Abstract:
Drilling a well to total depth without tripping the bit out of the hole despite encountering a troublesome zone is made possible by using a memory based composite material delivered with the drill pipe or advanced over it, as needed. The material can be activated as a troublesome zone is encountered and assumes as former configuration that places it in sealing relation to the troublesome zone in the bore hole while spacing it from the drill pipe so as to allow resumption of drilling with the troublesome zone isolated.

Description:
PRIORITY INFORMATION 
   This application claims the benefit of U.S. Provisional Application No. 60/580,576, filed on Jun. 17, 2004. 

   FIELD OF THE INVENTION 
   The field of this invention relates to drilling a wellbore and more particularly a monobore in a single trip before installing a casing or liner. 
   BACKGROUND OF THE INVENTION 
   The traditional way to drill a well involves starting with a large bore and drilling ever decreasing bores below so that a new section of casing can fit through the casing already run and cemented. In this technique, as each segment is drilled there is what is called flat time or time when no drilling is going on. Instead, time, which costs the operator money, is taken up tripping the drill bit out of the hole and running in each size of casing. 
   One more recent alternative to this well used technique is a monobore completion. In this type of well drilling a single size hole is drilled from the surface to total depth. Even with this technique, unless the productive interval is relatively shallow, any time a problem zone is breached in the drilling, the drilling has to stop and the bit pulled out of the hole so that casing or liner can be run to isolate the problem zone so that drilling can resume. This technique is necessary because the mud weight is the sole means of well control during this type of drilling and the problem zone needs to be isolated with cemented casing or liner before drilling can resume safely. 
   Another known technique is to drill with a downhole motor powered by flow from coiled tubing going through a lubricator for well control. Although a bore can be continuously drilled this way, it is limited to rather small bore sizes. 
   Accordingly for the larger bores, even the monobore technique does not reduce the flat time from tripping in and out of the bore as each section of casing or liner is run in after a segment of the monobore is drilled. 
   What is needed is a technique that allows the ability to deal with problem zones of any type while drilling so as to isolate them without having to pull the bit out of the hole. This problem is addressed for applications where drilling with a downhole motor and coiled tubing through a lubricator will not produce the required bore diameter. The technique involves being able to isolate the zone with the drill string and bit still in the hole in a manner that allows drilling to resume as the zone is isolated. In part the solution involves the use of composite memory materials to be delivered with the drill string or subsequently over it when the troublesome zone is encountered. Local application of energy or heat activates the material to another shape to seal the troublesome zone and, if previously attached to the drill pipe, to release from it to allow drilling to resume. This general description will be more readily understood by those skilled in the art from a review of the description of the preferred embodiment and the claims, both of which appear below. 
   SUMMARY OF THE INVENTION 
   Drilling a well to total depth without tripping the bit out of the hole despite encountering a troublesome zone is made possible by using a memory based composite material delivered with the drill pipe or advanced over it, as needed. The material can be activated as a troublesome zone is encountered and assumes as former configuration that places it in sealing relation to the troublesome zone in the bore hole while spacing it from the drill pipe so as to allow resumption of drilling with the troublesome zone isolated. 

   
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a run in view of the preferred embodiment showing the composite sleeves in position; 
       FIG. 2  shows one sleeve activated to seal against a troublesome zone and clear of the drill string; 
       FIG. 3  shows an additional sleeve in position against the zone; 
       FIG. 4  shows another sleeve in position against the troublesome zone; 
       FIG. 5  is an alternate embodiment in the run in position during drilling; 
       FIG. 6  shows the drilling reaching a troublesome zone and a sleeve being delivered from above to near the bottom hole assembly; and 
       FIG. 7  shows the sleeve actuated against the troublesome zone and away from the drill string to allow drilling to continue. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a drill string  10  just reaching a problem zone  12  in a wellbore  14 . The drill bit is at the lower end of the drill string and is omitted from  FIGS. 1-4 . Those skilled in the art will appreciate that the drill bit can be coupled with an under-reamer to expand the drilled hole produced by the bit, in a known manner. Mounted to the drill string  10  to one or more stands of pipe are a sleeve  16 . This sleeve is made from an elastic memory composite material and is commercially available from Composite Technology Development Inc of Lafayette, Colo. This company describes this product and its current attributes and applications as follows:
         Elastic Memory Composite (EMC) materials are based on thermoset shape memory polymers, which enable the practical use of the shape memory properties in fiber-reinforced composites and other specialty materials. The applications for these revolutionary new materials are broad ranging, including mission-enabling components for spacecraft, performance enhancing and cost saving industrial and medical applications, deployable equipment for emergency and disaster relief, and improvements in the performance of sports equipment.       
   EMC materials are similar to traditional fiber-reinforced composites except for the use of an elastic memory thermoset resin-matrix. The elastic memory matrix is a fully cured polymer, which can be combined with a wide variety of fiber and particulate reinforcements and fillers. The unique properties of the matrix enable EMC materials to achieve high packaging strains without damage. Strains are induced by elevating the temperature of the EMC material and then applying a mechanical force. The shape memory characteristics enable the high packaging strains to be “frozen” into the EMC by cooling. Deployment (i.e., shape recovery) is effected by elevating the temperature. The temperature at which these operations occur is adjustable. 
   At lower temperatures, the performance of EMC materials follows classical composite laminate theory. At higher temperatures, EMCs exhibit dramatically reduced stiffnesses due to significant matrix softening of the resin. Adequately addressing the mechanics of the “soft-resin” will enable the EMC materials to provide repeatable stowage and deployment performance without damage and or performance changes. Products fabricated from these materials can be deformed and reformed repeatedly. Products utilizing EMC materials can be fabricated with conventional composite fabrication processes and tooling. EMC Materials:
         Can be formulated with low cost components   Use standard existing polymer and composite manufacturing processes   Regain original shape with applied heat, no other external force is required   Possess widely adjustable deformation and reformation temperatures are   Are suitable for repeated deformation and reformation cycles   Reform accurately to original shape   Maintain high strain capability when heated   Enable large volume reduction for packing   Issues such as shelf life, chemical reaction, toxicity, explosion hazard, or environmental impact are not of concern       

   Polymers have a characteristic temperature, called the glass transition temperature (Tg), at which the polymer softens. CTD&#39;s elastic memory polymer becomes both soft and highly ductile above this transition temperature. Below this temperature the polymer is hard and rigid, or glassy. Above TG the elastic memory polymer can be highly deformed and stretched into a different shape, such as folded into a compact shape. When held in this shape and cooled, it retains the new shape indefinitely. When reheated above TG, the material reforms to its original shape without external force, and regains its original properties once cooled. Thus an EMC tubular structure could be heated, collapsed and stowed, and then later reformed simply by heating. 
   EMC materials are ideally suited for deployable components and structures because they possess high strain-to-failure ratios, high specific modulus, and low density. By contrast, most traditional materials used for deployable structures have only two of these three attributes. 
   Initial EMC development efforts have targeted space applications. Tremendous support for the development of CTD&#39;s EMC materials has been received from NASA, the Air Force, BMDO and other Government agencies, and the aerospace industry. EMC materials have the potential to enable a new generation of space deployable components and structures, which would eliminate nearly all the limitations and shortfalls of current spacecraft deployable technologies. 
   With that as a background on the preferred material for the sleeve  16  those skilled in the art will appreciate that the original dimensions for fabrication of sleeve  16  will approximate its desired final dimensions in the wellbore after activation, as shown in  FIG. 2 . The outer dimension  18  needs to be large enough after activation, to sit firmly against the troublesome zone  12  in a way that one or more than one sleeve  16  can isolate the zone upon deployment. Rubber end rings could be used to enhance the sealing ability. At the same time, the inner dimension  20  should clear the outside wall  22  of the drill string  10  so that the drill string  10  can be rotated with minimal and preferably no contact to the sleeve or sleeves  16 . After initial forming to these general dimensional specifications, the sleeve  16  can be raised above the glass transition temperature while mounted over a stand of drill pipe so that while in the fluid form its shape can be reconstituted to fit snugly or even loosely over the stand of drill pipe  10 . The reformed exterior dimension  24 , shown in  FIG. 1  should preferably be smaller than the bore being drilled either by the bit or by an associated under-reamer. In that way the sleeve  16  will not be damaged by advancement of the bit and will preferably have minimal contact with the borehole wall during drilling. Loosely fitting the sleeve  16  to a stand of drill pipe  10  allows for some relative rotation between them should the sleeve  16  make contact with the borehole  14  during drilling. 
   Additionally, the activation temperature of the sleeves  16  can be adjusted to be higher than the anticipated well fluid temperature to avoid deployment without introduction of an energy source, schematically labeled E in  FIG. 2  to cause transition back to the original shape.  FIG. 3  illustrates that two sleeves  16  can be placed next to each other, or three or more as illustrated in  FIG. 4 . Sealing material can also be incorporated into one or more sleeves  16  so that when it is activated the sealing is enhanced by the presence of the sealing material, shown schematically as  26  in  FIG. 3 . 
     FIGS. 5-7  illustrate drilling the borehole  14  with a bit  28  and an under-reamer  30  located above it. The sleeves  16  are not in position during drilling. However, when a problem zone  12  is encountered the sleeve or sleeves  16  can be lowered over the drill pipe  10  or expanded from drill pipe  10  as shown in  FIG. 6 . An energy source E is delivered through the drill pipe to the vicinity of the sleeve  16  and it resumes its original shape taking its outer wall against the borehole  14  and its inner wall away from the drill string  10 , as shown in  FIG. 7 . In this variation of the technique, the sleeve or sleeves  16  can be allowed to travel to near the bottom hole assembly by gravity or with reverse circulation outside the drill string  10  or by use of a direct or indirect force from outside or inside the drill string  10 . Thus whether the sleeve or sleeves are delivered with the drill pipe or inserted in the wellbore  14  after the troublesome zone is encountered, the desired result on activation is the same, isolation with an ability to continue drilling. 
   It should be noted that more than one troublesome zone  12  can be isolated in the techniques described above. The troublesome zones can be close together or thousands of feet apart. If the sleeves closest to the bottom hole assembly have already been activated to isolate a higher troublesome zone  12 , remaining sleeves on the drill string  10  can be used to isolate another zone further down the bore. If the sleeves  16  are secured to the drill pipe one above the other, it will mean that to isolate a lower zone after an upper zone has been isolated, the drilling will need to continue to position the remaining sleeves opposite the new lowers zone because the lowermost sleeves have been deployed above. The inside dimension of the deployed sleeve or sleeves need to be large enough to allow the remaining undeployed sleeves to pass, as drilling continues. Similarly, if the additional sleeves are to be subsequently delivered from the surface after one zone has already been isolated, then those new sleeves must clear through the previously deployed sleeves as the new sleeves travel down the drill pipe  10 . Alternatively, to the extent space is available, the sleeves can be nested near the bottom hole assembly and constructed to activate at different temperatures with the outermost sleeve activated at the lowest temperature. If done in that manner, several sleeves can be run in with the drill string  10  and while positioned close to the bottom hole assembly. When done this way, there is no need to drill further into a subsequent troublesome zone after an earlier deployment in a higher troublesome zone, as the next available sleeve  16  would already be in close proximity to the bottom hole assembly. 
   Although elastic memory composite materials are preferred, the invention encompasses a technique that allows isolation of troublesome zones without having to pull out of the hole, thereby allowing drilling to progress until total depth is reached. Other materials and techniques that make drilling to depth without pulling out of the hole while having the ability to isolate one or more troublesome zones is within the scope of the invention. 
   While the preferred embodiment has been set forth above, those skilled in art will appreciate that the scope of the invention is significantly broader and as outlined in the claims which appear below.