Pipe joints or couplings – Particular interface – Tapered
Reexamination Certificate
1999-03-02
2001-06-12
Luu, Teri Pham (Department: 3627)
Pipe joints or couplings
Particular interface
Tapered
C285S390000, C285S355000
Reexamination Certificate
active
06244631
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to oilfield drill pipe of the type commonly used to drill an oil or gas well. More particularly, this invention relates to an improved drill pipe having a pipe section, a pin tool joint and a box tool joint configured for providing high fluid flow rates and high strength, while also providing high drilling efficiency and relatively low cost.
BACKGROUND OF THE INVENTION
Various prior art articles and papers discuss drill pipe design considerations. Those familiar with the design, manufacture and use of drill pipe recognize that a selected drill pipe design is based upon numerous factors, including casing/hole considerations, predicted well loads, and hydraulic requirements. The manufacture of drill pipe also takes into consideration metallurgy, high-torque tool joints, and top drive matching strength.
Although the existing drill pipe is available in various standard sizes, it frequently does not meet all the objectives of the driller. The deficiencies of existing drill pipe are particularly acute when the driller is engaged in extended reach drilling (ERD). A standard 5-inch drill pipe is generally considered inadequate for most ERD applications due to hydraulic and torsional limitations. In most applications, ERD projects utilize either or both 5½-inch and 6⅝-inch drill pipe, which is commercially available in standard sizes from various companies.
One of the significant deficiencies of 5½-inch drill pipe is its hydraulic limitations, particularly when drilling deep wells. An exemplary 5½-inch drill pipe string provides the ability to sustain 787 kips in tension and from 33 ft-kips to 45 ft-kips or more in torsion, depending on the tool joint selection. While a 5½-inch drill pipe string is generally able to sustain the desired drilling torque and tensile loads, this size drill string commonly provides a very high pressure drop at conventional flow rates. Commonly from 900 to 1100 gpm is required to effectively clean a 12¼ inch hole at high inclinations, and practical experience has shown that undesirable pressure losses are experienced when drilling under these conditions. A 5½-inch drill pipe is thus inadequate for many ERD applications and has substantial hydraulic limitations in other applications, particularly when used in long hole sections.
An alternative available to the driller is to utilize the next commercially available size of drill pipe, namely 6⅝-inch drill pipe, to reduce hydraulic pressure losses at the elevated flow rates required for effective hole cleaning. The problem is that a 6⅝-inch drill pipe represents an over-design from the viewpoint of drill loads, is inefficient from a space standpoint, and can limit setback capability. Moreover, 6⅝-inch drill pipe may require rig modifications for implementation compared to using 5½-inch drill pipe, and 6⅝-inch drill pipe cannot be used inside 9⅝-inch casing or 8½-inch open hole. The 6⅝-inch drill pipe thus overcomes most of the hydraulic limitations of a 5½ drill pipe, but is over-designed structurally, is dimensionally inefficient, may not be used after 9⅝-inch casing is set, and requires a variety of associated upgrades.
The disadvantages of the prior art are overcome by the present invention, and an improved drill pipe is hereinafter disclosed that has enhanced strength and fluid flow characteristics and in many applications will not have the disadvantages of either 5½-inch or 6⅝-inch drill pipe.
SUMMARY OF THE INVENTION
The present invention provides a reliable and cost-efficient drill pipe with high strength and good fluid flow characteristics to optimize drilling for various applications, including ERD projects. A drill pipe according to the present invention includes an elongate pipe section, a pin tool joint, and a box tool joint. The pipe section has a central axis and a substantially uniform pipe outer diameter and a substantially uniform pipe inner diameter along substantially its entire length. A pin tool joint may be affixed by welding to an axial end of the pipe section and has external pin threads and at least one pin shoulder. A box tool joint is provided at the opposing axial end of a pipe section and has internal threads for mating engagement with the external threads of a mating drill pipe and at least one box shoulder for engagement with the pin shoulder of the mating drill pipe. The pin tool joint and the box tool joint each has a substantially uniform tool joint outer diameter along its axial length and a substantially uniform tool joint inner diameter along its axial length. The drill pipe has a ratio, R, that may expressed as:
R
=
(
P
ID
+
TJ
ID
)
(
TJ
OD
-
P
OD
)
According to the present invention, R is greater than or equal to 8.0, and preferably is less than or equal to 8.8.
In a preferred embodiment of the invention, the pipe section outer diameter is from 5¾ inches to 6 inches, and the tool joint outer diameter is less than or equal 7 inches. The tool joint inside diameter is greater than or equal to 4 inches, and is preferably less than or equal to 4¼ inches. The pin tool joint internal thread and the box tool joint external thread are preferably each tapered. As previously noted, both the pin tool joint and the box tool joint may each be welded to the pipe section. In the preferred embodiment, a second pin shoulder is provided on the pin tool joint, and a second box shoulder is provided on the box tool joint. These first and second shoulders mate to form a body double shoulder tool joint connection.
It is an object of the present invention to provide an improved drill pipe with enhanced strength and fluid flow capability. More particularly, it is an object of the invention to provide a drill pipe consisting of an elongate pipe section, a pin tool joint, a box tool joint, with a ratio having a numerator being the sum of the pipe section ID and the tool joint ID and the denominator being the difference between the tool joint OD and the pipe section OD. This ratio, R, is greater than 8.0, and preferably is from 8.1 to 8.5.
It is a feature of the present invention that the improved drill pipe has significantly improved fluid flow characteristics compared to conventional 5½-inch drill pipe, but does not have the deficiencies of 6⅝-inch drill pipe.
Yet another feature of the present invention is that the improved drill pipe may be reliably used for extended reach drilling (ERD) operations.
It is a feature of the present invention that the drill pipe includes a pipe section having an outer diameter of from 5¾ inches to 6 inches, and that the tool joint have an outer diameter of less than or equal to 7 inches.
Another feature of the invention is that the tool joint inner diameter is from 4 inches to 4¼ inches.
It is an advantage of the present invention that the drill pipe may utilize a pin tool joint and a box tool joint that have previously been commercially used in prior art drill pipe.
These and further objects, features, and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.
REFERENCES:
patent: 3508771 (1970-04-01), Duret
patent: 3822902 (1974-07-01), Maurer et al.
patent: 4192533 (1980-03-01), Blose
patent: 4538840 (1985-09-01), DeLange
patent: 4591195 (1986-05-01), Chelette et al.
patent: 4955644 (1990-09-01), Pfeiffer et al.
patent: 5505502 (1996-04-01), Smith et al.
patent: 5826921 (1998-10-01), Woolley
patent: 5908212 (1999-06-01), Smith et al.
patent: 6010163 (2000-01-01), Cerruti
British Steel Corporation Tubes Division, VAM Catalogue 850, pp. 16-17, 1986.*
World Oil's 1986 Tubing Tables, Gulf Publishing Co.*
Petroleum and natural gas industries—Steel pipes for use as drill pipe—Specification, ISO 11961, 1996.*
M.L. Payne et al: “Purpose-Built Drillpipe for Extended Reach Drilling”, IADC/SPE Drilling Conf., 39313, Mar. 3-6, 1998,
Bailey Edmond I.
Payne Michael
Smith Jackie E.
Browning Bushman
Luu Teri Pham
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