Patent ID: 8590629

Claim:
A flow stop valve positionable in a downhole tubular, the flow stop valve comprising: a housing; a first receiving portion and a second receiving portion attached to first and second ends of the housing respectively by attachments arranged between the housing and the first and second receiving portions, such that a flow through the flow stop valve is permitted in an area defined between the housing and the first receiving portion and in an area defined between the housing and the second receiving portion; and a valve element slidably received in the first and second receiving portions, the valve element and the housing together forming a valve to selectively prevent flow through the flow stop valve: wherein the flow stop valve is configured such that a pressure difference acts on the valve element such that the flow stop valve is in a closed position when the pressure difference is below a threshold value thereby preventing flow through the downhole tubular, and the flow stop valve is in an open position when the pressure difference is above the threshold value thereby permitting flow through the downhole tubular, wherein the pressure difference comprises one of a difference between a fluid pressure outside of the downhole tubular and a fluid pressure inside of the downhole tubular, and a difference between a fluid pressure at the first end of the housing and a fluid pressure at the second end of the housing, and wherein a first end face of the valve element and the first receiving portion define a first chamber and a second end face of the valve element and the second receiving portion define a second chamber, the first and second chambers being prevented from being in flow communication with first and second ends of the housing respectively when the flow stop valve is in the closed position.