PRESSURE PULSE ANALYSIS OF GAS LIFT WELLS J.S. Gudmundsson, I. Durgut Norwegian University of Science and Technology 7491 Trondheim J. Rønnevig, K. Korsan, H.K. Celius Markland AS 7462 Trondheim 2001 Fall ASME/API Gas Lift Workshop November 12-13, 2001, Aberdeen

Contents of Paper Introduction Pressure Pulse Generation Mass Flow Rate Line Packing Multiphase Mixtures Operational Issues Wells and Pipelines Limited-Installation Test Gas Lift Analysis Concluding Remarks

Pressure Pulse Technology Gas-Liquid Mass Rate Flow Condition Analysis Wells and Flowlines Field Tested Offshore On-Demand Testing Quick-Acting Valve Pressure Transducers Patented World-Wide Licensed to Markland

A B LAB Pressure Time A B

Pressure Pulse Mass Rate No Calibration Needed Δp (Pa) = ρ u a a (m/s) = ΔL/ Δt G (kg/s.m2) = ρ u w (kg/s) = G A w (kg/s) = Δp A/a

Pressure Pulse FLOW CONDITION ANALYSIS A quick-acting valve stops the flow. The wellbore pressure drop needed to overcome wall friction during production, becomes available as static pressure at wellhead. This change in pressure propagates continuously at the speed of sound back to the wellhead. The resulting pressure-time log can be used in flow condition analysis. In-house rapid pressure transient and speed of sound models and commercial wellbore flow model used (convert to pressure-distance log).

Pressure Pulse Flow Condition Analysis Oil Producer Example 2 4 7 6 9 3 5 10 8 Reflections: 1 = diameter change at 382 m 2 = diameter change above SCSSV 3 = diameter change below SCSSV 4,5,6 = secondary reflections 7 = Bubble point (2300 m) 8 = secondary reflection from bubble point 9 = diameter reduction before inflow zone 10 = bottom hole 1

Pressure Pulse Limited-Installation Test Offshore Well A Measured depth 4440 m, vertical depth 2270 m Tubing ID reduced from 4.89” to 3.55” at 650 m depth Oil gravity 35 API, gas gravity 0.89 GOR 24.8 Sm3/m3, produced GOR 635 Sm3/m3 Liquid production rate 1167 Sm3/day, WC 66.8% WHP 67 bar, BHP 234 bar WHT 76 C, BHT 100 C Void fraction at wellhead 0.63

1100 meters 1750 meters 2100 meters

Pressure Pulse Gas Lift Analysis Well B Vertical well 3500 m deep Tubing ID 0.1 m Gravity oil 32 API, gas 0.85, water 1.103 GOR 50 Sm3/m3, WC 50% WHP 50 bara Liquid production rate 400 Sm3/d Gas injection rate 100 MSm3/d Valves 1100 m, 1750 m and 2100 m depth

Pressure Pulse Analysis of Gas Lift Wells CONCLUDING REMARKS Pressure pulse technology used for gas-liquid mass rate and wellbore flow condition analysis. On-demand testing. Technology is flexible, robust and gives highly-repeatable results. Limited and extensive-installations tested offshore. Location of active gas lift valve simulated for typical well using models of rapid transients, sound speed and wellbore flow models. Pressure pulse technology can be used for a range of applications, including gas lift optimisation (allocation of injection gas).