Flow assurance has been a major problem in the development of a heavy oil field. It is not common that this issue has a multiplier effect from reservoir up to processing facilities, reducing productivity and in turn, increasing financial burden. Many of oil and gas operators in Indonesia have spent a lot of capital to deal with managing complex reservoirs with severe flow assurance issues, namely high water cut, excessively viscous oil and its effect on fluid flow.
Y Field has been produced for thirty years and currently produces 2800 BOPD with fluctuations in flow rate. This field is characterized by extreme oil viscosity, up to 4000 cP at surface condition, which leads to high backpressure while delivering fluid to pipeline system. This viscous oil creates unstable flow, causing unfavorable flow-pattern; slug flow to annular flow. As a result, the water and oil are not coherently arrived at the same time at receiving facilities, leading to highly frequent occurrence of oil-water slug phenomenon. Chemical injection efforts do not show significant impact toward the production, therefore an alternative approach is generated to address the production problem.
A new approach is presented in this publication to reduce the occurrence of severe slugging phenomenon by performing water blending scheme during fluid transportation. The idea is based on a hypothesis that performing forced emulsion of brine and heavy oil promotes dispersion of oil into small droplets which can be carried out by injected water under relatively low velocity of fluid flow. This idea is quite interesting since it is simple to perform, by only directing produced water from water zones below hydrocarbon bearing zone or by reactivating high water cut wells to the pipeline system.
In order to increase the efficiency of forced emulsion process, we approximated the minimum acceptable water cut to develop sufficient emulsion viscosity to prevent exceeding backpressure. Based on simulation using commercial software, the result shows that water cut should be maintained above 80%. A lower water cut will lead to high backpressure which will delay arrival time of oil for more than one day behind the water arrival. This result infers that one of the available solutions to handle severe slugging is by modifying water cut profile during hydrocarbon transportation. This approach gives a new insight into marginal field optimization.