Autonomous Valve, A Game Changer Of Inflow Control In Horizontal Wells.
- Vidar Mathiesen | Bjernar Werswick (Statoil ASA) | Haavard Aakre (Statoil) | Geir Elseth (Statoil)
- Document ID
- Society of Petroleum Engineers
- Offshore Europe, 6-8 September, Aberdeen, UK
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 5.6.4 Drillstem/Well Testing, 5.2 Reservoir Fluid Dynamics, 5.3.2 Multiphase Flow, 2.3.3 Flow Control Equipment, 2.4.3 Sand/Solids Control, 4.6 Natural Gas, 5.5 Reservoir Simulation, 1.6 Drilling Operations
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Horizontal wells with one or more branches have been used to maximize reservoir contact by Statoil and other oil companies for more than a decade. Frictional pressure drop and variation in permeability and mobility will naturally lead to non-uniform inflow profile along a well. Eventually, this will result in gas and/or water breakthrough, which may reduce the well performance and recovery significantly. The breakthrough typically occurs in the heal region of the well and in regions with high reservoir permeability. Inflow Control devices (ICDs) are flow resistance elements installed along the producing zone of a well to counteract the non-uniform inflow, hence improving the well performance. The technology is regarded as standard technology by the industry and classified as passive inflow control, since the geometry of the devices is fixed or preset prior to installation. Passive inflow control is applied to delay the unwanted gas/water breakthrough. However, once occurred, conventional inflow control will not reduce or stop the breakthrough. Statoil's new autonomous inflow control device (AICD) is an active flow resistance element distributed along the well, similar to conventional passive ICDs. Statoil's AICD will, in addition to delay the breakthrough, reduce the proportions of the breakthrough. The AICD will impose a relatively strong choking for low-viscous fluids and only minor choking for viscous oil. This is due to autonomous changes in the flow area internally in the AICD. With this technology the well performance and production can be higher after a breakthrough compared to conventional inflow control.
Statoil's AICD technology is piloted in two wells at two different fields in the North Sea. Each well is completed with 1-4 AICDs per screen joint, typically 200-400 per well. The AICD operates without need for human interventions and electric or hydraulic power. Well tests have shown that Statoil's AICD technology reduces the inflow of gas into the well from a reservoir containing light oil. Due to the restriction of the gas inflow, the drawdown can be kept high after breakthrough to
allow significant oil production from the remaining oil zones in the well.
Likewise, in a pilot well in a reservoir containing heavy oil, well tests have shown that Statoil's AICD technology reduces the inflow of gas into the well and preliminary evaluations indicate that even water inflow is reduced. Thus the drawdown can be kept high allowing high production from the remaining oil zones.
Horizontal wells with one or more branches have been used to maximize reservoir contact by Statoil and other oil companies for more than a decade [1-4]. Statoil started production from Troll in the fall of 1995. The thin oil layer was between 22 and 26 meters in the Troll oil province and 11 and 13 meters in the Troll gas province. In order to start profitable oil production from this thin layer, it was necessary to develop advanced drilling and production technology. Hence, the oil production wells drilled in Troll were horizontal wells, and most of the wells were controlled by inflow control devices which are friction elements distributed along the well for improving the well performance . The technology is regarded as standard technology by the industry and classified as passive inflow control, since the geometry of the devices are fixed or preset prior to installation.
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