Patent Application
20130105145
This application claims priority to Patent Application No. 2,752,022, filed in the Canadian Intellectual Property Office on Sep. 9, 2011, the entire content of which is incorporated herein.
This invention relates to tubulars for use in a wellbore, and more particularly, to tubulars for controlling flow of materials into the wellbore by reducing deformities in a screening assembly associated with the tubular.
Many reservoirs or aquifers consist of, or include, poorly cemented solids, such as sands, silts and shales. As such, when fluids are produced from such porous media, some of the solids may be mobilized and may move to the wellbore. If allowed to enter the wellbore, the solids may migrate into production equipment, for example, pumps, whose moving parts may become damaged or incapacitated by the solids.
To avoid or mitigate this problem, numerous solids control techniques for producing wells have been developed. These techniques normally involve installation of a screening or filtering device in that portion of the wellbore which is exposed to the reservoir.
There are two basic approaches to the design of these solids control devices.
In one approach, the means of structural support within the wellbore and the means of screening or filtering the fluids to exclude the mobile solids, involve the same basic piece of equipment. That is, within the wellbore, a length of structurally competent pipe, such as tubular steel, typically in the form of casing or tubing, is installed. This device is referred to as a liner. The wall of this liner is cut entirely through at intended locations with an array of numerous very narrow slots whose purpose is to allow entry of fluids into the wellbore while excluding solids of a certain size range. These devices, with their integral design of structural and screening functions, are referred to as slotted liners.
The second approach involves assemblies consisting of two basic elements. The first element is a tubular steel device whose walls are perforated by holes or apertures of a size clearly in excess of the sizes of solids particles to be excluded from entering the wellbore. Surrounding or wrapped around this tubular steel device with the large apertures is a device which, as the second element of the assembly, serves as a means of screening or filtering out the unwanted mobile solids before they enter the inner device. Thus, the fluids and mobile solids first encounter the screening or filtering device where solids beyond a certain size are impeded or screened out. All fluids and solids which are able to pass through the screening or filtering device are then also able to enter the wellbore via the inner tubular device without further impediment. Assemblies which use this second approach include, for example, precisely punched screens (PPS) and wire-wrapped screens (WWS).
Typically, the tubulars within a wellbore consist of many individual joints which are linked together. The usual means of joint linkage involves threaded connections.
The string of tubulars within a well is subject to stresses and corresponding strains. This is true in both vertical and horizontal wells and applies in environments where either thermal or non-thermal recovery processes are employed. In the case of a horizontal production well in a thermal recovery process environment, temperature variations, including temperature cycling, can subject the tubulars to stresses. If an interval of the tubular string incorporates a solids control device, such as those described above, the small or narrow apertures by means of which the screening or filtering of solids is accomplished may become distorted as a result of thermal strains. Those distortions can result in localized increases in aperture size which will, in turn, diminish the effectiveness of the device in providing solids control. Alternatively, in the reverse case, the distortions can result in localized shrinkage in aperture size to increase the propensity for the apertures to be plugged by fine particles, thus blocking the flow of fluids entirely.
One of the available techniques to mitigate these distortions involves a product known as a DuraWav™ assembly which comprises an expandable/compressible connection between individual joints of the solids control device that relieves the stresses caused by expansion or contraction of the tubulars in a wellbore. However, the DuraWav™ expansion joint is designed to perform two functions concurrently. It is designed to absorb strain and also to shoulder the structural load associated with the weight of the tubular assembly. As such, its structural strength, and its associated functionality, must be adequate to undertake the more strenuous of these two functions—a requirement which is correspondingly costly. In contrast to this, applicant has developed apparatus that separates the two functions so that the heavy structural characteristics required for the load bearing function of the base pipe, and the associated cost, are not reflected in the stress-relieving function.
Accordingly, the present invention provides a wellbore assembly comprising:
a tubular member adapted to be connected to other tubular members, the tubular member having a side wall defining a hollow interior and an array of openings therethrough to permit material into the interior;
a screening element extending about the tubular member over the array of openings to control the material that reaches the array of openings; and
a stress relieving arrangement associated with the screening element to permit relative movement between the screening element and the tubular member.
In a further aspect, the present invention provides a wellbore assembly comprising:
a tubular member adapted to be connected to other tubular members, the tubular member having a side wall defining a hollow interior and an array of openings therethrough to permit material into the interior;
means for screening material extending about the tubular member over the array of openings to control the material that reaches the array of openings; and
means for permitting relative movement between the tubular member and the means for screening material.
The present invention serves to maintain solids control in production wells while accommodating stresses and strains that occur within the solids control tubulars in those wells. More specifically, with respect to the specially sized apertures within a tubular assembly that control the entry of solids into the wellbore, the present invention mitigates distortion of those apertures, said distortion often occurring as a result of strains to the assembly. In petroleum recovery operations involving high temperatures, such as those that employ steam, the strains experienced within the tubular assemblies and their associated solids control devices are often significant and require means to accommodate them.
The assembly of the present invention offers a means of relieving stress in wellbore equipment that includes an inner tubular structural element and a outer screening element.
Aspects of the present invention are illustrated, merely by way of example, in the accompanying drawings in which:
Referring to
Means for screening material, preferably in the form of a screening element 14, extends about the base pipe over the array of openings 12 to control the material that reaches the array of openings. Screening element 14 is wrapped or mounted over the base pipe to act as a solids control device. In the illustrated embodiment, screening element 14 is equivalent to a precisely punched screen (PPS) and is formed into an outer sleeve mounted substantially co-axially about the base pipe and is formed with critically sized apertures 16 for solids control. Alternatively, the means for screening material may be a wire-wrapped screen (WWS).
In a preferred arrangement, the outer sleeve configuration of screening element 14 is mounted to the base pipe by means of welding 20 at opposite ends of the screening element so that material is limited to entering the annular space 22 between the screening element and side wall 8 of the base pipe through apertures 16.
Tubular member 4 in the form of the base pipe provides both structural support for the screening element 14, and, via large openings 12, a means of conveying material filtered by screening element 14 into the interior 10 of the pipe.
Wellbore assembly 2 also includes means for permitting relative movement between the tubular member and the screening element 14 in order to lessen the stresses and strains on the screening element and to minimize deformation of the apertures 16 in screening element 14. In the illustrated embodiment, the means for permitting relative movement comprises a bellows structure 24 formed within the screening element 14. Preferably, bellows structure 24 comprises a plurality of corrugations formed in the actual screening element 14. While bellows structure 24 is shown with angular corrugations of generally triangular cross-section in
When a well containing a wellbore assembly as illustrated is subjected to high temperatures, such as those associated with a thermal recovery operation, the resulting thermal stresses tend to induce strains on the assembly including the screening element 14. In the prior art, these strains could deform the apertures in the screening element, at least some of which apertures would experience enlargement at localized sites. As a consequence, the screening element no longer retained the proper aperture size originally designed for solids control. This, in turn, led to, or contributed to, the failure of the screening element as a means of solids control, with the result that unwanted solids, which might damage downhole production equipment or otherwise impede or burden production operations, passed through the distorted apertures and through the larger openings in the base pipe, and thus entered the wellbore.
With respect to the arrangement of the present invention, the means for permitting relative movement between the screening element and the base pipe allows for relieve of stresses and accommodates strains that might otherwise build up in the screening element. For example, in the case of the present wellbore assembly being used in a vertical well, where the weight of the string of pipe is important, one end of the means for permitting relative movement is anchored by welding or the like to the base pipe. The other end is mounted to the outer screening element, which is the lighter than the base pipe. The screening element associated with a particular base pipe is not attached to any other screening element or base pipe. Thus, the means for permitting relative movement is required to moderate the stresses associated with only a single unit of pipe, and to bear the weight burden of only a single screening element and does not bear the burden of an accumulated weight of tubulars. In other words, in the present arrangement when used in a vertical well, the load bearing function is carried out by the body of the base pipe, and by the coupling points between joints of said base pipe, such as their threaded connections 6. The screening element 14 which is mounted about an individual unit of base pipe, in contrast, is not rigidly linked to the cumulative load associated with the base pipe. As stresses are imposed, for example due to thermal variations, the base pipe and outer sleeve element experience strains to varying degrees due to expansion or contraction with respect to each other. The means for permitting relative movement relieves stresses that might otherwise occur by accommodating or absorbing those strains. Furthermore, the means for permitting relative movement accomplishes this while bearing none of the burden associated with the weight of the base pipe, and while bearing the weight of the associated screening element.
In the case of horizontal wells, the cumulative weight of base pipes is not an issue as it is in vertical wells. However, thermal operations will induce strains in the base pipe and the outer screening element 14 because of the opportunity for relative movement, and the arrangement of the present invention also accommodates these strains. For example, in a horizontal well which is being used in a thermal recovery process, such as steam injection in an oil sand, the borehole will typically collapse along much of its length around the pipe assembly during the early stages of operation. This is a reflection of the uncemented nature of the sand. This collapse will inhibit to varying degrees the relative movement of base pipe and the surrounding screening element 14. However, to the extent that some relative movement occurs, the resulting stresses can be mitigated by the means for permitting relative movement. Typically, at least one means for permitting relative movement is associated with each base pipe.
In a horizontal well, the base pipe and the screening element may be lying along the bottom of the borehole. Thus, there may be areas of weighted contact between them. Such circumstances may inhibit the movement of the base pipe with respect to the screening element. To facilitate relative movement of the base pipe with respect to the outer screening element, separating means for maintaining a stand-off or gap between the two may be employed. In a particular embodiment directed to this circumstance which is best shown in
In summary, the above-described wellbore assembly with its base pipe and co-axially wrapped screening element with stress relief means, allow the wellbore to retain its functionality by avoiding deformation of the screening element and allowing it to maintain its solids control function in environments of high temperature and mechanical stress.
While the base pipe and associated outer screening element constitute a functional unit, they are not a fixed structural unit by virtue of the stress relieving means associated with the screening element which permits relative movement between the base pipe and screening element.
Although the present invention has been described in some detail by way of example for purposes of clarity and understanding, it will be apparent that certain changes and modifications may be practised within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,752,022 | Sep 2011 | CA | national |
