This paper presents a practical approach toward cost optimization of a thermal recovery project in a heavy oil green field in Kuwait. This objective is achieved by understanding total cost breakdown for Capital Expenditure (CAPEX) and Operating Expenditure (OPEX) for all assets (natural and physical) during the economic horizon of the project and the identification of root causes of cost drivers that cause the total cost to increase, potential project delay and poor performance. Complex cause and cost effect relationships are visualized using causal maps and loss causation models for seven most important group of risks during field life cycle. Uncertainties are addressed by comparison with analog fields undergoing Cyclic Steam Stimulation and Steamflood. One-way sensitivity analyses and stochastic modeling of key cost drivers solve a critical uncertainty, lack of OPEX data during commercial operations. Other application includes assessment of risks affecting total cost per barrel and selection of best strategy for risk mitigation with their costs and benefits. A work vs. total undiscounted cost breakdown structure showed the 12 most critical cost drivers, where 70% corresponds to OPEX and 30% to CAPEX, fuel for steam flooding being the highest with 55%. A map with 17 elements was analyzed for associated physical assets, 2 causation maps describes 14 causes of total costs for surface and subsurface, including identification of key uncertainties and risks. Seven most significant groups of risks (total 66 risks) were modeled to visualize the impact on cost, people (health & safety) and environment with all mitigation actions ranked by cost benefit. Understanding causes of high cost per barrel and their relationship with uncertainties and risks for a green heavy oil field, is a formidable tool for multidisciplinary cost optimization as it provides a common language that is understood by all disciplines involved.