Connection

Details Connection Connection

1999-08-10

2002-11-26

Nicholson, Eric K. (Department: 3626)

Pipe joints or couplings

Particular interface

Tapered

C285S331000, C285S340000, C285S355000

Reexamination Certificate

active

06485063

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a connection for drill pipe and more particularly, pin and box connectors disposed on the ends of tubular members for connecting the tubular members for the drilling of bore holes in the pipeline and utility industry.
Drill strings are specifically designed for the installation of telephone lines, fiber optic cable, sewage lines, water lines, and similar installations relating to utilities for the pipeline and utility service industry. The typical objective is to drill a bore hole from point A to point B, generally under some type of obstacle or structure for the installation of a utility. Typically the bore hole distance drilled is between 200 and 600 feet. Also typically the bore hole is shallow and is generally horizontal.
In a typical drilling operation, a bit, such as a fishtail bit, is mounted on the end of the drill string with a transmitter located just behind the bit. The drill string is placed in compression and rotated to rotate and apply force on the bit to drill the bore hole. Fluids are circulated through the drill string and bit and then back up the annulus formed between the wall of the bore hole and drill string to moisten the earth through which the bit is drilling. This lessens the tendency for the drill string to stick in the bore hole. A hand-held receiver is located above ground to follow the transmitter and determine the orientation of the bit, i.e. inclination and azimuth. The operator then adjusts the orientation of the bit if the bit varies from the trajectory of the proper bore hole path between points A and B.
Once the bore hole is drilled under the obstacle, then the bit is removed and a reamer on a swivel is attached to the end of the drill string and the drill string and reamer are pulled back through the bore hole with the utility attached. The swivel is attached to the utility line such as a cable for example. The drill string is placed in tension as the reamer pulled back through the bore hole with the utility attached.
The operator minimizes the amount of fluid that is circulated through the drill string because too much fluid into the surrounding earth bore is undesirable. If too much fluid is circulated through and around the drill string, the fluid begins to wash out the sand, dirt, and earth causing a washout underneath the obstacle or structure, such as a highway or waterway, under which the bore hole is being drilled. Structural problems will be created if a void is formed underneath a highway or some other structure.
Drill strings for the pipeline and utility industry are much different from that used in the oilfield. In oil field drilling, a drill string is used to drill a wide open bore hole. Drilling fluid is circulated to remove cuttings and cool the bit. Thus, it is important that the connections in the drill string be sealed from pressure and fluid. Typically it is not important whether there is fluid leakage through the connection in a drill string for the pipeline and utility industry. Thus the connections between joints of drill pipe are not required to seal against pressure or fluids and heat and pressure are not of concern. The only pressure is the pump pressure for flowing drilling fluid.
When designing the drill string and other related tubular goods for a particular drilling application, not only must the physical orientation of the drill string be taken into consideration, but also the desired use. The drill string may be placed in a horizontal orientation, or in a vertical orientation, or in a deviated position. The actual orientation depends on the type of application.
The successful drilling of bore holes in the pipeline and utility industry requires the assembly of many individual tubular members into a drilling string. The actual assembly entails the make-up and torquing of individual tubular members. The actual drilling process involves multiple make-ups and breakdowns of the connections between individual tubular members of the drilling string. The number of makes and breaks depends upon the environment and the operator. Typically, a connection will be made up and broke out four or five times a day and could be as high as six or seven times a day. Thus, a connection between joints of pipe may have a 1,000 or more makes and breaks a year and therefore must be robust and rugged to withstand such use. Also, the assembly is performed very quickly since time considerations are very important.
Design considerations for the connections for the drill string joints include, but are not necessarily limited to, the repetitive coupling and uncoupling of the connections, torquing, bending, cyclic loading, fatigue, tensile loads, and compressive strength. The connection typically includes threaded pin and box connections. The threads must be capable of making up easily with other threaded joints. The longevity of the individual thread is also very important for several reasons. First, once a thread begins to deform, further deformation is usually exponentially increased thereafter. Second, once the thread has deteriorated, the entire drill string must be disregarded since the length of the drill string has very limited variance. Third, failure of the thread while the drill string is in the process of actually drilling a bore hole will cause substantial monetary damage. The preceding list is meant to be only illustrative.
Despite these designs, when a drill string member has a thread that is used in multiple applications for the drilling of bore holes in the utility and pipeline industries, the mating shoulders may become flared due to over torquing. Also, the prior art designs result in the thread profile becoming deformed which in turn causes the external and internal thread design profiles to lose their make-up capability and results in premature failure. Once deformation begins, continued use exponentially increases mating problems between cooperating tubular members. Further, the pin and box are unscrewed, and thereafter, when made up again, the deformation forces will only be enhanced. In other words, the multiple screwing and unscrewing of the connections accelerates the deformation process so that once the deformation begins to occur, the process will thereafter exponentially increase.
FIG. 1
illustrates a prior art connection and the inherent problem with multiple fastening and unfastening of prior art connections in the utility industry due to over torquing and cycling of the box and pin. The prior art connection typically includes a pin end
150
for mating with a box end
152
. The pin end
150
includes an annular shoulder
154
which is perpendicular to the axis of the connection. A round thread external thread profile
156
extends from shoulder
154
to an outer diameter
158
. A radial terminal end
160
, also perpendicular to the axis of the connection, extends from outer diameter
158
to an inner diameter
161
.
The box end
152
includes a radial terminal end
162
having a surface which is perpendicular to the axis of the connection. A round thread internal profile
164
extends from terminal end
162
to an internal surface
166
. A radial shoulder
168
extends from internal surface
166
to the internal diameter
170
of the tubular member.
As shown in
FIG. 1
, the radial terminal end
162
has slid on shoulder
154
and become deformed. One cause for this deformation may be the over torquing of the box
152
and pin
150
ends whereby the radial end
162
has been forced to slide outwardly on the face of shoulder
154
of the pin end
150
. The forces thus applied may also deform the radial end
160
of the pin
150
such that the radial end
160
has been deformed, and in particular, by the outer surface
158
and the matching inner surface
161
being expanded outward by the compressive action of the radial shoulder
168
being forced into the radial end
160
.
The pin and box are cut on a two inch cone taper. When the pipe string is driven, the outside cone of the box as the string is placed in compression, the outside cone of the box tends to

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