Hydraulically operated formation isolation valve for underbalanced drilling applications

#The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a formation isolation valve for use in underbalanced drilling applications.

#A formation isolation valve is typically used in underbalanced drilling operations to close off flow through a casing string while tripping a drill string, or otherwise when access to a wellbore below the valve is not required. The valve is opened when the drill string or other assembly (such as wireline tools, coiled tubing string, etc.) needs to be displaced downwardly through the valve. The valve is then closed when the assembly is displaced upwardly through the valve.

#Some formation isolation valves are operated hydraulically using control lines which extend to the surface. Pressure applied to the control lines at the surface is used to open and close such valves. However, these long control lines have significant disadvantages. For example, long control lines are expensive to purchase and install, long control lines have increased susceptibility to damage during installation and leakage thereafter, etc.

#FIG. 1 is a schematic partially cross-sectional view of a method of operating a well tool, the method embodying principles of the present invention;

#FIG. 2 is an enlarged scale schematic cross-sectional view of a device which may be used to remotely activate an actuator of a well tool in the method of FIG. 1;

#FIG. 3 is a schematic cross-sectional view of a well tool including an actuator which may be used in the method of FIG. 1; and

#Representatively illustrated in FIG. 1 is a method 10 which embodies principles of the present invention. In the following description of the method 10 and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. In general, the downward direction is illustrated as being further from the earth's surface along a wellbore, and the upward direction is illustrated as being toward the surface, but it will be appreciated by those skilled in the art that, in actual practice, wellbores are seldom consistently vertical.

#Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention. The embodiments are described merely as examples of useful applications of the principles of the invention, which is not limited to any specific details of these embodiments.

#As depicted in FIG. 1, an assembly 12 is being displaced downwardly through a tubular string 14. The assembly 12 is illustrated as comprising a drill string 16 having a drill bit 18 at a lower end. The drill string 16 may also include many other elements, such as a mud motor 20, etc.