Abstract
Field A is producing from natural depletion drive oil reservoirs with large gas cap. The field was under production curtailment, governed by gas-oil-ratio (GOR) limit to preserve the reservoir gas cap size. As the field continues to produce, the oil rate has declined while GOR increased exponentially. The reservoirs were at risked of being idle when the existing producers were forced to be shut-in due to GOR limit. This paper provides an insight of a late field life strategy in turning reservoir management constraints into business opportunity for more sustainable and economical domestic gas supply in Peninsular Malaysia.
Firstly, a temporary GOR relaxation was obtained with an objective driven data acquisitions were in place to monitor the reservoir performance. Concurrently, a Recovery Factor (RF) benchmarking study has also been conducted to identify for any infill oil development potential. A network model comprises reservoir, well and surface facilities constraints was developed, validated and history matched using the latest production and reservoir pressure data obtained. Subsequently, production sensitivities analysis was conducted at various GOR limit including gas cap blow down (GCBD) option, evaluated at different abandonment pressure to determine the best integrated field optimization opportunity.
Reservoir performance analysis during the temporary GOR relaxation confirms the oil production was not significantly impacted, the water cut remains stable, and the pressure depletion was minimal. The field RF has also exceeded the benchmark from other reservoirs with similar complexity and drive mechanism within the region. Hydrocarbon in-place validation suggests that neither oil infill development nor behind casing opportunity presence as the reservoirs has reached its optimum recoverable volume. Producing the field without GOR limit increases the RF of gas by 10% and continues oil monetization by another 2%, without risked the reservoir from being idle. In view of reservoir performance and critical high gas demand in Peninsular Malaysia, a decision was made to revise the production strategy to GCBD mode.
A prudent reservoir management demands a continuous, integrated, and dynamic process to maximize value from a reservoir over time. Production strategy should be revised upon new data becomes available from reservoir surveillance. The findings are critical in making timely recommendations on subsurface exploitation to deliver business needs for maximum value creation.
