Gas Well Deliquification Workshop Adams Mark Hotel, Denver, Colorado March 5 - 7, 2007 Effect of Liquid Loading on Production Analysis Cox, Sutton, and Conway
U.S. Gas Facts US Historical Gas Well Facts 500 10 Avg Well Rate MCFD 450 Unload Rate 9 Avg Wellhead Price $/MCF 400 8 Avg Wellhead Price, $/MCF Avg Gas Rate, MCFD/Well 350 7 300 6 250 5 200 4 150 3 100 2 50 1 0 0 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Source: EIA Natural Gas Annual 2007 Gas Well Deliquification Workshop 2 Mar. 5 - 7, 2007 Denver, Colorado
IHS Data Summary � 91% or 287,000 of US gas wells are potentially liquid loaded � These wells account for 65% of the total gas production � Average rate of unloaded wells – 1050 MCFD � Average rate of loaded wells – 56 MCFD 2007 Gas Well Deliquification Workshop 3 Mar. 5 - 7, 2007 Denver, Colorado
Purpose � Examine the affects of gas well liquid loading as it relates to production analysis and well performance. 2007 Gas Well Deliquification Workshop 4 Mar. 5 - 7, 2007 Denver, Colorado
Outline of Talk � Liquid loading what’s the problem � Laboratory experiments � Eclipse modeling work � Production analysis results � Field examples 2007 Gas Well Deliquification Workshop 5 Mar. 5 - 7, 2007 Denver, Colorado
Wellbore Dynamics - Loading 2007 Gas Well Deliquification Workshop 6 Mar. 5 - 7, 2007 Denver, Colorado
SLC Pressure Profile 2007 Gas Well Deliquification Workshop 7 Mar. 5 - 7, 2007 Denver, Colorado
Condensed Water Water Vapor Content, Bbls/MMCF 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 Water Condensation 2,000 4,000 6,000 Depth, ft 8,000 10,000 12,000 14,000 2007 Gas Well Deliquification Workshop 8 Mar. 5 - 7, 2007 Denver, Colorado
Liquid Loading – What’s the Problem? � Bottomhole pressure from surface data? � Additional back pressure on formation? � Imbibition of water into the formation flowing and static? � Will the well production improve if unloaded? � Do loaded well’s result in a false depletion stem and reservoir shape? 2007 Gas Well Deliquification Workshop 9 Mar. 5 - 7, 2007 Denver, Colorado
Field Examples of Production Analysis for a Loaded Well Wyoming Gas Well Radial Flow in 1 to 1 Rectangular Boundary Pre-loading 2000 100 1000 MCFD Match Unloading Rate, MCFD Kh = 20 md-ft BOPD Skin = -1.1 BWPD Area = 190 Acres 100 1500 75 P wD or P wD 'x 0.1 MCFD/FTP/CP BWPD/BOPD 10 1000 50 1 Actual PwD Actual PwD' 500 25 Analytical PwD Analytical PwD' 0.1 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 100000 0 0 t DA 7/28/2001 12/10/2002 4/23/2004 9/5/2005 1/18/2007 2007 Gas Well Deliquification Workshop 10 Mar. 5 - 7, 2007 Denver, Colorado
Simulation Cases Uniform – 40 acres Model Parameters Model Parameters Formation Top, ft 10,000 Initial Reservoir Pressure, psi 5000 Net Pay, ft 40 Gas Specific Gravity 0.69 Effective Gas Perm. Md 0.05, 0.5, 5 Fracture Half Length, ft 200 Fracture Conductivity, md-ft 75 Cases Simulation Controls • Base case no liquid in tubing • Flowing tubing pressure - 350 psia • Consider standing fluid to tubing tail • 2-3/8-in Tubing set at 8000’ (10,000’ well) • Consider imbibition • Single layer model 2007 Gas Well Deliquification Workshop 11 Mar. 5 - 7, 2007 Denver, Colorado
Production Profile - 0.5 md Case 2007 Gas Well Deliquification Workshop 12 Mar. 5 - 7, 2007 Denver, Colorado
Production analysis results Dry Gas Base Case SLC – 8000 ft Infinite Conductivity Fracture in 1 to 1 Rectangular Boundary at 2 years Infinite Conductivity Fracture in 1 to 1 Rectangular Boundary at 2 years 1000 1000 Match Simulation Match Simulation Kh = 16 md-ft, 20 md-ft Kh = 20 md-ft, 20 md-ft X f = 120 ft, 120 ft X f = 70 ft, 120 ft Area= 40 Acres, 40 Acres Area= 40 Acres, 40 Acres 100 100 P wD or P wD ' P wD or P wD ' 10 10 1 1 Actual PwD Actual PwD Actual PwD' Actual PwD' Analytical PwD Analytical PwD Analytical PwD' Analytical PwD' 0.1 0.1 0.0001 0.001 0.01 0.1 1 10 100 0.0001 0.001 0.01 0.1 1 10 100 t DA t DA Back pressure alone does not account for field observations. 2007 Gas Well Deliquification Workshop 13 Mar. 5 - 7, 2007 Denver, Colorado
Support for Imbibition Under Flowing Conditions Performed by Mike Conway the at Stim-lab Test parameters � 20/40 Brady sand 8 ft Gas dP � Determine effective 4 ft permeability. Water dP gal um � Liquid level Exit Pressure Metered controlled at the exit. Gas Rate Water Pump 2007 Gas Well Deliquification Workshop 14 Mar. 5 - 7, 2007 Denver, Colorado
East Texas Well 1000 500 MCFD FTP BWPD Installed Gas Rate & Tubing Pressure, (mscf/D, psi) Pumping Unit 750 Water Rate, bbl/D 500 250 250 0 0 8/1/2004 8/1/2005 8/1/2006 2007 Gas Well Deliquification Workshop 15 Mar. 5 - 7, 2007 Denver, Colorado
West Texas Well 1500 150 MCFD BWPD 1250 125 1000 100 BOPD/BWPD MCFD 750 75 500 50 250 25 0 0 4/20/2004 5/20/2004 6/19/2004 7/19/2004 8/18/2004 9/17/2004 10/17/2004 11/16/2004 12/16/2004 1/15/2005 2/14/2005 3/16/2005 4/15/2005 2007 Gas Well Deliquification Workshop 16 Mar. 5 - 7, 2007 Denver, Colorado
Alaska Well 20000 300 Gas Water FTP coil in coil chamber lift Installed 2-3/8x 1-3/4" 250 15000 200 Psi & Bw/D Mscf/D 10000 150 100 5000 50 0 0 5/24/2003 9/1/2003 12/10/2003 3/19/2004 6/27/2004 10/5/2004 1/13/2005 4/23/2005 8/1/2005 Date 2007 Gas Well Deliquification Workshop 17 Mar. 5 - 7, 2007 Denver, Colorado
Production Analysis Results Effects of Imbibition Transient Time Infinite Conductivity Fracture in 4 to 1 Rectangular Boundary at 2 years 1000 Match Simulation Kh = 18 md-ft, 20 md-ft X f = 30 ft, 120 ft L/W = 4 1 100 Area = 40 Acres, 40 Acres P wD or P wD ' 10 1 Actual PwD Actual PwD' Analytical PwD Analytical PwD' 0.1 0.0001 0.001 0.01 0.1 1 10 100 t DA Geometry change from radial to a 4 to 1 rectangle. 2007 Gas Well Deliquification Workshop 18 Mar. 5 - 7, 2007 Denver, Colorado
Production Analysis Imbibition During Boundary Dominated Flow Infinite Conductivity Fracture in 2.8 to 1 Rectangular Boundary at 2 years 1000 Match Simulation Kh = 18 md-ft, 20 md-ft X f = 45 ft, 120 ft Area = 29 Acres, 40 Acres 100 P wD or P wD 'x 0.1 10 1 Actual PwD Actual PwD' Analytical PwD Analytical PwD' 0.1 0.0001 0.001 0.01 0.1 1 10 100 t DA Liquid fills near wellbore fracture and matrix. Flow becomes slightly linear. 2007 Gas Well Deliquification Workshop 19 Mar. 5 - 7, 2007 Denver, Colorado
Observations � Static liquid column from a wellbore hydraulics view had little effect on the drainage volume estimates for the well. � High permeability cases under estimate flow capacity if the additional pressure drop was not accounted for. � Standing liquid above the perforations causes damage to the near well permeability. 2007 Gas Well Deliquification Workshop 20 Mar. 5 - 7, 2007 Denver, Colorado
Observations � Loading during the transient flow results in a reduced flow capacity and a change in reservoir geometry. � Dropout during BDF results in a reduction in apparent drainage volume and a change in flow geometry. 2007 Gas Well Deliquification Workshop 21 Mar. 5 - 7, 2007 Denver, Colorado
Disclaimer The following disclaimer may be included as the last page of a Technical Presentation or Continuing Education Course. A similar disclaimer is included on the front page of the Gas Well Deliquification Web Site. The Gas Well Deliquification Steering Committee Members, the Supporting Organizations and their companies, the author(s) of this Technical Presentation or Continuing Education Course, and their company(ies), provide this presentation and/or training at the Gas Well Deliquification Workshop "as is" without any warranty of any kind, express or implied, as to the accuracy of the information or the products or services referred to by any presenter (in so far as such warranties may be excluded under any relevant law) and these members and their companies will not be liable for unlawful actions and any losses or damage that may result from use of any presentation as a consequence of any inaccuracies in, or any omission from, the information which therein may be contained. 2007 Gas Well Deliquification Workshop 22 Mar. 5 - 7, 2007 Denver, Colorado
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