The use of pipeline pigs is common. Pigs are now frequently required to provide a diverse range of functions or operations in pipelines that may extend for many miles and which may lie several hundreds of feet below the surface.

One of the difficulties in performing pig operations in such conditions results from the limited feedback of information that is available, particularly in relation to the launch and the arrival of the pig, but also in relation to its position at any time. This is seen as a significant disadvantage as the consequences of failing to pass the pig through the pipeline to its intended destination can be substantial.

A common practice until now has been to pump an excessive amount of fluid behind the pig in order to compensate for any inefficiencies or obstructions that might hinder the pig travel. Typically, an operator might pump approximately 120 per cent of the line volume in an effort to be sure that the pig has successfully reached its intended destination for retrieval or otherwise.

However, it is recognised that even with overpumping, it is still not possible to be certain that the pig has been successfully launched or performed its required travel.

There are other disadvantages with overpumping also, including for example the time required to do so,

together with the undesirable discharge of additive chemicals that may be harmful to the sea ecology and again a waste that further causes economic inefficiencies.

It is therefore an object of the present invention to provide an improved means of tracking a pig in a pipeline, and clearly such means requires to provide feedback data to a remote location.

A further and related object of the present invention is to enable better control of pipeline pigging operations, with greater certainty of the successful launch and travel of the pig in the pipeline.

According to a first aspect of the present invention there is provided apparatus for tracking a pig in a pipeline, the apparatus comprising a detectable means and a sensor for detecting the detectable means, wherein the sensor is linked to an activation means for activating a signalling device for transmitting a signal to a remote receiving station upon or shortly after the detection of said detectable means.

The detectable means is preferably mounted on the pig and the sensor is preferably strategically located in a fixed position relative to the pipeline.

The detectable means may be a magnet.

The signalling device may be provided in a floatable casing, such as a buoy, wherein the floatable casing is held to the pipeline in a submerged state until it is activated by the activation means, upon which the

signalling device is released and floats to surface from where it may transmit said signal to the remote receiving ~ Preferably the activation means is an electronic signal transmitted from circuitry associated with the sensor.

In one option, the signalling device may be adapted to send a radio signal directly to the remote receiving station. In another option, the signalling device may be adapted to send a telephone call via the global cellular satellite system. In a yet further option, the signalling device may be adapted to transmit an email message via an alternative dedicated satellite system, such as the Orbcomm satellite system.

Notably these options for transmitting a signal to the remote receiving station are suitable for use over long distances. Where the signal is not required to travel for several miles or more, the signalling device may merely comprise a means for transmitting an acoustic signal. For example, the signalling device may largely comprise of an acoustic transponder.

The remote receiving station may be provided on a boat or ship.

According to a second aspect of the invention, there is provided a method of detecting the position of a pipeline pig from a remote receiving location, wherein the method comprises locally detecting the pig at a predetermined location relative to the pipeline, generating a first signal upon such detection so as to activate a signalling device for generating a second signal and then

transmitting said second signal to the remote receiving station.

The pig may be detected by providing a detectable means such as a magnet on the pig and using one or more sensors located strategically on the pipeline for detecting the presence of the magnet or other detectable means.

Preferably the method includes detecting the launch of the pig and there is a first sensor provided on the pipeline at a position in relative proximity to the launching position of the pig, whereupon the detection of the pig by the first sensor is indicative of the pig having been launched.

Preferably the method includes detecting the arrival of the pig and there is also provided a second sensor located on the pipeline at or near the intended destination of the pig, whereupon the detection of the pig by the second sensor is indicative of the pig having reached its intended destination.

Preferably, the first signal is electronic, while the second signal may be a radio frequency signal, telecommunication signal or an acoustic signal.

The method may comprise the steps of: a) detecting the pig shortly after it has been launched with the use of a first sensor; b) generating a first signal so as to activate an acoustic signalling device adapted to transmit a second signal upon said activation; and c) receiving or detecting the second signal at a

remote receiving station.

The method may also or alternatively comprise the steps of: a) detecting the pig as it reaches or approaches an intended destination with the use of a sensor located at the point of detection; b) generating a first signal so as to release a buoyant signalling device that then floats to surface; c) transmitting a second signal from the signalling device; and d) receiving or detecting the second signal at a remote receiving station.

In order to provide a better understanding of the invention, an example embodiment and methodology for using same will now be described with reference to the accompanying sole Figure, in which there is schematically illustrated various components which co-operate to allow the invention to operate.

Thus, with reference to the Figure, a pipeline 1 is located several hundreds of feet below the surface 2 of the sea. A pig 3 adapted to travel through the pipeline 1 is shown positioned adjacent an inlet 4.

In the example now described, it is intended that the pipeline pig 3 be launched from a position adjacent the inlet 4 and travel the length of the pipeline 1 to a destination at 5. The destination 5 may be several miles from the inlet 4.

Located on the pig 3 is a series of magnets 20. The magnets 20 are detectable by a first and second sensor 7,8. The first sensor 7 is positioned in close proximity to the launch site 4 of the pig 3, while the second sensor 8 is positioned just before the intended destination site 5 of the pig 3. In the example, the sensors employ the method of magnetic anomaly detection to detect the presence of the pig at their respective locations in the pipeline. This detection method will be known to those skilled in the art associated with pig detection on land lines.

A respective activation means is associated with each sensor 7,8. A first activation means 9 is adapted to send an electronic signal to an acoustic transponder 10.

A second activation means 11 is adapted to send an electronic signal to a signalling device 12.

A vessel 13 floats above the launch site 4 and carries on-board personnel who are able to control and or monitor the pigging operation. The vessel 13 provides a base, otherwise referred to herein as a remote receiving station. Typically, the vessel 13 also provides the power and apparatus suitable for pumping the pig 3 through the pipeline 1.

Having regard to the first sensor 7 and associated apparatus, in use when the pig 3 is launched, it will imminently pass the first detector or sensor 7 causing an electronic signal to be sent to the acoustic transponder 10. Once activated by the electrical signal, the transponder 10 then further transmits an acoustic signal which is received by an appropriate receiver associated with the vessel 13. The receiver might, for example, be

in the form of an over-side transducer 6. This indicates to on-board personnel, or indeed personnel at any location having communication with the receiver, that the pig 3 has been successfully launched.

Subsequently, upon the arrival of the pig 3 at its intended destination 5, the pig 3 will be detected by the second sensor 8. As before, the second sensor 8 will transmit a signal, typically but not essentially being an electronic signal to the activation means. However, activation in this case involves the release of a signalling device 12 housed in a buoyant casing. The release causes the device 12 to quickly rise to surface 2 after which it may transmit a signal that may be received by the remote receiving station on the vessel 13.

In the Figure there is illustrated a satellite communication link 14, which is intended to represent a variety of present and future satellite options suitable for relaying the signal transmitted from the signalling device to the remote receiving station. As previously mentioned herein, the signal may be by radio frequency (in which case the satellite relay would not be employed) or by telephone or email communication, each utilising an appropriate satellite system.

One presently available transmitting means is known as the GSC 100, available from the US company Magellan Corporation. This is a small handsize package comprising a combined GPS/ORBCOMM transceiver suitable for acting as the signalling device referred to herein.

It should also be understood that the invention is not limited to any number of sensors or the position at which

they are located. For example an additional sensor may be located halfway along the pipeline 1 which would activate a further signalling device when the pig 3 was detected at that location.

The signalling device would be retrievable as it floats on the sea surface. In one embodiment, it may be adapted to transmit a signal every fifteen minutes to allow its whereabouts after release to be detected or traced.

Further modifications and improvements may be incorporated without departing from the scope of the invention herein intended.