JPS6221956B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to earth boring drill pipes, and more particularly to tool joints for interconnecting sections of drill pipes.

Deep wells, such as oil and gas wells, are drilled by rotating drill bits that are rotated by strings of drill pipe. Each drill pipe is about 30
It is completed by connecting together the individual members with a length of feet (9 m). Each member is connected to each other by a threaded joint called a tool joint.
The tool fitting must withstand the torques normally experienced during drilling and must also provide a sealing function to prevent drilling fluid being pumped down the drill pipe from leaking out of the fitting. Must be. Because drilling fluids are aggressive, their leakage from tool joints causes wear and premature failure.

The tool joint is composed of a pin member and a box member. The pin member has external threads and an external annular connecting shoulder. The box member has internal threads and a surface or rim that abuts the connecting shoulder. Conventional drill pipes include an inner shoulder within the box member that is to be contacted by the abutment surface of the pin.
When the tool joint members are connected, a torque is exerted between the box end face and the pin connection shoulder to create a pressure of approximately 1/2 the yield strength.

If additional torque is applied during drilling, for example due to a bit or pipe becoming stuck, pins and boxes can be subjected to forces that exceed their yield strength. Therefore, it is very important to use a tool joint that has the ability to withstand large torques, preferably greater than the drill pipe itself.

The present invention provides a tool joint with substantially increased yield strength without increasing pin or box thickness or further hardening the steel. The box is provided with an inner shoulder on the underside of the screw. The pin has a surface at its tip that abuts the inner shoulder within the box. The dimensions of the pin and box are calculated so that the end face of the box contacts the outer shoulder of the pin when hand-tightened. However, a gap exists between the pin end face and the inside shoulder of the box. When the tool joint is fully connected to its normal connection torque, the box end faces will abut the outer shoulder of the pin with a normal pressure of approximately 1/2 the yield strength of the tool joint. The pin end face exerts little or no pressure on the inside shoulder of the box under normal connection torque.

During a drilling operation, if additional torque is applied, the tool joint tightens further, forcing the pin end face to abut the inside shoulder of the box. The tip portion of the pin is selected to reach its yield strength at approximately the same time, and no later than, the sink portion of the box and the root portion of the pin reach their yield strength. The inner connecting shoulder increases the amount of torque required to pull the tool joint apart.

Embodiments of the present invention will be described below with reference to the drawings.

The drawing shows an upper drill pipe member 11 mounted within a lower drill pipe section 13. The ends of the drill pipe members 11 and 13 are connected to each other to form a tool joint. A pin 15 is formed at the lower end of the upper drill pipe member 11 and the lower end of the lower drill pipe section 13 (not shown). Pin 15 connects to outer annular connecting shoulder 17
has. A relief groove 19 is provided on the inner circumference of the outer shoulder 17. The root part 21 is the outer shoulder part 1
It extends downward from 7. The root portion 21 is cylindrical and unthreaded. A benchmark shoulder 23 is formed at a short distance downwardly from the connecting shoulder 17 for use in measuring the amount of metal removed from the connecting shoulder 17 during rework.
A set of screws 25 are attached to the lower pin 15 of the root portion 21.
formed on top. Thread 25 is tapered and terminates in a cylindrical tip portion 27. The tip portion 27 has a surface 2 which is a circular rim located in a plane perpendicular to the axis of the upper drill pipe member 11.
It ends with 9.

The upper end of the lower drill pipe section 13 is similar to the upper end of the upper drill pipe member 11 (not shown).
It is formed as a box 31. box 3
1 receives a pin 15 and also includes a rim or surface 33 at its upper end. Surface 33 is a circular, flat surface located in a plane perpendicular to the axis of lower drill pipe section 13. Surface 33 abuts outer shoulder 17 of pin 15. The bore of box 31 includes an upwardly directed shoulder 35 formed a short distance below surface 33 for use as a benchmark. Benchmark 35 serves to allow the user to know the amount of metal removed from surface 33 during rework.

A cylindrical sinkhole portion 37 is located directly below the benchmark 35. The sinkhole portion 37 extends approximately the same length as the root portion 21, but has an inner diameter that is larger than the inside diameter of the root portion 21. As a result, an annular cavity is formed between the root portion 21 and the sinkhole portion 37. A set of internal threads 39
is located below the sinkhole portion 37. screw 3
9 is tapered and is formed to mesh with the screw 25.

The box 31 has a cylindrical root portion 41 located below the screw 39. Root portion 41 terminates in an upwardly directed annular inner shoulder 43 . The inner shoulder 43 lies in a plane perpendicular to the axis of the lower drill pipe section 13 and is configured to be abutted by the pin end surface 29 . The relief groove 45 is formed at the intersection of the inner shoulder portion 43 and the root portion 41. The axial passage 47 of the box 31 below the inner shoulder 43 is connected to the axial passage 49 of the pin 15.
has a diameter equal to the diameter of Concave annular range 5
1 is formed on the outer side wall of the sinkhole portion 37. The recessed area 51 has a diameter slightly smaller than the outer diameter of the part containing the screw 39.

Box 31 and pin 15 are dimensioned so that the distance from outer shoulder 17 to pin end face 29 is slightly shorter than the distance from box end face 33 to inner shoulder 43. Also, Box 31
and the pin 15 is dimensioned such that a gap exists between the pin end face 29 and the inner shoulder 43 when the two members 11 and 13 are tightly connected by hand without the use of a wrench or tool. ing. When hand-tightened, there is no pressure between the box end face 33 and the outer shoulder 17, but they are in contact with each other.

In operation, drill pipe members 11 and 13 are connected with a torque that creates a pressure equal to approximately 2/1 of the yield strength of pin root portion 21 and box sink portion 37. Yield strength is at the pin base 21
Alternatively, it is a pressure (compressive force or tensile force) that causes permanent deformation in the box sink hole portion 37.
As torque is applied, the sinkhole portion 37 contracts and the pin root portion 21 extends, so that the pin end surface 29 advances downwardly. Under the application of the necessary torque for connection, the pin end face 29 either has a negligible clearance from or is in contact with the inner shoulder 43. However, the inner shoulder 43
The pressure at is less than the pressure at the outer shoulder 17.

The drill pipe member is then lowered into the well and rotated for drilling. During drilling, if the movement of the drill bit or structure at the lower end of the drill string becomes heavy, the joint experiences additional torque. With this additional torque, the sunken hole part 3
7 is further contracted and the pin root portion 21 is further extended, so that the pin end surface 29 is pressed against the inner shoulder portion 43 and comes into tight contact. Ideally, the yield strength of the tip portion 27 is reached at approximately the same time as, or no later than, the cumulative yield strength of the pin root portion 21 and box sink portion 37 is reached. Dimensions are selected. The additional pressure exerted on the inner shoulder 43 by the pin end face 29 significantly increases the amount of torque required to yield the tool joint.

Root portion 21, sink hole portion 37 and tip portion 2
7 then serves as spring means for pressing the box end face 33 tightly against the outer shoulder 17 with a pressure that exceeds the pressure exerted by the pin end face 29 on the inner shoulder 43. The length of these members is such that, if subjected to additional torque during drilling, there is sufficient spring action to allow deformation of these members, thereby causing pin end face 29 to abut inner shoulder 43. has been selected. To explain how these dimensions are determined, the API
(American Petroleum Institute) Demonstrates a modification of a standard 32/1 inch (8.89 cm) IF tool fitting. First, holes 47 and 49 are standard diameter holes for a tool joint of this size;
It is 6.82cm. The outside diameter of the pin root portion 21 is selected to be 9.36 cm, which is the minimum outside diameter of a standard tool joint pin in its last engaged pin thread. The minimum thickness of the root portion 21 is selected to ensure that the pin 15 has no lower strength than the root portion of conventionally known pins. The cross-sectional area of the root portion 21 is calculated to be 31.56 cm ² .

To ensure that the sinkhole portion 37 is not damaged substantially earlier than the pin root portion 21,
The cross-sectional area of the sinkhole portion 37 is selected to be substantially the same as the cross-sectional area of the root portion 21. To accomplish this, in the preferred embodiment, the diameter of the sinkhole is determined by the standard sinkhole diameter of the tool joint box. The outer diameter of the recessed area 51 is then calculated to make the cross-sectional area of the sink portion 37 substantially the same as the cross-sectional area of the pin root portion 21. The recessed area 51 serves to prevent wear on the outer diameter of the sinkhole portion 37. (Otherwise, the cross-sectional area would be reduced below the design requirement.) If reduced below the design requirement, the sinkhole section 37 would fail at an earlier point than the root section 21. Dew. In the preferred embodiment, the outer diameter of recessed area 51 is 12.22 cm. In a preferred embodiment, its internal diameter is chosen to be 10.35 cm, resulting in a cross-sectional area of 33.11 cm ² . The difference between the cross-sectional area of the pin base portion 21 and the cross-sectional area of the sink hole portion 37 is 1.55 cm ² ,
The difference is about 5%.

Next, the length of sinkhole portion 37 is selected. This length must be long enough to produce the necessary deformation when torqued. In the preferred embodiment, the length of the sinkhole section 37 was selected to be 2 inches (5.08 cm). The length of the root portion 21 is slightly longer due to the screw engagement, 5.56 cm.
was selected.

The magnitude of the displacement in yield strength is then determined by dividing the yield strength of the steel used in this tool joint by Young's modulus. This value is 8,
274/1,971,970=0.004cm/1cm. That is, when this type of steel is subjected to a stress of 8.274 bar, it will deform (compress or expand) by 0.004 cm per cm of the length of the member.

During connection, the sinkhole portion 37 contracts and the root portion 21 expands. At a torque that produces a pressure of 1/2 of the yield strength or 4.147 bar, 0.004 cm/1 at 5.56 cm
Multiply by cm and divide by 2 to get 0.011125 cm. Sink hole portion 37 is 2 inches (5.08 cm) long.
Multiply 0.004cm/1cm and divide by 2, base part 2
1 multiplied by the cross-sectional area of the sinkhole portion 37. As a result, the total deformation at 1/2 of the yield strength is 0.00967 cm. Therefore, the total relative movement of the pin end face 29 at 1/2 of the yield strength is 0.011125 cm and 0.00967 cm or
The sum is 0.02079cm. The deformation at 3/4 of the yield strength is 0.03119cm, and the deformation at the yield strength is
It is 0.04160cm.

The length of the tip section 27 is selected to allow the tip section to reach yield strength at the same time as, or slightly earlier than, the pin root section 21 and the sinkhole section 37. To avoid making the length of the tip part longer than necessary, a norm was chosen in which the pin end face 29 first contacts the inner shoulder 43 at 3/4 of the yield strength. At this point, the pin root portion 21 and the sink hole portion 37 are 0.03119 below the pin end surface 29.
cm is moving. To reach yield strength, the pin root portion 21 and the sink hole portion 37 must undergo an additional deformation of 0.01038 cm. This deformation causes the tip portion 27 to shrink by 0.01038 cm. The length of the tip portion 27 is selected so that the yield strength is reached when it is shrunk by 0.01038 cm. As mentioned above, the deformation of this type of steel is the yield strength versus Young's modulus or 0.004 cm/
Occurs at a rate of 1 cm. The length of the tip section 27 must be 2.54 cm since the shrinkage required for the tip section 29 to reach yield strength at the same time as the pin root section 21 and sink hole section 37 is approximately 0.01016 cm.

With respect to the outer diameter of the tip portion 27, the screws 25 and 3
9 were decapitated as much as possible without reducing their strength. The selected length is approximately 6.0325 cm.
A diameter slightly smaller than the smallest outer diameter at the truncated ends of these screws was selected as the outer diameter of the tip portion 27, which in the preferred embodiment is 8.097 cm.

The next dimension to be determined is the position of the inner shoulder 43. The design standard is 1/2 of the yield strength at the outer shoulder 17.
At the full coupling torque that produces a pressure of , the pin end face 2
9 exerts little (if any) pressure on the inner shoulder 43. The pin end face 29 was previously determined to move 0.02080 cm downward at full connection torque and a pressure of 1/2 yield strength. Pin end face 29 and inner shoulder 43 when tightened by hand
The 0.030cm gap between the
For a movement of 0.02080cm, it will be reduced to about 0.0101cm. When an additional torque is applied to exert pressure on the outer shoulder 17 to 3/4 of its yield strength, the pin root portion 21 and the sink hole portion 37 experience an additional deformation of 0.01038 cm. This causes the pin end face 29 to initially contact the inner shoulder 43 at a pressure of 3/4 of the yield strength. The additional torque resulting in a pressure of 3/4 to 1 times the yield strength, if unconstrained, would move the pin end face 29 downward an additional 0.01038 cm. However, since the pin end face 29 is in contact with the inner shoulder 43 at 3/4 of its yield strength, the tip portion 27 will shrink by 0.01038 cm. This is the amount of deformation experienced by tip portion 27 at yield strength. Therefore, the tip portion 27 reaches its yield strength at the same time as the pin root portion 21 and the sink portion 37.

In order to obtain the desired gap of 0.030 cm between the pin end face 29 and the inner shoulder 43 when tightening by hand, the distance from the box end face 33 to the inner shoulder 43 is equal to the distance from the pin outer shoulder 17 to the pin end face 29. than distance
The distance is selected to be 0.030 cm larger, that is, 14.584 cm. Although this is the ideal dimension, the actual manufacturing tolerances for these dimensions are 14.554 and 14.584
Plus 0 and minus 0.0127cm from the total dimensions in cm
It is. As a result, the pin end surface 29 when tightening by hand
The gap between the inner shoulder portion 43 and the inner shoulder portion 43 is between a minimum value of 0.0177 cm and an ideal maximum value of 0.030 cm. If the tool joint has a minimum clearance rather than an ideal clearance, the tip portion 27 will yield before the pin root portion 21 or the sinkhole portion 37 yields. Also, at full coupling torque, the pin end face 29 exerts a compressive force on the inner shoulder 43. The reason is that due to the total deformation of 0.02080cm from when hand-tightened until a pressure of 1/2 of the yield strength is applied, the minimum gap of 0.0177cm when hand-tightened is the tip part 27.
This is because it shrinks by 0.00254cm. A deformation of 0.00254 cm occurs in the tip portion 27 at a pressure of 3/4 of the yield strength,
On the other hand, the pin root portion 21 and the sink hole portion 37 are at a pressure of 1/2 of the yield strength. Tip part 27 is 0.0101
Its yield strength is reached at a contraction of cm. When the torque of the pin root part 21 and the sink hole part 37 increases from 1/2 to 3/4 of the yield strength, these members
Deforms 0.01038cm. Therefore, the tip portion 27
The root part 21 and the sinkhole part 37 have the yield strength.
Yield strength is reached before reaching 3/4. Although this may cause cracking in the tip portion 27, this is less harmful than if cracking were to occur in the root portion 21 or the sinkhole portion 37. Cracking of the tip portion 27 does not cause separation of the drill string. Up to and beyond the point where tip section 27 yields, it has no ability to withstand additional torque.

Through standard calculations, the pin root portion 21 or the sink hole portion 3 of the above-mentioned tool joint in the ideal dimensions.
The torque to yield 7 is 12.7 foot pounds (175.6 kg cm). In comparison, a conventional conventional tool joint with an outer diameter of 12.7 cm and an inner diameter of 6.826 cm only has the ability to withstand an additional torque of 762.73 N·cm at yield strength. This increase in the torque required to yield the tool joint further reduces the chance of drill string separation during drilling. The increased strength of the tool joint is achieved without the need to increase the thickness of the metal or increase the strength of the steel.

Although the invention has been described in terms of one embodiment thereof, it will be apparent to those skilled in the art that various modifications may be made within the scope of the invention.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a tool joint constructed in accordance with the present invention. DESCRIPTION OF SYMBOLS 11... Upper drill pipe member, 13... Lower drill pipe part, 15... Pin, 17... Outer shoulder part, 1
9... Relief groove, 21... Root portion, 23... Benchmark shoulder, 25... Screw, 27... Tip portion, 29... Pin end face, 31... Box, 33... Box end face,
35...Benchmark, 37...Sinkhole part, 39...
Internal thread, 41... Root portion, 43... Inner shoulder portion, 45
...Escape groove, 47, 49...Axial direction passage, 51...Concave range.

Claims (1)

[Claims] 1 A drill pipe tool joint between a first drill pipe member 11 formed with a pin 15 at one end and a second drill pipe member 13 formed with a box 31 at one end, said pin being connected to the outer shoulder 17. The box has a series of engaging parts including, in this order, a root part 21, an external thread 25, a tip part 27, and a pin end face 29, and the box has a box end face 33 and a sink hole part 37.
and an internal thread 39, a root portion 41, and an internal shoulder 43 in this order, each of the series of engagement portions of the pin being connected to the series of engagement portions of the box, respectively. The root portion 21 of the pin is configured to engage a corresponding portion of the pin.
and the axial length and radial thickness of the tip portion 27 and the sink hole portion 37 and root portion 41 of the box are such that the axial length and radial thickness of the box end face 33 when the joint is tightened to half its yield strength.
The pressure with which the pin end face 29 is pressed against the outer shoulder 17 is greater than the pressure with which the pin end face 29 is pressed against the inner shoulder 43, and the joint flexibly compresses the sink portion 37 and the tip portion 27. Further, when the base portion 21 of the pin is flexibly extended and further tightened, the sink hole portion 3
7 and the root portion 21 of the pin, the tip portion 27 is configured to reach its yield strength at a time not later than the time at which at least one of the root portion 21 of the pin reaches its yield strength.