SUBSEA GAS BOOSTING Jon Steinar Gudmundsson October 8, 2008

Alphabeta Production Gas initially in place 94.4×109 Sm3 Reserves in place 56.6×109 Daily volume flow rate (total) 7.75×106 Sm3/d Hourly mass flow rate (total) 239×103 kg/h Number of wells 4 Tubing diameter (ID) 0.15 m Hourly mass flow rate per well 61×103 Molecular weight 17.45 kg/kmol

Alphabeta Natural Production 4 Wells

Alphabeta Pressures Constant Total Field Rate 240,000 kg/h Year WHP (bara) PLEM Difference (bar) 234 176 2 209 157 19 4 193 145 31 8 159 119 57 16 91 68 108 PLEM = Pipeline End Manifold (75% of WHP)

Industrial Jet Pump pipe mixer diffuser nozzle

Pump Performance ESDU industrial jet pump experience and performance data used in calculations Pressure loss coefficients for LP, HP, M and D sections in series, K=(Δp)/(0.5ρu2) Performance numbers M, N, R, η, C in terms of flow, pressure, geometry, hydraulic efficiency and density Review of literature of jet pumps in single and multiphase service

Performance Numbers

Performance Equation

Alphabeta Pump Parameters Year Difference (bar) C (-) N M η 0.23 0.00 2 19 0.21 0.15 1.9 0.29 4 31 0.19 0.25 1.6 0.40 8 57 0.46 0.90 0.41 16 108 0.084 0.87

Alphabeta Drive Fluid Rate Year Difference (bar) Gas Density (kg/m3) Gas Flow Rate (m3/h) M (-) Drive Fluid 139 1719 2 19 124 1927 1.9 1039 4 31 114 2096 1.6 1343 8 57 92 2598 0.90 2962 16 108 50 4780

Drive Fluid Volume Rate and Mass Rate Year Difference (bar) Drive Fluid (m3/h) (kg/h) (-) 2 19 1039 622,000 4 31 1343 803,000 8 57 2962 1,770,000 16 108

Subsea Gas Boosting

Alphabeta Phase Envelope

Alphabeta Hydrate 100% and 75% Produced Gas + 25% Drive Fluid 75+25%

Pipeline Diameter Constant Gas Production, Increasing Drive Fluid

CFD Simulation

Performance Simulation (CFD)

Concluding Remarks Field and well performance assumed; high quality offshore resource Performance of jet pumps well known, but not for HP natural gas (K factors?) High drive fluid rate and hence large pipe diameter (dense phase transport) 14% greater cumulative production first 8 years with pressure boosting

Alphabeta Natural Gas Field Drainage area 80 km2 Reservoir thickness 25 m Average reservoir pressure 285 bara Average reservoir temperature 88 oC Water depth 800 Reservoir depth 2600 Average permeability 200 mD Porosity  % Water saturation 20 % Recovery factor 60 Life time of reservoir Years

Alphabeta Pressures Constant Total Field Rate 240,000 kg/h Year G [GSm3] p/z [bara] p BHP WHP 2 5,7 287 264 258 209 4 11,3 268 246 239 193 8 22,6 232 200 159 16 45,3 136 124 91

Alphabeta Reservoir Performance

Alphabeta Inflow Performance

Pressure Loss Coefficients ESDU