37 th Gas-Lift Workshop Houston, Texas, USA February 3 7, 2014 Acoustic Techniques to Monitor and Troubleshoot Gas-lift Wells Carrie-Anne Taylor, Engineer Lynn Rowlan, Engineer Echometer Company Feb. 3-7, 2014 2014 Gas-Lift Workshop 1
Introduction The distance to the fluid level provides beneficial information throughout the life of a gas-lift well. Fluid level depths with respect to valves Depth to the deepest mandrel uncovered Verify Unloading process is proceeding properly Find holes, restrictions Wellbore problem or equipment malfunction? How can acoustics aid in Troubleshooting? Feb. 3 7, 2014 2014 Gas-Lift Workshop 2
Determine Fluid Level Depths with Respect to Valves **BP Homa A-1 Casing 12-05-07 IMP (08:04:01) Wellbore Overlay 1 2 3 4 5 6 7 8 9 10 The fluid level is quickly and easily identifiable between the 9 th and 10 th Gas-lift Valves. Liquid Level
Acoustic pulses reflect off gaslift valves and other anomalies. GLV 1 GLV 2 GLV 3 GLV 4 GLV 5 GLV 6 GLV 7 GLV 8 GLV 9 LL 7971 9 10 Not all markers exactly line up with their respective reflections. Acoustic Velocity changes with respect to pressure and temperature as the depth of the wellbore increases. Gas-lift Valve Depths from Wellbore Schematic: GLM 1 2894 GLM 5 5738 GLM 9 7598 GLM 2 4028 GLM 6 6208 GLM 10 8117 GLM 3 4819 GLM 7 6675 GLM 4 5320 GLM 8 7091 2014 Gas-Lift Workshop 4
Acoustic Velocity Between Downhole Markers Feb. 4 8. 2013 2013 Gas-Lift Workshop 5
Acoustic Velocity Profiles in Gas-lift Wells Depends on: 1. Gas gravity / composition 2. Temperature along wellbore 3. Pressure profile in well 4. Can be determined from counting collar echoes or identifying downhole markers detected during a shot 5. Uniform Gas Composition when Gas is Flowing 6. Acoustic Velocity Usually Increases with Depth Due to Higher Temperature 6
Gas-lift Mandrels are Excellent Downhole Markers Purpose Accurately calculate the distance to the liquid level plus other downhole reflectors such as gas lift valves and mandrels, tubing collars, subsurface safety valves and possible holes or other problems. Distances Determined using echoes from gas-lift valves at known distances from the wellhead. Accounts for Variations of acoustic velocity commonly observed in most wellbores due to variations of temperature, pressure and gas composition as a function of depth. Feb. 3 7, 2014 2014 Gas-Lift Workshop 7
Downhole Markers for Accurate Acoustic Velocity and Fluid Level Analysis Apply Low Pass Filter to reduce high frequency noise and see detail. Feb. 3 7, 2014 8
Wellbore Schematics Provide Downhole Markers 9
Acoustic Velocity is Calculated Between Markers Along the Shot Trace S 2 3 4 5 6 7 10
If the Acoustic Velocity is out of Range, THERE IS A PROBLEM Awareness of the calculated Acoustic Velocity is important: Quality check for correct marker selection. Accurate fluid level calculations. Verify gas gravity and uniform gas composition in the well. Acoustic Velocity typically displays an increasing trend in producing gas-lift wells. Feb. 3 7, 2014 2014 Gas-Lift Workshop 11
Direction of Kick Across Mandrels Feb. 4 8. 2013 2013 Gas-Lift Workshop 12
Shape and Direction of Echoes from Valves and Mandrels Two factors determine the direction of kick of Gas-lift Mandrels on the acoustic trace: 1) Physical characteristics of the mandrels 2) Is the operator shooting down the tubing or the casing? On the casing side, the mandrels take up space within the annulus, resulting in a downward reflection kick. On the tubing side, the recess within the mandrel where the valve is located results in an upward reflection kick. Feb. 3 7, 2014 Photo: courtesy of Lufkin Industries Tubing and Casing acoustic traces can be overlaid for comparison and troubleshooting. 2014 Gas-Lift Workshop 13
Mandrel Design Determines Direction of Kick Shot Down Tubing Displays Upkick at Mandrel Increase in area = Upkick Shot Down Casing Displays Downkick at Mandrel Decrease in area = Downkick
mv Overlay Casing and Tubing Shots for Troubleshooting Sec 0 1 2 3 4 5 6 7 8 9 10 Tubing Shot Casing Shot Ft 0 1000 2000 3000 4000 5000 6000 Can help identify problems by answering questions: Do the mandrel reflections line up? Are there additional upkicks or downkicks indicating possible holes, restrictions or other problems? Feb. 3 7, 2014 2014 Gas-Lift Workshop 15
Problems in the Tubing String Feb. 4 8. 2013 2013 Gas-Lift Workshop 16
Upkick Identifies Hole in Tubing Fluid Level
Compare Shots Down Tubing & Casing Hole in Tubing @ 6868 Tubing Shot Casing Shot
Compare Shots Down Tubing & Casing LL Tubing LL GLV9 Casing 19
Compare Shots Down Tubing & Casing Overlaying the Tubing and Casing shots based on time verifies an upkick at the hole in the tubing in both shots. The Depth Reference line gives an accurate depth to the hole of 1083ft. Feb. 3 7, 2014 2014 Gas-Lift Workshop 20
Fluid Levels During Unloading Sequence Feb. 4 8. 2013 2013 Gas-Lift Workshop 21
Acoustics Provide Valuable Details During Unloading Sequence Shots down the Casing Annulus provide a quick look at uncovered mandrels as the annular fluid level drops during the Unloading process. The operating valve is quickly and easily identified. Or the depth to the deepest valve above the annular fluid level, when checks valves are present. GLM 1 GLM 2 GLM 3 GLM 4 LL
Troubleshooting a Problem Well Feb. 4 8. 2013 2013 Gas-Lift Workshop 23
9:53am LL 174.7psi 162.8psi 144.8psi 89.8psi 169psi 155psi 10:00am GLV1 LL 10:05am GLV1 GLV2 LL 10:18am GLV1 GLV2 GLV3 LL 10:44am GLV1 GLV2 GLV3 GLV4 LL 11:12am GLV1 GLV2 GLV3 GLV4 EOT LL
Fluid Levels fluctuate with an increase or decrease in tubing pressure. 2500 Fluid Level Depth Tubing Pressure 180 3000 3500 150 4000 4500 120 5000 90 5500 6000 0 20 40 60 80 100 120 60 140
Horizontal Gas-Lifted/Plunger Lifted Well Feb. 4 8. 2013 2013 Gas-Lift Workshop 26
Stratified Gas Flow Regimes Exist in Horizontal Gas Wells 1. The ability to see past the end of the tubing is unusual in a vertical plunger lift well, because the liquid level is normally at the end of the tubing. 2. In horizontal wells, stratified flow exists; it is not uncommon to see features in the wellbore in the horizontal section past the end of the tubing. 3. Horizontal section appears to be relatively dry (no liquid level); but a significant amount of liquid enters the tubing. Feb. 3 7, 2014 2014 Gas-Lift Workshop 27
Overlay Wellbore Profile Quick placement and verification of: Gas-lift valves and mandrels End of the Tubing Perforation Intervals Feb. 3 7, 2014 2014 Gas-Lift Workshop 28
Horizontal Plunger Lifted Well GLV 1 @ 1712' GLV 2 @ 3014' GLV 3 @ 4092' GLV 4 @ 4797' GLV 5 @ 5256' GLV 6 @ 5716' GLV 7 @ 6176' GLV 8 @ 6570' GLV 9 @ 7031 The fluid level is at a measured depth of 9118ft. Gas-lift Valves can be used to confirm the end of the tubing and the top of the perforations. 29
Reflections can be identified to the Toe Due to Stratified Gas Flow in the Horizontal section of the well. Perf LL 1 2 3 4 5 6 7 8 9 EOT The top perforation upkick used to determine the depths in the well.
Conclusion Beneficial information is obtained throughout the life of a gas-lift well by determining the distance to the fluid level. Knowing the Acoustic Velocity profile of a well provides critical information for verifying gas composition and fluid level accuracy. Identifying reflection kicks across valves and mandrels result in more accurate depth analysis. Operating valves are identified quickly and easily. Troubleshooting techniques aid in identifying downhole problems. Feb. 3 7, 2014 2014 Gas-Lift Workshop 31
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