WO2005080745A1

WO2005080745A1 - Drill pipe header

Info

Publication number: WO2005080745A1
Application number: PCT/GB2005/000632
Authority: WO
Inventors: Kjetil Bekkeheien; Inger Kjellovoll; Arne Torsvoll; Per Horsrud
Original assignee: Statoil Asa; Cockbain, Julian
Priority date: 2004-02-20
Filing date: 2005-02-21
Publication date: 2005-09-01
Also published as: GB0617000D0; GB2426274B; GB2426274A

Abstract

A drill pipe header comprising a hollow cylindrical body adapted at each end to engage the end of a drill pipe and having a mud inlet port in the side wall of the body and a valve. In a first position the valve seals the inlet port and permits mud flow between the ends of the body and in a second position prevents mud flow between the ends of the body and permits mud flow from the inlet port to the lower end of the body.

Description

Drill Pipe Header

This invention relates to improvements in and relating to apparatus for sub-surface drilling, in particular for drilling into hydrocarbon or other subsurface reservoirs . More particularly it relates to header units for drill pipes, to drill pipes incorporating such header units, and to a method of drilling using such pipes. Sub-surface drilling involves driving a drill bit using a remote drive motor, the bit and the motor being connected via a drill string consisting of interlocked hollow drill pipes, each generally about 9m long and about 20cm external diameter. During the drilling operation, drilling mud is pumped down to the drill bit through the drill string and back up the bore hole outside the drill string to the surface. The rising mud carries debris away from the area of the bit and the mud coming out of the bore is cleaned and re-used. As the bore gets longer, the drill string needs to be lengthened. To do this the drive motor is disengaged from the top end of the drill string, a fresh drill pipe, or more generally a stand comprising three drill pipes with a total length of about 27m, is fitted onto the top of the drill string, the drive motor is engaged with the top of the fresh drill pipe or stand, and drilling is recommenced. During the fitting of the fresh drill pipe or stand, pumping of mud, which enters the drill string at the site of the drive motor, is stopped and when drilling recommences, mud pumping also recommences. This has the effect that the flow of mud in the bore ceases during the fitting of the new drill pipe or stand. Restarting the mud flow requires a higher pressure than is required simply to maintain the mud flow and this pressure surge can cause the mud to damage the formation - the rock surrounding the bore hole. Moreover, while mud flow is halted, debris can settle - building up in the vicinity of the drill bit, and the pressure towards the drill bit will decrease as friction loss-to-pressure disappears when drill string rotation stops . It is therefore desirable to maintain mud flow during the period when a new drill pipe or stand is being fitted. A device to achieve this, the Maris continuous circulation coupler, has been developed by Maris International of the UK and is described at Maris ' website www.marisint.co.uk and in WO 00/22278. This device is essentially a sleeve which surrounds the top end of the drill string and which is capable of being partitioned to form a lower and an upper chamber allowing mud to be pumped into the lower chamber and hence into the drill string while a new drill pipe or stand is fitted. The Maris coupler however is relatively bulky, making its deployment on existing drilling rigs problematical and expensive. We have now realized that continuous mud circulation can be achieved in a much simpler manner using a valved header unit which is placed on the top of each new drill pipe or stand and which will form and remain an integral part of the drill string, i.e. it will travel down the bore hole as the drill string is lengthened. Thus viewed from one aspect the invention provides a drill pipe header comprising a hollow cylindrical body adapted at each end to engage the end of a drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow between the ends of said body and in a second position prevents mud flow between the ends of said body and permits mud flow from said port to the lower end of said body. Viewed from a further aspect the invention also provides a drill pipe having a header according to the invention engaged at one end thereof. If desired, the header unit may form an integral part of a drill pipe. Thus viewed from a further aspect the invention provides a drill pipe having at one end thereof a header comprising a hollow cylindrical body adapted at the open end thereof to engage the end of a further drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow along the length of the pipe and header and in a second position prevents mud flow along the length of the pipe and header and permits mud flow from said port to the other end of said pipe. Viewed from a further aspect the invention also provides a method of sub-surface drilling operation wherein a drill bit connected to one end of a drill string is driven by a drive motor engageable with the other end of said drill string, wherein mud is pumped through said drill string towards said drill bit, and wherein said drill string is extended by disengaging said motor from said other end, engaging one end of a drill pipe with said other end of said drill string, and engaging said drive motor with the other end of said drill pipe, characterised in that said other end of said drill string is provided with a header comprising a hollow cylindrical body adapted at the open end thereof to engage the end of a further drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow along the length of the pipe and header and in a second position prevents mud flow along the length of the pipe and header and permits mud flow from said port and down the drill string, and in that mud is caused to flow through said inlet port while said drive is disengaged. In the header, the valve may be a single valve or multiple valves. Thus one valve may serve to open or close the mud inlet port while another may serve to permit or prevent mud flow along the length of the cylindrical body. Whatever particular design is adopted, in the first position the valve or valves should desirably permit equipment to pass through the length of the header without being stopped or hindered by the valve (s) . Header units having valves which can be operated to prevent fluid flow along the drill string are well known in the industry. One particularly suitable valve design is known as a Kelly valve. (Headers with Kelly valves are available for example from WNCO Valve International of Odessa, Texas, US) . The Kelly valve is a ball which sits in a chamber within the cylindrical header and is rotatable about an axis perpendicular to the header's cylindrical axis. Perpendicular to the axis of rotation, a cylindrical aperture extends through the ball . Thus in one position this aperture is aligned with the header's cylindrical axis so allowing fluid to flow through the header. With the ball rotated through 90° however, the aperture is perpendicular to the header's cylindrical axis and the ball thus prevents fluid flow. In the headers of the invention, the valve is preferably a modified Kelly valve having a further aperture in the ball perpendicular to the first and not penetrating through the entire ball . The combined aperture is thus T shaped. Desirably the vertical of the T opens through a plurality of smaller apertures (preferably ones elongated in the axial direction of the bar of the T) into the bar of the T. In this way the vertical of the T is less likely to "snag" or interfere with equipment passed down through the drill string. In one valve position, the bar of the T is aligned parallel to the header's cylindrical axis with the vertical of the T pointing away from the mud inlet port . Rotated through 90°, one end of the bar of the T points towards the mud inlet port and the vertical of the T is parallel to the header's cylindrical axis pointing to the lower end, i.e. to the drill string. The "ball" in a Kelly valve need not of course be spherical. A cylindrical valve member, mounted with its cylindrical axis perpendicular to the cylindrical axis of the header and with apertures perpendicular to its own cylindrical axis will of course function in the same manner; likewise, cylindrically symmetrical deformed spheroids may be used (the "ball" in the WNCO Kelly valves is just such a deformed spheroid, more particularly a cylinder with rounded ends) . In an alternative embodiment, the valve in the header of the invention comprises two valves: an upper valve which opens or closes the inner bore of the cylindrical body - e.g. a conventional Kelly valve or ball valve; and a lower valve in the form of a cylindrical sleeve, with its cylindrical axis parallel to that of the header cylinder, which is displaceable in its axial direction, or preferably is rotatable about its cylindrical axis under the action of a key-driven gear, between a position in which the mud inlet port is open and a position in which the mud inlet port is closed. If the sleeve is rotatable it is preferably provided with an aperture in its side wall to permit mud flow when the valve is in the open position. The header of the invention, in this form may comprise two headers engaged together, the upper one containing the valve for shutting off flow along the header's cylindrical axis (i.e. for example a conventional header) and the lower one containing the mud inlet port and the valve therefor. Thus viewed from a further aspect the invention provides a drill pipe header comprising a hollow cylindrical body adapted at each end to engage the end of a drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow between the ends of said body and in a second position permits mud flow from said port to the lower end of said body. Viewed from a yet further aspect the invention provides a drill pipe having at one end thereof a header comprising a hollow cylindrical body adapted at the open end thereof to engage the end of a further drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow along the length of the pipe and header and in a second position permits mud flow from said port to the other end of said pipe. Other valve systems, well known in the art may of course be used. The valve in the header of the invention is preferably mechanically operated, e.g. by the turning of a key. This is a preferred operating mode since it reduces the risk to the workers on the drilling platform. This is the operating technique conventional for Kelly valve headers . Electrical or magnetic or electromagnetic valve operation is possible but for safety reasons is not currently preferred, however automatic operation, e.g. actuated by a pressure sensor, may be a desired back-up so that any sudden change in pressure within the drill string will cause the valve to close the central passage through the drill string. Nonetheless automated valve operation, obviating the need for personnel to be present at the head of the drill string, may in due course be preferred. In the headers of the invention, the valve will almost invariably be preferably such as to allow equipment to be passed through, i.e. down inside the drill string. This is important as it may be necessary to drill out a clogged drill string, to introduce explosives, to introduce logging equipment, to inject well treatment agents, etc. The Kelly valve and slieve valves described above are thus particularly desirable valve formats as they allow the header to have an internal diameter through the valve (s) which is the same as or closely similar to the internal diameter of the drill pipes. The external diameter of the header of the invention must of course be no greater than the internal diameter of the bore hole (which is determined by the size of the drill bit or casing) . Preferably the header's external diameter is within 3cm of the external diameter of the drill pipes in the drill string, more preferably within 2cm, especially preferably within 1cm. The header ' s external diameter however may have to be greater than that of the drill pipes in order to mount the valve within an environment capable of withstanding the injection pressure of the drilling mud. The header of the invention is adapted for engagement with a drill pipe. Generally this will mean that the open ends are provided with a screw fitting which tightens under the rotation experienced under the action of the drive motor. Preferably the upper end is provided with a female screw section and the lower with a male screw section. The header cylinder will generally be a construct of two (or more) cylindrical sections so as to allow internal placement of the valve. This is conventional for headers including Kelly valves. The sections may screw together or may be welded together - again this is conventional . The mud inlet port in the header of the invention is preferably provided with a further valve, separately operable, so as to optimize operator safety. Likewise it is preferably provided with an external cap that may be put in place after mud injection ceases so as to minimize damage to the inlet port during its time down- hole (the drill pipes will generally be re-used for drilling at different sites) . Particularly preferably, the mud injection port will be provided with a pressure sensor and/or a bleed mechanism so that the operator will be warned if there is a pressure differential that would make it dangerous to open the port or attach a mud injection hose. For operation of the method of the invention, it is preferred that the mud pump be attached via a valved hose to the mud injector port of the drive motor assembly. The mud pump is preferably provided with a further valved hose capable of mating engagement with the inlet port of the header of the invention at the top of the drill string. That hose is preferably connected before the drive motor is disengaged and mud pumping through the mud inlet port preferably is begun before, simultaneously or very shortly after mud pumping through the drive motor assembly ceases. The cylindrical shell of the header of the invention is preferably made of metal of a thickness and strength comparable to the drill pipe or a conventional Kelly valve containing header. The header should thus be capable of withstanding the torque experienced during drilling, pressure differentials, stretch due to stuck drill string, vibration, etc. likely to be experienced in use. Again this is purely conventional for header units . Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a cut-away schematic drawing of a first header according to the invention; Figures 2A and 2B are cut-away schematic diagrams of a second header according to the invention; and Figures 3a and 3b are schematic drawings of a drilling platform before and during placement of a fresh stand. Referring to Figure 1 there is shown a header 1 having a hollow cylindrical body 2 provided with male 3 and female 4 screw portions for engagement with drill pipes, a mud inlet port 5 and upper 6 and lower 7 valves . The upper valve 6 is a conventional Kelly valve. The lower value 7 comprises a hollow cylindrical slieve 8 having an aperture 9 in its side wall and gear teeth 10 around its circumference. Gear teeth 10 engage with a gear wheel 11 operable from outside the header via drive shaft 12. To keep the slieve in place, it is provided with sealing rings 13. Mud inlet port 5 has a removable cap 14 and an external section 15 engageable with a mud hose 16. In use, cap 14 is removed, hose 16 engaged, valve 6 is shut, valve 7 is opened, the drive motor is disengaged and a fresh drill string is screwed into female section 4. The drive motor is re-engaged, valve 6 is opened, valve 7 is shut, hose 16 is disengaged and cap 14 is replaced. Referring to Figures 2A and 2B there is shown a header according to the invention having a modified Kelly valve 17. The header 1 has a cylindrical body 2 with upper female 4 and lower male 3 screw portions for engagement with drill pipes . The body 2 has a mud inlet port 5 into which a cap 14 may be placed. The modified Kelly valve is a ball 17 with a T shaped aperture therethrough. It is rotatable, using a key and drive shaft not shown, about an axis perpendicular to the drawing. In the position shown in Figure 2A, mud flow along the length of the header is permitted and mud inlet port 5 is closed. Rotation through 90° (clockwise) to the position shown in Figure 2B closes the header to mud flow along its length and allows mud flow from the inlet port. Referring to Figure 3A, there is shown a drilling platform 20 having a drive motor 21 engaged with header 1 at the top of drill string 22. Mud pump 23 is attached to header 1 and drive motor 21 via hoses 24 and 25 which are provided with valves 26 and 27. The valve of the header 1 is then adjusted to permit mud flow into the inlet port, and drive motor 21 is disengaged from the header. A stand 28 with a further header 29 is then fitted to the open end of header 1 when the drive motor is in its raised position as shown in Figure 3B .

Claims

Claims :

1. A drill pipe header comprising a hollow cylindrical body adapted at each end to engage the end of a drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow between the ends of said body and in a second position prevents mud flow between the ends of said body and permits mud flow from said port to the lower end of said body.

2. A drill pipe header comprising a hollow cylindrical body adapted at each end to engage the end of a drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow between the ends of said body and in a second position permits mud flow from said port to the lower end of said body.

3. A drill pipe having a header according to either of claims 1 and 2 engaged at one end thereof .

4. A drill pipe having at one end thereof a header comprising a hollow cylindrical body adapted at the open end thereof to engage the end of a further drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow along the length of the pipe and header and in a second position prevents mud flow along the length of the pipe and header and permits mud flow from said port to the other end of said pipe.

5. A drill pipe having at one end thereof a header comprising a hollow cylindrical body adapted at the open end thereof to engage the end of a further drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow along the length of the pipe and header and in a second position permits mud flow from said port to the other end of said pipe.

6. A method of sub-surface drilling operation wherein a drill bit connected to one end of a drill string is driven by a drive motor engageable with the other end of said drill string, wherein mud is pumped through said drill string towards said drill bit, and wherein said drill string is extended by disengaging said motor from said other end, engaging one end of a drill pipe with said other end of said drill string, and engaging said drive motor with the other end of said drill pipe, characterised in that said other end of said drill string is provided with a header comprising a hollow cylindrical body adapted at the open end thereof to engage the end of a further drill pipe, having a mud inlet port in the side wall of the said body and having a valve which in a first position seals said port and permits mud flow along the length of the pipe and header and in a second position prevents mud flow along the length of the pipe and header and permits mud flow from said port and down the drill string, and in that mud is caused to flow through said inlet port while said drive is disengaged.