Wells – Processes – Placing or shifting well part
Reexamination Certificate
2000-01-10
2002-05-14
Bagnell, David (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S386000, C166S142000, C166S186000, C166S210000
Reexamination Certificate
active
06386292
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a method and an apparatus for connection with a tubing string for use in a wellbore for regulating the flow of a fluid within a wellbore annulus between the tubing string and the wellbore. Preferably, the invention is used for selective steam injection of a desired hydrocarbon producing zone within an underground formation or for isolating the wellbore annulus to prevent heat loss when injecting down the tubing string.
BACKGROUND OF INVENTION
Wellbore packers are typically suspended in a wellbore from a tubing string or other pipe extending to the surface. These packers are employed for providing a downhole seal between the tubing string and the surrounding wellbore in order to prevent the flow of fluids through an annulus defined between the tubing string and the wellbore. Such packers are desirable for a number of uses, including providing a seal or barrier such that fluid may be selectively injected to or at a desired level in the wellbore to a desired zone within the surrounding formation.
For instance, a zone may be isolated for steaming by pulling the tubing string and installing one or more packer cup along the tubing string at predetermined positions. When top zone steaming of a formation is required, one or more packer cups is installed along the tubing string such that the packer cups are located below the zone to be steam injected when the tubing string is run back into the wellbore. Steam is then directed through the wellbore annulus. The packer cup provides a seal between the tubing string and the wellbore and prevents the steam from passing through the wellbore annulus below the desired zone.
When an intermediate or middle zone is desired to be isolated for steaming, the cups are employed in a straddle application. Specifically, packer cups are installed along the tubing string such that the packer cups are located above and below the zone to be isolated when the tubing string is run back into the wellbore. Further, for steam injection, a perforated joint of pipe is installed between the packer cups. The steam is injected through the tubing string with the downhole pump seated and exits the tubing string through the perforated joint into the wellbore annulus at the desired level. The packer cups again provide a seal between the tubing string and the wellbore and maintain the steam within the desired level of the wellbore annulus such that the steam is directed into the desired zone of the formation.
When the lower or bottom zone is desired to be isolated for steaming, the packer cups are located above the zone to be steamed and the steam is injected through the tubing string with the downhole pump unseated or removed.
In any case, once the formation has been steamed, the tubing string must again be pulled from the wellbore so that the packer cups may be removed. Once removed, a pump is installed and the tubing string is run back into the wellbore to permit production of the well. Specifically, production from all zones is permitted to commingle and flow down to the pump for pumping from the well.
Often in wells that have only one zone, the wells are steamed down the tubing string and a wellbore packer or packer cups are used to prevent steam from entering or refluxing in the wellbore annulus. Steam flow or reflux in the wellbore annulus results in heat loss to the well casing, cement and earth. Again, following steaming, the wellbore packer must be removed for the production cycle in order to allow produced gases to flow up the wellbore annulus.
U.S. Pat. No. 3,701,382 issued Oct. 31, 1972 to Williams, U.S. Pat. No. 3,897,824 issued Aug. 5, 1975 to Fisher, U.S. Pat. No. 4,151,875 issued May 1, 1979 to Sullaway, and U.S. Pat. No. 3,420,305 issued Jan. 7, 1969 to Alexander et. al. each describe a wellbore packer which is fixed in position within the wellbore through release of a releasable connection, and in particular, through shearing of a shearing element. Typically, shearing occurs upon vertical reciprocation of the tubing string.
For example, Williams describes a packer which is held in a retracted position, while lowering into the wellbore, by shearable screws or pins. The screws or pins are sheared when relative upward movement or upstrain of a packer body with respect to the mandrel is effected. To remove the packer, a downward relative movement is applied to move the packer back to the retracted position. However, since the releasable connection, i.e. shear pin, has been broken, further means are required to lock the packer in the locked position. It is thus clear that the packer may not be repeatedly used for multiple operations without removing the packer from the wellbore between uses and replacing the releasable connection.
As indicated, the above described wellbore packers require pulling of the tubing string either to remove the wellbore packer in order to permit fluids to subsequently flow through the wellbore annulus or to replace or refit the wellbore packer for repeated uses. Pulling the tubing string and either replacing or removing the wellbore packer is both time consuming and costly.
Therefore, it is desirable for the packer to be releasable and returnable to an open position to permit multiple operations or uses. In other words, the packer is preferably capable of being both set or closed and unset or opened from the surface for any number of uses without the need to pull the tubing string. In its closed condition, the wellbore annulus is sealed. In its open condition, the packer permits fluid to flow through the wellbore annulus from above the packer to below the packer and vice versa. Further, in its open condition, the packer may be moved to a new desired location in the wellbore, where it may be reset or closed for further use.
As a result, wellbore packers have been developed which provide expandable and retractable packing elements. To seal the wellbore annulus, the packing elements are expanded or extended radially outwards for engagement with the wellbore. More particularly, the packing element is compressed longitudinally within the wellbore to cause lateral expansion of the packing element with sufficient pressure to seal against the wellbore. However, it has been found that after being compressed for an extended period of time that the packing element may not return to its original condition upon release of the longitudinal compression. As a result, the compressed packing element may remain in a sealing condition or it may otherwise interfere with the subsequent passage of fluid through the wellbore and thus, may need to be removed or replaced.
Thus, although these packers may be closed and opened from the surface any number of times as necessary for the desired application, the packer, including the packing element, may impede or otherwise interfere with the flow of fluid through the wellbore annulus. Thus, wellbore packers have been developed which provide a bypass passageway to allow fluid to pass by the packing element. The bypass passageway is typically associated with a bypass valving mechanism for opening and closing the bypass passageway as desired.
However, these bypass passageways tend to be relatively narrow in that the flow paths provided for the fluid flow are too small, which restricts the flow of fluid through the wellbore annulus. Thus, a fully satisfactory response is not provided to the need for a relatively unrestricted flow through the annulus. As well, these relatively small passageways have a tendency to become plugged or clogged by sand and other particulate matter contained within the wellbore fluids.
Further, as indicated, the valving mechanism or structure provided for the bypass passageway is separate from the mechanism or structure provided for actuation of the packing element. In other words, two distinct sealing mechanisms, actuated independently, are provided for the bypass passageway and the packing element. As a result, the overall structure of the packer is relatively complex.
Finally, many wellbore packers which are capable of being selectively
Bagnell David
Browning Bushman PC
Walker Zakiya
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