Patent Application
20120292013
The field of the invention is subterranean barriers and more particularly inflatables that are set with gas that is internally generated.
Barriers are used in subterranean locations to isolate zones in a wellbore. These barriers are known as packers or bridge plugs and come in a variety of designs depending on the application. Some are set in surrounding casing or liner and some are more suited to open hole setting. Typically packers have a sealing element and slips and that assembly is axially compressed so that it extends radially to seal against a surrounding tubular and to hold the seal to the tubular with slips that bite into the surrounding tubular wall. The setting of such packers can be with string manipulation, or using tubing pressure after dropping a ball or even hydrostatic pressures available in the annulus around a string that supports such a packer.
Another packer style is an inflatable that features a flexible element that defines a sealed annular space between itself and a mandrel. A valve assembly admits fluid into the annular space under the element and prevents overpressure while holding in the admitted pressure to maintain the set position. Such inflatables are run into open hole and set and are also run through tubing and set in larger casing among the many possible applications. They are typically inflated with a dropped ball and pressure built on the seated ball that allows fluid past the valve assembly of the packer to inflate it. The sealing element is reinforced for pressure rating as well as to control the manner in which it grows radially to meet the surrounding wellbore wall or surrounding tubular.
Various attempts have been made in the design of inflatables to maintain their set position after inflation in the face of changing wellbore conditions. Temperature changes can affect the internal pressure in the inflatable and some of the ways to compensate for internal pressure changes have involved the insertion of solids in the annular space under the element whose volume can change such as by swelling when the inflate fluid is introduced. This concept is illustrated in U.S. Pat. No. 7,597,152. Another approach is to introduce solids and then let the carrying fluid escape with the idea that the packed in solids will hold the set position of the element as shown in U.S. Pat. No. 7,178,603. U.S. Publication 2007/0295498 illustrates a manufacturing technique for a swelling element that is not an inflatable to control unwanted flow between the mandrel and the element after the swelling occurs.
Techniques for gas generation to place barriers in wellbores are described in U.S. Pat. No. 7,642,223 in the context of placement of a plugging material in the formation to control flow and using the generated gas to aid in such placement. Other applications employ dissolvable metals to generate gas in a downhole tool where the generated pressure is then deployed to move a piston to set a downhole tool. This is described in U.S. Pat. No. 7,591,319.
The present invention deals with a technique for actuation of inflatables with gas generated within the annular space between the element and the mandrel. A reactant is introduced in sufficient quantity within the annular space to initiate the reaction and the gas generation while the actual inflation is accomplished by the generated gas. These and other aspects of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is determined by the appended claims.
An inflatable packer contains a reactive metal in an annular space between the mandrel and the element. A fluid is admitted into the annular space to start a reaction that gives off gas. The generated gas fills the annular space, increases the annular pressure, and inflates the element in the process. The actuating fluid can be water and the generated gas can be hydrogen. The volume of the reactants can also increase as they swell due to the chemical reaction that generates the gas. A valve arrangement associated with the mandrel retains the gas pressure and prevents over-pressurization during and after the reaction. The packer can be set in a surrounding tubular or in open hole.
The space 22 is occupied with preferably a reactive and/or dissolvable metal such as aluminum, tin, magnesium or zinc or combinations of them and preferably water is admitted through passage 18 but in quantities short of inflation of the element 24. The mixing of the water entering at passage 18 and the reactive metal 26 already in space 22 starts the reaction that generates the gas and as shown in
As an alternative the added reactant can be stored in the space 22 but in a manner that is separated from the reactive metal 26 and the two can then be brought into contact at the time it is desired to set the packer P. The water or other trigger fluid can be encapsulated until the desired time and then the barrier can be broken with an applied force, for example. The reactants can be separated by a wall that is breached to allow the reactants to contact as another example. Applied tubing pressure can act to breach the wall.
It should be noted that the added reactant is provided in a small amount so that its added volume may not even cause visible movement in the element 24. Rather it is the volume of generated gas and the increase in internal pressure from the reaction that causes the element 24 to contact and seal against the borehole 10 and to a lesser degree the volume change of the reacted materials also boosts the internal pressure and helps to hold the internal pressure in the space 22 in conjunction with the valve assembly 20. The added material can be water based mud as opposed to plain water. The reaction can also give off some heat which can have a transient effect on the internally generated pressure as the reaction is occurring.
The present invention allows the setting of an inflatable without high pressure fluid or cement pumping equipment and thus saves the operator money and makes it possible to use inflatables where surface conditions of lack of space would have otherwise precluded inflatable use.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
