Downhole Fluid Flow Control System and Method Having Autonomous Closure

A flow control screen comprising:

• a base pipe with an internal passageway;
• a filter medium positioned around the base pipe;
• a housing positioned around the base pipe defining a fluid passageway between the filter medium and the internal passageway;
• a flow control assembly positioned in the fluid passageway, the flow control assembly having a fluid flow path for a flowing fluid;
• a first flow control component disposed in the fluid flow path having a positive flowrate response to decreasing fluid viscosity;
• a second flow control component disposed in the fluid flow path in parallel with the first flow control component having a negative flowrate response to decreasing fluid viscosity;
• and
• a valve disposed in the fluid flow path in series with and downstream of the first and second flow control components, the valve having a first inlet path for fluid from the first flow control component and a second inlet path for fluid from the second flow control component,
• wherein, decreasing the fluid viscosity of the flowing fluid increases a ratio of the flowrate through the first control component to the flowrate through the second flow control component;
• and
• wherein, when the ratio reaches a predetermined level, the valve autonomously shifts from an open position to a closed position.

A downhole fluid flow control method comprising:

• positioning a fluid flow control system at a target location downhole, the fluid flow control system including a flow control assembly having a fluid flow path for a flowing fluid, first and second flow control components disposed in parallel in the fluid flow path, the first flow control component having a positive flowrate response to decreasing fluid viscosity and the second flow control component having a negative flowrate response to decreasing fluid viscosity and a valve disposed in the fluid flow path in series with and downstream of the first and second flow control components, the valve having first and second inlet paths for fluid from the first and second flow control components, respectively;
• flowing fluid through the fluid flow path of the flow control assembly through the first and second flow control components and the valve;
• decreasing the fluid viscosity of the flowing fluid;
• increasing a ratio of the flowrate through the first control component to the flowrate through the second flow control component;
• reaching a predetermined ratio of the flowrates;
• and
• autonomously shifting the valve from an open position to a closed position.