Abstract:
An impervious metallic liner for the isolation of the well bore from the formations of an oil or gas well below a casing string; the liner being flattened to run through the casing string, but is inflated to occupy the space directly below the casing string rather than occupying the conventional area radially inward from the position occupied by the casing string.

Description:
BACKGROUND OF THE INVENTION 
     The field of this invention of that of liner hangers for the isolation of the well bore of oil and gas wells from the earth formations through which the oil or gas well is being drilled. 
     As different producing, water, and other formations through which the drilled well will pass must be isolated from each other, a casing string must be cemented in place to isolate each zone. An oil or gas well is typically drilled by first deciding the minimum bore of the production string of casing, or the last pipe to be cemented in place and will be continuous from the surface all the way down to the oil or gas producing formations. This production string of casing must be large enough to allow the production tubing landed inside it to flow enough oil or gas to make the well economic. 
     Each casing set point requires that an additional concentric casing string be set. A typical set of casing strings in a subsea environment from the inside out would be 7″ 9.625″ 11.750″, 13.375″, and 16″ set within an 18.750″ bore blowout preventer stack, and 20 and 30″ casing strings set before the 18.750″ bore blowout preventer stack is installed. Each casing string occupies a certain amount of radial space, requiring that the next string of pipe be progressively smaller. That program provides a maximum of 5 casing set points with blowout preventer protection during drilling. 
     Typically, a casing string, i.e. 11.75″ outer diameter, is installed in a drill well bore suspended from the surface to a depth such as 10,000 feet deep. After cementing the 11.750″ casing in place, a hole is drilled with a bit through the 11.750″ casing, i.e. 10.50″ diameter hole to 12,000 feet deep. Into this hole a 9.625″ outside diameter casing can be landed and cemented in place. If the 9.625″ casing string is suspended from the surface and is therefore 12,000 feet long, it is called a casing string. If, however, the 9.625″ casing is only 2000′ long and is suspended by a hanger from the lower end of the 11.750″ casing string, it is called a liner. The use of a liner can save substantially on the cost of casing and cement, e.g. 10,000 feet of casing not purchased. The well program would be followed with a 7.000″ casing string continuous from the surface to the bottom of the well as the production casing string. 
     The 9.625″ liner in the example above would have saved the operator the 10,000 feet of pipe not purchased, with the cost of a conventional liner hanger being generally offset by the cost of the surface casing hanger. The liner still “costs” the drilling company the “radial space”, forcing the next string to be progressively larger. 
     In this conventional scenario, if an unexpected pressured formation is encountered and requires that an extra casing string is set, it would probably be 5.500″ in size. With the 5.500″ size, the tubing string landed inside would be reduced from 3″ to 2″, substantially restricting the flow of production from the well. Flow from wells is especially important offshore where the high cost of drilling and producing wells demands a high flow rate to be economic. Cases have been seen of abandonment of wells when an extra pressurized reservoir zone was encountered and the driller realized that his final well bore size would be too small to be economic. 
     SUMMARY OF THE INVENTION 
     The object of this invention is to provide a liner which does not occupy “radial space” in the well bore and therefore does force each previously set casing hanger to be a step larger in diameter. 
     A second object of the present invention is to provide the capability of installing multiple liners in a drilling program to compensate for unforeseen well control situations. 
     A third object of the present invention is to provide a liner that can be rolled up for compact storage and shipment. 
     Another object of the present invention is to provide a liner assembly that is compact enough to be airlifted out to an offshore drilling vessel. 
     Another object of the present invention is to provide an expandable liner which is metallic in construction and impervious to fluid flow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a section through the oil or gas well as would remain after the previous casing string has been set and landed in place. 
     FIG. 2 is a section through the oil or gas well showing the bi-center bit approaching the specialized shoe. 
     FIG. 3 is a section through the oil or gas well showing the bi-center bit centralized and drilling within the pilot section of the existing float shoe. 
     FIG. 4A is a front view of the reeled liner as it would be shipped to the well site. 
     FIG. 4B is a side view of the reeled liner illustrating the position of the float shoe and support means. 
     FIG. 5 is a section showing that the liner is inserted into the well, but has not been inflated. 
     FIG. 6 is a section of the flattened liner as seen in FIG. 5 showing it relative size to the casing string through which it passed. 
     FIG. 7 is a section through a liner which has been flattened to a different pattern. 
     FIG. 8 is a section through the float shoe showing the means to allow for holding pressure on the first pressure cycle and then not holding pressure on subsequent pressure cycles. 
     FIG. 9 is a section through the liner support means. 
     FIG. 10 is a section showing that the liner has been expanded into an enlarged section at the lower end of the casing string. 
     FIG. 11 is a section through the oil or gas well showing the liner as landed, expanded and sealing in the lower end of the casing string. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, an oil or gas well  10  is shown with a subsea housing  11  at the top with a 13.625″ nominal housing bore  12  at the top. The subsea housing  11  is supported on a surface casing string  13  which penetrates the seafloor  14 . Within the housing bore  12  and on shoulder  15  a casing hanger  16  is landed. Casing string  17  having a well bore  18  extends down into the well and terminates in a casing shoe  20 . 
     Casing shoe  20  attached to casing string  17  by casing coupling  21  and has a landing profile  22  near its upper end. Below the landing profile is a support profile  23 , and enlarged pipe section  24 , and a float shoe portion  25 . Immediately above the float shoe portion is a standard cement annular portion  30  with a pilot bore  31  and a through bore  32 . In the bore of the landing profile  22 , the enlarged pipe section  23 , and the pilot bore  31 , a low strength material  33  is cast in place which will be usefully removed as seen further in this description. 
     Referring now to FIG. 2, a bi-center bit  40  is run into the enlarged pipe section. The bi-center bit includes a pilot bit portion  41 , a fixed hole opener section  42 , and a rotatable hole opener section  43  mounted on a spiral  44 . Conventionally, a special trip with a collapsible hole opener is required because a bi-center bit cannot be started within the casing due to the potential of damage to the bit. In this invention, the pilot bit is automatically centralized within the pilot bit preparation  45  to allow it to be concentric within the well prior to the beginning of rotation. The combination of this centralization and the enlarged pipe section allow for the immediate rotation of the bi-center bit without the need for a conventional hole opener run. 
     Referring now to FIG. 3, the pilot bit  41  is now drilling out the low strength material  33  as the rotatable hole opener section  43  contacts the top  50  of the standard cement annular portion  30  and remains vertically stationary as it rotates until the fixed hole opener section  42  catches up with it and they begin to drill the cement section together. At that time the pilot bit, rotatable hole opener section, and fixed hole opener section work together to drill out the cement shoe and continue to drill the oil or gas well deeper. 
     Referring now to FIG. 4, the liner of this invention is delivered to the well site on a reel  60  with a float shoe  61  near its outer end  62  and a support section  63  near its inner end  64 . The liner  65  is folded and flattened and rolled up on the reel for ease of transportation and storage. Either an 11.750″×0.250 wall×1000 ft. or a 9.625″×0.156 wall×2000 ft. liner can be airlifted for offshore service at about 30,000 lbs. The package size would be approximately 12 ft.×12 ft.×2.5 ft. 
     Referring now to FIG. 5, the liner is unreeled into the well bore  18  until drill string threaded connection  66  is attached to the upper thread  67  of the support section  63 . The lowering continues until expandable landing ring  68  engages landing profile  22  to position the support section  63 . The main portion of the liner  65  is in a flattened state suspended in the drilled well bore  69 . 
     Referring now to FIG. 6, the section through the well bore  69  and liner  65  shows that the liner has multiple folds to make it both flat and able to be rolled on a reel, and also of a smaller dimension that the hole through which it must pass. The liner is preferably of a size such that the circumference of the inner diameter when expanded to a circular shape is slightly larger than the inner diameter of the casing string through which it passed. In this style, it is effectively invisible with respect to view from the top of the well. 
     Referring now to FIG. 7, an alternate folding style is illustrated which yields a smaller package for entering into the well bore but somewhat more complex to fold and will tend to make a larger diameter reel for transportation. 
     Referring now to FIG. 8, a float shoe  61  depends from the lower end of the liner  65 , having a plug  81  with a seal  82 . Shear pins  83  hold the plug  81  in an initial position against the spring  84 . The first time the liner  65  is pressurized for inflation, the shear pins  83  shear and allow the plug  81  to move down against shoulder  85 . After the inflation pressure is released, the spring  84  will move the plug  81  out of the bore  86  and allow for cement to be circulated through the shoe to cement the liner in place. 
     Referring to FIG. 9, the support section  63  is shown in greater detail prior to inflating the liner  65 . After the inflation cycle and the opening of the float shoe as described above, a cementing plug (not shown) will be pumped down the bore  90  of the running string  91  until it hits shoulder  92  of cement cup  93  and pumps it to the float shoe  61 . 
     As the cementing plug and cement cup  93  approach the cement shoe, a support shoulder dart (not shown) is placed in the bore  90  of the running string  91  until it lands and stops on shoulder  94 . The support shoulder dart seals below the port  95  to allow high pressure from above in the running string to be vented to the inner diameter of the packer  96 . The packer expands to expand the upper section  100  of the liner  65  out to engage the profile  101  of the support section  63 . The profile  101  is made of a high yield material relative to the strength of the upper section  100  such that when the upper section  101  is expanded and released a compressive load will be retained between the surfaces. 
     After the upper section  100  is engaged and supported within profile  101 , the running string  91  is rotated to the right to unscrew from the connection to the top of the liner at thread  102 . Spring loaded milling cutters  103  are automatically deployed and remove any unexpanded section of the liner as the unit moves upward. 
     Referring now to FIG. 10, the upper end  100  of the liner  65  is supported in support profile  101 , and the milled end  110  of the upper section is seen remaining. The interface  111  between the liner upper end  100  and the support profile  101  provides for mechanical support of the liner (in addition to the cement) plus a metal to metal seal between the two parts. 
     Referring now to FIG. 11, a completed view of an installed invisible liner is seen after a conventional bit is used to drill out through the float shoe and continued to drill the well deeper. 
     The foregoing disclosure and description of this invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as the details of the illustrated construction may be made without departing from the spirit of the invention.