Olga

TABLE OF CONTENTS

1. Slugging 3
1.1 Preliminary Pipeline Sizing 3
1.2 Terrain Slugging – Normal Operation 7
1.3 Terrain Slugging – Mitigation Alternatives 9
1.4 Production Ramp-up 10
1.5 Decretisation Sensitivity (Optional) 11
1.6 Slugtracking Module 11

2. PVTsim – fluid properties 142.1 Gas Condensate Fluid Property File 14
2.2 Harthun Fluid Property File 17
2.3 Mixing condensate and water 18

3. PIPELINE SHUT-IN AND START-UP 19
3.1 Shutdown Simulations 21
3.2 Start-up Simulations 22
3.3 Depressuring Simulations 23
3.4 Depressuring Simulations – Comp. Tracking (Optional)24

4. GAS CONDENSATE PIPELINE 25
4.1 Geometry Modification 25
4.2 Steady State Simulations 28
4.3 Pigging Simulations 29
4.4 Turndown Ramp-up 30

5. THREE PHASE FLOW – WATER MODULE 31

6. You get a fax – results within TWO HOURS? 32

7. (Optional) SEPARATORS AND CONTROLLERS 35Slugging

The Harthun field has recently been discovered, located approximately 4.3 km due south of the existing Wigoth Alfa platform in 255 m water depth. It is proposed to develop this field via a single subsea wellhead and pipeline to the Wigoth Alfa platform to allow the field potential to be fully assessed during an extended test phase prior to full field development. The fieldwill flow at production rates of between 5 and 15 kg/s.

Wigoth Alfa is located in 270 m of water with the production deck located 30 m above sea level. There is an existing 300 m long 4 inch riser on Wigoth Alfa which was pre-installed during the construction phase of the platform to accommodate future subsea field developments. The riser has an internal diameter of 0.1 m with awall thickness of 7.5 mm and no insulation.

Recent topsides modifications involving the installation of multiphase well test meters has allowed the existing Test Separator to be freed up as a dedicated Harthun production separator. The Test Separator operating pressure is to be maintained at 50 bara to allow the gas to be feed forward to the export compression system.(Preliminary topsides studies indicate that there is not sufficient spare capacity in the flash gas compressor to handle the additional gas from Harthun).

The minimum ambient temperature can be assumed to be 6°C. The ambient heat transfer coefficient, (from the outside of the pipe structure to the surroundings), can be assumed to be 6.5 W/m²/K in the absence of any other data.You are required to perform a study into the technical viability of producing Harthun over Wigoth Alfa, taking account the following:-
• pipeline size required,
• production stability during both full production and well testing phases
• insulation requirements during both normal production, well testing and shutdown
•establish any limitations due to the existing topsides facilities during both normal operating and transient operations.

A number of hints have been prepared to help you to complete this task. It is recommended that you read these prior to commencing each activity.

1 Preliminary Pipeline Sizing

The first task is to establish the pipeline size andinsulation level required to achieve the desired production and turndown rates. This can be done by performing a series of steady state simulations using an assumed pipeline profile. However, there is very little information currently available, specifically, there is no seabed profile with the only information being the water depth at the Harthun well and the existing platform information....