Assessing the Impacts of Groundwater Intrusion to Production Efficiency and Proposing Solutions to Enhance Oil Recovery from Fractured Basement Reservoir in SuTuDen Field,Offshore Vietnam

摘要

Based on the observed phenomenon of formation water intrusion in SuTuDen oilfield,i.e.,high reservoir pressure,high constituent percentage of formation water in produced water,stable isotopes tracing,as well as strong-water drive mechanism confirmed by matching & calibrating the production parameters,the authors assessed the impacts of water drive to the production and proposed methods to enhance recovery.The results of water analysis with low TDS(12g/l)indicate the formation water accounts for a significant ratio of the produced water.Among factors affecting production efficiency,the critical ones are fault-fracture characteristics,origins of water,range of hydrodynamic relationship,design plans and well completion.In order to mitigate the negative impacts and increase the positive impacts of these factors,a series of intervention solutions must be considered including combined ESP-Gaslift installation,gas assisted gravity drainage,water or gas injection in selective zones,infill drilling in poorly connected areas.The basement reservoir SuTuDen oilfield is affected by natural water aquifer hence it is necessary to implement recovery solutions such as adjusting the design,maintaining the reservoir pressure,in-fill drilling,artificial lift,stimulating the near-wellbore zone,optimizing the production-injecting regime.When the wells have already been invaded by water,it is very difficult and costly to maintain the cumulative production.Therefore,the mitigation measures should be applied early from the design stage,especially the compatible operating regime,help reducing the water invasion and achieving optimal production.The result of the methods should allow an increase in the overall recovery factor from 36.1% to 39.8%,equivalent to 18.52 MMbbl.