Challenges Related to Proper Development of a CBM Resource

Water treatment and discharge: Water produced from a wellbore is likely to be saline with iron oxide in suspension. Water treatment and abstraction are regulated by SEPA (Scottish Environment Protection Agency) under various permits governing the quality of the water and volume licenced for discharge. Extra consideration to any proposed water treatment and discharge scheme should be given in an area where discharge into a saline receiver is not possible. Any water treatment and discharge scheme is required to be consented both by the Local Planning Authority and by SEPA.
Drill Cuttings: Whilst drilling the wellbore, cuttings of rock formation are produced from the well. These are minimal but are classed as inert waste and can be removed from the drill site to landfill under licence with SEPA.
Ground Water: In previous CBM developments, interference with ground water has been experienced, typically when gas-bearing coal seams are close to surface and so interact with the aquifer. The depth of Scottish coals and their isolation from ground water movement significantly reduces any risk of interplay. This risk should always be further mitigated by good industry practice in wellbore design, casing and cementing. Wellbore engineering is assessed by the DBERR (Department of Business Enterprise & Regulatory Reform) and the HSE prior to drilling. SEPA manage the drilling of wellbores under the abstraction licencing system and address geological issues.
Noise: The drilling stage of a borehole is the most intrusive to the surrounding area; the drilling of a well requires to be undertaken on a 24hr basis for circa 60 days. This is governed by the local authority planning process. Noise surveys for the rig site set up should be considered on sites where receptors fall within noise contours of the survey, with appropriate mitigating measures being employed to overcome acoustic intrusion.
Traffic: The drilling stage of a wellbore is again the busiest stage of the development, the construction of the site and the supply of equipment throughout the 60 days is the most traffic intensive. This is governed by the Planning Authority in consultation with the local roads department, to ensure safe and orderly movement to and from the site.
Visual: Sites should be located by operators in areas capable of minimising visual intrusion where possible. Visual impact at the drilling stage can be addressed by the use of equipment with a small footprint both in terms of surface area and height. Lighting used at night during drilling can be intrusive and mitigating measures should be taken to ensure that night time operations are specifically addressed. These issues are addressed by the local authority planning process.
Flaring and Venting: At times during a pilot production test and also in the wider success case cluster growth and development, it can be necessary to either vent or flare gas. These operations can only be carried out under agreement with the DBERR and the HSE and provision should be made in a planning permission application to address these operations.
Boundary Treatments: Boundary treatments for sites should be considered distinctly in each phase. The drilling phase requires men to move freely amongst equipment and to have sufficient space to work safely. The site should also prevent those from outside entering without appropriate control. In the production phase the equipment should be protected in a manner akin to Transco Substations. Currently this is addressed by the planning authority.
Well Spacing/Density: The number of wells in an area has to be managed. Current understanding of the dynamics of coal seams in Scotland suggests that one well site every square kilometre should be sufficient to ensure efficient production of the resource. However the production qualities of a particular coal seam may require a site up to every ½ km.