Patent Application
20130032354
1. Field of Invention
The invention is directed to pressure relief devices for compensating for pressure changes within sealed or isolated zones of an annulus of an oil or gas wellbore.
2. Description of Art
Sealing or isolating zones or areas of an annulus of wellbores is well known in the art. In general, one or more wellbore barriers such as packers or bridge plugs are disposed with in a wellbore above and below a “zone” or area of the wellbore in which production, or other wellbore intervention operations are performed. In some instances, the isolated zone is not being produced or intervention operations are not being performed, however, tubing, e.g., an inner casing, is disposed through this zone so that oil or gas production or other downhole operations can be performed below the isolated zone. In these instances, the fluid trapped or sealed in this isolated zone can expand or contract depending on the temperature of the fluid trapped in the isolated zone. When the temperature increases, such as during production from other zones within in the wellbore, the fluid expands and can cause damage to the inner casing of the wellbore, the outer casing of the wellbore, other components within the wellbore, or the formation itself. When the temperature decreases, such as when fluid is pumped or injected into the wellbore, the fluid contracts and can cause damage to the inner casing of the wellbore, the outer casing of the wellbore, other components within the wellbore, or the formation itself.
In situations where wells are designed with multiple barriers, such as packers, bridge plugs and the like, in the annular space, fluid becomes trapped in the space between these barriers. If the temperature of this trapped fluid increases, such as during production from the well, pressure within this isolated annular space increases. If the temperature of this trapped fluid decreases, such as during injection of fluids into the well, pressure within this isolated annular space decreases. In some situations, these pressure changes can be substantial and may cause failure of critical well components, including damage to the formation itself.
The pressure relief devices disclosed herein facilitate compensation of the pressure within the isolated wellbore annulus. Broadly, the pressure relief devices disclosed herein comprise a tubular member having a housing disposed on an outer wall surface of the tubular member. The housing includes a housing chamber and one or more ports disposed through the housing. An expandable member is disposed within the housing chamber. An interior portion of the expandable member is in fluid communication with the one or more ports. An outer wall surface of the expandable member isolates the remaining volume of the housing chamber to provide a sealed chamber. The sealed chamber can be maintained at atmospheric pressure or at a charged pressure.
The pressure relief devices can be disposed on a tubular string and located within a wellbore. As pressure in an environment located outside the pressure relief device, referred to herein as an “outside environment,” such as within an isolated wellbore annulus, increases such as due to an increase in temperature within the outside environment, the resultant increase in pressure is distributed through the port and into the interior of the expandable member causing expansion of the expandable member. As pressure within the outside environment decreases, such as due to a decrease in temperature within that environment, the resultant decrease in pressure is compensated by pressure moving from the interior of the expandable member, through the port, and into the outside environment. As a result, the likelihood that the change in pressure within the outside environment will cause damage to the wellbore or the tubing disposed within the wellbore or any other wellbore component within the outside environment is decreased.
During expansion of the expandable member due to the increased pressure within the outside environment exerting force on the hydrostatic side of the expandable member, the volume of the interior of the expandable member is increased and the volume of the sealed chamber becomes decreased. Decreasing the volume of the sealed chamber energizes the fluid or gas contained in the sealed chamber. Conversely, when the hydrostatic pressure is decreased, the compressed fluid or gas in the sealed chamber exerts a force on the sealed side of the expandable member to force the expandable member back until equilibrium of pressure on both sides of the expandable member is established, or until the expandable member can no longer move, such as due to all of the fluid within the interior of the expandable member being forced out by the pressure of the fluid within the sealed chamber. In other words, the atmospheric pressure or gas pressure within the sealed chamber acts as a return mechanism for the piston.
While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.
Referring now to
Housing 30 comprises upper end 31 and lower end 32, and inner wall surface 33 for connecting housing 30 to outer wall surface 22 of tubular member 20. Housing 30 also comprises housing chamber 34 and outer wall surface 35. One or more ports 36 are disposed through one or both of upper and lower ends 31, 32. As shown in
In the embodiment of
Expandable member 40 is disposed within housing chamber 34. Expandable member 40 comprises upper end 41, lower end 42, interior 44 defined by inner wall surface 45, and outer wall surface 46. Interior 44 is in fluid communication with each of ports 36 so that inner wall surface 45 of expandable member 40 which defines interior 44 is referred to herein as the hydrostatic side of expandable member 40. Outer wall surface 46 of expandable member 40 is also referred to herein as the sealed side of expandable member 40 because sealed chamber 50 is defined by outer wall surface 46 of expandable member 40 and upper end 31, lower end 32, and inner wall surface 33 of housing 30. Thus, sealed chamber 50 comprises a portion of housing chamber 34.
Expandable member 40 can be formed out of any material known or desired that permits expansion of expandable member 40. Suitable materials include elastomers such as rubbers, ethylene-propylene terpolymers (EDPM), and the like.
In one particular embodiment, sealed chamber 50 comprises a pressure disposed therein. The pressure within sealed chamber can be atmospheric pressure or can be a charged pressure. A charged pressure means that a fluid such as nitrogen or some other gas or fluid is pumped into sealed chamber 50 to a desired pressure. For example the pressure within sealed chamber 50 can be charged to the operational pressure of pressure relief device 10. Operational pressure is defined herein as the pressure anticipated at the location within the wellbore where pressure relief device 10 will be disposed. As noted above, the charged pressure within sealed chamber 50 can be established using air, nitrogen, or any other gas or fluid desired or necessary to provide the desired pressure within sealed chamber 50. The charged pressure can be established by pumping the gas or other fluid through charge port 39. Charge port 39 can include a one-way check valve 18 or other device known in the art to facilitate injection of the gas or other fluid so that the charged pressure remains within sealed chamber 50.
In the embodiment of
In one specific operation of pressure relief device 10, pressure relief device 10, disposed in the contracted position (shown in
Expandable member 40 continues to expand within sealed chamber 50 until the pressure on both inner wall surface 45 and outer wall surface 46 reach equilibrium, or until expandable member 40 can no longer expand due to the size of sealed chamber 50. In so doing, the pressure being exerted on the inner wall of the casing, or the inner wall of the formation, or the outer wall surface of the work string, is spread out and lessened, which decreases the likelihood of failure of any of the casing, the formation, or the work string, or any other wellbore component disposed in the isolated wellbore annulus.
Thereafter, if the pressure within the isolated wellbore annulus decreases, such as due to a temperature decrease due to cessation of production operations through the work string, the compressed atmospheric pressure or compressed fluid pressure within sealed chamber 50 exerts a force against outer wall surface 46 of expandable member 40 that is greater than the hydrostatic pressure within interior 44, i.e., the hydrostatic pressure acting on inner wall surface 45. Accordingly, expandable member 40 contracts from the expanded position (
In another particular embodiment, one or more ports 36 is disposed only through lower end 32. Location of the one or more port 36 through lower end 32 facilitates retaining gas within housing chamber 34 in the event that expandable member 40 fails. For example, in an embodiment in which sealed chamber 50 contains a gas, such as nitrogen, in the event that expandable member 40 fails, the gas will not be allowed to flow out of housing chamber 34. Instead, it would be trapped above any fluid that previously flowed through the one or more ports 36 into interior 44 of expandable member 40. Thus, failure of expandable member 40 will not result in loss of the gas from housing chamber 34.
It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, the sealed chamber of the pressure relief devices are not required to be charged with a gas or other fluid before use. Instead, sealed chamber may be an atmospheric chamber such that no charging of the sealed chamber required. In addition, the pressure relief devices disclosed herein can be used in circumstances in which the pressure within the wellbore annulus increases or decreases. Moreover, of the use of “upper” and “lower” in describing the embodiments is not intended to limit the direction of the pressure relief devices when in operation. In other words, the pressure relief devices are not required to be disposed in a wellbore where the “upper” structures are toward the top of the wellbore and the “lower” structures are toward the bottom of the wellbore. Accordingly, the use of “upper” and “lower” herein is not intended to limit the orientation of the pressure relief devices within a wellbore. Moreover, a rupture disk or other device can be disposed within the port(s) so that fluid is not permitted to flow through the port(s) until the pressure relief device is located within the well at the desired depth. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.
