GB2403538A

GB2403538A - Communication link between seismic sondes in a well and the surface

Info

Publication number: GB2403538A
Application number: GB0315721A
Authority: GB
Inventors: Paul Steven Jaques
Original assignee: ABB Offshore Systems Ltd
Current assignee: Baker Hughes International Treasury Services Ltd
Priority date: 2003-07-04
Filing date: 2003-07-04
Publication date: 2005-01-05
Also published as: GB0315721D0; WO2005006019A1

Abstract

A number of seismic (or microseismic) sondes 1 are clamped 3 to the casing 2 of a hydrocarbon production well (eg a subsea well). The sondes 1 are connected by cables 4 (eg twisted pair), or a common cable, to a distribution box 5. A cable 6 (eg multiple twisted pairs) transmits analogue signals to a multiplexer/digitizer 8 mounted just below well head/tubing hanger 7, at or near the land surface or seabed S. Data may then be transmitted via a single core or fibre optic cable over long distances to the sea surface, or to a remote control system in the case of a land based well. Since the multiplexer/digitizer is not mounted close to the fluid extraction area, it is not subject to high pressures and temperatures, and hence less susceptible to failure.

Description

FLUlD PRODUCTION WELLS INCLUDING SEISMIC SONDES The present invention

relates to the use of seismic sondes in fluid production wells, such as hydrocarbon production wells.

Microseismic analysis ofthe geographical strata around the bore of fluid production well is typically effected by the use of sondes using geophones, mounted downhole in the area of the fluid extraction. A typical four element geophone assembly is known in the industry as a PS 3 tool. This requires, typically, eight electrical wires to communicate data fi om the sonde to the surface of the well. Usually, a number of sondes are mounted in the well at different levels in the bore and thus with a typical set of four sondes, there are thity-two wires that connect to the surface. Each of these wires has to pass through the well hanger through a pressure seal. The signal from each geophone is analogue, and in any particular case there is a maximum practical transmission distance of the signal through the wires. For example, with thin wires encapsulated in a 1/4" steel tube and with signals at fi equencies in the range 0-2000H:z, the distance could be of the order of 2 kilomeh es. Particularly in the case of subsea hydrocarbon production wells, the distance from the geophones in the bore and the sea surface will often exceed this distance. Thus, the problems are the difficulty and expense of passing a large number of wires through sealed interfaces through the well hanger and the difficulty of communication of the analogue data over distances exceeding, for example, 2 kilometres. A possible solution to these problems is to digitise and multiplex these signals, by an electronic unit mounted downhole close to the fluid extraction area.

However, the temperatures here can exceed 200 degrees centigrade which means that this unit would have to use special, expensive high temperature electronics.

More particularly in relation to the above, Fig. ] shows the lower and upper sections of a hydrocarbon production well. The lower section is in the region ofthe fluid extraction area, whilst the upper section is close to the well head. The lower section shows a configuration of sondes 1 secured to the well casing 2 by clamps 3, at different levels.

The wires from each sonde, typically four twisted pairs in a tubular steel cable 4, connect to a junction box 5 mounted in the sonde location area of the well. Connection to the well head control system fiom the junction box 5 is effected by a single tubular steel cable 6, containing at least sixteen twisted pairs, via a sealed interface at the well head/tubing hanger 7. As stated before, the arrangement of Fig. 1, in the case of subsea hydrocarbon production wells, is impractical when the distance from the sondes to the sea surface, where the control system is typically located, exceeds 2 kilometres. A possible solution to this problem is the addition of a multiplexing electronic control unit within, or close to, the junction box 5, which transmits the data via a single cored cable or an optical fibre to the surface, thus overcoming the transmission distance problem, but resulting in the need for expensive high temperature electronic units.

According to the present invention from one aspect, there is provided a fluid production well, including: a plurality of seismic sondes located in the well below a surface; means in the well for receiving signals from the sondes; a communication link in the well from said receiving means; and signal processing means coupled with said communication link for processing signals from the receiving means, said processing means being located at or adjacent said surface.

Each of said sondes could be coupled to said receiving means via twisted pair wiring.

Said sondes could be coupled to said r eceiving means via a common cable.

Said sondes could be clamped to a casing of the well via respective clamps.

Said communication link could comprise a single cable, for example one comprising twisted pairs of wires.

Said signals fiom said receiving means are preferably analogue signals.

Said processing means preferably comprise a digitising and multiplexing electronic unit.

According to the present invention from another aspect, there is provided a method of processing signals from a plurality of seismic sondes located below a surface in a fluid production well, including the steps of: receiving said signals by receiving means in the well; transmitting signals fiom said receiving means via a communication link in the well to a location at or adjacent said surface; and processing said signals firom said receiving means at said location.

The present invention will now be described, by way of example, with r eference to the accompanying drawings, in which: Fig. I is a schematic view of a hydrocarbon production well not in accordance with the present invention; and Fig. 2 is a schematic view of an example of a hydrocarbon production well according to the present invention.

The example of Fig. 2, in which items which correspond with those in Fig. 1 have the same reference numerals as in Fig. ], overcomes the problems described above, by locating a digitiser and multiplexer and a single core cable or optical fibre driver, just below the well head/tubing hanger. This is thus a hybrid analogue/digital solution. The positioning of the sondes and their cabling 4, to the distribution box 5, is as in Fig. 1.

Likewise, the cable 6, firom the distribution box 5, transmits analogue signals through the multiple twisted pairs cable through the well to the land surface or sea bed surface S. but terminates in a digitiser/multiplexer/driver electronic unit 8, mounted just below the well head/tubing hanger 7. This electronic unit 8 contains, in practice, duplicated functions, to provide dual redundancy, in order to maintain high availability of the system, since retrieval of the unit is not simple because it is below the well head/tubing hanger. Although an arrangement of four sondes has been described, it follows that other arrangements of more or fewer sondes can be accommodated by suitable design of the digitiser/mu]tiplexer/driver unit 8. The arrangement reduces the costs and raises the reliability of geophone communication systems, where the transmission distance has to exceed 2 kilometres.

5The above example also provides the following advantages: the transmission of data from geophones in all types of wells, both land based wells where the control system is remote from the well head as well as subsea wells; 10it may be provided by adding to an existing arrangement so no system modification is necessary for a downhole installation that is already completed.

it is possible, in the case of a subsea installation, to connect the digital multiplexed signals from the geophones from cable 6 to a well tree subsea electronics 15module (SF,M) so that they can be integrated into an existing umbilical to the surface; it is likely to be easier to access the digitiser/multiplexer/driver unit 8 if failure occurs, since it is just below the wellhead/tubing hanger, as opposed to accessing a similar high temperature unit mounted downhole at the fluid extraction level; both the temperature and pressure of the environment of the digitiser/multiplexer/driver are much lower than if it were lower in the we]]; and wel]head penetration is much simpler than that for the lair I arrangement. -s-

Claims

1. A fluid production well, including: a plurality of seismic sondes located in the well below a surface; means in the well for r eceiving signals from the sondes; a communication link in the well from said receiving means; and signal processing means coupled with said communication link for processing I signals fiom the receiving means, said processing means being located at or adjacent said surface.

2. A fluid production well according to claim 1, wherein said sondes are microseismic sondes.

3. A fluid production well according to claim] or 2, wherein each of said sondes is coupled to said receiving means via twisted pair wiring.

4. A fluid production well according to any preceding claim, wherein said sondes are coupled to said receiving means via a common cable.

5. A fluid production system according to any preceding claim, wherein said sondes are clamped to a casing of the well via respective clamps.

6. A fluid production well according to any preceding claim, wherein said communication link comprises a single cable.

7. A fluid production system according to claim 6, wherein said cable comprises twisted pairs of wires.

8. A fluid production system according to any preceding claim, wherein said signals fiom said receiving means are analogue signals.

9. A fluid production system according to any preceding claim, wherein said processing means comprises a digitising and multiplexing electronic unit.

10. A fluid production well according to any preceding claim which is a hydrocarbon production well.

1]. A method of processing signals from a plurality of seismic sondes located below a surface in a fluid production well, including the steps of: receiving said signals by receiving means in the well; transmitting signals from said receiving means via a communication link in the well to a location at or adjacent said surface; and processing said signals from said receiving means at said location.

12. A fluid production well substantially as herein described with reference to Fig. 2 of the accompanying drawings.

] 3. A method of processing signals from a plurality of seismic sondes, substantially as herein described with reference to Fig. 2 of the accompanying drawings.