The exploitation of coal bed methane relies on the desorption process. Although in its infancy in the UK, it has been used in the USA since the early 1960s. Jim O'Leary,
Wells Team Leader, San Juan North Major Project, BP in the USA and Steve Jewell,
Chief Operating Officer, Composite Energy in the UK presented their different projects on a four-way link between Edinburgh, Aberdeen, Houston and London.
They described their respective projects, explaining the challenges and design issues affecting coalbed methane wells.
In the San Juan Basin, BP has 1,020 wells producing 650 million cu ft per day. The current programme envisaged drilling 1,000 additional wells at a capex of 100$ million per annum. Five seams were being targeted at an average depth of 2,500 ft.
The coal seams were in the Upper Cretaceous. Future developments include fracture stimulation. There is also a coil tubing development pilot to evaluate CTD hybrid drilling against conventional rotary steerable tools.
In the UK the first licences were issued in the 1990s. Composite Energy secured its
PEDL 133 licence in 2004 and completed its initial work programme by March 2005.
In Scotland, the coal seams are in the Carboniferous and suffer from low permeability. Nevertheless, the estimate of gas resource is substantial. There are multiple commercial options in the area. Composite Energy has taken the approach of being the drilling rig owner and operator. The company plan to drill a six well pilot at
Airth and a six well pilot at Longannet. Both up-dip (American) and down-dip
(Australian) techniques will be applied. It was noted that the Composite Energy presentation was the first time this information had been made publicly available.
(Steve Jewell, Composite Energy & Jim O’Leary, BP - 13 December 2006)