Active Control of Gas Lift Wells Simulation and Experimental Series Gisle Otto Eikrem Department of Engineering Cybernetics Norwegian University of Science and Technology

Overview – Gas Lift Wells Instability in multiphase flow Stabilization methods Simulaton results Experimental results Summary 20 November 2018

Gas Lifted Well Well Data: Annulus Tubing · 2048 m vertical well 0.5 kg/s 15bara Well Data: · 2048 m vertical well · 5 inch tubing · 2.75 inch production choke · 0.5 inch injection orifice Annulus Refer to the number of gas lifted wells in Shell, “10.000 wells worldwide are operated with gaslift. Shell produces about 800.000barrels/day from gaslifted wells". Tubing 20 November 2018

Unstable Flow 20 November 2018

Production Curve Optimal region Theoretical production Stable region Unstable region The optimal region is given from the object function which includes the production and price of oil and gas and the cost related to the gas injection rate. There may also be limitations in the availability of lift gas and compressor capacity. 20 November 2018

Introduction – Video I 20 November 2018

Multiphase Video I Video of severe slugging in gas lift well 20 November 2018

Introduction – Video II 20 November 2018

Video of controlled multiphase flow Multiphase Video II Video of controlled multiphase flow Stable flow 20 November 2018

Stabilizing Options How to stabilize severe slugging in gas lift wells Choking Size of orifice / critical flow Increase gas rate Automatic control 20 November 2018

Minimum Flow Curve Gravity dominated pressure drop - unstable friction dominated pressure drop - stable “Gravity” “Friction” Gravity dominated - small rate reduction Pressure increase Decreasing inflow Unstable! Friction dominated - small rate reduction Pressure decrease Increasing inflow Stable 20 November 2018

Control Principle The Principle behind control of severe slugging in gas lift wells Stabilize pressure in bottom of well Production choke controls pressure PT 20 November 2018

Control Structures Casing Head Pressure Downhole Pressure 20 November 2018

OLGA Results Control of Downhole Pressure 20 November 2018

OLGA Results Control of Casing Head Pressure 20 November 2018

The Laboratory Production Tubes Control Panel Reservoir Valve and Gas Injection 20 November 2018

Laboratory Setup 20 November 2018

Control Structures Casing Head Pressure Downhole Pressure 20 November 2018

Experimental Results Control of Downhole Pressure 20 November 2018

Experimental Results Control of Casing Head Pressure 20 November 2018

Summary How to stabilize gas lift wells Possible control structures Simulation results Laboratory experiments 20 November 2018