METHOD AND APPARATUS FOR CAUSING PRESSURE VARIATIONS IN A WELLBORE

摘要

A method and apparatus for causing pressure variations in a wellbore. A valve mechanism and a sealing device are provided in the wellbore. The valve mechanism is part of a valve device actuatable between open and closed positions. Actuation to the closed position allows an increase in pressure below the sealing device. Actuation to the open position allows fluid to pass through the valve device up the wellbore. The valve device is alternately actuated between closed and open positions to cause cyclical pressure variations below the sealing device. The valve device includes the valve mechanism, a fluid passage, a control mechanism and a delay mechanism for delaying actuation. The increase in pressure in the wellbore below the sealing device is caused by either or both of a fluid entering the wellbore from an adjacent formation or the introduction of a pressurized fluid into the wellbore below the sealing device.