Presented By Dr. Youness El Fadili February 21 th 2017
Outline Introduction Objective Critical rate definition Theory and development of New model Application and comparison of the New model Experimental setup Experimental results Conclusion and Recommendations
Production Rate What is Liquid Loading Flowing CR Loading Intermitting Loaded Time 3
Gas (Mscf/d) Psc (psig) Gas (Mscf/d) TP, CP, Psc (psig) Effects of Liquid Loading Unstable production Potential EUR 700 MMscf. Potential revenue $2.1MM Potential EUR 234 MMscf. Potential revenue $0.71M. P&A candidate
Basis of Droplet Model Drag Force Balance Gravity Vertical Flow Patterns Droplets fall at below critical velocity condition 5
Droplet Model and its Evolution Particle Terminal Velocity 4 V c = 3 g l ρ g ρ g 30 Coleman We = ρ 2 g d p V c σ g c d p C d lb f /ft=6.852 10-5 dyne/cm C d 60 Turner Critical Gas Velocity, ft/sec V c = 1.593 ρ l ρ g ρ g 2 σ 1 4 Critical Gas Rate MMscf/d q c = 3.067 P A V c T Z Particle Reynolds Number (N Rep )
Modified Droplet Model, Horizontal Wells Belfroid et al. (2008): Turner and Fiedler shape function V c = 1.593 ρ l ρ g ρ g 2 σ 1 4 sin 1.7ω 0.38 0.78 Veeken et al. (2009): observed rate and Turner Ratio, TR q c = 1 bq Turne r bq Turner 1 2 + 4a. c. Q Turner 2a. Q Turner 2 0.5 where, a = -2.17 x 10-6, b = 3.09x10-3, and c = 1.02
Horizontal Wells Geometry
Effect of Geometry on Flow Flow conduit Liquid droplets entrained in gas stream BUR 2 BUR 1 Liquid droplets
Fractional Energy Loss 1 0.95 0.9 0.8 y = 0.0406x 0.7537 R² = 0.982 (V i 2 -Vb 2 )/Vi 2 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Jayaratne and Mason (1964) Regression Curve Maximum Limit 0 10 20 30 40 50 60 70 80 90 Angle of Impact (q i )
Example It is desired to determine the effective gas rate for a horizontal well with the following characteristics: - Tubing pressure = 100 psi - Temperature = 80 o F - Tubing size = 2 7/8 - Maximum BUR = 20 o /100 ft - Water gravity1.07 - Gas gravity = 0.64 - Z factor = 0.95 - Surface tension= 60 dynes/cm
Example Determine the fractional energy loss V c 2 V b 2 V c 2 = 0.0406 20 0.7537 = 0.388 Calculate the restitution velocity Makeup Drag Makeup velocity 1 V b 2 V c 2 = 0.388 V b = 0.78V c V g 0.78V C F d,mup = F d,before F d,after = 0.392F d,before V eff = 1.6258V c Thus, the effective velocity and rate to keep the well from loading up is: V eff = 35.47 ft/sec q eff = 689 Mscf/d For comparison, - Coleman rate is 425 Mscf/d - Turner rate is 505 Mscf/d
Gas Rate (mscf/d) Gas Rate (mscf/d) Compressor Performance Analysis 3306 TAA Gas Rate in Mscf/d at different P discharge Psuc @ Pd 1200 psi @ Pd 1100 psi @ Pd 1050 psi 60 650 650 650 50 546 550 550 50 657 650 647 40 550 520 517 40 619 625 629 3306 NA Gas Rate in Mscf/d at different P discharge Psuc @ Pd 1200 psi @ Pd 1100 psi @ Pd 1050 psi 60 518 522 523 50 435 438 440 50 549 565 575 40 433 453 452 40 526 532 546 3306 TAA Gas Rate in Mscf/d at different P discharge Psuc '@ Pd 600 psi '@ Pd 1050 psi 60 1121 650 50 983 647 40 805 629 Spacer 3306 NA vs. TAA 700 650 600 550 500 450 400 60 50 50 40 40 Suction Pressure (psig) Volumetric Efficiency Comparison @ Pd 1200 psi @ Pd 1100 psi @ Pd 1050 psi @ Pd 1200 psi @ Pd 1100 psi @ Pd 1050 psi 1200 1100 1000 900 '@ Pd 600 psi 800 '@ Pd 1050 psi 700 600 40 45 50 55 60 65 Suction Pressure (psig) 16
Experimental Setup BV Bypass BV BV Choke 3 Phase Separator CV CTB BV CV BPV BV CV Liquids line from compressor scrubber to CTB Sales line Meter LP ~ 30 psi CV BV BV Compressor Casing Tubing Gas Recycle Line FRV 25 psi Suction Controller Valve set at 40 psi Injection Meter Bypass CV BV CV B V MV 70 psi Formation Supply Gas - BPV: Back Pressure Valve. BV: Ball Valve MV: Motor Valve. CV: Check Valve. FRV: Fuel Recycle Valve. CTB: Central Tank Battery.
3 Phase Test Separator with recycle line
Injection Gas Meter
3 Stages Dual Reciprocating Compressor: Front View
3 Stages Dual Reciprocating Compressor: Side View
Common Operational Issues Causes Solutions Max discharg e - The volume of liquid accumulated in the wellbore is high. - Malfunctioning discharge valve. - Reduce liquid volume in the well, i.e. swabbing, pushing fluid back to formation - Check the discharge valve for proper functioning. Low suction - Low gas supply to - Increase supply gas by adding compressor. a recirculation line - Malfunctioning suction - Check the suction valve for valve. proper functioning. - Suction line leak. - Check suction line for leaks - Add fuel recycle valve 22
PVT Tubular Data Production Data Horizontal Wells Examples Horizontal Well 1 Horizontal Well 2 q o (BO/d) 2.39 61.50 q w (BW/d) 19.52 2.00 q g (Mscf/d) 273 181 FTP (psia) 110 92 T surface ( o F) 80 60 T formation ( o F) 223 130 OGR (bbls/mmscf) 3.3 90 WGR (bbls/mmscf) 27 3 WOR 8.18 0.03 Tubing OD (in.) 2.875 2.875 d (in.) 2.441 2.441 Casing OD (in.) 5.5 7 Casing ID (in.) 4.892 6.276 Liner Top (ft) 12,950 8,177 Liner OD (in.) 3.5 4.5 Liner ID (in.) 2.992 4 Absolute roughness (in.) 0.0006 0.0006 Depth (ft) 12,863 8,306 Max BUR o /100 ft 12.34 18.34 API 65 40 N 2 Mol % 0 1.686 CO 2 Mol % 0 0.843 H 2 S Mol % 0 0.003 Specific gas gravity 0.65 0.7 Specific water gravity g w 1.02 1.02 Specific oil gravity g o 0.72 0.83
Produced Gas (Mscf/d) Injected Gas (Mscf/d), Water (BWPD) Identifying Critical Gas Rate: Horizontal Well 1 290 285 280 Gas (Mscf/d) Injected Gas * 10 Water (BWPD) 50 45 40 275 35 270 30 265 25 260 20 255 15 250 10 245 5 240 0 5 10 15 20 25 30 35 40 Time (Days) 0
Horizontal Well 1 Observed critical gas rates and percent deviation for horizontal well 1 Actual Lift Rate, Mscf/ d 730 Absolute Percent Deviation, % Coleman model Mscf/ d 455 38 Turner model, Mscf/ d 541 26 New Model, Mscf/ d 692 5 Belfroid model, Mscf/ d 495 32 Veeken model, Mscf/ d 579 21
Total Gas (Mscf/d) Total Fluid (BFPD) Identifying Critical Gas Rate: Horizontal Well 2 800 70 750 65 700 650 60 600 55 550 500 450 Total Gas (Mscf/d) Fluid (BFPD) 50 45 400 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Days 40 26
Horizontal Well 2 Observed critical gas rates and percent deviation for horizontal well 2 Actual Lift Rate, Mscf/ d 684 Absolute Percent Deviation, % Coleman model Mscf/ d 404 41 Turner model, Mscf/ d 481 30 New Model, Mscf/ d 648 5 Belfroid model, Mscf/ d 506 26 Veeken model, Mscf/ d 512 25 27
FBHP (psig) Total Gas (Mscf/d) Gradient 500 490 480 Unstable BHP indicating subcritical condition even at rates proposed by other models Compressor shut downs 1100 1000 470 900 460 450 440 430 800 700 600 420 410 650 to 720 Mscf/d rate yield lowest BHFP FBHP (psig) 400 Total Gas (mscf/d) 400 8:24:00 9:36:00 10:48:00 12:00:00 13:12:00 14:24:00 15:36:00 16:48:00 18:00:00 Time 500 28
Don t Set and Forget: Dynamic Operation
Conclusions & Recommendations 1. The new model accounts for the effects of wellbore geometry on liquid loading and predicts the critical gas rate for horizontal and deviated wells. 2. Experimental work with 2 horizontal wells showed the new model prediction is within 5% from actual. 3. Conventional vertical models should not be used for horizontal and deviated wells. 4. In vertical wells, the new model collapses to Coleman model..
Conclusions & Recommendations 5. The new model yields best results for gas rates less than 10,000 Mscf/d and for BUR s between 3 o and 30 o /100 ft. 6. Don t set and forget. Optimization through surveillance with good automation setup.
References Youness El Fadili, Subhash Shah A new model for predicting critical gas rate in horizontal and deviated wells, Journal of Petroleum Science and Engineering, December 3rd 2016. http://dx.doi.org/10.1016/j.petrol.2016.11.038 Questions??
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