Abstract:
The present invention provides an encapsulation for housing instrumentation lines, control lines, or instruments downhole. In one use, the encapsulation resides between an expandable downhole tool, such as an expandable sand screen, and the wall of the wellbore. The encapsulation is specially profiled to allow the downhole tool to be expanded into the wall of the wellbore without leaving a channel outside of the tool through which formation fluids might vertically migrate. The encapsulation is useful in both cased hole and open hole completions.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to expandable sand screens and other expandable tubulars. More particularly, the present invention relates to a profiled encapsulation for use with an expandable sand screen or other expandable downhole apparatus. The profiled encapsulation houses instrumentation lines or control lines in a wellbore. 
   2. Description of Related Art 
   Hydrocarbon wells are typically formed with a central wellbore that is supported by steel casing. The steel casing lines the borehole formed in the earth during the drilling process. This creates an annular area between the casing and the borehole, which is filled with cement to further support and form the wellbore. 
   Some wells are produced by perforating the casing of the wellbore at selected depths where hydrocarbons are found. Hydrocarbons migrate from the formation, through the perforations, and into the cased wellbore. In some instances, a lower portion of a wellbore is left open, that is, it is not lined with casing. This is known as an open hole completion. In that instance, hydrocarbons in an adjacent formation migrate directly into the wellbore where they are subsequently raised to the surface, possibly through an artificial lift system. 
   Open hole completions carry the potential of higher production than a cased hole completion. They are frequently utilized in connection with horizontally drilled boreholes. However, open hole completions present various risks concerning the integrity of the open wellbore. In that respect, an open hole leaves aggregate material, including sand, free to invade the wellbore. Sand production can result in premature failure of artificial lift and other downhole and surface equipment. Sand can build up in the casing and tubing to obstruct well flow. Particles can compact and erode surrounding formations to cause liner and casing failures. In addition, produced sand becomes difficult to handle and dispose at the surface. Ultimately, open holes carry the risk of complete collapse of the formation into the wellbore. 
   To control particle flow from unconsolidated formations, well screens are often employed downhole along the uncased portion of the wellbore. One form of well screen recently developed is the expandable sand screen, designated by the Assignee as ESS®. In general, the ESS is constructed from three composite layers, including a filter media. The filter media allows hydrocarbons to invade the wellbore, but filters sand and other unwanted particles from entering. The sand screen is connected to production tubing at an upper end and the hydrocarbons travel to the surface of the well via the tubing. The sand screen is expanded downhole against the adjacent formation in order to preserve the integrity of the formation during production. 
   A more particular description of an expandable sand screen is described in U.S. Pat. No. 5,901,789, which is incorporated by reference herein in its entirety. That patent describes an expandable sand screen which consists of a perforated base pipe, a woven filtering material, and a protective, perforated outer shroud. Both the base pipe and the outer shroud are expandable, and the woven filter is typically arranged over the base pipe in sheets that partially cover one another and slide across one another as the sand screen is expanded, or is expanded directly. The expanded tubular or tool can then be expanded by a cone-shaped object urged along its inner bore or by an expander tool having radially outward extending rollers that are fluid powered from a tubular string. Using expansion means like these, the expandable tubular or tool is subjected to outwardly radial forces that urge the expanding walls against the open formation or parent casing. The expandable components are stretched past their elastic limit, thereby increasing the inner and outer diameter of the tubular. 
   A major advantage to the use of expandable sand screen in an open wellbore like the one described herein is that once expanded, the annular area between the screen and the wellbore is mostly eliminated, and with it the need for a gravel pack. Typically, the ESS or other solid expandable tubular is expanded to a point where its outer wall places a stress on the wall of the wellbore, thereby providing support to the walls of the wellbore to prevent dislocation of particles. Solid expandable tubulars are oftentimes used in conjunction with an expandable sand screen to provide a zonal isolation capability. 
   In modern well completions, the operator oftentimes wishes to employ downhole tools or instruments. These include sliding sleeves, submersible electrical pumps, downhole chokes, and various sensing devices. These devices are controlled from the surface via hydraulic control lines, electrical control lines, mechanical control lines, fiber optics and/or a combination thereof. For example, the operator may wish to place a series of pressure and/or temperature sensors every ten meters within a portion of the hole, connected by a fiber optic control line. This line would extend into that portion of the wellbore where an expandable sand screen or other solid expandable tubular or tool has been placed. 
   In order to protect the control lines or instrumentation lines, the lines are typically placed into small metal tubings which are affixed external to the expandable tubular and the production tubing within the wellbore. In addition, in completions utilizing known non-expandable gravel packs, the control lines have been housed within a metallic rectangular cross-sectioned container. However, this method of housing control lines or instrumentation downhole is not feasible in the context of the new, expandable completions now being offered. 
   First, the presence of control lines behind an expandable tubular interferes with an important function, which is to provide a close fit between the outside surface of the expandable tubular, and the formation wall. The absence of a close fit between the outside surface of the expandable tubular and the formation wall creates a vertical channel outside of the tubular, allowing formation fluids to migrate between formations therein. This, in turn, causes inaccurate pressure, temperature, or other readings from downhole instrumentation, particularly when the well is shut in for a period of time, or may provide a channel for erosive wear. 
   There is a need, therefore, for an encapsulation for control lines or instrumentation lines which is not rectangular in shape, but is profiled so as to allow a close fit between an expandable tubular and a formation wall or parent casing. There is further a need for an encapsulation which resides between the outside surface of an expandable and the formation wall, and which does not leave a vertical channel outside of the expandable tubular when it is expanded against the formation wall. Still further, there is a need for such an encapsulation device which is durable enough to withstand abrasions incurred while being run into the wellbore, but which is sufficiently deformable as to be deformed in arcuate fashion as to closely reside between an expanded tubular and the wall of a wellbore, whether cased or open. 
   SUMMARY OF THE INVENTION 
   The present invention provides an encapsulation for housing instrumentation lines, control lines, or instruments downhole. In one use, the encapsulation resides between an expandable downhole tool, such as an expandable sand screen, and the wall of the wellbore. The encapsulation is specially profiled to allow the downhole tool, e.g., ESS, to be expanded into the wall of the wellbore without leaving a channel outside of the tool through which formation fluids might vertically migrate. The encapsulation is useful in both cased hole and open hole completions. The profile is generally derived from the bore hole i.d. (or parent casing i.d.) and the o.d. of the expanded tubular. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
       FIG. 1  is a section view showing an open hole wellbore with a typical expandable sand screen and tubulars disposed therein. A profiled encapsulation of the present invention is shown in cross-section running from the surface to the depth of the expandable completion. 
       FIG. 2  is a top section view of an expandable sand screen completion within an open wellbore. The sand screen is in its unexpanded state. Visible is a top view of a profiled encapsulation of the present invention residing in the sand screen-formation annulus. 
       FIG. 3  is a top section view of an expandable sand screen before expansion, and a blow-up view of a portion of the expandable sand screen. 
       FIG. 4  is a top section view of an expandable sand screen within an open wellbore. The sand screen is in its expanded state. Visible is a top view of a profiled encapsulation of the present invention residing in the sand screen-formation annulus. 
       FIG. 5  depicts the expandable sand screen of  FIG. 4 , expanded against a cased hole wellbore. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  is a section view showing an open hole wellbore  40 . The wellbore  40  includes a central wellbore which is lined with casing  42 . The annular area between the casing  42  and the earth is filled with cement  46  as is typical in well completion. Extending downward from the central wellbore is an open hole wellbore  48 . A formation  50  is shown adjacent the wellbore  48 . 
   Disposed in the open wellbore  48  is a downhole tool  20  to be expanded. In the embodiment shown in  FIG. 1 , the tool  20  is an expandable sand screen (ESS®). However, the tool  20  could be any expandable downhole apparatus. An ESS  20  is hung within the wellbore  40  from a hanging apparatus  32 . In some instances, the hanging apparatus is a packer (not shown). In the depiction of  FIG. 1 , the hanging apparatus is a liner  30  and liner hanger  32 . A separate packer  34  may be employed to seal the annulus between the liner  30  and the production tubular  44 . 
   Also depicted in  FIG. 1  is an encapsulation  10  of the present invention. The encapsulation  10  is shown running from the surface to the liner hanger  32 . The encapsulation  10  is secured to the production tubular  44  by clamps, shown schematically at  18 . Clamps  18  are typically secured to the production tubular  44  approximately every ten meters. The clamps  18  are designed to expand with the tool  20  when it is expanded. The encapsulation  10  passes through the liner hanger  32  (or utilized hanging apparatus), and extends downward to a designated depth within the wellbore  40 . In the embodiment shown in  FIG. 1 , the encapsulation  10  extends into the annular region (shown as  28  in  FIG. 2 ) between the expandable sand screen  20  and the open hole wellbore  48 . Note that the expandable sand screen  20  of  FIG. 1  has already been expanded against the open hole formation  50  so that no annular region remains. The ESS  20  is thus in position for production of hydrocarbons. 
     FIG. 2  presents a top section view of an encapsulation  10  of the present invention. The encapsulation  10  resides in this depiction within an open hole wellbore  48 . As in  FIG. 1 , the encapsulation  10  is disposed in the annular region  28  defined by the expandable sand screen  20  and the formation wall  48 . The encapsulation  10  is designed to serve as a housing for control lines or instrumentation lines  62  or control instrumentation (not shown). For purposes of this application, such lines  62  include any type of data acquisition lines, communication lines, fiber optics, cables, sensors, and downhole “smart well” features. The encapsulation  10  may optionally also house metal tubulars  60  for holding such control or instrumentation lines  62 . 
   The encapsulation  10  is specially profiled to closely fit between the sand screen  20  and the surrounding formation wall  48  after the sand screen  20  has been expanded. In this way, no vertical channel is left within the annular region  28  after the sand screen  20  is been expanded. To accomplish this, an arcuate configuration is employed for the encapsulation  20  whereby at least one of the walls  12  and  14  is arcuate in shape. In the preferred embodiment shown in  FIG. 2 , both walls  12  and  14  are arcuate such that a crescent-shape profile is defined. Thus, the encapsulation  10  shown in  FIG. 2  comprises a first arcuate wall  12  and a second arcuate wall  14  sharing a first end  15 ′ and a second end  15 ″. However, it is only necessary that the outside wall  12  be arcuate in design. 
   The encapsulation  10  is normally fabricated from a thermoplastic material which is durable enough to withstand abrasions while being run into the wellbore  40 . At the same time, the encapsulation  10  material must be sufficiently malleable to allow the encapsulation to generally deform to the contour of the wellbore  48 . This prevents annular flow behind the sand screen  20 . The encapsulation  10  is preferably clamped to the expandable tubular  20  by expandable clamps (not shown). The expandable clamps are designed to provide minimal restriction to the tubular i.d. 
   In  FIG. 2 , the sand screen  20  is in its unexpanded state. In the embodiment of  FIG. 2 , the sand screen  20  is constructed from three composite layers. These define a slotted structural base pipe  22 , a layer of filter media  24 , and an outer encapsulating and protecting shroud  26 . Both the base pipe  22  and the outer shroud  26  are configured to permit hydrocarbons to flow therethrough, such as through slots (e.g.,  23 ) or perforations formed therein. The filter material  24  is held between the base pipe  22  and the outer shroud  26 , and serves to filter sand and other particulates from entering the sand screen  20  and the production tubular  44 . The sand screen  20  typically is manufactured in sections which can be joined end-to-end at the well-site during downhole completion. It is within the scope of this invention to employ an encapsulation  10  with one or more sections of expandable sand screen  20  or other expandable downhole tool. 
   In  FIG. 3 , the sand screen  20  is again shown in cross-section. A portion  20   e  of the sand screen  20  is shown in an expanded state, to demonstrate that the sand screen  20  remains sand tight after expansion. (Note that the expanded depiction is not to scale.) Radial force applied to the inner wall of the base pipe  22  forces the pipe  22  past its elastic limits and also expands the diameter of the base pipe perforations  23 . Also expanded is the shroud  26 . As shown in  FIG. 4 , the shroud  26  is expanded to a point of contact with the wellbore  48 . Substantial contact between the sand screen  20  and the wellbore wall  48  places a slight stress on the formation  50 , reducing the risk of particulate matter entering the wellbore  48 . It also reduces the risk of vertical fluid flow behind the sand screen  20 . 
     FIG. 4  is a top section view illustrating the wellbore  48  and the sand screen  20  expanded therein. Expansion is within the open wellbore  48  of FIG.  2 . Visible is the top view of a profiled encapsulation of the present invention residing in the sand screen-formation annulus  28  (shown in FIG.  3 ). The encapsulation  10  has been expanded by a conformed cone or roller apparatus or other expander tool (not shown) to provide a close fit between the sand screen  20  and the formation  48  such that no annular region  28  remains as would permit measurable vertical fluid movement behind the sand screen  20 . 
     FIG. 5  depicts an expandable sand screen  20  expanded against a cased hole wellbore. Casing is shown as  52 , and the cement is shown as  56 . The casing  52  is perforated  53  to allow hydrocarbons to pass into and through the sand screen  20 . This demonstrates that the encapsulation  10  of the present invention has application to a cased hole completion as well as an open hole completion. Those of ordinary skill in the art will appreciate that hydrocarbons will enter the casing through perforations  53 . 
   While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.