Heavy-load landing string system

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 of FIG. 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 in FIG. 6 engaging a tubular member.

FIG. 8 is a partial cross-sectional view of the slip embodiment shown in FIGS. 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 of FIG. 9.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 depicts a schematic view of a floating platform 100 lowering a tubular string 101 into a well 102 in accordance with the present invention. Tubular string 101, in one preferred embodiment, will be a casing string, and floating platform 100 will be equipped with a drilling rig including vertically extending derrick 103. Said drilling rig in general, and said derrick in particular, will further include a hoisting system that includes traveling block 104 and elevators 105. Sub-sea tree 106 is positioned on the sea floor, and a marine riser 107 extends from said sub-sea tree 106 to floating platform 100. Rig floor 1 10 provides a work surface below derrick 103. Master bushing 1 11, which is disposed within rig floor 1 10, provides access from rig floor 110 to marine riser 107 and, ultimately, well 102.

Casing string 101 is inserted into well 102 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 bushing 111, through marine riser 107 and subsea tree 106, and ultimately into well 102. Once a desired length of casing has been inserted, casing hanger 108 is connected to casing string 101. Casing hanger 108 is a device that serves to anchor a casing string, such as casing sting 101, 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.

Landing string 109 is attached to casing hanger 108. As noted earlier, landing string 109 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 convey casing string 101 into well 102 until casing hanger 108 is landed into sub-sea well head 106. In this manner, tubular string 101 can be safely lowered to a predetermined depth within well 102.

FIG. 2 depicts a schematic view of the high capacity slip apparatus, continuous bowl insert and split master bushing of the present invention. Slip apparatus 2 comprises a plurality of cooperating slip segments 20, 21 and 22 which are described in greater detail below. Said slip segments 20, 21 and 22 are hingedly connected; as such, slip apparatus 2 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 within continuous bowl insert 200. Although not shown in FIG. 2, the outer surface of slip apparatus 2 is tapered; said slip segments 20, 21 and 22 are wider at the top, and narrower at the bottom.

Said bowl insert 200 is tapered, such that top 201 of bowl insert 200 has a larger inner and outer diameter than bottom 202 of bowl insert 200. Said bowl insert 200 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 insert 200 is in turn received within split master bushing 111, which is mounted within the rig floor of a drilling rig; split master bushing has a lateral split 112 that permits said split master bushing 111 to be installed within a rig floor, such as rig floor 110 depicted in FIG. 1. Bowl insert 200 and split master bushing 111 have aligned central bores that provide access to a marine riser (such as marine riser 107 in FIG. 1) and, ultimately, a well (such as well 102 in FIG. 1).

Referring to FIG. 3, the high capacity landing string of the present invention comprises a plurality of pipe joints, such as landing string joint 300, having threaded connections. (Landing string joint 300 is one continuous length of pipe, but is broken into sections for clarity of illustration in FIG. 3). Landing string joint 300 has a threaded connection disposed at each end; female box-end connection 301 is disposed at one end of joint 300, while male pin-end connection 302 is disposed at the opposite end of joint 300. Although such connections can incorporate any number of different thread configurations, in the preferred embodiment box-end connection 301 has internal “FH” female threads 303, while pin-end connection 302 has external male “FH” threads 304.

Immediately adjacent to box-end connection 301 is a length of thick-walled tube section 305. Although such thick-walled tube section 305 can span the entire length of each joint 300 (that is, from box-end connection 301 to pin-end connection 302), in the preferred embodiment said thick-walled tube section 305 extends approximately 6 feet from the base of box-end connection 301, that being the area in which slips typically come in contact with the outer surface of landing string joint 300. 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) comprises tube section 306 having a relatively thinner wall than said thick-walled section 305. By limiting the amount of thick-walled section 305 to only that portion of joint 300 which will come in contact with slips, the weight of landing string joint 300 is reduced.

As with conventional drill pipe and landing strings, threaded box-end connection 301 and pin-end connection 302 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 and 306 that extend between such connections. Thus, tapered section 307 transitions from box-end connection 301 to thick-walled tube section 305 on one end of joint 300, while tapered section 308 transitions from pin-end connection 302 to tube section 306 at the opposite end of joint 300.

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 tapered section 307 which transitions from the larger outer diameter of box-end connection 301 to the relatively smaller outside diameter of thick-walled tube section 305. The taper angle of tapered section 307, as shown by angle “A” in FIG. 3, will be in the range between 18 degrees and 90 degrees. In the preferred embodiment, the angle of tapered section 307 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 section 306 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 section 305 is constructed from S-135 material and has a wall thickness of 1.7″; and
• box-end connection 301 and pin-end connection 302 are constructed of 120 KSI material, while threads 303 and 304 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 apparatus 2 includes first slip segment 20, with said first slip segment 20 having a generally arcuate inner face 6 and a generally arcuate outer face 8. Slip segment 20 has a top end 10 and a bottom end 12. As seen in FIG. 4, the slip segment's profile is generally in a wedge shaped contour with the outer face 8 being tapered to bottom end 12.

Slip segment 20 contains a handle member 14, with the handle member 14 being connected to slip segment 20 with conventional means such as pins and cotters. Attachment means for attaching slip segment 20 with slip segment 21 includes the slip segment 20 containing a pair of projections 16a, 16b that have openings therein for placement of a hinge assembly 18 for connection with the second slip segment 21.

The outer face and inner face of slip segments 20, 21 and 22 are connected by a series of ribs. Each slip segment may be formed as a single wedge block. However, such construction can make slip apparatus 2 very heavy. By incorporating a series of ribs (seen generally at 70), rotary slip apparatus 2 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 arcuate inner face 23 and a generally arcuate outer face 24. Slip segment 21 has a top end 26 and a bottom end 28. As noted earlier, said slip segment's profile is generally in a wedge-shaped contour with the outer face 24 being tapered to the bottom end 28.

Slip segment 21 contains a handle member 30, with the handle member 30 also being connected to said slip segment 21 with conventional means such as pins and cotters. Slip segment 21 also includes a pair of projections 32a, 32b that have openings therein for placement of hinge assembly 18 for connection with first slip segment 4. Second slip segment 21 also contains second attachment means for attaching to third slip segment 22 which includes a second pair of projections 34a, 34b that also have openings therein for placement of hinge assembly 36 for connection with third slip segment 22.

Third slip segment 22 also contains a generally arcuate inner face 40 and a generally arcuate outer face 42. Slip segment 22 has a top end 44 and a bottom end 46. The slip segment's profile is also a wedge-shaped contour with the outer face 42 being tapered to the bottom end 46.

Third slip segment 22 contains handle member 48, with said handle member 48 also being connected to third slip segment 22 with conventional means such as pins and cotters. Third slip segment 22 also contains a pair of projections 50a, 50b that have openings therein for placement of hinge assembly 36 for attachment with second slip segment 21. Inner face 40 of slip segment 22 will have disposed therein insert die members that will be described in greater detail later in the application.

Insert dies 90, having a plurality of teeth-like projections 122, are disposed along the inner face 6 of slip segment 20, inner face 23 of slip segment 21 and inner face 40 of slip segment 22. Said insert dies have generally arcuate faces which have similar curvature as said inner faces 6, 23 and 40. Although the length of slip segments 20, 21 and 22 can be varied for particular applications, in the preferred embodiment of the present invention said slip segments are about 20 inches in length.

FIG. 5 depicts a cross-sectional view of slip apparatus 2 without inserts taken from line A-A of FIG. 4. It should be noted that like numbers appearing in the various figures refer to like components. Thus, there is shown first slip segment 20 with inner face 6, and further, inner face 6 having a longitudinally disposed slot 54. Slot 54 will cooperate with and retain insert die members 90. FIG. 5 also shows rib 70 connecting inner face 6 with the outer face 8, as previously noted. First slip segment 20 is attached to second slip segment 21 via hinge assembly 18 through the projections 16a of first slip segment 20 and the projections 32a of second slip segment 21.

Also shown in FIG. 5 is second slip segment 21 with inner face 22, and further, the inner face 22 having a longitudinally disposed slot 56. Slot 56 will cooperate with and retain insert die members 90. FIG. 5 also shows rib 58 connecting inner face 22 with the outer face 24, as previously noted. Second slip segment 21 is attached to third slip segment 22 via hinge assembly 36 through the projections 34a of second slip segment 21 and the projections 50a of third slip segment 22.

FIG. 5 also depicts third slip segment 22 with inner face 40, and further, the inner face 40 having a longitudinally disposed slot 60. Slot 60 will cooperate with and retain die insert members 90. FIG. 5 also shows rib 62 connecting the inner face 40 with the outer face 42, as previously noted.

FIG. 6 depicts a side sectional view of first slip segment 20. In FIG. 6, slip segment 20 is shown without insert dies along inner face 6. FIG. 6 depicts a taper angle of the outer surface 8 of slip segment 20 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” in FIG. 6). It should be noted that the “maximum” 15 degree taper angle is denoted by “X” in FIG. 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 joint 300. The taper angle of the outer surface 8 of slip segment 20 is 12 degrees. Slip apparatus 2 is inserted into an insert bowl (not shown in FIG. 7) which is received within a master bushing, which is in turn received within a rotary table. Teeth-like projections engage slip segment 20 as well as the other two slip segments 21 and 22 (which are not shown in this view) thereby suspending tubular member 300 from the rotary table. The load of tubular member 300 and any attached tubular members will be transferred from teeth 122 of insert die members 90 to slip segment 20.

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. The slip apparatus 2 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 a slip bowl 200. Rotary slip apparatus 2 is configured to fit into insert bowl 200, which in turn is set into rotary bushing 111 and rotary table on the rig floor, as is understood by those of ordinary skill in the art. The inner portion of insert bowl 200 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 joint 300. The rotary slip apparatus 2 is inserted into insert bowl 200 and is positioned to surround landing string joint 300. Downward force generated by the weight of joint 300 causes slip apparatus 2 to also be lowered into insert bowl 200. Due to the wedge shaped design, slip apparatus 2 engages tubular landing string joint 300, preventing landing string joint 300 from falling through insert bowl 200. As noted earlier, transverse load “C” is also reduced due to the taper of the slip apparatus 2 and the corresponding inner surface of insert bowl 200. 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 the elevator bushings 400 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 and 404. Such elevator bushings can be easily installed within conventional elevators used on drilling rigs. Said busing segments each have a tapered support shoulder 410. The taper angle of said support shoulder 410 corresponds to the taper angle of taper 307 of landing string joint 300 (depicted in FIG. 3). In the preferred embodiment, such taper angle is 45 degrees.

FIG. 10 is a side cross-sectional view of the elevator bushings 400 of the present invention taken along line A-A of FIG. 9. Said bushings define a tapered internal support shoulder 410, 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 tapered support shoulder 410 of elevator bushing 400 of the present invention is situated near top 405 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.

Claims

1. A system for landing tubular goods comprising:

a. a plurality of pipe sections having a first and second end, wherein each pipe section comprises: i a threaded male connection disposed at said first end; ii a threaded female connection having an outer diameter disposed at said second end; iii a tubular body having an outer diameter disposed between said threaded connections, wherein the outer diameter of said threaded female connection is greater than the outer diameter of said tubular body; and iv a tapered shoulder between said threaded female connection and said tubular body, wherein the angle of said taper is in the range between 18 degrees and 90 degrees.

b. a slip apparatus having a tapered outer surface;

c. a slip bowl insert having a tapered inner surface, wherein the taper angle of said inner surface is substantially equal to the taper angle of said outer surface of said slip apparatus; and

c. elevators having a top, a bottom and a tapered shoulder, wherein the angle of said tapered shoulder is in the range between 18 and 90 degrees, and is substantially equal to angle of the tapered shoulder of said pipe sections.

2. The system of claim 1, wherein the angle of the tapered shoulder of said pipe sections is 45 degrees.

3. The system of claim 1, wherein the angle of the tapered surface of said elevators is 45 degrees.

4. The system of claim 1, wherein said tapered surface of said elevators is situated near the top of said elevators.

5. The system of claim 1, wherein said tubular body further comprises a thick-walled section disposed adjacent to said tapered shoulder.

6. The system of claim 5, wherein the length of said thick-walled section is about 6 feet.

7. The system of claim 1, wherein said slip bowl insert has a continuous inner surface.

8. The system of claim 1, wherein said slip apparatus further comprises:

a. a first slip segment having an arcuate inner face and a tapered outer face, wherein said outer face has a taper angle in a range between 11 and 15 degrees;

b. a second slip segment having an arcuate inner face and a tapered outer face, wherein said outer face has a taper angle that is substantially equal to the taper angle of the outer face of said first slip segment;

c. a third slip segment having an arcuate inner face and a tapered outer face, wherein said outer face has a taper angle that is substantially equal to the taper angle of the outer face of said first and second slip segments;

d. means for attaching said first slip segment with said second slip segment; and

e. means for attaching said second slip segment with said third slip segment.

9. The system of claim 7, wherein the length of said first, second and third slip segments are at least 20 inches.

10. The system of claim 7, wherein the taper angle of the outer faces of said first, second and third slip segments are about 12 degrees.

11. The system of claim 9, wherein the taper angle of the inner surface of the slip bowl insert is about 12 degrees.

12. A landing string comprising a plurality of pipe sections having first and second ends, said pipe sections further comprising:

a. a threaded male connection disposed at said first end of each pipe section;

b. a threaded female connection having an outer diameter disposed at said second end of each pipe section;

c. a tubular body having an outer diameter disposed between said threaded connections, wherein the outer diameter of said threaded female connection is greater than the outer diameter of said tubular body; and

d. a tapered shoulder between said threaded female connection and said tubular body, wherein the angle of said taper is in the range between 18 degrees and 90 degrees.

13. The system of claim 12, wherein the angle of the tapered shoulder of said pipe sections is 45 degrees.

14. The system of claim 12, wherein said tubular body further comprises a thick-walled section disposed adjacent to said tapered shoulder.

15. The system of claim 14, wherein the length of said thick-walled section is about 6 feet.

16. A slip system comprising:

a. a slip apparatus having a tapered outer surface; and

b. a slip bowl insert having a tapered inner surface, wherein the taper angle of said inner surface is substantially equal to the taper angle of said outer surface of said slip apparatus.

17. The slip system of claim 16 further comprising:

a. a first slip segment having an arcuate inner face and a tapered outer face, wherein said outer face has a taper angle in a range between 11 and 15 degrees;

b. a second slip segment having an arcuate inner face and a tapered outer face, wherein said outer face has a taper angle that is substantially equal to the taper angle of the outer face of said first slip segment;

c. a third slip segment having an arcuate inner face and a tapered outer face, wherein said outer face has a taper angle that is substantially equal to the taper angle of the outer face of said first and second slip segments;

d. means for attaching said first slip segment with said second slip segment; and

e. means for attaching said second slip segment with said third slip segment.

18. The system of claim 17, wherein the length of said first, second and third slip segments are at least 20 inches.

19. The system of claim 17, wherein the taper angle of the outer faces of said first, second and third slip segments are about 12 degrees.

20. The system of claim 19, wherein the taper angle of the inner surface of the slip bowl insert is about 12 degrees.

21. The slip system of claim 16, wherein said slip bowl insert has a continuous inner surface.

22. Landing string elevators comprising a top, a bottom and a tapered shoulder, wherein the taper angle of said tapered shoulder is in the range between 18 and 90 degrees.

23. The elevators of claim 22, wherein the angle of the tapered shoulder of said elevators is 45 degrees.

24. The elevators of claim 22, wherein said tapered shoulder of said elevators is situated near the top of said elevators.