Publications

A commingle production strategy is commonly used to unlock and produce all hydrocarbon opportunities within the wellbore in order to increase or maintain gas deliverability in stratified reservoirs. This strategy can have a significant impact on reservoir management as it becomes more challenging to analyse individual reservoir performance. It creates uncertainties in pressure and reserves estimations which can also impact the future field development strategy. Reservoir production allocation in commingled gas wells is usually based on well surveillance from production logging tool (PLT) surveys, which is commonly performed once a year. Production allocation from PLT results at two different times can have significantly different results. Typically the production allocation from each reservoir is corrected to align with the latest PLT survey with a constant allocation for any wellhead pressure (WHP) range. This allocation is then used until the next PLT run without considering the daily reservoir changes. This will lead to incorrect cumulative production allocation, impacting reserves and may result in sub-optimal production strategy decisions. A key challenge is deciding when to apply the new production allocation which represents the pressure changes in the reservoir for any WHP range. This paper presents a new approach to solve this challenge. The approach provides a methodology to have a continuous and dynamic allocation for any WHP range. By using nodal analysis and arithmetic progression approach, two commingled gas wells’ reservoir allocation in Natuna Sea are estimated and forecasted with in a 2% average error from the actual PLT survey result. This method was validated with a dynamic reservoir simulation and actual PLT results to ensure the robustness of the allocation approach. The main advantage of this method is to minimise PLT survey frequency whilst improving the cumulative production allocation quality and ultimately reducing uncertainty in reservoir reserves estimation.