Design, testing, qualification and application of orifice based inflow control devices

Abstract

Abstract Inflow control devices (ICD) are a relatively new type of completion component which are used in a wide range of wells. The ICD introduces a small controlled pressure drop which is used to modify the inflow profile from the formation into the completion. When combined with effective zonal isolation this modification of inflow has a number of benefits. It promotes an even inflow and removes the tendency for a high flux at the heel of the well. It also reduces the flux from highly permeable zones such as fractures. Both these benefits reduce the tendency for premature water or gas production and increase the oil recovery. Following water or gas break-through ICDs can then also preferentially choke these fluids in favour of oil production by leveraging non-linear relationship between phase velocity and ICD pressure drop. As such, ICDs can be viewed as having both proactive functionality to retard onset of water and gas coning and also reactive functionality to then retard extent of water and gas production. By limiting flow from each joint, ICDs also promote clean up along the entire length of a long horizontal well and reduce any tendency for hot spots to form at any part of the completion. Both these effects increase completion longevity. The pressure drop in the ICD is achieved by broadly one of two methods, either a small flow orifice or a long flow gallery. Both systems have advantages and disadvantages. This paper describes a comprehensive program which addresses the design, testing, qualification and application of an orifice based ICD system. A comprehensive test program was undertaken to address several aspects of the performance of these ICDs. Firstly the pressure drop through the ICD was measured for all sizes. This was done for various port configurations and over a range of oil viscosities. The results showed that the pressure drops were proportional to the density of the fluid and only weakly dependant on viscosity. Because of this the pressure drops can be described by Bernoulli's theory, modified with a discharge coefficient to account for inlet and outlet losses, and friction losses in the orifice. This discharge coefficient has been derived empirically, and corroborated by the close match achieved with test results and computational fluid dynamics modeling (CFD). An extensive set of tests was also performed to investigate whether the ICD would be prone to plugging by solids laden fluids. The solids concentration was varied up to a very high level of 1800lbs/1000bbls. The testing revealed no evidence of plugging. The third process which was examined in detail was erosion. By their nature orifice based ICDs generate high velocities. It is a concern that this may give rise to erosion in either the orifices or the diffusion chamber down stream of the orifices. Erosion of the orifices is of concern since even a small amount of erosion will cause a measurable change in pressure drop. A set of tests was undertaken at high sand loading to simulate erosion over the entire 20 year life of a well. The results showed that there was a small weight loss due to erosion on the orifice but that this had a negligible effect on pressure drop. The body of the ICD experienced virtually no erosion in the testing, only minor polishing. This comprehensive test program led to great confidence in the ability of the ICD to perform in a wide variety of producer and injector applications.