Rejuvenating Brown Field with Low-Cost Improvised Gas Injection – Success Story from Pilot to Proven – Efficient Replication

Abstract Rejuvenating a declining brown field has always been a challenge. Low-cost gas injection from available production in a compartmentalized field in offshore Malaysia with stacked reservoirs has increased recovery by more than 15%. The field has been producing for over 40 years with a decline rate of about 30%. Following a meticulous feasibility study, the first GI (gas injection) was successfully executed during the low oil price period in 2019-2020. This low-cost approach leveraged on existing infrastructure, improvised gas injection and repurposing idle wells. This pilot gas injection project successfully increased reservoir pressure in the depleted fault block, enabling the drilling of two (2) downdip infill wells, thus increasing production and reserves. Peak production from these infill wells even surpassed the initial production from this fault block enumerating the success of this GI project. A close monitoring of the Gi/Gp (Gas injection/Gas production) and IVRR (incremental voidage replacement ratio) helped to ensure better gas sweep with no gas breakthrough till date. Reserves as of date are twice that of the depletion reserves. Without gas injection these wells were unable to flow even with gas lift due to very low reservoir pressure. Careful pilot management and optimum positioning of injector to producer demonstrated the effectiveness of gas injection in this low-energy reservoir Encouraged by the positive pilot results, with good experience in GI management, more gas injection opportunities were quickly evaluated and replicated in other depleted fault blocks. Early indications from these expanded efforts show consistent success in increasing oil production by improving reservoir pressure. The current GI initiatives have already helped to reduce the decline of this field from 30-35% to 6-8%, increasing economic life of this field. This systematic fast replication highlights the scalability of gas injection for improved recovery. This paper provides stepwise approach and evaluation of the GI pilot design, data gathering, gas front monitoring, Gi/Gp, IVRR management for delayed gas breakthrough and efficient sweep resulting in pilot success. It also details the field wide further GI opportunity screening with option to convert existing producers to gas injectors with improvised GI through gas lift valves. This has also opened opportunities to investigate simultaneous up dip gas and downdip water injection in certain reservoirs of this field to further increase production by sandwiching, which is now captured in the next development initiative.