The present disclosure is generally related to controlling fluid flow in a wellbore and, more particularly, to annular flow control devices and their methods of use.
Recovery of valuable hydrocarbons in some subterranean formations can sometimes be difficult due to a relatively high viscosity of the hydrocarbons and/or the presence of viscous tar sands in the formations. In particular, when a production well is drilled into a subterranean formation to recover oil residing therein, often little or no oil flows into the production well even if a natural or artificially induced pressure differential exists between the formation and the well. To overcome this problem, various thermal recovery techniques have been used to decrease the viscosity of the oil and/or the tar sands, thereby making the recovery of the oil easier.
Steam assisted gravity drainage (SAGD) is one such thermal recovery technique and utilizes steam to thermally stimulate viscous hydrocarbon production by injecting steam into the subterranean formation to the hydrocarbons residing therein. As the temperature of the hydrocarbons increases, they are able to more easily flow to a production well to be produced to the surface. During injection of the steam, however, the steam is often not evenly distributed throughout the length of the wellbore such that a temperature gradient or energy gradient along the wellbore is generated and consists of some areas that are hotter or have more potential energy than other areas. As a result, hydrocarbons are often only efficiently produced across a narrow window of the wellbore where the temperature is able to increase to an effective point.
A number of devices are available for regulating the flow of steam into subterranean formations. Some of these devices are non-discriminating for different types of fluids and simply function as a “gatekeeper” for regulating injection rates of the steam into the formation. Such gatekeeper devices can be simple on/off valves or they can be metered to regulate fluid flow over a continuum of flow rates. Other types of devices that may be used to regulate the flow of steam into subterranean formations include tubular flow restrictors, nozzle-type flow restrictors, ports, tortuous paths, and other flow control devices. Such standard flow control devices, however, tend to expel steam at one point in the wellbore and water at another point. This is partially due to the effects of gravity on the steam, but also due to the fact that the steam can more easily exit through a flow control device as opposed to water flowing with the steam.
It would prove advantageous to have a system that uses flow control devices that are able to deliver a consistent heat flow along the entire length of a wellbore. It would similarly prove advantageous to have a system that uses flow control devices that are able to deliver a similar quantity of water and steam (assuming wet steam) into each section of the wellbore and otherwise deliver a consistent pressure drop along such lengths of the wellbore.
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USPTO Backgrounds