Dynamic IPR and Gas Flow Rate Determined for Conventional Plunger Lift Well

Transcription

1 Gas Well Deliquification Workshop Sheraton Hotel, Denver, Colorado February 17 20, 2013 Dynamic IPR and Gas Flow Rate Determined for Conventional Plunger Lift Well Lynn Rowlan

2 Determine Plunger Lift Gas Volume Produced per Cycle Problem: Compute the total cumulative standard volume of gas produced from well during the plunger cycle. Solution: From Tubing Intake Depth to Surface Know Volume of Tubing and Casing Annulus Use Gas Free Liquid to Reduce Volume Determine the mass of gas in the tubing and casing annulus as a Function of Pressure and Temperature at all Times During Cycle Use Mass Balance to Allocate Gas out of Formation, into/out of Casing Annulus, Tubing, and Down Flow Line Feb , Gas Well Deliquification Workshop Denver, Colorado 2

3 Account for Mass of Gas in Tubing and Casing Annulus at any Time During Cycle Total number of moles in tubing is given by: PV ZnRT n PV ZRT Where V = capacity of tubing/casing (cu. Ft) less liquid volume And P, T= average pressure and temperature in tubing Tubing and Casing Annulus are Divided into Short Segments. Feb , Gas Well Deliquification Workshop Denver, Colorado 3

4 T u b i n g D e p t h Pt, Pc psia Formation Feb , 2013 How is Gas Flow Rate Determined? Motor Valve Flow Line Flow rate Qout, SCF/D Where s the Plunger Vol Tubing Vol Casing Liquid Height P (bottom) Cas & Tub, psia Flow rate Qin, SCF/D For 1 Complete Cycle Well Model Allocates Gas between: 1. Casing Annulus, Tubing, Out of Formation, and Down Flow Line 2. Assume that no gas is temporarily stored in the formation 3. Gas flow from the formation is directly related to PBHP Gas Well Deliquification Workshop Denver, Colorado 4

5 T u b i n g D e p t h Pt, Pc psia Formation Feb , 2013 How is Gas Flow Rate Determined? Motor Valve Flow Line Flow rate Qout, SCF/D Where s the Plunger Vol Tubing Vol Casing Liquid Height P (bottom) Cas & Tub, psia Flow rate Qin, SCF/D For a Complete Cycle Gas that flows down the Flow Line is equal to the gas that flows out of the Formation. OR the total system pressure increases if all of the gas produced from the formation does not flow down the flow line. OR the system pressure decreases if MORE gas flows down the flow line than is produced from the formation Gas Well Deliquification Workshop Denver, Colorado 5

6 [A] Gas Volumes/Rates are Calculated Differently over Each of these Intervals Valve Closes, Shut-in Begins and Tubing Pressure Starts Increasing 1. Plunger hits Liquid 2. Plunger on Bottom [B] Valve Opens, Unloading Begins 3. Liquid Arrives, Tubing Pressure at Minimum 4. Plunger Arrives, After-flow begins Tubing Pressure Maximum Spike [C] Valve Closes, Cycle Repeats [A] 1 2 [B] 3 4 [C] Casing Pressure Tubing Pressure Acoustic Signal Feb , Gas Well Deliquification Workshop Denver, Colorado 6

7 Gas Volumes/Flow Rates: Formation, Casing, Tubing, Gas Slips by Plunger, and Flow Line Simple Mass Balance Used to Calculate Gas Volume Over Each of These Intervals Note: Cycle s Pressure at Beginning [A] is Greater than Pressure at End [C] A) Valve Closes (Shut In Begins) 1) Plunger Hits Liquid 2) Plunger on Bottom B) Valve Opens (Unloading Begins) 3) Liquid Arrives 4) Plunger Arrives C) Valve Closes (Shut In Begins) Afterflow Shut In Unloading [A] [C]

8 Acquired Plunger Lift Data Data Acquisition on 3 Channel 30Hz Frequency or Greater Gas Volumes/Rates Calculated Using Tubing, Casing Pressure and Acoustic Signals Casing Pressure Tubing Pressure Acoustic Signal Rate = Change in Volume per Time Step Feb , Gas Well Deliquification Workshop Denver, Colorado 8

9 Well Information Important to the Accuracy of Calculated Gas Volumes and Flow Rates 1. Average Joint Length Fall Velocity, Gas Specific Gravity, Acoustic Velocity, and Plunger Depth 2. Tubing & Casing Sizes and Weight /foot Gas Volumes and Gas Flow Rates 3. Tubing Intake Depth Gas Volumes, Gas Flow Rates, and Calculated Pressures Feb , Gas Well Deliquification Workshop Denver, Colorado 9

10 Gas Volume Flowing from Tubing/Casing Annulus Depend on Pressures & Gas Free Liquid Height Shut-in Casing Pressure Determines Gas Stored in Casing Annulus Gas Free Liquid Height Adjust Gas Volumes Shut-in Tubing Pressure Determines Gas Stored in Tubing [B-4] Gas Above Plunger goes Down Flow Line [A] [B] [4] [C] Feb , Gas Well Deliquification Workshop Denver, Colorado 10

11 During Shut-in Gas flowing from Formation is Captured in the Tubing/Casing Annulus Casing Pressure Increases Due to Gas being stored in Casing Annulus [1] [2] [B] [A] Gas Free Liquid Height subtracted from the Available Storage Volumes Tubing Pressure Increases Due to Gas being stored in Tubing Annulus Gas Volume Integrated over Tubing Length for Tubing & Casing Areas Feb , Gas Well Deliquification Workshop Denver, Colorado 11

12 Formation Gas Flow Rates - (Mscf/D) Tubing Gas Volume - (scf) Casing Gas Volume - (scf) Bottom Hole Pressure - (psi) Sum Casing Annulus+Tubing Gas Volumes During Shut-in to Determine Gas Flow From Formation Gas Flow Rate is the Change in Gas Volume over Each Time Step [A] Elapsed Time - minutes [B] Feb , IPR for the Well is Flow Rate as a Function of Flowing BHP Elapsed Time - minutes

13 Use Dynamic Inflow Performance Curve to Calculate Gas Flow Rates When Valve Open Predicted Static During Shut-in Period Calculated Gas Flow Rate from Formation versus FBHP at End of Tubing Curve Fit thru Measured Data Determines Well s Inflow Performance From Shut-in to Max Flow Rate Predicted Q-Max Can calculate Flow Rate From Formation for Any Flowing BHP. Feb , Gas Well Deliquification Workshop Denver, Colorado 13

14 Use Dynamic Inflow Performance Curve to Calculate Gas Flow Rates When Valve Open Formation Gas Flow Rates - (Mscf/D) Bottom Hole Pressure - (psi) During Period [B-C] Calculate Gas Flow Rate from Formation [A] Elapsed Time - minutes [B] Valve Open [C] Use Well s IPR Determined From Shut-in Period To Calculate Flow Rate From Formation for Any Flowing BHP Gas Well Deliquification Workshop Denver, Colorado 14

15 Gas Volume Flowing from Formation: During [A-B] Gas Stored in Tubing/Csg. Annulus During [B-C] Gas Volume is from IPR and FBHP Formation Gas Flow Rates - (Mscf/D) Formation Gas Volume - (scf) Cumulative Gas Volume Flowing from Formation 20.0 [A] [B] [C] Elapsed Time - minutes Flow Rate Function of Flowing BHP Feb , Gas Well Deliquification Workshop Denver, Colorado 15

16 During Unloading Gas Volume Slipping by the Plunger equals: Gas volume leaving Casing + Gas volume flowing from formation Gas Volume Remaining in Tubing when plunger arrives at surface Gas Volume Slips Past Plunger During Unloading [B-3 3-4] [A] Zero Gas Slips by Plunger During [A-1-2-B and 4-C] [B] [4] [C] Feb , Gas Well Deliquification Workshop Denver, Colorado 16

17 [B-3] Plunger comes to surface as all gas above Plunger goes down Flow line + gas that slips by the plunger [3-4] Only Gas Down Flow Line is gas slipping by plunger [4-C] Plunger is held at surface. Gas Down Flow Line equals decrease in casing volume + decrease in tubing volume + gas that flows out of the formation (IPR) [A] Gas Down Flow Line [A-1-2-B] is Zero Because the Valve is Closed [B] [3] [4] [C] Feb , Gas Well Deliquification Workshop Denver, Colorado 17

18 Gas Per Cycle Produced Down Flow Line During: Unloading (11min 26sec) 4.5 Mscf w/ Max 1400 MscfD Afterflow (9min 17sec) 3.23 Mscf w/ Max 635 MscfD High Gas Flow Rate When Valve is Open 7.73 Mscf/Cycle of Gas Produced Valve Open Turner Critical Rate [B] [3] [4] [C] Feb , Gas Well Deliquification Workshop Denver, Colorado 18

19 Gas Produced During Cycle: Gas Flow (Formation) = Mscf/Cycle ~ Mscf/D Gas Flow (Flow Line) = Mscf/Cycle ~ Mscf/D Gas Continually Flows From Formation Valve Open [A] Gas Flows Down Flow Line When Valve Open [B] [C] Feb , Gas Well Deliquification Workshop Denver, Colorado 19

20 Red Pen Off Chart MscfD Flow Rate? 100 Barton Chart 122 TWM Formation For a field reading for this chart: (line psi 150) x (diff. Psi 12 avg) = pressure extension Take square root pressure extension. Take your square root reading X orfice coef. ( 1 = 6.549) The answer will be a 24 hr flow rate in MCF Take MscfD and divide by 24 hrs for hourly Flowrate. Ex 150# x 12 = 1800 Square rt of 1800 = (psi extsion) x (orfice coef for 1 )= MscfD MCFD / 24 = MCFH MCFH x 8 hrs (Total flow time for day) = MscfD MscfD is the daily rate Quote of the Day: On a Barton chart if you have 10 pumpers read it you will have 10 different volumes. Blue pen - Static line pressure (% reading multiply by 1000 = Psi) (Ex 15% x 1000 = 150psi line psi is 150psi Green pen line temperature (% reading multiply by 150 = Deg F) (Ex 40% x 150 = 60 degrees line temperature is 60 degrees Red pen - Differential pressure (% reading multiply by 100 = H2O. (Ex 20% x 100 = 20 of water column

21 Gas Production Current = 100 Mscf/D (Read off Chart) Gas Flow from Formation = Mscf/D Gas Flow Down Flow Line = Mscf/D Gas In Gas Out?

22 Tested 8 Different Plungers in 1 Well for Gas Flow Rate During Cycle Had stable flow characteristics Effort made to not change the plunger control settings Normal functioning standing valve Tubing Intake of ft. One set of perforations feet 2 3/8 Tubing, 5.5 Casing, and No packer Produced 0.63 BPD water and no condensate Able to run on timer control in order to control the flowing environment Feb , Gas Well Deliquification Workshop Denver, Colorado 22

23 1.87% Error in Calculated vs Measured Gas Volume Company B dual pad seal Complete Cycle Valve Minutes Flow Line = 0 scf Plunger minutes Slips by Plunger = scf Flow Line = 2622 scf End of Cycle Flow Line = 5548 scf Elapsed Time - Minutes

24 Measured vs Calculated Gas Volumes for 1 Cycle Feb , Gas Well Deliquification Workshop Denver, Colorado 24

25 Company A Dual Pad Gas Volumes Gas Volume (scf/cycle) Calculated VERSUS Measured during cycle for all 8 plungers: Average Error 9.9% of the measured scf/cycle. Maximum Error of 16% Minimum Error of 1.9% Error =14.4% Feb , Gas Well Deliquification Workshop Denver, Colorado 25

26 Plunger Lift Gas Volumes Determined During Cycle

27 Determine Plunger Lift Gas Rates During Cycle

28 Conclusions 1. Gas Flow Rates Reasonably accurate (need more data) Expect some difference between EFM Gas Stacking can occur, but Chart and EFM can be over-ranged 2. Dynamic IPR Calculations Gas Flow Rate and FBHP determined During Shut-in Period Used to Calculate Well s IPR Varying Flow Rates versus Bottom Hole Pressure can be used to Calculate Formation Flow During the Entire Plunger Lift Cycle Feb , Gas Well Deliquification Workshop Denver, Colorado 28

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