European Conference Gas Well Deliquification 28-30 September 2009, Hampshire Hotel, The Netherlands Acoustic Liquid Level Testing of Gas Wells Originally Presented OKC POS 2009 - SPE 120643 Lynn Rowlan
Acoustic Fluid Levels Traditionally Fluid Level shot down the annulus where tubing collars are counted to determine depth Acoustic liquid levels typically used for: Well Potential and BHPs Artificial Lift Optimization Plunger tracking Gas Well and Liquid Loading Diagnostics
Fluid Level on Gas Well Gas Velocity Impacts Result of Acoustic Liquid Level Shot: 1. Below Critical Velocity: Usually see liquid level above bottom of Tubing 2. Above Critical Velocity: May not see a liquid level because liquid droplets may fill tubing and absorb all energy from shot May see bottom of tubing and/or perforations due to small amount of liquid
Acoustic Fluid Level Generate Blast at Surface to Creates Traveling Wave Acoustic Wave Travels in the Well at Speed of Sound Echoes RTTT from well bore change diameter recorded Reduction seen as a down-kick Increase is seen as an up-kick Fluid level gives large kick and lets almost no energy through Collars Level BANG! BANG!
Gas Gun Physical set-up on Well
Display of Reflections of Pressure Wave Initial Acoustic Pulse caused by explosion of compressed gas into the tubing or casing annulus, explosion into annulus forms compression traveling wave. Reflected Pulse caused by DECREASE in the annular cross- sectional area IS displayed as an downward kick on the acoustic trace. Acoustic Trace Acquired down the Tubing Showing Upkick from Hole in Tubing Reflected Pulse caused by INCREASE in the annular cross- sectional area IS displayed as an upward kick on the acoustic trace.
Shot Down Tubing Verify Liquid Level Above/Below Tubing Inlet End of Tubing
Use an Acoustic Fluid Level Instrument To Identify The Depth To The Hole 1. Shoot tubing/casing annulus while flowing up tubing With Casing Valve Closed the Fluid Level should be near tubing intake or below perforations (If no Hole)? Time 12:12:27
Shots Down Tubing & Casing Hole in Tubing @ 6868 Tubing Shot Casing Shot
Use Acoustic Surveys to Alert You to What is Downhole @ 4750 Tight Spot in Tubing Tight Spot End of Tubing @ 5050 1/8 Hole in Tubing 1/8 Hole Liquid Level
Acoustic Trace with Depth Determination 1 Sec Liquid Level Depth (LL) Collars count depth (C) is noted on the acoustic signal. Liquid Level Depth (LL) determined by multiplying the RTTT (Seconds) by the average of all collars counted (JTS/sec) times the average joint length (Feet). (5.566*20.5725*31.670 = 3626.41 feet) et)
Analysis Method: Automatic Collar Count 0 10 20 30 40 46 Automatic Collar Count analysis will determine the depth to the liquid level for most wells
Downhole Marker Using Known Perforation Depth to Determine Distance to the Liquid Level 2.631 sec? = 1875 ft 1369 ft 1.921 sec
Offshore Wellbore Schematic and Corresponding Acoustic Trace Offshore Wells: 1) Use of Downhole Markers most often used analysis Method.. 2) Acoustic Velocity Method often used initially to identify general location of Known Markers 3) Should use Deepest Marker for Depth to Liquid Level 4) Data Always Critical in Calculation of BHP
Analysis Method: Low Pass Filter Identifies Downhole Marker Gas Lift Mandrel High Frequency Noise See Downhole Anomalies: SCSSV@ 1575 X-NIPL@ 3161 GLM1@ 3618 GLM2@ 11743 BHP Ch@ 11798 CIM@ 11874 X-NIPL@ 11993 XO@ 12041 XN-NIPL@ NIPL@ 12374 SCSSV GLM1 Liquid Level
Depth Determination:Acoustic Velocity Depends on: Acoustic Velocity method Acoustic Velocity options: Manually entered Calculated based on SG of gas Calculated based on compositional analysis (Manual gas velocity can be used for approximations or in case where velocity already determined by downhole marker correlation in other shot) 1. Gas gravity / composition 2. Temperature along completion 3. Pressure in the completion (automatically calculated from measurements taken during the shots) 4. May use Casing Shot for Tubing SG
358 psi Gaseous dp/dt Gaseous Correction Tested Gas Production = 265 MCF/D Adjusted Gas Free 8636 Gaseous Height Closed Valve 2.5 Min. to Determined Gas Flow Rate and % Liquid Gas flowing into well FBHP = 1080.6 psi 1615 Gas Free
Gaseous Da, Adj. Gas Free Height Da = 9719 61.7 psi Da*dP/dT = 61813 Determine % Liquid 3427 Gas flowing into well PBHP = 373.9 psi 1615 Gas Free
Backpressure in a Liquid Loaded Well Liquid Level
Fluid Level Results on Gas Well Treated with Surfactant Foam 1/3 of Gaseous Liquid Gradient? - %Liquid
Static Fluid Level on Gas Well Measured Surface Pressure 2249.5 Psig 365.8 Psig Gas Column Pressure High Pressure Gas Pushed all but 87.8 ft of Liquid Back into Formation Easy to Observe Up-kick caused by the top perfs at 6032 feet (Next Slide) Collar Recesses Counted to Perforations Shut-in Gas Well
100.0 mv Acoustic Trace From Static Fluid Level on Gas Well Sec 0 1 2 3 4 5 6 7 8 9 10 C - -LL Collar Recesses Counted to Perforations 7 88 Sec Implosion ( ft ) 0 1000 2000 3000 4000 5000 6000 7000 7 8 Sec Collar Recesses Not Seen @ Low Pressure OR in Flush Joint Tubing BUT See Clearly @ High Pressure
Sec Analysis Method : Counting Collars versus Using Top of Perforations as Known Marker Depth 0 1 2 3 4 5 6 7 8 9 10 C - -LL Collar Recesses Counted to Perforations 100.0 mv Implosion Depth to LL = 6162.22 ( ft ) 0 1000 2000 3000 4000 5000 6000 7000 Sec 0 1 2 3 4 5 6 7 8 9 10 -DM -LL 6032 ft to Top of Perforations 100.0 mv Implosion Acoustic Velocity = 1420-1500 ft/sec Depth to LL = 6164.21 ( ft ) 0 1000 2000 3000 4000 5000 6000 7000 Comparison of Two Methods shows Depth to Liquid Level within 2 FeetF
General Comments 1) Acoustic fluid level measurements are easily performed in flowing or shut in gas wells 2) Recommended practice is to always acquire at least two (2) acoustic fluid level records when connected to a well 3) When shooting down the tubing, EUE collar recess Echoes can often be detected 4) Using an echo from a known down hole marker near the fluid level is usually the most accurate method to determine depth. 5) Using gas specific gravity or composition is often the least accurate depth determination analysis method
Questions?