An apparatus and method for installing casing into a wellbore is provided. The apparatus includes a piston assembly which is engagable with a casing string to be installed into a wellbore. The piston assembly works in conjunction with a previously installed section of casing in the wellbore to create a hydraulic piston system to aid in the installation of the casing string to which the piston assembly is attached into a wellbore. More particularly, the piston assembly in conjunction with an intermediate casing is used to aid in the installation of a casing string comprising production casing. A method of operating the piston assembly is also provided.

FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to the process of running in casing into a borehole. More particularly, relating to a method and apparatus for running in casing into a borehole by utilizing a previously installed casing as piston cylinder.  
         [0002]     In the recovery of formation fluids, such as oil, gas and mineral deposits, the drilling and completion of a well, whether it be vertical, deviated or horizontal, plays a vital role in the successful production of the formation fluids.  
         [0003]     In recent years the practice of drilling deviated and horizontal wells have become more desirable over vertical wells due to a higher production of formation fluid. A deviated well is termed as a wellbore that is not vertical. The term usually indicates a wellbore intentionally drilled away from vertical. A horizontal well is termed where the departure of the wellbore from vertical exceeds about 80 degrees. Note that some horizontal wells are designed such that after reaching true 90-degree horizontal, the wellbore may actually start drilling upward. In such cases, the angle past 90 degrees is continued, as in 95 degrees, rather than reporting it as deviation from vertical, which would then be 85 degrees. Because a horizontal well typically penetrates a greater length of the reservoir, it can offer significant production improvement over a vertical well. The operation of drilling deviated and horizontal wellbores is well known in the art and will not be discussed here.  
         [0004]     The rate of production or the amount of production of a well is directly related to the length in which the reservoir is penetrated. However, in deviated or horizontal wells it becomes increasingly difficult to run in casing as the length of the casing run in is increased. To increase the length of casing run into the reservoir many prior art devices have been implemented to attempt to increase the length of casing run in. One such device is described in U.S. Pat. No. 6,868,913, of which its entirety is incorporated herein by reference.  
       SUMMARY OF THE INVENTION  
       [0005]     In accordance with the present invention, to provide an apparatus and method to increase the length of casing that can be run into a wellbore.  
         [0006]     In general, in one aspect, a method of running in casing into a borehole having a previously installed section of casing is provided. The method including the steps of:  
         [0007]     (i) providing a piston assembly;  
         [0008]     (ii) engaging the piston assembly with a casing string to be installed into the borehole;  
         [0009]     (iii) inserting the casing string with the engaged piston assembly into the previously installed section of casing; and  
         [0010]     (iv) pressurizing the previously installed section of casing above the piston assembly with a fluid such that the piston assembly engaged with the casing string is forced to translate within the previously installed section of casing such that the casing string is pressed into the borehole.  
         [0011]     In general, in another aspect, a method of running in casing into a borehole having a previously installed section of casing is provided. The method includes the steps of:  
         [0012]     (i) providing a piston assembly;  
         [0013]     (ii) engaging the piston assembly with a casing string to be installed into the borehole;  
         [0014]     (iii) inserting the casing string with the engaged piston assembly into the previously installed section of casing;  
         [0015]     (iv) pressurizing the previously installed section of casing above the piston assembly with a fluid such that the piston assembly engaged with the casing string is forced to translate within the previously installed section of casing such that the casing string is pressed into the borehole;  
         [0016]     (v) equalizing pressure across said piston assembly; and  
         [0017]     (vi) disengaging the piston assembly from the casing string.  
         [0018]     In general, in another aspect, an apparatus for running in casing into a borehole having a previously installed section of casing is provided The apparatus includes a piston body having a forward end including an adaptor sub and an opposite rearward end, the piston body defining a longitudinal bore formed axially therethrough. A mandrill is slidably received within the longitudinal bore through the rearward end and is slidable within the longitudinal bore to a first position and to a second position. The piston body having a radial shoulder surface of a diameter to correspond to an interior diameter of the previously installed casing, such that when the piston body is positioned within the previously installed casing a sealing contact is made between the radial shoulder surface of the piston body and the interior surface of the previously installed casing. The piston body further defining at least one blind port hole formed therethrough from an exterior surface forward of the radial shoulder surface to the longitudinal bore, and defining at least one annulus port hole formed therethrough from an exterior surface rearward of the radial shoulder surface to the longitudinal bore, and wherein fluid communication is established between the at least one blind port hole and the at least one annulus port hole when the mandrill is positioned in the second position.  
         [0019]     There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.  
         [0020]     Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting.  
         [0021]     As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.  
         [0022]     For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated preferred embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:  
         [0024]      FIG. 1  is a schematic view of a conventional land well casing architecture;  
         [0025]      FIG. 2  is a schematic view of the preferred embodiment of the apparatus for running in production casing constructed in accordance with the principles of the present invention;  
         [0026]      FIG. 3  is a partial cross-sectional view of the apparatus positioned within a previously installed casing with the mandrill in the first downward position; and  
         [0027]      FIG. 4  is a partial cross-sectional view of the apparatus positioned within a previously installed casing with the mandrill in the second upward position. 
     
    
       [0028]     The same reference numerals refer to the same parts throughout the various figures.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     Referring now to the drawings, and particularly to  FIGS. 1-4 , a preferred embodiment of the apparatus of the present invention is shown and generally designated by the reference numeral  10 .  
         [0030]     In  FIG. 1 , a schematic diagram of a typical well  100  is shown. The well  100  includes sections of casing  102  installed into concentric wellbores  104 , such as a conductor casing  106 , a surface casing  108  and an intermediate casing  110 . It should be appreciated the term casing used herein also includes liners or any other form of a tubular member. The casing  102  extend to varying depths according to the engineering of the well  100  and particularly to the different formations through which the wellbores  104  extend. The well  100  further includes a deviated or horizontal wellbore  109  into which a production casing string  112  is being run in.  
         [0031]     With reference to  FIG. 2 , an apparatus  10 , constructed in accordance with the present invention, is shown engaged with the casing string  112  and positioned within a previously installed section of casing, such as the intermediate casing  110 . The casing string  112  is generically illustrated for exemplary purposes only. The apparatus  10  is a piston assembly  10  including a piston body  12  having a forward end  14  and a rearward end  16 . The piston body  12  further defines a radial shoulder surface  18 , which is of a diameter to correspond to the I.D. of the intermediate casing  110  such that a sealing contact is made between the radial shoulder surface and the intermediate casing. The radial shoulder surface  18  includes a wear surface  20  and a sealing surface  22 .  
         [0032]     To aid in centralizing the piston assembly  10 , a centralizing member  114  can be engaged with the casing string  112 , and depending upon where the piston assembly  10  is engaged along the casing string  112 , a centralizing member can be used forward and rearward of the piston assembly. The centralizing member  114  is a mechanical device to position casing concentrically in a wellbore. Usable centralizing members  114  are well known in the art and do not need to be described herein.  
         [0033]     Preferably, the piston assembly  10  is engaged with the casing string  112  between the liner hanger, not shown but well known in the art, from which production casing depends (not shown) and the second to the last joint of pipe, in the casing string, required to land the liner hanger in its engineered well position within the intermediate casing  110 .  
         [0034]     Now with reference to  FIGS. 3 and 4 , a partial cross-section of the piston assembly  10  engaged with the casing string  112  and positioned within the intermediate casing  110  is shown. The piston assembly  10  further includes a mandrill  24  and an adaptor sub  26 . The adaptor sub  26  and the mandrill  24  allow connection of the piston assembly  10  with casing string  112 . The mandrill  24  is slidably received through the rearward end  16  of the piston body  12  by a longitudinal bore  28 . The mandrill  24  is positionable in a first forward position as shown in  FIG. 3  and in a second rearward position as shown in  FIG. 4 . The mandrill  24  is positioned in the first forward position during running in of the casing string  112  and then positioned in the second rearward position upon completion of running in the casing string. The mandrill  24  when positioned in the first forward position, as shown in  FIG. 3 , the first end  30  thereof is engaged with the adaptor sub  26  as shown. Preferably, the first end  30  of the mandrill  24  is threadably engaged with the adaptor sub  26 .  
         [0035]     The piston body  12  further defines at least one blind port hole  32  formed therethrough from an exterior surface  33  forward of the radial shoulder surface  18  to the longitudinal bore  28 , and at least one annulus port hole  34  formed therethrough from an exterior surface  35  rearward of the radial shoulder surface to the longitudinal bore. Preferably, four blind port holes  32  and four annulus port holes  34  are formed through the piston body  12  radially therearound and offset at 90 degrees. The blind port holes  32  and the annulus port holes  34  a restricted from fluidic communication when the mandrill  24  is in the first forward position, as shown in  FIG. 3 , and are in fluidic communication when the mandrill is in the second rearward position, as shown in  FIG. 4 .  
         [0036]     The piston assembly  10  further includes at least one projection  36  extending into the longitudinal bore  28  approximate the rearward end  16  of the piston body  12 . Preferably, there are two opposed projections  36 . Most preferably, there are four projections  36  spaced radially around the rearward end  16 . The projections  36  can be spaced radially around the rearward  16  at an offset of 90 degrees.  
         [0037]     A cooperating slot  38  formed longitudinally along the exterior surface  39  of the mandrill  24  receives each projection  36 . Each slot  38  is formed along the exterior surface  39  of the mandrill  24 , such that when the mandrill is in the first forward position, each projection  36  is free from engagement with the cooperating slot  38  and the mandrill is free to rotate about its axis within the longitudinal bore  28 . And such that when the mandrill  24  is in the second rearward position, each projection  36  is engaged with the cooperating slot  38  and the mandrill is rotationally locked with the piston body  12 .  
         [0038]     A piston body  12  further defines at least one longitudinal passage  40  or channel formed through the radial shoulder surface  18  from the annulus side or rearward side of the radial shoulder surface to the blind or forward side of the radial shoulder surface. A check valve  42  is fitted within each passage  40  and allows fluid to flow from the blind side of the radial shoulder surface to the annulus side of the radial shoulder surface when pressure within the intermediate casing on the annulus side is below a predetermined value.  
         [0039]     Additionally a plurality of O-ring seals  44  can be positioned along the longitudinal bore  28  to providing sealing between the mandrill  24  and the interior surface of the longitudinal bore.  
         [0040]     In use, it can now be understood, the piston assembly  10  is engaged or otherwise installed inline in the casing string  112  between the casing hanger from which the casing to be installed depends and the second to the last joint of casing string pipe required to land the liner hanger in its engineered well position.  
         [0041]     The casing string  112  with the engaged piston assembly  10  is inserted into the intermediate casing  110  using surface equipment well known in the art to a predetermined point. The casing string  112  can be inserted into the intermediate casing to the predetermined point through such methods as gravity feeding or floating, both well known in the art. While these two methods are mentioned, it should be appreciated that other methods can be used to insert the casing string  112 . During this process, fluid is free to flow from the blind side of the piston body  12  to the annulus side of the piston body through the passages  40 .  
         [0042]     Once the casing string  112  with the engaged piston assembly  10  is inserted to the predetermined point, the intermediate casing  110  above the radial shoulder surface  18  is pressurized with a fluid, such a drilling fluid. The intermediate casing  110  can be pressurized with drilling fluid through known techniques and equipment. One such technique that is possible is through the use of drilling fluid pump connected to a source of drilling fluid and to the wellhead through a kill line and other conventional equipment.  
         [0043]     The pressurization of the intermediate casing  110  creates a pressure differential across the piston assembly  10  and forces the piston assembly, which is engaged with the casing string  112 , to translate through the intermediate casing and into the wellbore  110 , thereby pressing production casing attached to the casing string  112  into the wellbore.  
         [0044]     Once the casing string  112  has reached a position within the intermediate casing  110  that facilitates landing of the production casing to the intermediate casing, the intermediate casing is depressurized. The pressure cross the piston assembly is then equalized by establishing the blind port holes  32  in fluidic communication with the annulus port holes  34  by moving the mandrill  24  from the first forward position to the second rearward position. Once pressure is equalized across the piston assembly  10 , the piston assembly is backed off from the installed production casing and withdrawn from the well  100  using known methods.  
         [0045]     A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.