Underbalanced well completion

Equipment and methods for use in conjunction with an underbalanced well completion. A valve 12 for use in a subterranean well 16 in conjunction with a tool 22 conveyed through the valve 12 in a container 26 is provided. The valve 12 includes a passage 18 formed longitudinally through the valve 12, a closure assembly 28 which selectively permits and prevents flow through the passage 18, and an engagement device which engages the container 26 as the tool 22 is conveyed through the passage 18. The closure assembly 28 permits flow through the passage 18 when the container 26 is conveyed into the passage 18, and the closure assembly 28 prevents flow through the passage 18 when the container 26 is removed from the passage 18. Engagement between the container 26 and the engagement device separates the tool 22 from the container 26.