Start-Up Procedures Not Discussed 11
CGC Example Of CO Operating Mode Separator Compressor Sales Meter CO = Circulate Only No Reduction Of FTP Well Capable Of Only 100 MCFD Sales Critical Rate Is 500 MCFD (loading problem) Design Compressor To Circulate 500 MCFD Total Flow Up Tubing Is 600 MCFD Now Above Critical Carries Out Liquids If Sales Decline to 0, Still Carries Liquids Thus, A Permanent Solution 12
Same Rate Up Tubing Same FBHP Separator Be efore Lo oading Same FTP Same Low CP Same Rate Same Low FBHP CGC Achieves es Same FBHP That Existed Before Loading Separator Compressor After Loadin g w/ CG GC 13
CGC CO Operating Mode CO = Circulate Only No Reduction Of FTP LOADING CGC CO MODE CRIT TICAL RA ATE Maintains Low FBHP Continuously Down To 0 Rate A Permanent Solution NATURAL FLOW THIS CONDITION IS RECREATED CGC Maintains Lowest FBHP, Down To 0 Rate, Prevents Loading Permanently 14
Facts & Info CO Operating Mode Separator Sales Meter Compressor 50-100 HP 1-2 Stage CO = Circulate Only No Reduction Of FTP CP-TP and Pd-PsPs Both Small Low Compression Ratio & Low HP No Controls No Control Problems No Split Of Discharge Between Sales & Circulation Compressor Cylinder Is The Controller Increasing LP Is Not A Problem If LP Increases, Ps Increases If Ps Increases, Circulation Increases Well Is Then Even More Resistant To Loading THAT IS GOOD 15
What CGC Can t Do Not Intended For Large Volumes Of Liquid Better For Modest Volumes Of Liquid Volumes Typically Found In Gas Wells With Liquid Loading Can t Remove Tall Columns Of Liquid Or Large Slugs Well Must First Be Unloaded By Another Means When Possible, Chosen Method Of Unloading Is To; SI & Build Pressure Force Liquid Back Into Formation Create Dry Wellbore Then Start CGC & Unload Well The Start-Up Procedure (barely touched upon here) Is Critical To The Success Of CGC CGC Circulation Then Prevents Future Liquid Loading 16
CGC Is Counter-Intuitive Separator Sales Meter Compressor Reasons Why People Think CGC Can t Work: Can t Force Liquid id Into Formation Can t Circulate Or,, Can t Circulate and Sell Need Gas Lift Valves Injecting Places Back-Pressure On Formation Or, Gas Will Enter The Formation Need A Packer Need N d An Outside Source Of Gas (buy-back b meter) On The Contrary, CGC: Is A Direct Solution To The Problem (Increases Velocity) Should Be An Obvious Solution 17
Continuous Gas Circulation; C+R Separator Compressor C+R Operating Mode C+R = Circulate + Reduce FTP Conventional Compressor Location Need Controls To Split Flow Disadvantages: Added Controls & Operating Complexity Compression Ratio & HP Increased The Big Advantage: Possible Increased Production CGC (to control loading) + Lower FTP Sales Formation Gas=Sales Gas Circulated Gas Formation + Circulation = High Velocity Controls Not Shown & Start-Up Procedures Not Discussed 18
LIQUID LOADING AT VARIOUS PRESSURES THE BIG PICTURE 1100# 900# 700# 500# 300# 100# TURNER 4000 P (psi) FBH 3500 3000 2500 2000 1500 1000 ow Critica al Well Bel Inject The Difference Compres ssor Abov ve Critical Flow In Tubing Above Critical As Well Declines, Inject More Always Remain Above Critical Even As Rate Declines To 0 500 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 MMCFD 19
CGC C+R Operating Mode LOADING CRIT TICAL RA ATE Use One Compressor To Both Reduce FTP & Circulate Control Loading Down To 0 Rate A Permanent Solution No Other Method Can Both Reduce FTP & Control Loading NATURAL FLOW Circulate CGC; C+R MODE Prevents Loading Permanently C+R = Circulate + Reduce FTP 20
CGC Production & Economics Other AL Methods May Be Cheaper Than CGC But, Will Production Be As Great? 45 MCFD Gain CO Mode Following PL & Foam In Barnett Shale 170 MCFD Gain C+R Mode Following Wellhead Compression But, Will Ultimate Gas Recovery Be As Great? Science/Nodal Suggests That EUR With CGC Will Be Greater Should Cheaper AL Methods Be Installed First? Then Install CGC When Those Methods Fail? May Be More Profitable To Install CGC Initially Install CGC As The Initial & Final Solution To Liquid Loading CGC Is Not Cheapest, But MAY BE MOST PROFITABLE Because Of: Higher Producing Rates Greater Ultimate Recovery 21
Compression (wellhead or central) NATURAL FLOW COMPRESSED CRITIC CAL RAT TES Considering Compression? Also Consider C+R Mode C+R Can Both Reduce FTP & Control Liquid Loading Compression Often Fails To Control Liquid Loading Loading Again A Problem Compression Reduces FTP & FBHP Reduces Critical Rate (but not to 0 ) Not A Permanent Solution What Should Be Installed Next? 22
Gas Lift LOADING GAS LIFT CRIT TICAL RAT TE Considering GL? First Try CGC Nearly Identical Performance No GL Valves No Packer No Buy-Back Meter No Need To Pull Well If CGC Works, You Save $$ If It Doesn t Work, Install GL Trying CGC 1 st Is A No Lose Deal NATURAL FLOW Maintains Low FBHP, Down To 0 Rate, Prevents Loading Permanently 23
Appalachian Basin Gas Well Deliquification Seminar Marietta College, Marietta, Ohio June 7-8, 2010 Questions? Jim Hacksma - Consultant
Comparison Summary METHOD Velocity Strings Foam Plunger Lift Beam Pump CGC CO Mode CGC C+R Mode Compression Gas Lift COMMENTS Expensive Must Change Tubing Size Often. Reduces R d Critical Rate, But Not To 0. Not t Permanent. Reduces Critical Rate, But Not To 0. Not Permanent. As A Well Declines, Flows Shorten & Shut-Ins Lengthen. Back-Pressure On Formation Increases. Fewer Trips Eventually None. Not Permanent. To Avoid Gas Lock: Pump-Off Control Gas Engine Auto Stop/Start Can Prevent Liquid Loading Down To Nearly 0 Gas Rate. A Permanent Solution. Can Prevent Liquid Loading Down To Nearly 0 Gas Rate. A Permanent Solution. Plus Reduced FTP. No Other Method Can Both Control Loading & Reduce FTP. Reduces Critical Rate, But Not To 0. Not Permanent. Considering Compression? Then Also Consider C+R Mode. C+R Mode Can Both Reduce FTP And Permanently Control Loading. Considering GL? First Try CO Mode Much Cheaper No GL Valves No Packer No Buy-Back Meter Don t Pull Well If It Works, You Save $$ If It Doesn t, Install GL A No Lose Deal 25
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