US3881755A

US3881755A - Drillstring structure

Info

Publication number: US3881755A
Application number: US266085A
Authority: US
Inventors: Siro Brunato
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-06-26
Filing date: 1972-06-26
Publication date: 1975-05-06
Anticipated expiration: 1992-05-06

Abstract

Two way flow tube system for deep water circulating mud drillstrings. The two-way flow tube system is arranged between the power swivel and the drilling bit. It has an upper end of one of the flow ways hydraulically communicating with a circulating mud inlet. The lower end thereof is hydraulically connected with the circulating mud outlet at the drillstring bit. The upper extremity of the other of the flow ways is hydraulically connected with the circulating mud outlet. The lower extremity thereof opens into the surrounding environment. Thereby the mud present in the surrounding environment may flow into the other flow way.

Description

United States Patent 1191 Brunato May 6, 1975 DRILLSTRING STRUCTURE 745,916 5/1944 285/137 R [76] inventor: Siro Brunato, Via G. Galli 23,

Melegnano Italy 2007 Primary Examiner-Thomas F. Callaghan [22] Filed: June 26, 1972 Attorney, Agent, or FirmDr, Guido Modiano; Dr. 211 App]. N11; 266,085

[52] U.S. 285/137 A; 138/115; 285/334 51 1111. C1 F16] 39/00 ABSTRACT [58] Field of Search 285/137 R, 137 A, 333,

285/334, 355, 390; 138/116, H7, 115, 155 Two way flow tube system for deep water circulating mud drillstrings. The two-way flow tube system is ar- [56] References Cited ranged between the power swivel and the drilling bit.

UNITED STATES PATENTS It has an upper end of one of the flow ways hydraulically communicating with a circulating mud inlet. The $33231 Z1332 3332?.5:5::JJJJJJJJJJJJJJJJJJJ: iii/5Z5 low end llleleol ls hydraulically comlwed wllll llle 1355:2396 10 1920 Decker 138/1 16 circulating mud Oullel at the drlllslring The "PP 1,876,627 9/1932 Davis et al. 285/333 x extremity of the other of the flow y is hydraulically l,953,70l 4/1934 Clark et al.... 138/! I5 X connected with the circulating mud outlet. The lower ,627 3/1938 Hinde iter-.. 285/333 X extremity thereof opens into the surrounding environ- 3 9 8/1967 Price 285/l37 R merit. Thereby the mud present in the surrounding en- 3,489,438 l/l970 McClure 285/334 X vironmem may flow into the other n way.

FOREIGN PATENTS OR APPLICATIONS 773,67l 9/l934 France 285/137 R 1 Claim, 7 Drawing Figures PATENTEDMAY' 6:975

SHEEI 10F 2 121 3 PR/ORART PMENIEBHAY' ems SHEET 2 BF 2 DRILLSTRING STRUCTURE BACKGROUND OF THE INVENTION The present invention relates to drillstrings and drillpipes thereof particularly for use in offshore drilling.

As known at present in the art for drilling offshore wells on the seabed use is made of a vessel or floating unit which is held on the vertical axis of the well to be drilled both with static mooring systems and selfadjusting propulsors.

One of the main elements common to the known technologies is the riser" tube which has a diameter of either 16 or 24 inches fixed by means of a flexible seal joint to a safety equipment located at the wellhead on the seabed. This riser tube from the safety equipment extends upwardly to a determined level above the water level and is kept constantly in a tensioned condition through a pneumatic jack system arranged on the unit.

The riser has two important functions, i.e., the return of the drilling mud to the surface and guiding of tools into the well.

On the other hand it is due to the structure of this riser tube at present in use that serious limitations arise in drilling offshore wells to a substantial depth. In fact, the weight of the riser, its diameter, fatigue stress and tensioning limitations are the most limiting parameters.

SUMMARY OF THE INVENTION The main object of the invention is that of substantially eliminating the above mentioned limitation in drilling offshore wells to a larger water depth then that attained heretofore.

Still another object of the present invention is that of providing a tube system having a simple structure al lowing to eliminate the conventional riser tube.

These and still further objects are attained by a twoway flow tube system arranged between the power swivel and the drilling bit of a deep water circulating mud drillstring, the two-way flow tube system having an upper end of one of the flow ways hydraulically communicating with a circulating mud inlet, the lower end thereof being hydraulically connected with the circulating mud outlet at the drillstring bit, and having the upper extremity of the other of the flow ways hydraulically connected with the circulating mud outlet, the lower extremity thereof opening into the surrounding environment thereby allowing the mud present in the surrounding environment to flow into said other flow way.

BRIEF DESCRIPTION OF THE DRAWING An embodiment of the invention is illustrated in the accompanying drawings in which:

FIG. 1 shows diagrammatically a conventional drillstring;

FIG. 2 shows diagrammatically a drillstring including the two-way flow tube system according to this invention;

FIG. 3 shows a lateral view, partly in section, of the twoway flow tube;

FIG. 4 is an enlarged representation, partly in longitudinal section of a joint of two two-way flow tubes;

FIG. 5 is a top view of FIG. 3, shown in an enlarged scale;

FIG. 6 is a cross-section according to VlVl of FIG. 3;

FIG. 7 is a view from below of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS The conventional drillstring shown in FIG. 1 comprises a kelly joint 1, conventional drillpipes 2, drillcollars 3 and a bit 4. This drillstring is capable of carrying out the normal sequence of known drilling operations. The equipment includes further a safety equipment 5 of known type, i.e., of the type manufactured by Cameron Iron Works Houston Shaffer Tool Works Beaumont This safety equipment is installed at the wellhead on the seabed 8. Two hoses are attached to this equipment, one of the hoses is a chokeline 6 and the other a kill-line 7, which are employed during particular emergencies to re-establish the hydrostatic control of the well 10.

The conventional offshore drilling equipment comprises always a riser tube 8, which has a diameter preferably of either 16 or 24 inches and which carries out two important functions:

return of the drilling mud to the surface,

guiding of tools into the well.

The riser 8 is suspended by means ofa series of pneumatic jacks (not shown) installed in a known manner on the floating unit. Owing to the complications involved, the riser represents, given the actual offshore drilling technologies (ambient conditions and design characteristics) the most restrictive piece of equipment as far as the operating water depth is concerned.

The elimination of the riser in the offshore drilling equipment should therefore be considered a great technological achievement in offshore drilling technologies.

FIG. 2 illustrates the offshore equipment in which use is made of the applicant's structure.

In order to nullify the vertical oscillation otherwise transmitted to the drillstring by the floating unit due to wave action, use is advantageously made of a conventional Motion Compensator, for instance of the type manufactured by Vecto Offshore Industries, Inc Ventura California Shaffer Tool Works Beaumont The rotation is transmitted to the drillstring by means of an electric power swivel also of conventional type, such as the one manufactured by Bowen Tools, Inc. Houston The power swivel allows the circulation of the mud and for the purpose it is connected with a mud inlet pipe 13 through which the mud enters the drillstring and the mud outlet pipe 14 through which the mud flows out from the drilling string.

The two-way flow drill pipe system I5 of the drillstring extends from the power swivel 12 down to beyond the safety equipment 5 and constitute the socalled top section of the drilling string. This section is variable in length according to drilling progress underneath the safety equipment.

The lower end of the two-way flow drill pipe system of this invention is connected to the conventional drillpipes 2 and near the connection point lateral apertures 15a are provided in the peripheral wall defining that flow way which is destined to allow the circulation of the mud from the well towards the outlet end 14. Conventional drill collars 3 and a conventional bit 4 complete the drillstring. A rotating head preventer 16', for instance of the type manufactured by Hydril Company Los Angeles protects against loss of circulating mud and provides the hydraulic seal against the drillpipes of the invention. It may operate in a manner similar to a slufiing box.

Advantageously guidelines 17' are provided for han dling the equipment.

During drilling operations, the circulating mud is pumped through the swivel l2 and descends into the well passing first through one of the two flow ways of the drillpipes l5 and then through the conventional drillpipes 2 and finally exits through the bit 4, rising to the surface along the well annular space and, at the top of the section, through the second flow way of the drillpipes 15.

From the foregoing it will be understood that the offshore equipment including the structure of this invention allows the elimination of the riser tube, makes it possible to operate in considerable depths of water, eliminates the chokeand kill-lines, simplifies the subsea equipment, and allows better operating conditions.

It is further important to note that the operating safety has been increased with the equipment of this in vention, inasmuch as the drilling mud circulates in a closed circuit and at an adjustable pressure, allowing for a continuous well control and rapid intervention in case of gas manifestation.

FIGS. 3 to 7 illustrate the structure of the two-way flow pipe of this invention. The partition wall divides the interior of the pipe in two

flow ways

16 and 17, respectively. At both ends of the pipe, pipe heads l8 and I9 are provided. the pipe head 18 having an inner female screw thread 21 and the pipe head 19 having an outer male screw thread 22. these male and female screw threads of corresponding adjoining pipes being adapted to mutually mate as shown in FIG. 4.

At the ends of both pipeheads l8 and 19,

abutment surfaces

23 and 24 are provided, respectively. The abutment surface 23 is provided with a circular recess for receiving a gasket 25. Also the abutment surface 26 of the partition wall 20 has a recess for receiving a diametral portion of the gasket 25 as visible in FIG. 5. The partition 20 enlarges near the head 19 of the pipe to form an enlarged abutment surface 27 in order to guarantee a seal effect over a certain angle. From FIG. 7 of the drawing it clearly appears that the abutment surface 27 tapers from the periphery towards the center of the tube. In this manner the union of the two joints is ensured as long as thread slippage remains within the abovementioned angle alpha.

The described pipe structure provides a simple and effective joint.

The known component parts of the described drillstring are disclosed in the Composite Catalog of Oilfield Equipment and Services published by World Oil.

1 claim:

1. A two-way flow tube for a drillstring comprising a longitudinal partition wall within the interior of the tube, extending over the length of the tube and separating the tube into two longitudinal tubular compartments, the tube having a female inner screwthread at one end thereof and a mating male screw thread at the other end thereof, said partition wall having abutment surfaces at both extremities thereof for sealing engagement with partition walls of corresponding two-way flow tubes, said partition wall extending according to a diametral plane and having at, at least one end thereof a seat for a sealing gasket, wherein the tube ends have circular abutment surfaces, at least one of said surfaces having circular seats for sealing gasket means, and wherein the partition wall has enlargements at, at least one end thereof thereby to increase the abutment surfaces thereof, said enlargements tapering from the periphery towards the center of the tube at least at the abutment surfaces thereof.

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