1. 1 10 th September 2014 Practical Methods for Predicting Hydrate Formation during Gas Well Testing in Ultra-Deep Water Alex Lowden Academic Supervisor: Alain Gringarten Industry Supervisor: Tim Whittle (BG Group)

2. 2 Gulf of Mexico Oil: Shenandoa, Anadarko – 2013/ 5,800 Oil: Coronado, Chevron – 2013/6,127 Oil: Gila, BP – 2013/4,900 Oil: Dantzler, Noble – 2013/6,580 Oil: Block 525, Shell – 2014/7,479 Oil: Exploratus-1, Pemex – 2014/8,202 Oil: Maximino, Pemex – 2013/9,570 Canada Oil: Harpoon, Statoil – 2013/3,630 Oil: Bay Du Nord, Statoil – 2013/3,874 Cote d’Ivoire Oil: Block CI-100, Total – 2013/7,400 Brazil Oil: Block BM-S-50, Petrobras – 2013/6,183 Oil: BM-POT-17 Block, Petrobras – 2013/5,712 Malaysia Gas: Block SK318, Shell – 2014/6,963 Israel Gas: Tamar SW. Noble – 2013/17,420 Gas: Karish Alon C, Noble – 2013/5,742 Angola Oil/Gas: Block 20, Sonangol, BP – 2014/12,703 Gabon Gas: Diaba License G4-223, Total – 2013/5,673 Congo Oil/Gas: Marine 12, Eni – 2013/9,882 Cyprus Gas: Block 12 (Aphrodite), Noble – 2013/5,574 Block/prospect, Operator, Year, Water Depth > 3,000ft India Gas: Block CYD5, Cauvery Basin, Reliance – 2013/5,717 South China Sea Gas: Lingshiu 17-2, CNOOC – 2014/11,512 Mozambique Gas: Area 4, Alguha, Eni – 2013/8,537 Gas: Area 4, Coral, Eni, 2013/6,676 Gas: Area 1, Orca, Anadarko – 2013/3,481 Tanzania Gas: Tangawizi-1, Statoil – 2013/7,544 Gas: Mronge-1, Statoil – 2013/8,200 Gas: Taachui-1, BG – 2014/3,270 Gas: Piri, Exxon – 2014/7,440 Gas: Ngisi-1, Mkizi 1-3, BG – 2013&2014 /4,600-5,900 Deepwater Oil & Gas Discoveries 2013/14

3. 3 What Are Gas Hydrates? http://i.ytimg.com/vi/nUluhIa-hzA/0.jpg. Accessed 01/09/14 Crystalline solid compounds Stabilised by encapsulating a low molecular weight guest molecule Growth occurs in the presence of water/gas At low temperatures and elevated pressures http://i.ytimg.com/vi/nUluhIa-hzA/0.jpg. Accessed 01/09/14

4. 4 The Problem: Hydrate formation during gas well testing in deep and ultra-deep water

5. 5 The Solution: To provide a fast and reliable method to predict gas temperatures during well testing The Problem: Hydrate formation during gas well testing in deep and ultra-deep water

6. 6 Presentation Workflow 1 The Deepwater Environment Modelling temperature during a Shut-in Period Field application Modelling temperature during a Flowing Period 2 3 4 A) B) A) Theory Programme Development and Testing B) Theory Programme Development and Testing

7. 7 The Deepwater Environment Depth, mss Ocean Temperature, ͦC 4 8 12 16 20 24 0 0 500 1000 1500 2000 2500 3000 Sea Current Velocity, m/s 0 0.2 0.4 0.5

8. 8 Presentation Workflow Modelling temperature during a Shut-in Period 2 A) B) Theory Analytic solution Programme Development and Testing

9. 9 Theory: Shut-in Period A solution for the temperature at any point in the riser as a function of shut-in time Gas hydrate formation typically starts at a gas-water interface Sea Current Direction Multi-layer composite cylinder Transient heat conduction in the radial direction Heat transfer to the surrounding ocean by forced convection As seawater flows around the riser: Boundary layer

10. 10 Theory: Shut-in Period How is heat transferred from the gas to the surrounding ocean? 2. Condensate water layer 3. Riser Annulus Multilayer conduction problem Condensate Water Layer Gas + Condensate Water 1. Production tubing and outer riser Using a Green’s function approach to derive a solution to this problem

11. 11 Theory: Shut-in Period How is a solution obtained? Condensate water layer Annulus fluid Multilayer conduction problem Condensate Water Layer Gas + Condensate Water

12. 12 Programme: Shut in Period Within 4 minutes, a well test planner can predict gas temperatures for a shut-in operation Programme tested against transient data from a DST conducted in deepwater Calculated temperatures are within +-5% of gauge data for all shut-in periods

13. 13 Presentation Workflow Modelling temperature during a Flowing Period 3 A) B) Theory Programme Development and Testing New approach to improve the accuracy of existing heat transfer calculations

14. 14 Theory: Flowing Period Can this numerical method be used to create a programme? Methods of solving this equation in the literature make a number of assumptions Solving this equation using numerical integration RK-4 Numerical IntegrationHasan et al (2005) Analytic Solution

15. 15 Theory: Flowing Period Approach: numerically solve for the fluid temperature and pressure Well test planners can use this programme to quickly check if operating conditions are within the hydrate formation region 4 Hours 0.5 Hours 0 Hours 0.5 Hours 4 Hours Run time for each temperature and pressure traverse is less than a minute

16. 16 Programme: Flowing Period The accuracy of this programme is verified against field data and calculations from OLGA To test the programme, transient temperature profiles were calculated for flowing periods of the DST Comparison with dynamic multiphase flow simulator +-10% Gauge Depth

17. 17 Presentation Workflow Field application Gas hydrates formed during a flowing period of the DST 4

18. 18 Gas Hydrate Formation Well Configuration 2 Hours 1 Hour 5 Hours Flowing gas temperatures over the length of the well:

19. 19 Summary 1) A theory has been developed to better predict gas temperatures during well testing in an offshore environment 2) From this theory, programmes have been developed that allow reliable gas temperature profiles to be computed on a spreadsheet, in a short time frame