The present invention relates generally to devices for cementing tubing or casing in downhole environments, and more particularly to a reverse circulation device, which easily attaches to tubing or casing and has improved sealing characteristics.
During downhole cementing operations, fluid circulation is generally performed by pumping down the inside of the tubing or casing and then back up the annular space around the casing. This type of circulation has been used successfully for many years. However, it has several drawbacks. First, the pressures required to “lift” the cement up into the annular space around the casing can sometimes damage the formation. Furthermore, it takes a fair amount of time to deliver the fluid to the annular space around the casing in this fashion.
In an effort to decrease the pressures exerted on the formation and to reduce pump time requirements, a solution involving pumping the fluid down the annular space of the casing rather than down the casing itself has been proposed. This technique, known as reverse circulation, requires lower delivery pressures, because the cement does not have to be lifted up the annulus. Furthermore, the reverse circulation technique is less time consuming than the conventional method because the fluid is delivered down the annulus only, rather than down the inside of the casing and back up the annulus. Accordingly, the cement travels approximately half the distance with this technique.
There are a number of drawbacks of current reverse circulation methods and devices. Such methods require a wellhead or other conventional surface pack-off to be attached to the surface casing that is sealably attached to the casing being cemented in place via the reverse circulation technique. These structures are often permanent and expensive, thus increasing the cost of completing the well. Furthermore, current surface pack-off equipment requires a threaded or flanged connection be at the surface casing for attaching thereto. This again adds unnecessarily to the complexity of the system, and thus its cost.
The present invention is directed to a surface pack-off device, which attaches between surface pipe and casing that allows for reverse circulation down the annulus of the casing to be cemented without a need for threaded or flanged connections.
More specifically, the present invention is directed to a removable surface pack-off device, which comprises a housing adapted to be mounted between the ends of an inner casing and an outer casing at or near the surface of a well. The device further includes at least one fluid passage disposed within the housing, which is adapted to pass fluid from a location outside of the well into an annulus formed between the inner and outer casings. In one aspect, the surface pack-off device according to the present invention includes means for sealing the housing to an inner casing and an outer casing. In one embodiment, the sealing means includes a first pressure-activated seal disposed between the inner casing and the housing and a second pressure-activated seal disposed between the outer casing and the housing.
In another aspect, the surface pack-off device according to present invention includes means for removably attaching the housing to the inner and outer casings. In one exemplary embodiment, the removable attachment means includes an attachment assembly, which comprises a pair of retaining wings mounted to an outer surface of the housing, a clamp defined by a pair of flanges, which is adapted to be secured to an outer surface of the outer casing, and a pair of retention bolts, which are mounted to the pair of retaining wings at one end and the pair of flanges at the other. In another exemplary embodiment, the removable attachment means comprises a plurality of holes drilled into the outer casing, which are adapted to receive a corresponding plurality of bolts, which secure the housing to the outer casing. The surface pack-off device according to the present invention is easily removed from the surface pipe and casing so that once the cementing operation is completed it can be used for a cementing operation at another well location.
The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the exemplary embodiments, which follows.
A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, which:
The details of the present invention will now be described with reference to the accompanying drawings. Turning to
The housing 110 has an upper portion, which in one exemplary embodiment seals against an outer surface of the inner casing 120, as shown in
A plurality of fluid passages 140 are formed within the housing. The fluid passages 140 pass fluids, e.g., cement, from outside of the well into annulus 125. In one exemplary embodiment, four fluid passages 140 are provided. The four fluid passages are equally spaced around the circumference of the housing 110. Each fluid passage 140 has a corresponding inlet connector 142. The inlet connectors 142 couple the surface pack-off device 100 to a fluid supply line (not shown), so that fluid can be injected into annulus 125. In one exemplary embodiment, the inlet connectors 142 are a Model No. 1502 by Weco. As those of ordinary skill in the art will appreciate, the number and size of the fluid passages may be varied depending upon a number of factors, including, the amount of fluid needing to be delivered and the desired rate at which the fluid is to be delivered.
The surface pack-off device 100 further includes an energized cup-type or lip seal 150, which seals the housing 110 to the inner casing 120 when the fluid is injected into the annulus 125, as shown in
The surface pack-off device 100 further includes a protective sleeve 170, which is designed to fit around the outer circumferential surface of the inner casing 120, as shown in
The surface pack-off device 100 further includes an attachment assembly 180, which is designed to removably attach the device to the surface ends of the inner and outer casings 120 and 130. In one embodiment, the attachment assembly 180 includes a pair of retaining wings 182 mounted to the outer cylindrical surface of the housing 110, as shown in
An alternate embodiment of the attachment assembly 180′ is shown in
The surface pack-off device 100 may also include one or more eye hooks 190 (one shown) attached to the top of the housing 110. The eye hook 190 is provided to enable well operators to easily lift the surface pack-off device 100 onto, or off of, the surface of the well casing assembly during installation and removal, respectively.
In the embodiment of the surface pack-off device 100 shown in
Therefore, the present invention is well-adapted to carry out the objects and attain the ends and advantages mentioned as well as those which are inherent therein. While the invention has been depicted, described, and is defined by reference to exemplary embodiments of the invention, such a reference does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. The depicted and described embodiments of the invention are exemplary only, and are not exhaustive of the scope of the invention. Consequently, the invention is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.