Patent Publication Number: US-7721798-B2

Title: Wireline entry sub

Description:
FIELD OF THE INVENTION 
   The invention relates to an oil field tool for handling wireline and, in particular, a wireline entry sub. 
   BACKGROUND 
   Conventional oil field casing may be used as the drillstring for drilling oil and gas wells to simultaneously drill and case the wellbore. Once the wellbore is drilled to the desired depth, the casing is cemented into the earth without withdrawing it from the wellbore. A retrievable drilling assembly, including a bit and borehole enlarging tool, may be attached to the bottom end of the casing for drilling. This drilling assembly often includes other components such as mud motors, MWD collars, LWD collars, non-magnetic drill collars, steel drill collars, and stabilizers. 
   Once the casing is drilled to the desired casing setting depth, the drilling BHA is retrieved from the casing with a wireline before the casing is cemented in place. In some cases the BHA must be retrieved and replaced before the casing is drilled to its terminal depth, for example to replace a worn drill bit or to replace some other failed component in the BHA. A provision must be made for the wireline to be run through the casing to retrieve the BHA. It is often advantageous to circulate drilling fluid down the ID of the casing while the wireline is being run and the BHA recovered to assure that any influx of formation fluids is circulated out of the well in a controlled manner. It is also advantageous to reciprocate the casing while the BHA is being recovered so that the casing does not become stuck in the borehole. A top drive and a casing drive system may be used to support the casing to permit circulation and reciprocation of the casing. A top drive is often used to rotate the casing for drilling. The casing may be attached to the top drive with a casing drive system that grips the top of the casing without screwing into its upper threaded connection. The casing drive system also provides seals so that drilling fluid can be circulated down the inside diameter of the casing to flush cuttings away from the drill bit and up the annulus between the casing and the borehole wall. 
   The drilling rig used to drill with casing may be a specially designed rig that facilitates the efficient operation of the wireline for running and retrieving the drilling BHA. The rig also must be equipped with a wireline unit that is capable of handling the drilling BHAs. For rigs designed for casing drilling, this wireline unit may be provided as an integral part of the rig. 
   Access for the wireline is provided through the top of the swivel, which may be incorporated as an integral part of the top drive. The wireline access through the top of the swivel may be facilitated by utilizing a split crown block and split traveling block. Split blocks are ones where the sheaves used for carrying the drilling line are divided into two groups spaced laterally apart. The split crown arrangement allows a wireline sheave to be hung at the crown of the rig so the wireline can be aligned with the central axis of the drillstring. The split traveling block provides room for a wireline stripper assembly and wireline BOP to be attached to the top of the swivel to prevent the pressurized drilling fluid from escaping around the wireline as it is being run into and pulled from the casing. In some situations, it may be sufficient to provide only a split traveling block as the fleet angle from having the crown sheave offset slightly from the central axis of the drillstring. 
   The drilling BHA may be quite heavy and weigh as much as 30,000 pounds. A large braided cable, for example ¾″ in diameter, may be required to support this much weight and the sheaves used with such a cable are relatively large in diameter, for example 30″ in diameter. It is important that the sheaves and wireline pressure control equipment be positioned so that the wireline can enter the casing along its central axis. Otherwise, the cable will exert lateral forces on the casing or other equipment and will quickly cut into the equipment as it is run into and out of the well. In some situations, it may be advantageous to use a drilling rig that is designed specifically for drilling with casing when one is available. Often such a rig may not be available or only a portion of the well may be drilled with casing so that it may be more convenient to use a conventional rig. 
   There are only a few drilling rigs in the current fleet of rigs available for use in drilling oil and gas wells that are equipped as described above for using casing as the drillstring. It is possible to modify any drilling rig to include the facilities needed to easily handle the wireline when drilling with casing. Most conventional drilling rigs do not include split crown blocks and split traveling blocks to facilitate wireline access along the central axis of the drillstring. The time required to modify the rig to accommodate these parts and the capital cost of the modifications may not be justified when the rig is used to drill only a portion of a well with casing. Furthermore, the owner of the rig may not allow structural changes to be made to the rig. This is particularly true for expensive offshore rigs. 
   There are devices described in the prior art for providing wireline access to the ID of a drillstring. For example, U.S. Pat. No. 6,202,764 describes a wireline entry sub that can facilitate wireline use on a rig. Although such a wireline entry sub has been described, it is desirable that an improved sub be provided. 
   For example, in some cases, particularly for offshore rigs, the space for placing a wireline reel and tensioning unit near the drilling floor may be limited. Therefore, the wireline unit may be placed away from the rig floor. However, the wireline, which may be operating under a high-tension load, may be a hazard to rig personnel moving about the area. 
   SUMMARY 
   In accordance with a broad aspect of the present invention, there is provided a wireline entry sub, comprising: a body including an upper end, a lower end and a longitudinal, center axis therebetween, the body adapted for use with a wellbore string of tubulars; an opening on the body open a depth from a body outer surface to at least the longitudinal center axis; a wireline passage extending through the body from the opening to open adjacent the lower end; and a wireline pulling device on the sub body to apply pulling force to a wireline. 
   It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable for other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Although many different embodiments of the invention are possible, with reference to the figures as appropriate. It is understood that while the invention is described below in use with wireline (whether “slick line”, braided cable, electric line, etc.), the invention is not limited to use with wireline, rather other small diameter conduits such as coiled tubing may be used with it as well. 
       FIG. 1  is a side elevation view of one embodiment of a wireline entry assembly of the present invention in an operational setting with some internal components shown in phantom. 
       FIG. 2  is a sectional view through another wireline entry sub. 
       FIG. 3  is a sectional view along line II-II of  FIG. 2 . 
       FIG. 4  is a schematic sectional view through another wireline entry sub. 
       FIG. 5  is an enlarged view of one possible linear wireline puller useful in a wireline entry sub. 
       FIG. 6  is an enlarged view of a portion of the wireline entry sub of  FIG. 4  with the linear wireline puller of  FIG. 5  shown installed. 
   

   DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS 
   The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. 
     FIG. 1  shows a wireline entry assembly in an operational setting, including an entry sub  10  made up in a drill string  20  in conjunction with a top drive unit  30 . A wireline  40  passes from a storage reel  50 , through a traction head  82 , into entry sub  10  and, thereafter, downhole. While a top drive unit is shown, it is to be understood that the entry sub could be installed in communication with a drill string in other ways. For example, a wireline entry sub could be supported in a rig, such as by being supported from the hook of a rig. 
     FIGS. 2 and 3  show detailed views of entry sub  10 . Entry sub  10  has a generally elongated tubular central body including an upper end  60  and a lower end  70 . Upper end  60  has a bore  60   a  therethrough and lower end  70  has a bore  70   a  therethrough. Fluid passage  75  extends to fluidly connect upper end bore  60   a  and lower end bore  70   a . A flow-through fluid path therefore exists through the entire length of entry sub  10 , which permits fluid circulation down through the entry sub and the drill string using the existing rig pumping equipment. In this embodiment, fluid passage  75  extends through the sub body about opening  15  (see  FIGS. 2 and 3 ) to connect upper end bore  60   a  and lower end bore  70   a . Thus, the flow-through fluid path is maintained about the opening to permit fluid circulation down through the entry sub. 
   Upper and lower ends  60 ,  70  are adapted to connect into drill string  20  directly or indirectly below top drive  30 , one example of which is shown in  FIG. 1 . As such, in one embodiment ends  60 ,  70  may be formed as threaded connections to permit in-line threaded connection to drill string  20 . Alternately, end  60  may have an inside or an outside diameter formed to be gripped by, or attach to, a tubular gripping device, such as by a casing gripping tool available from Tesco Corporation. In another embodiment, lower end  70  may be formed to grip drill string  20  in any of various ways. Alternately, another gripping device, such as for example, an elevator, may be employed between the entry sub and the drill string to support the drill string at the lower end of the entry sub. However, it is to be understood that various forms of connection may be employed. 
   Upper and lower ends  60 ,  70  may have a common center axis Xs that is not angled or displaced from the center axis Xd of drill string  20 , but instead is substantially coincident therewith, as shown for example in  FIG. 1 . When entry sub  10  is made up in drill string  20  and engaged by a top drive, the entirety of drill string  20  may be lifted by raising the top drive unit  30  with the rig drawworks. Accordingly, entry sub  10  is made of materials and has dimensions sufficient to give entry sub  10  sufficient tensile strength to lift drill string  20 . By way of example only, entry sub  10  may be made of high strength carbon steel, stainless steel, or other similar materials. The “straight-line” aspect of the tool, that is, the center or lift axis of entry sub  10  being substantially coincident with the center axis of drill string  20 , results in no undesirable bending moment or canting when drill string  20  is lifted with entry sub  10  in place. 
   Entry sub  10  has an opening  15  formed between upper and lower ends  60  and  70 . Opening  15  extends a depth into the sub at least ½ the sub&#39;s outer diameter so that opening  15  is open to the sub center axis Xs. Opening  15  may take various forms. For example, in one embodiment an intermediate body portion of the sub is formed as a hollow tube such that opening may be defined as the entire hollow space within the tube. A wireline entry port  76  may be formed in the opening to provide access to a passage  76   a  through which the wireline may extend through the entry sub toward its lower end. In the illustrated embodiment, entry port  76  is formed as a hole in the base of opening  15 . In another embodiment, the port may be an enlarged opening through the end of the entry sub through which wireline may pass before entering a smaller port on a component such as a pack off or blow out preventer connected adjacent the lower end of or below the entry sub. Passage  76   a  in the illustrated embodiment opens into fluid passage  75  or bore  70   a  of the lower end. A seal assembly  78  may be mounted in port  76  to seal about wireline passage therethrough into bore  70   a  of lower end  70 , and thence into the bore of drill string  20  leading downhole. Bore  70   a  and the aperture through seal assembly  78  may be substantially concentric with the center axis Xs of sub  10  and of drill string  20 . 
   Traction head  82  is connected to entry sub  10  in association with opening  15 . Traction head  82  includes one or more traction generating members such as a driven sheave  83  for generating a pull force on the wireline. In the illustrated embodiment, traction head  82  includes a driven sheave  83  and an idler sheave  84 . The idler sheave may also be driven, if desired. 
   In the one embodiment, traction head  82  may be connected to entry sub  10  via a bracket  86 . Wireline  40  passes through traction head  82 , through seal assembly  78  and through lower end  70  before passing downhole. Traction head  82  is positioned and/or configured such that wireline  40  roved through it comes off adjacent seal assembly  78  and may be substantially aligned with the center axis of both lower end  70  and drill string  20 . Wireline  40  may therefore enter seal assembly  78  in a “straight line” position with respect to the center axis of drill string  20 , as readily seen in the Figures. 
   Traction head  82  may be driven in various ways, as by use of motors mounted on the entry sub or spaced therefrom but in communication with the traction head. However, if a top drive is available in the rig, it may be worth considering that a top drive  30  often cannot be used to rotate the drill string while wireline operations are in progress because rotating the drill string with the wireline inside it might damage the wireline and it has been determined that the power rating of the top drive may be approximately the same as that needed to drive a wireline driven sheave. Thus, the sub may include a drive mechanism for the traction head that is connectable for drive communication to top drive  30 . The drive mechanism may include for example a drive shaft  90  connectable at one end to receive rotational drive from the quill  31  of top drive  30 . At an opposite end, drive shaft  90  includes a connection to a drive mechanism of traction head  82 . As such, the rotational power of the top drive can be used to directly power traction head  82  on the entry sub. Thus, traction head  82  can exert the required pulling force to trip the wireline through drill string  20 , but the high-tension wireline is contained in a small, relatively low risk area between driven sheave  83  and seal assembly  78 , which are mounted close and possibly directly adjacent each other on the entry sub itself. Storage reel  50  is used to roll up the wireline, but it can be positioned safely and conveniently almost anywhere on the rig with any tension in the wireline adjacent the storage reel being significantly less than that tension in the wireline extending between the seal assembly and the driven sheave. In addition, storage reel  50  could be substantially smaller than a reel intended also to develop wireline pulling capacity. Storage reel  50  may be positioned on the rig floor, as shown, if there is adequate space for it. Alternately, the storage reel may be positioned elsewhere with possibly an intermediate sheave between traction head  82  and storage reel  50  to appropriately direct the wireline. Storage reel  50  may require a small power unit to pick up the slack created by traction head during wireline retrieval from downhole. 
   Drive shaft  90  may take various forms to act to transmit the top drive power to drive the traction head. In one embodiment, for example, drive shaft  90  includes a ring gear attached to the driven sheave and formed to engage a pinion gear on the top drive shaft. In another embodiment, the drive shaft may be connected to the top drive shaft and may be formed to operate a hydraulic motor for the driven sheave. These drive arrangements convert the rotation of the top drive shaft to rotation of a drive shaft of the traction head. The drive mechanism of the wireline sub may also operate to reduce the rotational speed of the top drive output shaft relative to the driven sheave. 
   A swivel bearing  94  may be connected between upper end  60  and quill  31  to permit the quill and drive shaft  90  to rotate without imparting rotation to the sub itself so that the sub may remain rotationally stationary while the drive shaft is driven therein. A connection  95  may be provided between entry sub  10  and a non-rotating portion of top drive  30 , if desired, to further stabilize the entry sub. 
   In a typical use, entry sub  10  is positioned in the rig above drill string  20  by any of various means. In the illustrated embodiment, entry sub  10  is connected below top drive  30  as by threading, gripping, etc. and above drill string by threading, gripping, spears, packers, seals etc. Thereafter, wireline  40  from reel  50  is roved about traction head  82 , through seal assembly  78 , and out through lower end  70 . Wireline tools may then be connected to wireline  40  and lowered into drill string  20 . Once the drill string, entry sub  10  and top drive  30  are connected, the top drive may be driven to rotate drive shaft  90  to drive traction head  82 . Wireline entry sub  10  and head  82  thereby feeds wireline in or out of the well as desired to position tools at a desired downhole depth or to retrieve tools from the hole. All or substantially all rigging of the wireline sub and wireline tools may be done from the relative safety of the rig floor. Control of the head may be achieved through the top drive controls such that a separate wireline control panel need not be provided, if desired. 
   Lift forces on drill string  20  with entry sub  10  in place are axial. For example, with entry sub  10  of the present invention, the lift axis of the entry sub is substantially coincident with the center axis of the drill string, and no torque or bending moments are transferred to drill string  20  upon lifting drill string  20  with entry sub  10  in place. 
   A positive flow control valve (commonly known in the industry as a “TIW” valve) may be placed in drill string  20  below entry sub  10 , to permit pressure isolation of drill string  20  while entry sub  10  along with wireline and wireline tools are rigged up. 
   In certain operational situations where wireline operations are conducted under high pressure a wireline blow out preventer assembly  96  may be employed in lower end  70  or may be positioned in a sub below sub  10 , in addition to or alternately from seal assembly  78 . 
   Referring to  FIGS. 4-6 , another embodiment is shown including another wireline fraction arrangement on a wireline entry sub  110 . Entry sub  110  has a generally elongate central body comprising an upper end  160  and a lower end  170 . Upper end  160  has a bore therethrough and lower end  170  has a bore  170   a  therethrough. In this embodiment, a fluid bypass  175  extends to fluidly connect the upper end bore and lower end bore  170   a . Fluid bypass  175  is formed through a tube  175   a  extending alongside the sub body and connected to ports  175   b  through the sub body. Fluid bypass  175  provides for fluid circulation down though the entry sub and the drill string using the existing rig pumping equipment, but avoids the need to bore a passage about the opening area, which may weaken the body at that point. In one embodiment, an external line such as tube  175   a  may extend beyond the lower end to a component connected therebelow such that fluid bypasses lower end  170  altogether. 
   Upper end  160  is adapted to connect directly or indirectly to top drive  30  and lower end  170  is formed to support one or more tubulars  120  connected therebelow. As such, ends  160 ,  170  may be formed as threaded connections to permit in-line threaded connection to a drill string. However, it is to be understood that other forms of connection may be employed. 
   Entry sub  110  has an opening  115  formed between upper and lower ends  160  and  170 . Opening  115  extends a depth into the sub at least ½ the sub&#39;s central body outer diameter so that opening  115  is open to the sub center axis Xs. A wireline entry port  176  is formed in the base of opening  115  and extends along center axis Xs to open into bore  170   a  of the lower end. 
   In this embodiment, a sheave  182  is mounted in association with opening  115  to accept and guide wireline  40  between a supply reel (not shown) and through entry port  176 . Sheave  183  is positioned such that wireline  40  may come off substantially aligned with the center axis of both lower end  170  and the tubulars  20  connected therebelow to pass through sub  110  and downhole in a “straight line”. 
   Also in this illustrated embodiment, wireline pulling force is applied by a linear wireline puller  185  mounted in entry port  176 . Wireline puller  185  may be embodied in various ways. In one embodiment, for example, wireline puller  185  includes a pair of facing drive chains  186  or conveyors that are biased together to engage and drive wireline  40  therebetween. Although various mechanisms are possible, in one embodiment, continuous drive chains  186  are driven on gears  187  such that rotation in direction y drives wireline movement in direction z. Pressure plates  188  may bias, as by hydraulic force arrows H, the chains together. The chains may include an elastomeric contact surface to reduce or eliminate any crushing damage to the wireline and to create a high friction coefficient against the wireline, if desired, to enhance grip of the wireline. 
   Linear wireline puller  185  may be connected to a drive mechanism  189  for conveying power from top drive  30  or from another source such as a hydraulic or electric motor. The drive mechanism may include for example gear mechanisms, hydraulic pump/motor systems, as previously described or various other means. 
   In this embodiment, linear wire puller  185 , when driven to operate, can exert the required pulling force to trip the wireline through tubulars  20 , but the high-tension wireline is contained within the body of entry sub. This provides an extra measure of safety even over the embodiment of  FIGS. 1 ,  2  and  3 . 
   Wireline entry port  176  may include a wireline blow out preventer assembly  196 , wireline cleaner  197  or other devices, as desired. Alternately, these or other components may be positioned in subs connected below sub  110 . 
   If desired to facilitate handling, a wireline entry sub may include a transportation skid  198 , as is shown in  FIG. 3 . 
   Of course the embodiments shown and described herein can be modified in various ways. For example, various approaches may be taken to install the entry sub in a rig, to permit fluid conveyance through or about the entry sub as by internal or external fluid passages, or by introduction of fluid to a lower end of the sub or therebelow. As another example, other wireline pulling mechanisms or top drive-connectable drive mechanisms could be used. 
   The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are know or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 USC 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or “step for”.