GB2289117A

GB2289117A - Downhole telemetry system

Info

Publication number: GB2289117A
Application number: GB9509120A
Authority: GB
Inventors: George Swietlik
Original assignee: Pilot Drilling Control Ltd
Current assignee: Pilot Drilling Control Ltd
Priority date: 1994-05-04
Filing date: 1995-05-04
Publication date: 1995-11-08
Anticipated expiration: 2015-05-04
Also published as: GB9509120D0; GB9408823D0; GB2289117B

Abstract

In well drilling, a downhole telemetry system, employing pressure pulsing of mud flow down a drillstring, comprises a valve having a pattern of orifices which variably chokes mudflow to cause dependent variations in back-pressure at the surface. The pattern of orifices is preferably formed by one or more orifices in each of two mutually telescoping sleeves 116, 120 whose relative positions determine the orifice pattern and total mud throughflow area. One sleeve is preferably fixed and the other sleeve slides or turns in dependence on the parameter being telemetered. The telemetry system may be reversed in operation to allow remote operation of downhole equipment from the surface. <IMAGE>

Description

"Telemetry and/or Remote Operation" This invention relates to telemetry and/or remote operation, and relates more particularly but not exclusively to apparatus and methods for telemetry from a downhole location in a well, to a surface location, and additionally or alternatively for remote operation at a downhole location in a well, from a surface location.

During the drilling of a deep well intended for the eventual production of hydrocarbons, it may happen that instrumentation or a specialised tool is deployed downhole, and that information must be telemetered from the instrumentation or tool and up the well to the surface and/or that operational signals must be telemetered from the surface and down the well for remote operation of the instrumentation or tool. The physical separation of the downhole equipment from the surface (which may be hundreds or thousands of feet) and other circumstances preclude many conventional forms of telemetry and remote operation. Proposals have been made to provide a telemetry function in wells being drilled with the aid of a flow of mud down a drillstring, by intermittently choking the flow of mud so as to produce a pulse or series of pulses in the mud pressure as monitored at the surface.However, the proposed mud pulsing arrangements rely on poppet valves or plunger/orifice systems which present restricted mud flow areas even when "open" and therefore cause a high pressure drop; such problems could not be expected to be obviated if the arrangements were adapted to remote operation.

According to a first aspect of the present invention there is provided apparatus for producing or responding to a controlled flow of fluid, said apparatus comprising first orifice means and second orifice means, said first orifice means having a first pattern of orifices therethrough, said second orifice means having a second pattern of orifices therethrough, said first and second orifice means being relatively mounted and relatively movable to present a combined pattern of orifices therethrough, said combined pattern being variable in dependence upon the relative positions of said first and second orifice means, fluid flow direction means to direct at least a part of said flow of fluid through said combined pattern of orifices, and means to vary the relative positions of said first and second orifice means to produce or respond to the controlled flow through the combined pattern of orifices.

The means to vary the relative positions of the first and second orifice means may do so in accordance with information to be telemetered or, alternatively, the relative positions of the orifices may be varied in response to fluid flow controlled to telemeter operational signals.

Said first and second orifice means are preferably formed as respective sleeves dimensioned to be a mutual sliding fit for mutual telescopic movement and/or for mutual rotational movement. One said sleeve is preferably anchored to be immobile, and the other said sleeve is coupled to or integral with a movable element whose movement and/or position is to be telemetered by said apparatus in use thereof. Said first and second patterns of orifices may be respective pluralities of through ports in the walls of said first and second sleeves, the first and second patterns of through ports in respect of the mutual location of ports in each pattern, together with the dimensions and alignments of the individual ports in each pattern being mutually identical or mutually non-identical.Said first and second patterns of orifices are preferably such that the ports thereof undergo sequential opening and closing when the sleeves undergo relative movement in any single direction.

Said first and second patterns of orifices may alternatively be a respective single through port in the walls of said first and second sleeves.

Said fluid flow direction means preferably comprises seal means and a hollow tube slidingly sealed thereby to a housing means of said telemetry apparatus, one said sleeve being secured on or integral with an end of said tube to co-operate with the other said sleeve, said one sleeve receiving or delivering fluid through said tube, said other sleeve delivering or receiving fluid around the outside thereof, and said tube being coupled to or integral with or constituting said movable element.

The total orifice area of said combined pattern of orifices is preferably greater than the cross-sectional area of the bore of said hollow tube.

Said combined pattern of orifices may be cyclically variable with regular increments of relative movement between said first and second orifice means whereby to telemeter such increments of regular movement, but said combined pattern preferably has at least a substantial element of acyclic variability whereby to telemeter absolute relative positioning of said first and second orifice means.

Said apparatus may include bias means biassing at least one of said first and second orifice means to tend to bring said first and second orifice means to a preferred relative position. Said bias means may comprise a spring.

According to a second aspect of the present invention there is provided a telemetry method for telemetring information from a downhole tool or instrumention at a downhole location in a well, up the well to a surface location, said downhole location being supplied with pressurised fluid conveyed down the well in a hollow tubular string, said method comprising the steps of providing apparatus according to the first aspect of the present invention, coupling said apparatus to said string to cause at least a substantial fraction of said fluid to flow through said apparatus, causing said flow direction means to direct at least a substantial proportion of said substantial fraction through said combined pattern of orifices, and linking said tool or instrumentation to said position variation means to vary the relative positions of said first and second orifice means in accordance with said information to be telemetered whereby to cause pressure variations in said fluid which are detectable at said surface location.

According to a third aspect of the present invention there is provided a remote operation method for telemetring operational signals from a surface location down a well to a downhole tool or instrumention, pressurised fluid being conveyed in use down the well in a hollow tubular string, said method comprising the steps of providing apparatus according to the first aspect of the present invention, coupling said apparatus to said string to cause at least a substantial fraction of said fluid to flow through said apparatus, causing said flow direction means to direct at least a substantial proportion of said substantial fraction through said combined pattern of orifices, and linking said tool or instrumentation to be operated in accordance with the telemetered operational signals whereby pressure variations in said fluid which are produced at said surface location result in remote operation of said tool or instrumentation.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawing wherein: Figs. 1, 2 and 3 are longitudinal sections of a first embodiment, in three successive stages of operation thereof; Figs. 4 and 5 are respective longitudinal sections of two of the principal components of the first embodiment; Figs. 6 and 7 are respectively a longitudinal section and a plan view of another component of the first embodiment; Fig. 8 is a transverse cross-section of the components of Figs. 4 and 5 mutually co-operating; Figs. 9 and 10 are graphs relating to the performance of the first embodiment; Fig. 11 is a longitudinal section of part of a second embodiment; Figs. 12 and 13 are respective longitudinal sections of two of the principal components of a third embodiment; and Fig. 14 is a graph illustrating a particular advantage of the present invention.

Referring first to Fig. 1, a first embodiment 100 of mud pressure pulse telemetry apparatus in accordance with the invention comprises a housing 102 having an upper part 104 secured to a lower part 106 by means of a screw-thread connection 108. The upper end of the upper housing part 104 is formed as a standard taperthread box connector 110 by which the apparatus 100 is connected in use to a drill string (not shown).

An annular seal 112 is clamped between the upper and lower housing parts 104 and 106. A tube 114 is slidingly sealed to the seal 112 for longitudinal movement therethrough (as will subsequently be shown in Figs. 2 and 3). The tube 114 is connected to downhole apparatus (not shown) in such a manner that the longitudinal position of the tube 114 with respect to the housing 102 is representative of the information to be telemetered uphole by the apparatus 100.

A first sleeve 116 is connected to the top of the tube 114 for longitudinal movement therewith. The sleeve 116 has a predetermined pattern of slots 118 cut through the sleeve wall (see also Fig. 4).

A second sleeve 120 (see also Fig 5) is secured to a static mounting 122 (see also Figs. 6 and 7) which is secured in the throat of the housing 102 to permit mud flow through and past the mounting 122 without unduly impeding mud flow, and to hold the second sleeve 120 immobile with respect to the housing 102. The second sleeve 120 has a predetermined pattern of slots 124 cut through the sleeve wall.

It is to be noted that the slot patterns 118 and 124 each comprise slots of mutually different sizes, and that the patterns 118 and 124 are mutually different; the significance of these distinctions will be detailed below with reference to Figs. 9 and 10.

It is also to be noted that the mobility of the first sleeve 116 and the fixed position of the second sleeve 120 are such that the first sleeve 116 telescopically slides within the second sleeve 120. A peripheral seal 126 on the first sleeve 116 forms a sliding seal with the bore of the second sleeve 120.

Successively higher positions of the tube 114 within the housing 102 result in progressively increased insertion of the first sleeve 126 onto the second sleeve 120, as may be seen by looking in turn at Figs.

1, then at Fig. 2, and finally at Fig. 3. (Such progressive insertion of the first sleeve 116 into the second sleeve 120 is fully reversible, and any relative position within the range available can be taken up at any time, as dictated by the instantaneous longitudinal position of the tube 114 in accordance with the information to be telemetered).

In each of the different mutual positionings of the sleeves 116 and 120 as shown in Figs. 1 - 3, a different combined pattern of slots is presented to the flow of mud down through the apparatus 100, i.e. from the connector 110, through the mounting 122, down the outside of the second sleeve 120, through at least some of the slots 124, and then through at least some of the slots 118 (or possibly through one or more slots of one slot pattern alone, e.g. as in Fig. 1 for the lowermost slots in the sleeve 116). Possible net orifice sizes presented to mud flow by such variable combined slot patterns is graphically illustrated in Fig. 9, wherein the horizontal axis represents the relative axial displacement of the sleeves 116 and 120 (in inches) and the vertical axis represents the total throughflow area (in square inches).The resultant variations in mud pressure due to the variable choking effect of the variable combined slot pattern are illustrated in Fig.

10 for various rates of mud flow. In Fig. 10, the horizonal axis is the same as the horizontal axis in Fig. 9, while the vertical axis in Fig. 10 represents the pressure drop (impounds per square inch or 'psi') produced by the sleeves 116 -and 120 at a the respective relative position, for a throughflow of 200 gpm (gallons per minute) (lower graph), 250 gpm (middle graph), and 330 gpm (upper graph).

As an example of downhole equipment whose status can be telemetered by the apparatus 100, there may be cited the downhole stabiliser described in GB2134162, whose diameter may be controllably varied by telescopic movement of certain parts of the stabiliser.

Fig. 11 shows an alternative form of sleeve 216 which may be substituted for the sleeve 116 in the first embodiment, the second sleeve preferably undergoing similar modifications.

Figs. 12 and 13 (which correspond to Figs. 4 and 5 respectively) show the form of an inner sleeve 316 and an outer sleeve 320 designed for mutual rotational movement in a third embodiment of the present invention (as distinct from the mutual telescoping movement of the first and second embodiments).

The sleeves in the above and other embodiments of the invention may be arranged for any suitable combination of mutual telescopic movement and mutual rotational movement.

Although the telemetry apparatus in accordance with the invention is particularly applicable to telemetry from a downhole location, the apparatus may be employed to telemeter information from other locations (eg a surface location).

In some previously proposed mud-pulsing systems, pressure pulses could be created through a throat restriction in the mud-flow-carrying bore of the drillstring, but such a throat restriction reduces the perceived effect of the pulses since the flow is already reduced by the throat restriction. It is a particular advantage of the present invention that it does not have a throat restriction in the bore of the pipe where the mud flows through under pressure, ie the flow is full-bore before the pulses are produced.

Important benefits of the present invention include reduced problems with erosion, together with improved hydraulic performance in deep wells and/or with flow in smaller diameter pipe as in the case of slim-hole drilling or coiled tubing work since there are no further reductions in total flow area through the mudpulsing telemetry system of the present invention.

Fig. 14 graphically illustrates the above-detailed advantage of the present invention. (In Fig. 14, the horizontal axis is flow rate in gallons per minutes ('gpm'), while the vertical axis is pressure drop in pounds per square inch ('psi')). Fig. 14 is a graph showing a nominal increase in background pressure drop (vertical axis, lower graphs) over the interval of the orificed sleeves with increasing flow rates or pumping rates (horizontal axis), and the resultant pulse amplitude (vertical axis, upper graphs). Since the background pressure drop with the present invention is relatively low in comparison to the intentional pressure pulse, the present invention can produce a higher pressure pulse for a given set of conditions than can prior art pulsing systems.

Exemplary embodiments of the invention have so far been described in the context of their use for telemetry (from downhole to surface) of information (particularly information indicative of position, which may in turn be indicative of another parameter transduced to position). These embodiments can be adapted to telemetry, from the surface to a downhole location, of information indicative of operational signals for the remote operation of downhole equipment.

For example, if the sleeve 116 were biassed upwards by means of a suitable spring (not shown), controlled variation of the pumping pressure produced at the surface would force the sleeve 116 downwards against the spring bias by a controlled displacement, so controlling the position of the tube 114 relative to the remainder of the apparatus 100. Such controlled movement of the tube 114 can be utilised (for example) to operate a downhole tool (eg a multi-position tool) or to initiate operation of the tool (eg by opening a valve supplying hydraulic power to the tool).

In use of the apparatus for remote operation, the position-dependent variation in the orifice pattern gives a form of feedback to the surface which is indicative of the response of the arrangement to variation of pumping pressure for remote operation.

Moreover, the slide positions giving maximum flow area through the orifices cause localised dips or notches in the graph of displacement versus pumping pressure (by reason of temporarily reduced back pressure), such that the movable parts of the remote operation apparatus preferentially take up such positions in operation, leading to improved stability and repeatability.

While certain modifications and variations have been described above, the invention is not restricted thereto, and the modifications and variations can be adopted without departing from the scope of the invention as defined in the appended claims.

Claims

1 Apparatus for producing or responding to a controlled flow of fluid, said apparatus comprising first orifice means and second orifice means, said first orifice means having a first pattern of orifices therethrough, said second orifice means having a second pattern of orifices therethrough, said first and second orifice means being relatively mounted and relatively movable to present a combined pattern of orifices therethrough, said combined pattern being variable in dependence upon the relative positions of said first and second orifice means, fluid flow direction means to direct at least a part of said flow of fluid through said combined pattern of orifices, and means to vary the relative positions of said first and second orifice means to produce or respond to the controlled flow through the combined pattern of orifices.

2 Apparatus as claimed in Claim 1, wherein the means to vary the relative positions of the first and second orifice means does so in accordance with information to be telemetered.

3 Apparatus as claimed in Claim 1, wherein the relative positions of the first and second orifices are varied in response to fluid flow controlled to telemeter operational signals.

4 Apparatus as claimed in any preceding Claim, wherein said first and second orifice means are formed as respective sleeves dimensioned to be a mutual sliding fit for mutual telescopic movement and/or for mutual rotational movement.

5 Apparatus as claimed in Claim 4, wherein one said sleeve is anchored to be immobile, and the other said sleeve is coupled to or integral with a movable element whose movement and/or position is to be telemetered by said apparatus in use thereof.

6 Apparatus as claimed in Claim 4 or 5, wherein said first and second patterns of orifices are respective pluralities of through ports in the walls of said first and second sleeves.

7 Apparatus as claimed in Claim 6, wherein said first and second patterns of orifices are such that the ports thereof undergo sequential opening and closing when the sleeves undergo relative movement in any single direction.

8 Apparatus as claimed in Claim 6, wherein said first and second patterns of orifices are each a respective single through port in the walls of said first and second sleeves.

9 Apparatus as claimed in any of Claims 5-8, wherein said fluid flow direction means comprises seal means and a hollow tube slidingly sealed thereby to a housing means of said telemetry apparatus, one said sleeve being secured on or integral with an end of said tube to co-operate with the other said sleeve, said one sleeve receiving or delivering fluid through said tube, said other sleeve delivering or receiving fluid around the outside thereof, and said tube being coupled to or integral with or constituting said movable element.

10 Apparatus as claimed in Claim 9, wherein the total orifice area of said combined pattern of orifices is greater than the cross-sectional area of the bore of said hollow tube.

11 Apparatus as claimed in any preceding Claim, wherein said combined pattern of orifices is cyclically variable with regular increments of relative movement between said first and second orifice means whereby to telemeter such increments of regular movement.

12 Apparatus as claimed in any preceding Claim, wherein said combined pattern of orifices has at least a substantial element of acyclic variability whereby to telemeter absolute relative positioning of said first and second orifice means.

13 Apparatus as claimed in Claim 3 or in any of Claims 4-12 as dependent on Claim 3, wherein said apparatus includes bias means biassing at least one of said first and second orifice means to tend to bring said first and second orifice means to a preferred relative position.

14 Apparatus as claimed in Claim 13, wherein said bias means comprises a spring.

15 A telemetry method for telemetring information from a downhole tool or instrument ion at a downhole location in a well, up the well to a surface location, said downhole location being supplied with pressurised fluid conveyed down the well in a hollow tubular string, said method comprising the steps of providing apparatus according to Claim 2 or to any of Claims 4-12 as dependent on Claim 2, coupling said apparatus to said string to cause at least a substantial fraction of said fluid to flow through said apparatus, causing said flow direction means to direct at least a substantial proportion of said substantial fraction through said combined pattern of orifices, and linking said tool or instrumentation to said position variation means to vary the relative positions of said first and second orifice means in accordance with said information to be telemetered whereby to cause pressure variations in said fluid which are detectable at said surface location.

16 A remote operation method for telemetring operational signals from a surface location down a well to a downhole tool or instrumention, pressurised fluid being conveyed in use down the well in a hollow tubular string, said method comprising the steps of providing apparatus according to Claim 3 or to any of Claims 4-14 as dependent on Claim 3, coupling said apparatus to said string to cause at least a substantial fraction of said fluid to flow through said apparatus, causing said flow direction means to direct at least a substantial proportion of said substantial fraction through said combined pattern of orifices, and linking said tool or instrumentation to be operated in accordance with the telemetered operational signals whereby pressure variations in said fluid which are produced at said surface location result in remote operation of said tool or instrumentation.

17 Telemetry apparatus substantially as hereinbefore described with reference to Figs. 1-10 of the accompanying drawings, or to Fig. 11 of the accompanying drawings, or to Figs. 12 and 13 of the accompanying drawings.

18 Remote operation apparatus substantially as hereinbefore described.

19 A telemetry method substantially as hereinbefore described.

20 A remote operation method substantially as hereinbefore described.