Research On The Integral Optimization Of Injection And Production In Offshore Heavy Oil Reservoir

As the development of an offshore oil field goes on,both reservoir condition and production system working conditions keep changing.It turns out that the current production and injection proration is not the most efficient plan and some ESPs working conditions are different from the original design,with liquid rate out of the high efficiency range,which leads to more energy consumption.In this paper,actual platform constraints,the base of the optimization model,were studied.In order to optimize production and injection proration,reservoir numerical model was developed.Based on indicators such as total liquid volume,total oil volume and total injection volume,the best production and injection proration was selected automatically using multi-objective optimization algorithm NSGA-?.The chosen plan was able to produce the most oil with the least injection volume within liquid rate limit.Current production system conditions were taken into consideration,liquid lift ability of ESPs,gas-liquid ratio at the entrance of pump and critical pressure differential included.Choke diameter and pump frequency were optimized in combination to match chosen liquid rate with IPR curves,wellbore multiphase flow,ESP liquid lift ability,choke flow into account.The optimized choke diameter and frequency combination resulted in best combination of pump efficiency,system efficiency and electricity consumption per ton liquid.Finally,this paper took one offshore oil field in Bohai area as study object to validate that the proposed method can be used for optimization of offshore oil field production systems.