Abstract
One of the limiting factors affecting the length of horizontals wells has been the effective management of reservoir sweep with regards to wellbore influx. The added benefit of greater reservoir contact is met with increased differential drawdown across the well length and greater tendency to cut across heterogeneous formation with varying permeability. For many years, inflow control devices (ICDs) which restrict flow by creating additional pressure have been used to mitigate this problem. They are, however, passive in nature and once installed cannot be adjusted. In the event of water or gas breaking through in an oil well the disadvantage of the passive ICD become evident as the well would be quickly overtaken by the breaking fluid since they are usually designed to choke oil.
Autonomous ICDs (AICDs) are, however, self-regulating and are classed as active. Unlike its passive counterpart, which produces greater choking for higher density fluids, they in addition to choking oil, choke water and gas more readily. This prevents the well from being flooded when unwanted fluids break through therefore providing the advantage of being able to even out inflow into the well and in addition, choke compartments producing unwanted fluids leading to greater recovery, lower water cut and gas production.
This paper provides a comprehensive model of the autonomous ICD and goes further to show how this can be applied to modelling its influence on inflow distribution in a completed well system. The model is validated by comparing results obtained with tests carried out in a flow loop. A comparison of results obtained from the autonomous ICD and passive one is also shown to highlight the effectiveness of the autonomous ICD in flow regulation over the passive ICD.
