US20060102337A1

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Publication number: US20060102337A1
Application number: US11/273,455
Authority: US
Inventors: Gregory Elliott; Leianne Sanclemente; Richard Robichaux
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-11-12
Filing date: 2005-11-14
Publication date: 2006-05-18
Also published as: US7909106B2; US20080230217A1

Abstract

A tubular handling system includes a slip apparatus, a high capacity landing string and high capacity elevator bushings.

Description

CROSS REFERENCES TO RELATED APPLICATIONS

The present non-provisional patent application claims the benefit of U. S. Provisional Patent Application No. 60/627,341 filed Nov. 12, 2004.

STATEMENTS AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

NONE

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for landing heavy loads including, but not necessarily limited to, casing and other tubular goods in oil and gas wells.

2. Brief Description of the Prior Art

Standard rotary drilling rigs are typically comprised of a supportive rig floor, a substantially vertical derrick extending above said rig floor, and a traveling block or other hoisting mechanism having a set of elevators which can be raised and lowered within said derrick. In most cases, such derrick is situated above a well-bore to be drilled or serviced. During drilling or servicing operations, such rig equipment is often used to manipulate tubular goods, such as pipe, in and out of a well-bore.

Drill bits and other equipment used in connection with the drilling, servicing and/or equipping of wells are typically conveyed into and out of such wells on tubular pipe known as “drill pipe” or “drill string.” Further, once a well has been drilled to a desired depth, large diameter pipe called casing is frequently installed in the well and cemented in place. Such casing is typically installed to provide structural integrity to the well-bore and keep geologic formations isolated from one another.

Casing, drill pipe or other similar tubular goods are all typically introduced into a well in essentially the same manner; such pipe is inserted into a well in a number of different sections of roughly equal length. Single sections of pipe called “joints,” or groupings of joints commonly referred to as “stands,” are typically screwed together or otherwise joined end-to-end at the rig in order to form a substantially continuous “string” of pipe that reaches downward into the earth's surface. As the bottom or distal end of the pipe string penetrates further into a well, additional sections of pipe are added to the ever lengthening pipe string at the rig. Conversely, when pipe is being removed from a well-bore, the pipe string is pulled from the well and joints (or stands, as the case may be) are unscrewed in the rig derrick until all of the pipe has been retrieved from said well.

The specific process of inserting a string of pipe in a well is typically commenced by grasping a first section of pipe within elevators which are in turn attached to a traveling block or other hoisting mechanism operable within a rig derrick. The first section of pipe is lowered into a well-bore via such elevators, and thereafter suspended or hung in place at the rig floor using a device commonly known as “slips.” Once the slips have been set, and the section of pipe is secured in place at the rig floor, the elevators can be unlatched from said section of pipe.

Prior art slips generally have curved inner surfaces that correspond to the outer surface of pipe to be held within such slips. Teeth-like grippers known as “dies” are typically disposed along the inner face of such prior art slips. The outer surface of prior art slips is typically tapered so that it corresponds with a tapered inner face, or “bowl”, installed within a master bushing at the rig floor. Such slips fit within said bowl, and essentially wrap around or surround a portion of the outer surface of the pipe being gripped.

After a first section of pipe has been inserted into a well-bore and suspended by a set of slips, the uppermost end of said first section of pipe is generally situated a few feet above the rig floor. Thereafter, a second section of pipe is latched within the elevators attached to the traveling block, lifted within the drilling rig derrick and suspended vertically from the elevators. In this position, said second section of pipe is generally in linear alignment above the first section of pipe which was previously run into the well. The lower end of said second section is then connected to the upper end of said first section. Once connected, the two sections of pipe are thereafter lowered further into the well via the elevators attached to the traveling block. After the second section of pipe has been lowered to a desired level, said second section of pipe is then hung in place using the slips. Once the pipe is suspended in place using the slips, the elevators are unlatched and the process is repeated with successive sections of pipe until the desired length of pipe has been inserted in the well-bore.

It is the custom of the oil and gas industry to utilize threaded connections to connect sections of pipe together. It is further the custom in the oil and gas industry to insert sections of pipe into a well-bore so that male or “pin”-end threaded connections face downward, while female or “box”-end connections face upward. Thus, when individual joints of pipe are added to a string of pipe in a well in the manner described above, the pin-end of the upper joint of pipe (which is suspended from elevators within a derrick) is typically “stabbed” into the box-end of the lower joint (which was previously inserted and suspended in the well-bore). The upper joint is then rotated so that the mating threads of the two joints join together.

When running casing, individual sections of casing are inserted into a well-bore in this manner until the desired amount of casing has been joined together. After the final section of casing has been added, the entire column of casing, commonly referred to as a “casing string,” must typically be conveyed into a desired position within the well-bore. This process of lowering a casing string to its desired location within a well-bore, also known as “landing” the casing, is frequently accomplished using specialized drill pipe commonly referred to as a “landing string.” Landing of casing is accomplished by adding successive joints of landing string at the surface until the casing string is conveyed to a desired depth within the well-bore. Thereafter, the casing string can be cemented or otherwise secured in place, and the landing string can be removed from the well.

During the process of running a landing string into a well-bore, the inside surface of prior art slips presses against and “grips” the outer surface of the landing string. The tapered outer surface of the slips, in combination with the corresponding tapered inner face of a “bowl” in which the slips are received, cause the slips to tighten around the gripped pipe. In effect, the slips wedge between the bowl (which is itself received within a master bushing at the rig floor) and the pipe, thereby allowing the pipe to be suspended in place. As such, the greater the load being conveyed by the landing string, the greater the gripping force of the slips acting on such landing string. Accordingly, the weight of the casing string, and the weight of the landing string being used to “land” the casing string, impacts the gripping force applied by the slips. Put another way, the greater the weight of the pipe in the well, the greater the gripping force and crushing effect generated by prior art slips.

As the world's supply of easily accessible oil and gas reserves is depleted, a significant amount of oil and gas exploration has shifted to more challenging and difficult-to-reach environments, such as deep-water drilling locations. For many reasons, casing strings required for such deep water wells must be unusually long and strong. Such casing frequently has unusually thick walls, which results in such casing strings being relatively heavy. As a result, landing strings needed to land such casing strings must also be unusually long and strong and, therefore, unusually heavy in comparison to landing strings required in more typical wells.

Prior art landing string systems cannot effectively and consistently support the combined landing string and casing string weight associated with deep water wells due to the heavy weights of such pipe. Use of conventional prior art slips to support the combined weight of landing strings and casing strings have resulted in serious problems caused by tremendous gripping (collapse) force generated by such conventional slips. In some cases, the landing string can be excessively scored due to the teeth-like dies on the inside surface of the slips being pressed too deeply into outer surface of the landing string. In severe cases, the landing string has actually been crushed or otherwise deformed and thereby rendered unuseable. In some cases, the prior art slips themselves have experienced damage rendering them inoperable.

Thus, there is a need for a high capacity landing string system that can be used to convey heavy weight pipe, such as casing, into well-bores where the capacity of conventional landing strings, elevators and/or slips is insufficient to support the increased load of such heavy weight pipe. The components of such landing string system should be easily utilized on existing rigs, and should be compatible with existing pipe handling tools common to drilling rigs.

SUMMARY OF THE PRESENT INVENTION

The present invention pertains to a high capacity conventional landing string system that is capable of handling and conveying loads up to and in excess of 1,000 tons (2,000,000 lbs). In the preferred embodiment, the system of the present invention comprises three cooperating elements: (1) a high capacity landing string; (2) high capacity slips and accompanying bowl; and (3) high capacity elevator bushings. It is to be observed that, while the present invention references elevator bushings, certain elevators operate without such bushings. Thus, the discussion of elevator bushings set forth herein could easily also extend to other types of elevators that do not utilize bushings and is not intended to limit the scope of this invention.

High Capacity Landing String:

The high capacity landing string of the present invention comprises a plurality of pipe joints. The joints of said high capacity landing string have a threaded connection disposed at each end; in the preferred embodiment, one end of each joint has a box-end connection, while the other end of joint has a pin-end connection. Although such connections can incorporate any number of different thread configurations, in most cases such connections utilize existing thread configurations, such as widely accepted “FH” threads.

Immediately adjacent to the box-end connection of each joint is a length of thick-walled pipe. Although such thick-walled pipe can span the entire length of each joint (that is, from the box-end connection to the pin-end connection), in the preferred embodiment said length of thick-walled pipe extends approximately six (6) feet from the base of the box-end connection, that being the area in which slips typically come in contact with the outer surface of each joint of the landing string when it is being hung or suspended in the well using such slips. In the preferred embodiment, the remainder of each joint (that is, the portion extending from the end of said section of thick-walled pipe to the pin-end of the joint) comprises a tube body having a thinner wall than said thick-walled section.

As with conventional drill pipe and landing strings, the threaded connections of the high capacity landing string of the present invention have a larger outer diameter than the outer diameter of the adjacent tube body (both thick-wall and thin-wall portions) that extends between such connections. As such, a tapered section transitions from each connection to the tube body near such connection. On conventional prior art drill pipe and landing strings, the angle of such tapered sections are approximately 18 degrees near the box-end connection and 35 degrees near the pin-end connection. The high capacity landing string of the present invention comprises individual joints having a box-end taper (that is, a tapered transition between the box end connection and the tube body) having an angle greater than 18 degrees, but less than 90 degrees. In the preferred embodiment of the present invention, the taper angle of such box-end tapered section is about 45 degrees.

As set forth above, it is the custom in the oil and gas industry to insert sections of pipe into a wellbore so that male or pin-end connections face downward. As such, in most cases, the tapered section between a box-end connection and a tube body will act as a load-supporting shoulder when tubulars are being lowered into, or lifted out of, a wellbore via elevators as understood by those of ordinary skill in the art. It should be noted that the angle of the tapered transition section between the pin-end connection and the tube body typically does not act as a load-supporting shoulder, in elevators or otherwise, due to the customary orientation of the pipe. However, in the event that pipe is inserted into a well so that the pin-end connections face upward, then the taper angle of this tapered section would be a significant load-bearing shoulder and should be greater than 18 degrees but less than 90 degrees.

The dimensions, types and/or grades of material used to comprise the high capacity landing string of the present invention are ideally selected for desired strength characteristics. Such dimensions, types and/or grades can be tailored to meet particular applications or conditions to be encountered. Although the high capacity landing string can be constructed with any number of different dimensions, types and/or grades of material, in the preferred embodiment:

the tube body has an outer diameter of 6.625″, and is constructed from V-150 material and has a wall thickness of 0.9375″;
the thick-walled section of each joint is constructed from S-135 material and has a wall thickness of 1.7″; and
the pin-end and box-end connections are constructed of 120 KSI material and incorporate “FH” threads.
It is to be noted that a landing string having these characteristics can be used with conventional slips and elevators, offering time savings and versatility for rig operations.
High Capacity Slip Apparatus and Accompanying Bowl:

Compared to conventional slips, the high capacity slip apparatus of the present invention distributes loads more evenly over the full extent of said slip apparatus. In the preferred embodiment, the high capacity slip apparatus of the present invention comprises some combination of the following components: a larger slip body taper compared to conventional slips, longer length compared to conventional slips and insert dies that contact more of a pipe's external surface than conventional slips. Such changes improve the distribution of axial and transverse loading across the slip apparatus.

Additionally, in accordance with the preferred embodiment of the present invention, a split master bushing is installed within a rig floor. A continuous bowl insert having a tapered inner surface is received within said split master bushing. If desired, a ledge or “stop” can be disposed at the base of the bowl to further support the high capacity slip apparatus of the present invention and any associated pipe load. The high capacity slip apparatus of the present invention can be manually operated or, if desired, actuated using a hydraulic or pneumatic power source.

The high capacity slip apparatus of the present invention comprises a plurality of cooperating slip segments. In the preferred embodiment, said slip apparatus comprises a first slip segment having a first arcuate inner face and an outer face; a second slip segment connected to the first slip segment, wherein said second slip segment has an arcuate inner face and an outer face; and a third segment slip having an arcuate inner face and outer face. The inner faces of said first, second and third slip segments each have at least one longitudinally disposed slot and at least one ledge oriented substantially perpendicular to said slot.

The apparatus further comprises means for attaching the first slip segment with the second slip segment, and the second slip segment with the third slip segment, so that inner face of the first, second, and third slip segments can engage a first tubular member. In the preferred embodiment, such means for attaching said slip segments are hinges, wherein said hinges are located to minimize space existing between said slip segments when the high capacity slip apparatus of the present invention is engaged against a section of pipe.

A plurality of insert dies are included, wherein said dies each have shoulders that are configured to fit within the ledges of said slip segments. Said shoulders act to transfer a load from the such insert dies to a corresponding ledge. In one embodiment, said insert dies are constructed of a 8620 steel, 1018 steel, or a low carbon alloy steel material. The present invention utilizes insert dies having directional teeth.

In a preferred embodiment, a continuous bowl insert is received within a split master bushing which is in turn disposed within a rig floor. Said continuous bowl insert has an inner portion having a taper of greater than 11 degrees. The high capacity slip apparatus of the present invention contains an outer portion configured to fit into the inner portion of said bowl, with said outer portion of said slip apparatus having a taper complementary of the bowl's inner taper. In one preferred embodiment, the inner taper of said bowl insert, as well as the complementary outer surface of the slip apparatus, is in the range between 11 degrees and 15 degrees.

Transverse forces that allow slips to grip a section of pipe and hold it in place are the same forces that can act to crush such pipe. An advantage of the present invention is the ability to support an axial load without generating excessive transverse loading that can result in crushing of the tubular being gripped at the rotary table.

It is to be observed that while rotary slips are discussed in detail herein, the invention is applicable to other slips including, but not necessarily limited to, drill collar slips, casing slips and conductor slips.

High Capacity Elevator Bushings:

The present invention comprises at least one bushing that can be installed within conventional elevators used on drilling rigs. Said at least one bushing defines a tapered internal load support shoulder, wherein the taper angle of said load support shoulder is greater than 18 degrees and less than 90 degrees, and designed to complement the load shoulder of the high capacity landing string of the present invention which, in most applications, will be the box-end taper of such landing string. Prior art drill pipe, landing string elevators and elevator bushings have an 18 degree taper angle at the load support shoulder; such angle matches the taper angle on conventional drill pipe and landing strings. Further, unlike conventional elevator bushings that have support shoulders disposed within the body of such elevator bushings, the tapered support shoulder of the elevator bushing of the present invention is situated near the top of said bushing. The increased taper angle of such support shoulder, and the placement of such shoulder, reduces spreading forces on the elevator doors and the stresses at the bottom of the elevator body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic view of a string of tubular goods being lowered into a well from a floating platform in accordance with the present invention.

FIG. 2 is a schematic view of the high capacity slip apparatus, continuous bowl insert and split master bushing of the present invention.

FIG. 3 is a side cross-sectional view of the high capacity landing string of the present invention.

FIG. 4 is a perspective view of the high capacity rotary slip apparatus of the present invention.

FIG. 5 is a cross-sectional view of the slip apparatus taken from line A-A ofFIG. 4.

FIG. 6 is a side sectional view of a slip segment of the slip apparatus of the present invention, without inserts.

FIG. 7 is a partial cross-sectional view of the slip apparatus embodiment shown inFIG. 6 engaging a tubular member.

FIG. 8 is a partial cross-sectional view of the slip embodiment shown inFIGS. 6 and 7 engaging a tubular member within a continuous slip bowl of the present invention.

FIG. 9 is an overhead view of the elevator bushings of the present invention.

FIG. 10 is a side cross-sectional view of the elevator bushings of the present invention taken along line A-A ofFIG. 9.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 depicts a schematic view of a floatingplatform100 lowering atubular string101 into a well102 in accordance with the present invention.Tubular string101, in one preferred embodiment, will be a casing string, and floatingplatform100 will be equipped with a drilling rig including vertically extendingderrick103. Said drilling rig in general, and said derrick in particular, will further include a hoisting system that includes travelingblock104 andelevators105.Sub-sea tree106 is positioned on the sea floor, and amarine riser107 extends from saidsub-sea tree106 to floatingplatform100. Rig floor110 provides a work surface belowderrick103. Master bushing111, which is disposed within rig floor110, provides access fromrig floor110 tomarine riser107 and, ultimately, well102.

Casing string

101 is inserted into well102 by installing said casing string, one section at a time, in the manner previously described herein and as understood by those having ordinary skill in the art. Said casing is inserted through an opening in master bushing111, throughmarine riser107 andsubsea tree106, and ultimately intowell102. Once a desired length of casing has been inserted, casing hanger108 is connected tocasing string101. Casing hanger108 is a device that serves to anchor a casing string, such ascasing sting101, within a sub-sea tree; such casing hangers are well known in the art and are commercially available from a variety of sources including Vetco Gray, Inc. and Cooper Cameron Inc.

Landingstring109 is attached to casing hanger108. As noted earlier, landingstring109 consists of a plurality of individual sections of pipe that are used to convey a casing string into proper position in a well bore. Landing string will be threadedly connected, as previously described, to conveycasing string101 into well102 until casing hanger108 is landed intosub-sea well head106. In this manner,tubular string101 can be safely lowered to a predetermined depth withinwell102.

FIG. 2 depicts a schematic view of the high capacity slip apparatus, continuous bowl insert and split master bushing of the present invention.Slip apparatus2 comprises a plurality of cooperating

slip segments

20,21 and22 which are described in greater detail below. Said

slip segments

20,21 and22 are hingedly connected; as such,slip apparatus2 can be closed around the outer surface of a tubular member, such as drill pipe, landing string or the like. When closed around such pipe, said slip apparatus can be inserted withincontinuous bowl insert200. Although not shown inFIG. 2, the outer surface ofslip apparatus2 is tapered; said

slip segments

20,21 and22 are wider at the top, and narrower at the bottom.

Saidbowl insert200 is tapered, such thattop201 ofbowl insert200 has a larger inner and outer diameter thanbottom202 ofbowl insert200. Saidbowl insert200 beneficially has a continuous inner surface, such that it does not have any lateral openings, “splits” or gaps, which improves the overall strength characteristics of such bowl. Bowl insert200 is in turn received within split master bushing111, which is mounted within the rig floor of a drilling rig; split master bushing has alateral split112 that permits said split master bushing111 to be installed within a rig floor, such asrig floor110 depicted inFIG. 1.Bowl insert200 and split master bushing111 have aligned central bores that provide access to a marine riser (such asmarine riser107 inFIG. 1) and, ultimately, a well (such as well102 inFIG. 1).

Referring toFIG. 3, the high capacity landing string of the present invention comprises a plurality of pipe joints, such as landing string joint300, having threaded connections. (Landing string joint300 is one continuous length of pipe, but is broken into sections for clarity of illustration inFIG. 3). Landing string joint300 has a threaded connection disposed at each end; female box-end connection301 is disposed at one end of joint300, while male pin-end connection302 is disposed at the opposite end of joint300. Although such connections can incorporate any number of different thread configurations, in the preferred embodiment box-end connection301 has internal “FH”female threads303, while pin-end connection302 has external male “FH”threads304.

Immediately adjacent to box-end connection301 is a length of thick-walled tube section305. Although such thick-walled tube section305 can span the entire length of each joint300 (that is, from box-end connection301 to pin-end connection302), in the preferred embodiment said thick-walled tube section305 extends approximately 6 feet from the base of box-end connection301, that being the area in which slips typically come in contact with the outer surface of landing string joint300. The location of any associated welds are away from areas which come in immediate contact with slips and elevators. In the preferred embodiment, the remainder of each joint (that is, from the end of said section of thick-walled pipe to the pin end of the joint) comprisestube section306 having a relatively thinner wall than said thick-walled section305. By limiting the amount of thick-walled section305 to only that portion of joint300 which will come in contact with slips, the weight of landing string joint300 is reduced.

As with conventional drill pipe and landing strings, threaded box-end connection301 and pin-end connection302 of the high capacity landing string of the present invention have a larger outer diameter than the outer diameter of the

adjacent tube sections

305 and306 that extend between such connections. Thus, taperedsection307 transitions from box-end connection301 to thick-walled tube section305 on one end of joint300, while taperedsection308 transitions from pin-end connection302 totube section306 at the opposite end of joint300.

Conventional prior art drill pipe and landing strings have threaded connections, also commonly referred to as “tool joints”, having larger outer diameters than the outer diameter of the tube section extending between such connections. As such, conventional prior art drill pipe and landing strings have tapered sections that transition from such connections to the adjacent tube section situated between such connections. The taper angle of such tapered sections are typically approximately 18 degrees at the box-end and 35 degrees at the pin-end on conventional drill pipe and landing string joints.

The high capacity landing string of the present invention includes taperedsection307 which transitions from the larger outer diameter of box-end connection301 to the relatively smaller outside diameter of thick-walled tube section305. The taper angle oftapered section307, as shown by angle “A” inFIG. 3, will be in the range between 18 degrees and 90 degrees. In the preferred embodiment, the angle oftapered section307 is approximately 45 degrees.

The dimensions of the high capacity landing string, as well as the types and/or grades of material used for the high capacity landing string of the present invention, are ideally selected for desired strength characteristics. Such dimensions, types and/or grades can be tailored to meet particular applications or conditions to be encountered. Although such high capacity landing string can be constructed with any number of different dimensions, types and/or grades of material, in the preferred embodiment:

tube section306 has an outer diameter equal to 6.625″, is constructed from V-150 material and has a wall thickness of 0.9375″;
thick-walled tube section305 is constructed from S-135 material and has a wall thickness of 1.7″; and
box-end connection301 and pin-end connection302 are constructed of 120 KSI material, whilethreads303 and304 are standard “FH” threads.
It is to be observed that a landing string having these characteristics can be used with conventional slips and elevators offering time savings and versatility for rig operations.

FIG. 4 is a perspective view of the assembled rotary slip apparatus of the present invention.Rotary slip apparatus2 includesfirst slip segment20, with saidfirst slip segment20 having a generally arcuateinner face6 and a generally arcuateouter face8.Slip segment20 has atop end10 and abottom end12. As seen inFIG. 4, the slip segment's profile is generally in a wedge shaped contour with theouter face8 being tapered tobottom end12.

Slip segment

20 contains ahandle member14, with thehandle member14 being connected to slipsegment20 with conventional means such as pins and cotters. Attachment means for attachingslip segment20 withslip segment21 includes theslip segment20 containing a pair ofprojections16a,16bthat have openings therein for placement of ahinge assembly18 for connection with thesecond slip segment21.

The outer face and inner face of

slip segments

20,21 and22 are connected by a series of ribs. Each slip segment may be formed as a single wedge block. However, such construction can makeslip apparatus2 very heavy. By incorporating a series of ribs (seen generally at70),rotary slip apparatus2 of the present invention is generally lighter, but retains the necessary strength and integrity for use in gripping and retaining tubular members, as will be understood by those of ordinary skill in the art.

Slip segment

21 also contains a generally arcuateinner face23 and a generally arcuateouter face24.Slip segment21 has atop end26 and abottom end28. As noted earlier, said slip segment's profile is generally in a wedge-shaped contour with theouter face24 being tapered to thebottom end28.

Slip segment

21 contains ahandle member30, with thehandle member30 also being connected to saidslip segment21 with conventional means such as pins and cotters.Slip segment21 also includes a pair ofprojections32a,32bthat have openings therein for placement ofhinge assembly18 for connection withfirst slip segment4.Second slip segment21 also contains second attachment means for attaching tothird slip segment22 which includes a second pair ofprojections34a,34bthat also have openings therein for placement ofhinge assembly36 for connection withthird slip segment22.

Third slip segment

22 also contains a generally arcuateinner face40 and a generally arcuateouter face42.Slip segment22 has atop end44 and abottom end46. The slip segment's profile is also a wedge-shaped contour with theouter face42 being tapered to thebottom end46.

Third slip segment

22 containshandle member48, with saidhandle member48 also being connected tothird slip segment22 with conventional means such as pins and cotters.Third slip segment22 also contains a pair of

projections

50a,50bthat have openings therein for placement ofhinge assembly36 for attachment withsecond slip segment21.Inner face40 ofslip segment22 will have disposed therein insert die members that will be described in greater detail later in the application.

Insert dies90, having a plurality of teeth-like projections122, are disposed along theinner face6 ofslip segment20,inner face23 ofslip segment21 andinner face40 ofslip segment22. Said insert dies have generally arcuate faces which have similar curvature as said

inner faces

6,23 and40. Although the length of

slip segments

20,21 and22 can be varied for particular applications, in the preferred embodiment of the present invention said slip segments are about20 inches in length.

FIG. 5 depicts a cross-sectional view ofslip apparatus2 without inserts taken from line A-A ofFIG. 4. It should be noted that like numbers appearing in the various figures refer to like components. Thus, there is shownfirst slip segment20 withinner face6, and further,inner face6 having a longitudinally disposedslot54.Slot54 will cooperate with and retain insert diemembers90.FIG. 5 also showsrib70 connectinginner face6 with theouter face8, as previously noted.First slip segment20 is attached tosecond slip segment21 viahinge assembly18 through the projections16aoffirst slip segment20 and theprojections32aofsecond slip segment21.

Also shown inFIG. 5 issecond slip segment21 withinner face22, and further, theinner face22 having a longitudinally disposedslot56.Slot56 will cooperate with and retain insert diemembers90.FIG. 5 also showsrib58 connectinginner face22 with theouter face24, as previously noted.Second slip segment21 is attached tothird slip segment22 viahinge assembly36 through theprojections34aofsecond slip segment21 and theprojections50aofthird slip segment22.

FIG. 5 also depictsthird slip segment22 withinner face40, and further, theinner face40 having a longitudinally disposedslot60.Slot60 will cooperate with and retaindie insert members90.FIG. 5 also showsrib62 connecting theinner face40 with theouter face42, as previously noted.

FIG. 6 depicts a side sectional view offirst slip segment20. InFIG. 6,slip segment20 is shown without insert dies alonginner face6.FIG. 6 depicts a taper angle of theouter surface8 ofslip segment20 relative to a vertical axis. In the slip apparatus of the present invention, this angle is greater than 11 degrees, but less than 15 degrees. In the preferred embodiment, such taper angle is 12 degrees (as denoted by angle “A” inFIG. 6). It should be noted that the “maximum” 15 degree taper angle is denoted by “X” inFIG. 6.

Conventional prior art slips typically have a three inch (7.12502 degrees relative to the vertical axis as denoted by “Y”) or four inch (9.46232 degrees relative to the vertical axis as denoted by “Z”) taper per foot. This taper creates the wedge effect in a bowl that allows pipe to be suspended in place while connections are made to extend or shorten a drill string. Prior art tapers have generally yielded satisfactory results in conventional applications.

With the advent of deep water drilling and running of long strings of heavy casing, conventional slips have not proven to be entirely effective in connection with landing string applications. Due to extreme loads and the relatively minimal angle on the slip back and insert bowl, conventional slips can cause a crushing effect that can reach dangerous levels. When the angle on the back of the slip and the angle in the slip bowl are increased, this crushing effect is lessened. However, when this angle is increased, it can be more difficult to get slips to engage a section of pipe, especially when such slips must engage against a relatively light load. However, when running a landing string, the pipe has sufficient weight to allow the slips of the present invention to engage against a section of pipe.

FIG. 7 is a partial cross-sectional view of a slip embodiment of the present invention engaging against a tubular member, such as landing string joint300. The taper angle of theouter surface8 ofslip segment20 is 12 degrees.Slip apparatus2 is inserted into an insert bowl (not shown inFIG. 7) which is received within a master bushing, which is in turn received within a rotary table. Teeth-like projections engageslip segment20 as well as the other twoslip segments21 and22 (which are not shown in this view) thereby suspendingtubular member300 from the rotary table. The load oftubular member300 and any attached tubular members will be transferred fromteeth122 of insert diemembers90 to slipsegment20.

The transverse (horizontal) load, denoted by arrow “C”, is reduced so that in heavy weight applications, such as where a landing string is used to land casing, the crushing force has been reduced due to the novel taper of the slip and corresponding bowl insert (not seen in this view).

In normal operations, a tubular member may also be threadedly connected to the first tubular member as will be readily understood by those of ordinary skill in the art. After threadedly connecting the two tubulars, the operator lifts the tubulars using the elevators and then removes the slip apparatus from the slip bowl in the rotary table. The connected tubulars are then lowered to the desired depth using the elevators. Theslip apparatus2 may again be inserted into the rotary table and the process repeated as understood by those of ordinary skill in the art.

FIG. 8 is a partial cross-sectional view of the slip apparatus of the present invention engaging a tubular member within aslip bowl200.Rotary slip apparatus2 is configured to fit intoinsert bowl200, which in turn is set into rotary bushing111 and rotary table on the rig floor, as is understood by those of ordinary skill in the art. The inner portion ofinsert bowl200 contains a reciprocal taper, which in the embodiment shown is 12 degrees relative to the vertical axis, designated by the letter “D”. This view shows that the slips engage the landing string joint300. Therotary slip apparatus2 is inserted intoinsert bowl200 and is positioned to surround landing string joint300. Downward force generated by the weight of joint300 causes slipapparatus2 to also be lowered intoinsert bowl200. Due to the wedge shaped design,slip apparatus2 engages tubular landing string joint300, preventing landing string joint300 from falling throughinsert bowl200. As noted earlier, transverse load “C” is also reduced due to the taper of theslip apparatus2 and the corresponding inner surface ofinsert bowl200. Thus, by distributing the axial load “B” and reducing the transverse load “C”, heavy strings of tubulars, such as landing strings, can be safely lowered into a well.

FIG. 9 is an overhead view of theelevator bushings400 of the present invention. Said elevator bushings generally have a segmented construction that is well known to those skilled in the art comprising

bushing segments

401,402,403 and404. Such elevator bushings can be easily installed within conventional elevators used on drilling rigs. Said busing segments each have a taperedsupport shoulder410. The taper angle of saidsupport shoulder410 corresponds to the taper angle oftaper307 of landing string joint300 (depicted inFIG. 3). In the preferred embodiment, such taper angle is 45 degrees.

FIG. 10 is a side cross-sectional view of theelevator bushings400 of the present invention taken along line A-A ofFIG. 9. Said bushings define a taperedinternal support shoulder410, wherein the taper angle of said support shoulder is designed to complement the box-end taper of the high capacity landing string of the present invention. Further, unlike conventional elevator bushings that have similar support shoulders within the body of such elevator bushings, the taperedsupport shoulder410 of elevator bushing400 of the present invention is situated neartop405 of said bushings. The increased taper angle of such support shoulder, and the placement of such shoulder near the top of such bushings, reduces spreading forces on the elevator doors and the stresses at the bottom of the elevator body.

Although the present invention has been depicted in a particular form constituting a preferred embodiment, it will be understood that various changes and modifications in the illustrated and described structure can be effected without departure from the basic principles which underlie the invention. Changes and innovations of this type are deemed to be circumscribed by the spirit and scope of the invention except as such spirit and scope may be necessarily limited by the appended claims, or reasonable equivalents thereof.