Gas Locked Pumps are NOT Gas Locked!

9 th Annual Sucker Rod Pumping Workshop Renaissance Hotel Oklahoma City, Oklahoma September 17-20, 2013 Gas Locked Pumps are NOT Gas Locked! Lynn Rowlan Ken Skinner Echometer Company

Introduction Gas Locked Pumps are NOT Gas Locked! 1. Best to Keep Gas Out of the Tubing by Setting the Pump Intake Below the Perforations (Horizontal Wells?) 2. Or Use an Effective Downhole Gas Separator 3. Use a specialty pump such as a VSP pump to discharge gas into tubing. 4. Use longer stroke length to increase compression ratio 5. Proper Spacing to minimize dead space at bottom of stroke 6. Slippage thru Pump Clearances Partially Fills Pump Chamber 7. Sufficient Backpressure can Prevent Tubing Fluids from Unloading Unloading usually Caused by Poor Downhole Gas Separation with Gas Pumped into the Tubing Tubing Fluids Lighten and Tubing Liquids Flow Off. Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 2

What is a Gas Locked Pump Both traveling valve, TV, and standing valve, SV, remain closed during the entire stroke Pump is completely filled with gas Gas Lock occurs if: Downstroke the tubing pressure on top of the plunger is always greater than the compressed pressure inside pump chamber Upstroke the expanding pump chamber pressure is always greater than the outside wellbore pressure at the pump intake. TV and SV open if pressure below the valve is greater than the pressure above the valve. Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 3

Synthetic Pump Card Shape: Gas Locked Pump Gas Locked Pump...Both valves remain closed because the discharge tubing pressure, (P d ), is greater the pump chamber pressure, (P chamber ), which is also greater than the pump intake pressure, P int. The compression ratio of the sucker rod pump is too small, with the result that neither valve opens until the clearance space between valves fills by slippage of fluids past the plunger, or the fluid level is allowed to rise so that a smaller compression ratio is required to discharge gas from the pump into the tubing. Fo from Fluid Level P d > P chamber > P int P d > P chamber at bottom of stroke P chamber > P int at top of stroke Zero Load Line FoDn = 0 Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 4

Up Stroke PIVI PDVD Intake (-----) = (------) Discharge ZI ZD P D Fo reached when P chamber < P int P D V int V D P int Expansion Should Open SV Iso-thermal No Change in Rs Zero Load Reached P chamber > P D P int Compression Should Open TV Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 5

Gas Interference: Incomplete Pump Fillage and High Fluid Level Fo Well Fluid Level Above Pump Fo Rods Fo Pump < Fo Max Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 6

Synthetic Pump Card Example: Gas Interference Tubing anchored, EPT<MPT. Fo Max Unanchored tubing, EPT<MPT Fo Fluid Level Gas Interference is causing decrease in pump Fillage. Pump components are functioning properly. Usually unstable pump fillage and EPT changes from stroke-to-stroke. When gas interference is present expect increased rod-on-tubing wear due to rod buckling compressing gas in pump barrel. Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 7

Incomplete Pump Fillage Occurs from C to D on Pump Card Steps C - D in Pump Operation Pump acts as a Compressor on Down Stroke B A at [C] PB = PI D C PD PB PI - Discharge Pressure - Pressure in Chamber - Intake Pressure C) Standing Valve closes, when plunger reaches top of stroke, rods start to un-stretch to transfer fluid load, Fo, from rods [C] onto tubing [D]. D) Traveling Valve Opens when pressure in pump chamber >= Pump Discharge Pressure, PD. at [D] PB = PD C-D) Plunger applies pressure to fluids inside pump chamber, to compress fluids in Pump chamber and increase pressure. Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 8

Compression Ratio = (Swept+Unswept) Vol. Unswept Vol. High Compression Ratio Prevents Gas Lock By Pumping Gas into Tubing 2013 Sucker Rod Pumping Workshop 9 Space Pump High or High Tubing Pressure CR is Reduced PIVI PDVD (-----) = (------) ZI ZD Assume ZI = ZD PD = PIVI / VD VI Stroke Length (Swept Volume) Compression Ratio (CR) = VI / VD For TV to Open: PD - Pump Barrel Discharge Pressure = Intake Pressure x compression ratio A Unswept Volume VD PD Must be greater than Pressure in Tubing at Top of Plunger

10 Effect of PIP on Gas Compression i.e. Gas Interference or Fluid Pound Gas PIVI PDVD (-----) = (------) Intake ZI Intake ZD Discharge Iso-thermal No Change in Rs Liquid Discharge

Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 11 2.5 2.0 1.5 1.0 0.5 0-0.5 Fo Max Stroke 45 2.5 Gas Lock Cycles 2.0-1.0 0 53.9 1.5 Fo Max 1.0 0.5 0 2.5-0.5 2.0-1.0 0 53.9 1.5 Fo Max 1.0 0.5 Stroke 51 Stroke 77 0 2.5-0.5 2.0-1.0 0 1.5 54.0 Fo Max 1.0 0.5 0 2.5-0.5 2.0-1.0 0 54.3 1.5 Fo Max 1.0 0.5 0 Stroke 84 Stroke 139-0.5-1.0 0 53.9

Gas Lock Occurs, When Both: 1) Point A is Above 0 Line 2) Point C is Below Fo From the Fluid Level Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 12 Tag Bad for Equipment, but Many tag due to Gas Locking Fo From the Fluid Level C NOT GAS LOCKED A Tag

Pump Gas Up the Tubing 13 Gas Locked?

Pump Gas Up the Tubing Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 14

Tubing Liquid Stroke Length Gas Displaced by Liquid thru Tapered Tapered Barrel Well Fluids Oil Water Gas Beginning Sept. 11-14, 2007 (Upstroke) Top Pump Gas into Tubing Spacing at the well site: a. Touch bottom with tubing loaded with fluid b. Pick up overtravel length c. Pick up spacing allowance, normally 12" d. The lower end of the plunger should slightly enter the start of the VSP taper. This position gives the least amount of bypass slippage. After well has stabilized, space the plunger higher in small increments for more bypass slippage to achieve desired results. Re-space well as needed after stabilized: a. Lower rods for a light tag at pump, then raise slightly for stroking close to bottom without entering VSP taper. b. After accomplishing raise rods in 6 inch increments until bottom of plunger enters taper. "Spacing allowance: 30" down to 4,000 feet well depth, then add 6" for every 1,000 feet well depth below 4,000 feet. Spacing HF Variable Slippage Pump 2013 Sucker Rod Pumping Workshop with VSP 15

Using a Backpressure Valve can Prevent Unloading from in Gas Tubing Gas Flowing through Pump OR Pumped into Tubing Back-pressure valve maintains high tubing pressure to prevent gas from blowing all of the liquid out of tubing Without BPV Pump action erratic & discharge may STOP Pressure Gage Increase Pressure by Compressing Spring Flow Spring Force BPV Harbison-Fischer Model Illustrated Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 16

Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 17 Control Excessive Amount of Gas Pumped Into Tubing 1. ONLY Apply Backpressure to Gassy Wells that Unload Liquids from the Tubing and Downhole Pump Action Stops!!!! 2. Backpressure May Increases Operating Cost, But Allows You to Pump the Well 3. Backpressure Maintains Pump Action 4. Reduced Well Intervention by the Operator 5. Significantly Reduced Stuffing Box Leaks 6. More Consistent Production From Day-to-Day.

Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 18 Backpressure Recommendations 1. Gassy Wells Difficult to Sucker Rod Pump 2. Horizontal Laterals can Unload a LOT OF GAS 3. Sufficient Backpressure on Tubing can Improve the performance of Gassy Rod Pumped Wells 4. Sucker rod loading can be incorrect, because of the piston force, rod loading below the surface will be higher than measured 5. Use Backpressure ONLY IF a well is Flowing Off due to TOO Much Gas Produced Up the Tubing 6. If the tubing unloads and pump action stops, then try 200-300 Psi of backpressure on the tubing BUT use more if required by well

Compression Ratio = (Swept+Unswept) Vol. Unswept Vol. Compression Ratio High if VD fills with Liquid then Gas Pumped into Tubing 2013 Sucker Rod Pumping Workshop 19 VI A Space Pump High or High Tubing Pressure CR is Reduced Stroke Length (Swept Volume) Unswept Volume VD Compression Ratio (CR) = VI / VD Guarantee TV Always Opens: Force VD to equal Zero Fill Unswept Volume with Liquid CR becomes Infinity If Unswepth Volume Fills with Liquid, then Pump Chamber Pressure at Bottom of the Stroke Always Greater than Tubing Pressure on Top of Plunger at Discharge. TV ALWAYS OPENS IF VD=0

Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 20 Pump Slippage can Fill Unswept Volume with Liquid 1) Fluid that leaks back into pump between the Plunger OD and the Barrel ID 2) Leaks into the pump chamber between the standing valve and traveling valve 3) When traveling ball is on Seat. Pump Efficiency = BPD Tank / BPD Pump Slippage % = Slippage BPD / BPD Pump BPD Tank = BPD Pump - Slippage

Recommended Procedure to Select Pump Clearances 1. Use QRod predictive sucker rod design program to calculate pump displacement, assume 100% liquid pump fillage. 2. Input correct well parameters into QRod Tool - Pump Slippage Calculator, be sure to adjust water viscosity for the temperature at the pump 3. Examine Plot of Patterson Equation Pump Slippage vs Clearance and select pump clearance that gives the desired percentage of pump slippage. Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 21

651 BPD Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 22

QRod Slippage Plot vs Clearance Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 23

New pump w/ no wear or damage, Installed 0.009 in. clearance w/ 2.25 inch diameter & 4 foot plunger Pump Depth 7156

Stroke = 145 SPM=9.52 Depth= 7156 4 plunger % of BPD Production Rate or % of Each Stroke lost to Slippage 2-5 % minimum is needed for plunger/barrel lubrication Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 25

Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 26 Well Data Showing No Gas Interference with High Clearance Pump ~ 1 BPD Leaky Pump

Pump Slippage Calculations 10,029 Pump Depth ~ 1.5 Plunger 27 Leaky Pump

Gas Locked Pumps are NOT Gas Locked Slippage Can Fill Unswept Pump Volume 1) Unswept Space in Pump Filled with Liquid With 0.002 Clearance 2) IF Compression Ratio were 0, Liquid in Pump would Displace TV Ball off Seat. Leaky Pump Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 28

When Operator has a Gas Locked Pump the Pump Card Always Looks Like This 1) TV Stuck Open - Pump card on Zero Load, Looks like Deep Rod Part but often can tag or jar the rods and knock the debris out of the pump and re-start pump action. 2) SV Stuck Open Plots on the Fo from the Fluid Level line 3) Tubing Blown Dry Missing Buoyancy, plots as a flat line @ a height of Wra-Wrf lbs above the zero load line.. Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 29

Summary Pressure in barrel is a function of plunger travel and compressibility of fluid in barrel. A Sucker Rod Pump Intakes Well Fluids and Discharges into the Tubing Gas Pumped into the Tubing can be Detrimental to the Operation of the Sucker Rod Pumping System No Pump Action can Occur when too Much Gas is Pumped into the Tubing. Backpressure may be needed to Maintain Pump Action If the Pump has Clearance, then it is Impossible to Gas Lock a Pump Sept. 17-20, 2013 2013 Sucker Rod Pumping Workshop 30

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