IGas has reduced by nearly 1.5km the maximum depth of its proposed shale gas well at Tinker Lane in north Nottinghamshire.
Information submitted to the Environment Agency this month as part of a permit application for the site put the depth of the well at up to 1,840m.
But the planning application for the site near Barnby Moor, currently being considered by Nottinghamshire County Council, said the well would be a maximum of 3,300m deep.
A spokesperson for the company said today:
“In the planning application we allowed for the greatest depth for drilling in the same manner as we would when specifying the tallest rig height.
“The depth has been refined as we have gone through the environmental permitting exercise and the drilling activity will be constrained to the depths indicated in the environmental permit.”
DrillorDrop asked IGas whether the reduction in depth had any implications for the duration of the drilling process, estimated at four months, or truck movements during drilling, put at 13 in and 13 out each day. IGas replied:
“The planning application sets out to establish the parameters within which activities can take place.
“All things being equal potentially there should be less traffic movements as the proposed target depth is ca 1840mMD vs 3300mMD, however, drilling time is dependent on a wide range of factors including but not limited to depth.”
IGas has said the proposed vertical well at Tinker Lane will explore for gas in the Bowland shale and Millstone Grit Group of shales and tight sands. The applications for planning permission and environmental permit do not include hydraulic fracturing.
The permit application, submitted by an IGas subsidiary, has also reviewed the likelihood and severity of any accidents from the proposed drilling operation at Tinker Lane.
According to two risk assessments, accidents were not likely to be a “significant hazard” if measures were put in place to manage the risk and the site did “not represent a risk to groundwater”.
But the hydrogeological risk screening classed the loss of drilling muds during drilling as a high risk to contamination of groundwater. It assessed the likelihood as medium and severity of the consequences as high.
The risk assessments also listed other potential accidents or problems which would be of medium risk to contamination of land and water and harm to people or wildlife. They included:
- Spills of liquids
- Damage to the containment system on the site
- Overfilling of tanks
- Failure of storage tanks or pipework
- Vehicle accident on site
- Failure of the well cellar
- Ingress of gas or oil into the wellbore
- Well not capped or plugged effectively
For most of these problems, the risk assessment suggested they were unlikely to happen but classed the severity of the consequences as medium level.
But for spills of liquids the risk assessment said:
“Minor spills are reasonably likely to happen”.
To deal with these risks, the document recommended measures including a pollution prevention plan, staff would be trained and there would be an impermeable membrane under the site. Groundwater would be monitored and equipment and site surfacing inspected, the assessment said. To reduce the risk of drilling muds contaminating the aquifer, the assessment said non-hazardous materials would be used and volumes of drilling muds would be monitored.
The risk assessment classed another 12 potential accidents or hazards as a low risk. They included:
- Smells from the site
- Vehicle movements
- Mud on roads
- Arson or vandalism
- Loss of cement and spacer fluid into the formation through fissures
- Loss of drilling mud from drilling the wellbore beneath principal aquifers
One section of the permit application said the well would drill through the Nottingham Castle Sandstone aquifer. This has been classed by the Environment Agency as a principal aquifer of “high groundwater vulnerability” because overlying soils drain freely and the sandstones are highly permeable.
The documents said groundwater was abstracted at five licensed points within 2km of the site, all for agriculture. The closest abstraction point was under 1km downstream. The nearest surface water feature was the Ranskill Brook, 1.4km east of the site.
The environmental risk assessment stated there were no internationally or nationally important wildlife sites or priority habitats within 2km of the site. But there were two locally-important sites within 2km at Barnby Moor Local Wildlife Site and Daneshill Local Nature Reserve (LNR).
The hydrogeological risk screening identified two designated wildlife sites within 3km of Tinker Lane that may depend on water from the Nottingham Castle Sandstone. The Mattersey Hill Marsh Site of Special Scientific Interest and the Daneshill LNR are downstream of the proposed site. But the assessment concluded: “It is not considered that any pathway exists which could lead to an impact upon these sites”.
The waste management plan, included in the permit application, estimated waste volumes from the drilling operation:
- Drill cuttings: 180 tonnes
- Waste gravel and crushed rocks: 600 tonnes
- Concrete: 130 tonnes
- Freshwater drilling muds and waste: 650m3
The plan said it did not anticipate that drilling muds and waste would contain oil. The production of waste gas was said to be “unknown”. The plan also said the site would produce spent spacer fluid and suspension fluid and cement.
The waste management plan also listed volumes, the product names and functions of chemicals that would be used in the operations, if approved. These included components of cement, drilling muds, spacer fluids and contingency chemicals.
The Environment Agency has invited people to comment on the permit application. It said:
“We only issue a permit if we believe that harm to the environment, people and wildlife will be minimised and that the operator has the ability to meet the conditions of the permit.”
Permit application reference: EPR/EB3406XP/A001
Location of the site: Tinker Lane 1, Retford Road, Near Barnby Moor, Nottinghamshire, DN22 8PA
Deadline for comments: Wednesday 28 September 2016
DrillorDrop’s review of the planning application
Earlier this month the Environment Agency published its guidance on oil and gas exploration and extraction permits. Link here