Abstract: A valve for use in controlling flow in a subterranean well and using an expandable and contractable fluid sealing bellows is disclosed. The valve has a valve closure member such as a ball valve head acutated by an increase in control fluid pressure. Control pressure causes the bellows to expand or contract and a control rod engaging the bellows can be shifted. The control rod is part of an actuating mechanism for shifting the valve closure member between open and closed positions. The bellows can support the difference between control pressure and well pressure which are respectively present on the exterior and interior of each bellows element.

Abstract: A well tool or bridge plug for blocking fluid communication through well tubing. The present invention allows a fixed volume of liquid to be trapped within the well tubing while installing the plug. A piston means is releasably secured within the bridge plug. The piston means can slide relative to the housing of the bridge plug to compensate for any liquid displaced by inserting the bridge plug into the well tubing. The present invention is particularly adapted for use in through the flow line (TFL) or pumpdown well completions. However, the present invention could be used with wireline equipment.