Novel Density-Based Autonomous Inflow Control Device Using Artificial Gravity

Abstract

Abstract A new class of Autonomous Inflow Control Devices, AICDs, has been developed which balances production flow and restricts unwanted production fluids, even when there is no viscosity difference in the produced fluids. This novel AICD senses the density difference between oil and water and uses artificial gravity to amplify the buoyancy forces while eliminating the need for downhole orientation in the completion. AICDs have effectively reduced water production and increased oil recovery since their introduction in the early 2010s. During initial production, AICDs balance the flow across the production zone. In later production, AICDs automatically restrict the rate from zones producing water. Commercially available AICDs primarily operate by sensing the viscosity difference between oil and water. In very-light oil reservoirs, such as in parts of the Middle East, there is no significant viscosity difference. Previous density-based AICDs have been rejected because buoyancy forces are often overwhelmed by fluid forces and because they needed to be oriented with respect to Earth's gravity. Density-AICDs use floats that are buoyant in water and sink in oil to control fluid production. The key to the new density-AICD is that that the floats are housed in a spinning centrifugal rotor. This spinning density selector creates centripetal forces that multiply the buoyancy force thereby magnifying the difference between oil and water. The magnified buoyancy forces are stronger than fluid friction forces and are sufficient to overcome suction forces on the valve seats. The centripetal acceleration creates an artificial gravity that is much larger than Earth's gravity, eliminating the need to orient the density-AICD downhole. The density selector is spun by the production fluid so that larger centripetal forces are created in response to a larger drawdown. The result is a density-AICD that will operate in real-world conditions, especially in the light oil formations of the Middle East. The performance of this novel density-AICD has been measured in flow loop testing and demonstrated in computer modeling. The flow loop testing achieved substantial water restriction and continued oil flow using oil and water with identical viscosities.