All our wells are designed with safety and environmental protection as the foremost concern and they are subject to approval by the appropriate national and local authorities. Furthermore, as part of our HSEC programme, we have developed our own drilling standards which meet or exceed regulatory requirements, to ensure wells are designed and drilled safely and effectively.
Once a site has been constructed, a drilling rig will be mobilised and installed on the site ready to begin drilling the well. The depths of a given well will vary depending on the local geology and the prospective reservoir, but typically will be between 6,000 and 15,000 feet (2,000m to 4,500m) below the surface. Throughout the process, stringent environmental protection measures are adopted.
The well is drilled in a series of stages, known as hole sections, so that concentric strings of steel casing can be installed and cemented in place over each one. These methods prevent contamination of the ground water (see water protection) and also stabilise each hole section to allow the next stage to be drilled safely. The result is that the well is drilled in a series of reducing hole sizes, starting at over 20 inches (50cm) in diameter and reducing down to either 8 ½ inches or 6 inches (19cm or 15cm) depending on the well design.
The well starts at 20 inches in diameter and reduces down to 6 inches depending on well design.