Multiple Lead Threading

During the exploration for and the production of hydrocarbon products, i.e., oil and gas, like sections of casing are joined together, and like sections of tubing are also joined together for insertion down hole. Such joining together is normally accomplished by means of an intermediate coupling member. Commonly, such coupling member has oppositely directed threads interior of its opposed ends. Facing ends of adjacent casing or tubing sections, being exteriorly threaded, are then engaged and made up with said coupling ends. Certain problems have consistently occurred in the field where strings of casing and tubing are assembled. These problems have included the following (1) relative slowness in make-up, (2) tendency of the threads to gaul, especially when the coupling is broken loose, and (3) cross threading occurring, especially during make-up. Attempting to overcome these problems led to Aplicant's invention.

Some prior art utilization has been made of thread arrangements having plural leads. A search performed produced the following U.S. Pat. Nos. references: 1,407,335; 1,515,617; 1,645,032; 1,733,392; 1,802,668; 2,793,884; 2,885,225; 3,388,935; 3,794,364; 3,813,115; 3,876,319; and 3,917,319. None of the references found taught the use of plural leads in the thread system used on casing or tubing or on the coupling mechanism used to join together adjacent sections. Applicant's arrangement contemplates exteriorly threading the male (casing or tubing) member, interiorly threading the female (coupling) member, with all such threads having multiple leads.

FIG. 1 is a vertical section through a made-up coupling;

FIG. 2 is a perspective of the collar portion;

FIG. 3 is a top plan view of the collar; and

FIG. 4 is a partial perspective of one of the casing or tubing sections.

The nature of this invention is clearly shown in the drawings. As previously stated herein, the inventive nature of this application pertains to the multiple-lead threading provided to casing and/or tubing, such products being commonly used in oil field exploration and production.

FIGS. 1-3 depict a cylindrical collar, generally illustrated by numeral 10. Collar 10 includes an axial bore therethrough. The interior collar wall is interiorly threaded. Preferably such threading extends axially inward from each collar end, 11 and 12, to approximately the collar's axial center. Naturally such oppositely disposed threaded sections 14, 15 are threaded in opposite directions. Further, sections 14, 15 are radially tapered, i.e. collar 10 is thicker in the area of the collar's axial center than at collar ends 11 and 12.

Importantly, the threads comprising sections 14 and 15 possess multiple leads. As shown in FIGS. 2 and 3, there is a ninety degree rotational spacing between the four depicted leads, for example, those shown at 15-A,B,C,D.

FIG. 4 represents one end of either section 20 or 30, as shown in FIG. 1. As previously mentioned, such sections may be casing or tubing. Each casing or tubing end (only one end being shown in FIGS. 1 and 4) would be threaded, as at 24,34. The opposite ends of sections 20 and 30, not shown, would be similarly threaded, but in the opposite direction. For mating purposes with collar 10, threaded sections 24, 34, would be slightly tapered (at approximately the same angle of taper as collar sections 14, 15), and would have multiple leads (such as 24-A,B,C,D of FIG. 4) each being rotationally spaced by ninety degrees from its adjacent leads.

The typical thread form used is not critical to Applicant's invention. He has used buttress threads with a pitch of 5 per inch, and 8-round thread with its pitch of 8 per inch. It has consistently been found that field make-up or knock-down time is decreased, and any tendency to gaul and/or cross thread is greatly reduced. Applicant believes himself to be the first to teach the utilization of the concept of multiple lead threading in the art in question.

While only a single embodiment, i.e., 4-leads, has been depicted, it should be obvious that numerous embodiments would be possible by one skilled in the art without departing from the spirit of the invention, the scope of which is limited only by the following claims.