1. Field Of The Invention
The present invention relates to devices used in hydrocarbon producing wells, and more specifically, to devices that are used for venting gas or other production fluids from below a packer to above the packer.
2. Description Of The Related Art
Completion systems are well known in the art of well production, and can take many varied forms. Well completions typically have as common elements: a casing cemented in the well extending from a surface wellhead to the producing formation; a production tubing located concentrically inside the casing; and one or more well known devices (commonly called packers) that block, pack off, and seal the annulus formed between the casing and the production tubing, generally by means of a resilient sealing element. Placement of the packer in this way directs the hydrocarbons from the producing formation into the production tubing and to the earth's surface. It is not uncommon, during the process of producing the hydrocarbons, for gas or other production fluids to accumulate in the annulus below the packer. If the amount of gas or other production fluids accumulated in the annulus below the packer becomes too excessive, the gas or other fluids can interfere with the production process. Accordingly, in those situations, it becomes desirable to remove the gas or other fluids from the annulus below the packer.
To remove the gas or other production fluids from below the packer, the packer is provided with a secondary bore therethrough, and a device (commonly referred to as an annulus vent valve) for controlling fluid flow through the secondary packer bore is connected to the upper surface of the packer and positioned across the secondary packer bore. In this manner, when an operator at the earth's surface determines that an excessive amount of gas or other fluids are building up below the packer, the annulus vent valve can be remotely actuated from the earth's surface to open the packer bore thereby permitting the gas or other fluids below the packer to be produced to the earth's surface through the annulus above the packer. By bleeding gas or other production fluids from the annulus below the packer, the hydrocarbons exiting the producing formation can be produced to the earth's surface in a more efficient manner.
There has been a recent trend in the oil and gas industry whereby companies have extended their exploration efforts into greater and greater depths. This is especially true as it relates to exploration companies venturing into water depths greater than approximately 2,000 to 3,000 feet to drill for oil and gas, such as in the Gulf of Mexico. As a result of this trend, a problem has arisen with the operation of annulus vent valves of the type described above. The problem relates to the means by which the annulus vent valve is actuated, namely, by connecting a control conduit from the earth's surface to the annulus vent valve, and then applying hydraulic fluid through the control conduit to a piston within the annulus vent valve to overcome the force of a return spring and move a flow tube to open and close a closure member, such as a flapper, which blocks or permits fluid flow from the secondary packer bore into the annulus above the packer. More particularly, the problem relates to the column of hydraulic fluid in the control conduit extending between the earth's surface and the annulus vent valve; this is sometimes referred to as the "hydrostatic head". Heretofore, it has been economically feasible to design an annulus vent valve with a return spring capable of generating sufficient force to maintain the flapper in a closed position and overcome the force of the hydrostatic head. However, as wells are drilled to deeper and deeper depths, and as packers and annulus vent valves are set at deeper and deeper depths, the length of the hydraulic control line necessarily increases, as does the force of the hydrostatic head. This requires the use of a larger and larger spring to overcome the increase in the hydrostatic head. It has been determined that, when an annulus vent valve is set below certain depths, which is believed to be in the range of approximately 2,000 to 3,000 feet, it is no longer economically feasible to design an annulus vent valve with a power spring large enough to overcome the hydrostatic head and maintain the flapper in a closed position. The annulus vent valve of the present invention has been developed to solve this problem.