Enhancing Recovery and Value Optimization of Marginal Oil Fields in Onshore Thailand: A Gas Injection Approach

There are several marginal onshore oil fields in Thailand, of which the associated hydrocarbon gas has no commercial value as it is isolated from the sale gas pipeline. Field “A” is selected for the hydrocarbon gas injection study based on technical enhanced oil recovery (EOR) screening results. This study aims to optimize development strategies from primary recovery to EOR phases. The full-field geological model is utilized in the compositional simulation study to investigate the infill wells, waterflood improvement, and various gas injection schemes. The gas injection strategies include continuous gas injection, Double Displacement Process (DDP), and Water-Alternating-Gas (WAG). The results of waterflood improvement and infill well study suggest that terminating water injection provides higher oil recoverable volume and economical value. For the gas injection study, the optimum development scenario was DDP with a hydrocarbon gas injection rate of 1 MMscf/d and a water injection rate of 900 B/D. The DDP method can yield an incremental recovery factor of 7% above the optimal water injection scenario. This study proves that Field “A” could be further improved through gas injection and, moreover, it demonstrated a framework of gas EOR study and implementation in marginal oil fields.