Base Case Simulation Model Base case model is run by eclipse in order to predict field performance This model is utilized as the main reference for the use of comparing with other simulation Input Data Input Value Number of wells 32 Type of well Deviated Depletion method Natural depletion Production control mode Control by oil rate Oil Rate 150 SM3/Day Water Cut Limit for the field 0.5 Gas Oil ratio limit 100 SM3/Day Run Duration 20 years

Base Case Model Result

Base Case Simulation Result Base Case Model Result Cumulative Oil Production 32.78 million m3 Recovery Percentage 8.25% Drive mechanism Water aquifer and Gas Cap Pressure depletion 2.00 Bar/ Year Base Case scenario suggest that : Oil production shall be controlled by 150 SM3/Day GOR shall be controlled by 100 SM3/SM3 Water cut shall be controlled by 0.5 SM3/SM3 Secondary recovery shall start after 10-14 Years of the start of the primary production.

Development Strategy Based on the result obtained from the base case model-Gullfaks reservoir has dominant in water aquifer and gas cap as drive mechanism Able to support the reservoir pressure at a constant pseudo steady state decline rate Utilized water injection in order to support reservoir pressure and prevent further expansion of gas cap as the pressure drop below the bubble point Reservoir with big gas cap and water aquifer will result in 20-40% oil recovery Improved from primary recovery of 20 years production for 32 wells with only 8.25% oil recovery

Sensitivity analysis for Water Injection Strategy Sensitivity analysis shows to what extent the viability of a project is influenced by variations in major quantifiable Technique to investigate the impact of changes in project variables on the base case Purpose of doing sensitivity analysis is to help to identify the key variables which influence the project effectiveness Reservoir performance can be optimized by doing sensitivity analyses based on the simulation base case result Sensitivity analyses are also performed to rank the importance of reservoir parameters which affects production performance which are : Number of injection wells Injection rate Injection start time

Sensitivity analysis for Water Injection Strategy 1. Number of injection well Injection Well = C2,C3,C4,C5 and C6 Variable Case 1 Case 2 Case 3 Case 4 Case 5 Number of Injection well 1 2 3 4 5 Start of injection After 20 years of Primary Production Injection Rate Same as production control mode rate ( 150 SM3 ) Duration of injection Strategy 25 years Additional Oil Recovery 10.10% 10.23% 10.31% 10.25% 10.18% Optimum Recovery

Sensitivity analysis for Water Injection Strategy 2. Injection rate Variable Case 1 Case 2 Case 3 Case 4 Case 5 Number of Injection well 3 injectors Start of injection After 20 years of Primary Production Injection Rate (SM3/ Day ) 150 200 250 300 350 Duration of injection strategy 25 Years Additional Oil Recovery 10.31% 10.41% 10.62% 10.65% 10.63% Optimum Recovery

Sensitivity analysis for Water Injection Strategy 3. Injection start time Variable Case 1 Case 2 Case 3 Case 4 Case 5 Number of Injection well 3 injectors Start of injection after primary production ( Year) 5 10 15 20 Injection Rate ( SM3/ Day ) 300 Duration of Injection strategy 25 Years Additional Oil Recovery 10.49% 10.52% 10.74% 10.68% 10.65% Optimum Recovery

Sensitivity analysis for Water Injection Strategy Summary of analysis Variable Optimum Water injection case Number of injection Wells 3 injectors Start of Injection after primary production 10 years Injection Rate 300 SM3/ Day Duration of Injection strategy 25 Years Additional Oil recovery 10.74%

Proposed water injection strategy simulation result Water flooding data input Input value Number of wells 32 Type of wells Deviated Strategy method Water flooding Injection Rate 300 SM3/Day Injection Well C3, C4 and C6 Oil rate 30 SM3/ Day Water Cut Limit for the field 0.5 Gas oil ratio limit 100 SM3/SM3 Action if limits are violated Shut worst well

Proposed water injection strategy simulation result

Proposed water injection strategy simulation result

Proposed water injection strategy simulation result Comparison of simulation result between water injection and base case Water Injection Strategy Result Cumulative Oil Production 56 million m3 Recovery Percentage 10.74% Drive mechanism Water injection ( Secondary Recovery) Pressure depletion Maintain at 148-150 Bar/ Year of injection Base Case Model Result Cumulative Oil Production 32.78 million m3 Recovery Percentage 8.25% Drive mechanism Water aquifer and Gas Cap Pressure depletion 2.00 Bar/ Year