Review of Cabling Techniques and Environmental Effects Applicable

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Review of Cabling Techniques and Environmental Effects Applicable to the Offshore Wind Farm Industry – Technical Report and only causes localised disruption at the drill site which can be reinstated when the directional drilling equipment leaves the site. Figure 3.30 shows a typical directional drilling procedure. This procedure has been extracted from the LMR Drilling website (http://www.Imrdrilling.co.uk/intro. html). The directional drilling process can be undertaken in four separate phases and is described in detail below. Drilling the profile. A small diameter pilot hole is drilled under directional control to a predetermined path using a mud-motor or jet bit on the end of the pilot string. The pilot string is drilled up to 80 metres in length, then the washover pipe is advanced in rotary mode until it is approximately 30 metres behind the drill bit. Alternate pilot string and drilling operations take place until the exit point is reached. Then the smaller pilot string is removed. Enlarging the hole. Pre-reaming operations are carried out to enlarge the drilled hole to a size suitable for accepting the product pipe. Pull-back pipe is added behind the reamer. Depending upon the pipe diameter to be installed several pre-reaming operations may be necessary, each progressively enlarging the hole. Installing the pipe. The pull-back pipe is connected to a ‘cleaning’ reamer which in turn connects to a swivel joint, (to prevent pipe rotation) that is attached to the pipeline towhead. The drill rig is then used to pull the product pipe into the preformed hole. The drilling fluid consisting of water and clay minerals will remain in the annulus and protect the pipe. Figure 3.30: Typical Directional Drilling Procedure (http://www. Imrdrilling.co.uk/intro.html) 64
Site set up Cable types and installation techniques The directional drilling rig is set up on an appropriate landward site and the directional drill is commenced from the land site position to the target point on the shoreline. The target point on the shore would be the end point of the directional drill and the entry point for the subsea cable into the conduit which would be inserted into the drilled hole. For most directional drill sites where a duct is being installed to receive cables from an offshore wind farm, the footprint of the land site would typically be 30m x 30m in area. Drilling procedure The procedure basically consists of drilling out to the target position and then pulling a duct pipe back through the drilled hole. 65
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REVIEW OF CABLING TECHNIQUES AND EN
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Review of Cabling Techniques and En
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Abbreviations AIS Automatic Identif
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TTS Temporary Threshold Shift TWA T
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6 Good practice measures This secti
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7 Gaps in understanding Research fo
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References Introduction Sinden, G.
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Appendix A: Standards and codes of
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Printed in UK on recycled paper. De
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