GB2442522A

GB2442522A - Real Time Pressure Wave Telemetry Device

Info

Publication number: GB2442522A
Application number: GB0619459A
Authority: GB
Inventors: Luke Kuwertz; Geoffrey Downton
Original assignee: Gemalto Terminals Ltd; Schlumberger Holdings Ltd
Current assignee: Gemalto Terminals Ltd; Schlumberger Holdings Ltd
Priority date: 2006-10-03
Filing date: 2006-10-03
Publication date: 2008-04-09
Anticipated expiration: 2026-10-03
Also published as: NO20074955L; GB0619459D0; NO338730B1; CA2605045A1; GB2442522B; CA2605045C

Abstract

A real time telemetry system is disclosed for use with a drilling system including a rotary valve 28 controlling the supply of drilling fluid or mud to a downhole tool. The system comprises receiving data to be transmitted, encoding the data as a duration, and controlling the rotation the rotary valve 28 such that the rotary valve 28 is rotated for the said duration at a predetermined rotary speed to cause the formation of pressure fluctuations or waves in the drilling fluid or mud.

Description

REAL TIME TELEMETRY

This rnvantion relates to a teleinry system and in particular to a telematiy system suitable for use in the transmission of data in a borehole his desirable, m tbe drilling of a sulerranean borthole in a forrmiion, to be able to transmit data along the borehole. For example, where a steerable drilling system is being used and downhole sensors are pro'ided and arranged to output signals representative of, for example, the drilling direction, it is desirable to be able tO tr&L3flIt signal data representative of the drilling direction, in reel tiim, to an operator located at the surface.

A number of te1eniy systen are known which are capable of providing such transrrassion of data. However, such systems tend to be relatively complex and expensive, amid may not be able to transmit data in real tin. There are situations where the amount of data to be triwismitted is relatively small and the provision of such a telenEtmy system cannot be justified or,if provided, is not used to its fullest exterd. It is an object of the mvention to provide a telenEtry system of relatively simple and convenient form, suitable for use m such applications.

Accorthng to the present invention there is provided a tclemiy system for use in a drilling system including a rot valve controlling the supply of drilling flwd or nuid to a downhole tool, the system comprising receiving data to be tna-isrnitted, encoding the data as a duration, and controlling the rotation the rotary valve such thai the rotary valve is rotated for the said duration at a predetermined rotary speed to cause the formation of pressure fluctuations or waves in the drilling fluid or mud It has been found that the rotation of a rotary valve produces pressure fluctuations or waves m the drilling fluid or med supplied to, and through, the rotary valve, in use, and that these fluctuations or waves can be sensed, for example, at the surface. By appropriate control of the rotary valve, these pressure fluctuations or waves can be used to transmit sigrls, without requiring the provision of additional, coirq1ex doihk tools Consnt1y, data can be transmitted in real time to an operator located at the surface.

Conveniently, tbe drilling systeiri inchkies at least one downhole sensor, the output of which corrqrises the data to be transmiIt In order to irease tbe amount of data that can be transmitted using tbe system, two or iore predetermined rotary speeds may be chosen, each being indicative of the output of a respective sensor. Alternatively, the date may be encoded using a look-up table, a first signal transmitted by rotating the valve for a first duration at a first predetermined rotary speed being used to transrrnt information relating to one coordinate of the look-up table, a second signal transmitted by rotating the valve for a second duration at a second predetermined speed being used to transmit information relating to another coordinate of the look-up table.

The signal transmitted using the system ny be decoded by the operator simply by rrirnltonng for how long the pressure fluctuations or waves at the predetermined &equery are received This irny be achieved nnuaJly or automatically using an appropriated controlled device.

The signals trairnitted in this fashion are irost readily identifiable when the drill pipe is stationaiy. Conveniently, therefore, the system is used to transmit data shortly after the downhole tool has compled its start-up sequence when the pumps supplying the drilling fluid or nnid are switcIl i However, it ny be possible to use the system to trarisnit data to the surface at other tirrs.

11 invention 1l further be described, by way of example, with refence to the ac ompany g drawings, in whicK Figure 1 is a diagranintic view illustrating part ofa bottom hole assembly including a downhole tool controlled using a rotaiy valve; Figure 2 is a diagrammatic view illustrating the rotaiy valve; aixi Figures 3a and 3b are tables illustrating t'w possible encoding techniques.

Referring firstly to Figure 1, illustrated din rammatically is part of a bottom bole assembly 10 for ise in the forn.tion of a borile 14 in a subsurface formation 12 The assembly 10 comprises a drill bit 16 carried by a bias umt 20 A control unit 18 is operable to control the operation of the bias unit 20.

ebiwut2oincludcsabousing Zarrangedtocarryasenesofbiaspaiis 24 Each bias pail 24 is able to rrve between a retracted position and an extended position, piston arrangements 26 bemg provided to drive each pad 24 from its retracted position to its extended position. The piston arrangements 26 are operable independently of one another, the supply of fluid under pressure to the piston arrangements 26 being controlled by a rotaiy control valve 28 located within the control unit 18.

In use, the housing 22 is carried by or forir part of a dnll pipe or string which is rotated, orexanle from the surface or by adownhele located nkitor. [1 the piston arrangements 26 are supplied with fluid under pressure in turn, in synchronism with the rotalion of the housing 22, it will be appreciated that tie bi pads 24 are tmved, in turn, to their extemded positior. In their extended posmtioos, the pads 24 bear against the wall of the borehole 14 and a laterally direed reaion forceisppliedtothehousing22. Bycontrollingthepistoiiarrangements2óma mazuer synchmnised with the rotation of the housing 22, it will be appreciated thai t}erctionfofceacts1nasubetantia1lyconsisterddirectiorL Asthedrilibit l6is secured to the housing 22, ii will be appreciated that the operation of the bias imit in this manner also results in the application of a laterally directed force to the drill bit 16, thus urging the drill bit to form a curve or dogleg in the borehole 14.

The rotary control valve 28 corrçrises a face sealing valve of the type illustrated, diagrammatically, in Figure 2. The valve corrrises a rotary valve member 30 of disc-like form located within a chamber 32 to which drilling fluid or mud is splie1, in use, under pressure through the drill pipe through an inlet 34 Also located within the chamber 32 is an outlet member 36, also of disc-like form, a surface of the valve member 30 abutting a surface of the outlet member 36. The outlet member 36 is forrrl with a series of openings 38 extending from the surface against which the valve member 30 bears to the opposing surface thereol each opening communicating with a respective oullet 40. The outlets 40 communicate, in use, with respective ones of the piston arrangemenis 26. The openings 38 provided in the outlet member 36 are located at a common radial position The valve member 30 is provided with an arcuate opening 42 which extends from the surface thereof which abuts the outlet member 36 to the opposing surface thereof and which is provided at the same radial position as the openings 38 A control shall 44 extends into the chamber 32 and is connected to the valve member 30 to drive the valve member 30 for rotation.

It will be appreciated that, in use, fluid entering the chamber 32 passes through the arcuate opening 42 and into whichever of the openings 38 is aligned tewith, the fluid flowing through the respective outlet 40 to the associated piston wTangement 26 The selection of which, if any, of the outlets 40 to which ulwd is supplied by the valve 28 depends upon the angular position of the valve member 30 which, in turn, is dependent upon the angular position of the control shaft 44.

The control sha.ft44 may berot byarangeofdevices Forexample,an appropriately controlled electrically operated motor may be used to drive the shaft 44 and thereby control the operation of the valve 28 Alternatively, the control shaft 44 could be connected to an appropriately controlled roll stabilised platform. In either case, the movennl of the shaft 44 may be controlled in response to the output signais from one or nKre dowrihole sensors 46, for example arranged to sense the inclination of the housing 22 Systems of this type are well kiiown and so the operation thereof will not be desciibed in further detaiL Whilst the control shaft 44 is rotated, pressure fluctuations or waves are formed in the dnllmg fluid or naid in the diii! pipe as coirmmication commences, mmd subsequently is Ixoken, between the arcuate opening 42 and the openings 38, m turn. The pressure fluctuations or waves so formed can be sensed at the surface or at other locations spaced from the valve 28, especially at tinEs when the drill pipe is not beng rotated.

In accordance with the mvention, the formation of these pressure fluctuations or waves is harnessed to ab!e the transmission of data from the bottom hole assenly, for example to the surface. For example, where the sensor 46 is arranged to outpi a signal representative of the inclination of the bias unit housing 22, the output signal from the sensor 46 is encoded, for exairçle using the table sbon in Figure 3a to denve a duration representative of the sensed inclination. The rotary valve 28 is then driven for rotation at a predetermined rotary speed for the derived duration, thus transmitting a series of pressure fluctuations or waves through the drilling fluid or mud at a frequency related to the speed of rotation of the rotaiy valve for the derived duration. Surface located equipment sensitive to the pressure fltLtuaiions or waves in the fluid can be used to enable an operator to measure for how long the pressure fluctuatior or waves were transmitted at the predoterrnined frequency The duration can then be decoded to provide the operator th real time information represtative of the inclination of the housing 22 Forexample,ifthesensor46outptgindicalesthalthehousing 22 is inclined at an angle of 2.5 degrees, using the technique described hereinbefore with reference to Figure 3a, the rotnzy valve 28 is rotated k)r a period of 30 seconds at the predetermined rotary speed, for example at a speed causing pressure fluctuatoris or waves to be trismitted at a frequency of 6Hz. The operator, upon measuring that a 6Hz signal has been received for 30 seconds can ascertain, in real tin, that the inclination of the housing 22 is in the range 2-3 degrees It will be appreciated that other rotaiy speeds of the valve 28 may be used to transmit signals, and that the durations and ranges of inclination angles, and relationships therebetween, may be selected to suit the application in which the invention is used.

Where two or more sensors are provided, data representative of the outpts of the sensors may be trairnitled, in turn, for example with the rotaiy valve being rotated at diff&ent rotary speeds so as to provide an indication of for which parameter data is being transmitted.

Figure 3b illustrates an alternthve encoding technique which ny be used to transmit larger quantities of data using the system of the inventioa In this arrangement, the output signals from the sensors are encoded using a look-up table.

For example, if his determined that the toolface angle is 90 degrees and the deviation is 60%, tl using the look-up table shown in Figure 3b it can be seen that this combination of parameter values occurs in colwm 3, row 7 of the look-up table.

In this exanle the colunwi data is transmitted by rotating the valve 28 at a rotary speed to generate pressure fluctuations or waves at a frequency of 4Hz., and row data is transmitted by rotating the valve 28 to cause pressure fluctuations or waves at a frequency of 6Hz. Thus in order to transmit the data, the valve is rotated to cause a 4Hz signal to be transnutted for 3 iziits of time, ibr example 30 seconds, the valve subsequently being rotated to transmit a 6Hz signai for 7 units of time, for example seconds. Upon recaving these signals, the operator can decode the signals using the same look-up table to obtain, in real time, the toolface and deviation data.

If desired, the look-up table could be used to transmit tool stuS codes or As mentioned bereinbefore, this information is best transmitted when the drill string is not being rotated, and may conveniently be transmitted shortly after the dohoIe tool has completed its rtaitup procedure when the drilling fluid pumps are activated after recycling. However, it may be possible to successfully transmit and receive data using the system at other times The signal received at the surface may be measured simply by the operator detemuning for how long a signal at a predetermined frequency has been transmitted, which he then decodes. Alternatively, surface located equipment may be used to sense the transmission of signals at the predetennined frequency or frequencies, to measure for how long the signals are transmitted, to decode the signals aJi to produce an appropnale output for the operator The ability to transmit data in real time in accordance th the invention is advantageous in that, compared to conventional arrangements, data can be trrnitted in a relatively simple, quick and convenient manr. Data ci th be transmitled mere frequently and cost effectively than is possible with conventional arrangements. The real time trimssion of data also enables an operator to ascertain that the doshole equipment is opa1ing correctly, that communications links with the dohole equipment are functioning and may allow greater control ov the dowthole equipnuit as, for example, deviations from a desired path may be sensed and corrected mere quickly The system does not require the provision of additional downhole tools or equipment, hit rather may be implenfled simply by approxiate rmdification of the control system of a standard downhole tool.

It will be appreciated that a range of medifications and alterations may be made to the invention descnbed hereinbefore without departing from the scope of the invention.

Claims

1. A telemetry system for e in a drilling system including a rotary valve corilrothng the supply of drilling fluid or mud to a dowrihole tool, the system comprising receiving data to be transmitted, encoding the data as a duration, and controlling the rotation the rotaiy valve such that the rotary valve is rotated for the said duration ax a predetemiined rotary speed to cate the formation of pressure fluctuations or waves in the drilling fluid or mud.

2. A system accordmg to Claim 1, wherein the drilling system includes at least one downhole seor, the output of which connses the data to be transmitted.

3. A system according to Claim 2, wherein the drilling system uiciudcs a plurality of sensors, l wherein the roty valve is rotated at two or nre predetermined rotary speeds, each being indicative of the output of a respective sensor 4. A system according to Claim 1 or Claim 2., wherein the data is encoded using

a look-up table.

A system according to Claim 4, wherein a first signal transmitted by rotating the valve for a first duration at a first predetermined rotary speed is used to transmit information relating to one coordinate of the look-up table, a second signal transmitted by rotating the valve for a second duration at a second predetermined speed being used to transmit information relating to another coordinate of the look-

up table

6. A system according to any of the preceding claims, wherein data is transmitted whei the dnll pipe is not rotating 7. A system according to Claim 6, wherein the data is transmitted shortly after the downhole tool h conleted its st&t-up sequeiice when the pumps supplying the drillmg fluid or nnid are switched on.

8. A system according to any of the preceding c1airns wherein the downhole tool compns a bias unit