Effect of Liquid Loading on Production Analysis Cox, Sutton, and - - PowerPoint PPT Presentation

Gas Well Deliquification Workshop

Adams Mark Hotel, Denver, Colorado March 5 - 7, 2007

Effect of Liquid Loading on Production Analysis

Cox, Sutton, and Conway

• Mar. 5 - 7, 2007

2007 Gas Well Deliquification Workshop Denver, Colorado 2

U.S. Gas Facts

US Historical Gas Well Facts

50 100 150 200 250 300 350 400 450 500 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Avg Gas Rate, MCFD/Well 1 2 3 4 5 6 7 8 9 10 Avg Wellhead Price, $/MCF Avg Well Rate MCFD Unload Rate Avg Wellhead Price $/MCF

Source: EIA Natural Gas Annual

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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

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Purpose

Examine the affects of gas well liquid loading as it relates to production analysis and well performance.

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Outline of Talk

Liquid loading what’s the problem Laboratory experiments Eclipse modeling work Production analysis results Field examples

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Wellbore Dynamics - Loading

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SLC Pressure Profile

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Condensed Water

2,000 4,000 6,000 8,000 10,000 12,000 14,000 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Water Vapor Content, Bbls/MMCF Depth, ft

Water Condensation

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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?

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Field Examples of Production Analysis for a Loaded Well

0.1 1 10 100 1000 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 100000 tDA PwD or PwD'x 0.1 Actual PwD Actual PwD' Analytical PwD Analytical PwD' Radial Flow in 1 to 1 Rectangular Boundary Pre-loading

Match

Kh = 20 md-ft Skin = -1.1 Area = 190 Acres

Wyoming Gas Well

500 1000 1500 2000 7/28/2001 12/10/2002 4/23/2004 9/5/2005 1/18/2007 MCFD/FTP/CP 25 50 75 100 BWPD/BOPD MCFD Unloading Rate, MCFD BOPD BWPD

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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

• Base case no liquid in tubing
• Consider standing fluid to tubing tail
• Consider imbibition

Simulation Controls

• Flowing tubing pressure - 350 psia
• 2-3/8-in Tubing set at 8000’ (10,000’ well)
• Single layer model

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Production Profile - 0.5 md Case

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Production analysis results

0.1 1 10 100 1000 0.0001 0.001 0.01 0.1 1 10 100 tDA PwD or PwD' Actual PwD Actual PwD' Analytical PwD Analytical PwD' Infinite Conductivity Fracture in 1 to 1 Rectangular Boundary at 2 years

Match Simulation

Kh = 20 md-ft, 20 md-ft Xf = 120 ft, 120 ft Area= 40 Acres, 40 Acres 0.1 1 10 100 1000 0.0001 0.001 0.01 0.1 1 10 100 tDA PwD or PwD' Actual PwD Actual PwD' Analytical PwD Analytical PwD' Infinite Conductivity Fracture in 1 to 1 Rectangular Boundary at 2 years

Match Simulation

Kh = 16 md-ft, 20 md-ft Xf = 70 ft, 120 ft Area= 40 Acres, 40 Acres

Dry Gas Base Case SLC – 8000 ft Back pressure alone does not account for field

• bservations.

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Support for Imbibition Under Flowing Conditions

Performed by Mike Conway the at Stim-lab

8 ft Water dP Gas dP Exit Pressure 4 ft Metered Gas Rate Water Pump gal um

Test parameters 20/40 Brady sand Determine effective permeability. Liquid level controlled at the exit.

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250 500 750 1000 8/1/2004 8/1/2005 8/1/2006 Gas Rate & Tubing Pressure, (mscf/D, psi) 250 500 Water Rate, bbl/D MCFD FTP BWPD Installed Pumping Unit

East Texas Well

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250 500 750 1000 1250 1500 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 MCFD 25 50 75 100 125 150 BOPD/BWPD MCFD BWPD

West Texas Well

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5000 10000 15000 20000 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 Mscf/D 50 100 150 200 250 300 Psi & Bw/D Gas Water FTP Installed 2-3/8x 1-3/4" coil in coil chamber lift

Alaska Well

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Production Analysis Results Effects of Imbibition Transient Time

Geometry change from radial to a 4 to 1 rectangle.

0.1 1 10 100 1000 0.0001 0.001 0.01 0.1 1 10 100 tDA PwD or PwD' Actual PwD Actual PwD' Analytical PwD Analytical PwD' Infinite Conductivity Fracture in 4 to 1 Rectangular Boundary at 2 years

Match Simulation

Kh = 18 md-ft, 20 md-ft Xf = 30 ft, 120 ft L/W = 4 1 Area = 40 Acres, 40 Acres

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Production Analysis Imbibition During Boundary Dominated Flow

Liquid fills near wellbore fracture and matrix. Flow becomes slightly linear.

0.1 1 10 100 1000 0.0001 0.001 0.01 0.1 1 10 100 tDA PwD or PwD'x 0.1 Actual PwD Actual PwD' Analytical PwD Analytical PwD' Infinite Conductivity Fracture in 2.8 to 1 Rectangular Boundary at 2 years

Match Simulation

Kh = 18 md-ft, 20 md-ft Xf = 45 ft, 120 ft Area = 29 Acres, 40 Acres

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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.

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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.

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Disclaimer

The following disclaimer may be included as the last page of a Technical Presentation

• r 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.