At the CLG on Thursday 18th October the IGas Well Engineering Director gave us a heads up on the next phase of their programme at Tinker Lane. In short we are but weeks away from the start of the drilling programme which will commence with the mobilisation of equipment to site. The equipment needed will be delivered to site over 2-3 weeks. The drilling itself will take approximately 60 days, of 24 hour 7 day a week activity. This is somewhat less than original estimates as the depth is approximately 1,800 metres (subject to Geology) rather than an original depth (in the planning documentation of 3,300 metres). A bundle of information was supplied to the CLG and this is appended here.
It should be noted that the appendix contains information specific to the Marriotts Rig HH 220 and is for information only. The HH 220 and the VDD 370 are however very similar. Also in the bundle are average HGV movements during the mobilisation and later phases, a 2D survey across Tinker lane from Manton in the South West and well diagrams that show the lithology (colour coded formation structure) against the well designs. It is the latter diagram and in particular the PEDL 200 TL-1 “Well Design Schematic” that is referred to in the detailed description provided by IGas on Thursday.
If you want to dig deeper, then looking at the well diagram and from notes taken on the evening, read on!
The mobilisation process, cabins, materials casing will be sporadic over the 2-3 weeks. The main drilling rig will be moved to site in sections. Once the rig is up in position, testing of the equipment will follow. Drilling muds will be made up on site together with pressure and function testing of equipment (including Blow Out Preventors (BOPs). A rig acceptance test will be completed before agreement is given to proceed to spud the well. On acceptance the first move will be to drill the first hole which is the 17.5 inch hole through the existing 20 inch conductor
HSE (Health & Safety Executive) and OGA (Oil and Gas Authority) are informed that the well is spudded. Water based mud is used to drill through the aquifers (water bearing permeable rock). A 17.5 inch hole is driven 180 to 200 metres (until solid casing seat is encountered) then a 13.375 inch casing is cemented in place. (cement is pumped down the centre and returns via the annulus to completely fill it and allowed to cure). A full BOP is installed on the well at this point and the casing string is pressure tested to confirm integrity. The next section is a 12.25 inch hole also with water based mud down to 650-700 metres through multiple formations, upper coal measures etc.. A 9.625 inch casing is run down the hole, cemented, followed by pressure test of the casing string to confirm integrity.
There is then a switch over to oil based drilling mud. The final long section of 8.5 inch hole is drilled exclusively with oil based mud all the way to the bottom. The drilling stops at the coring points in the shale, where the drill string is changed to a coring string. Core sections are removed and drilling continued to a final depth (TD) determined by the IGas Geologist. If the results are not favourable the well may be cemented up/plugged as per the Well Abandonment Schematic. The OGA and HSE would require information on the geology encountered during drilling and coring before coming up with well abandonment requirements, i.e. where isolations are required. If results are favourable or if the well is deemed to be of interest a 5.5 inch casing will be installed to the bottom. The final, 5.5 inch casing is not cemented back to surface but back into the previous 9.625 inch casing allowing for monitoring of the annulus (looking for leakage by monitoring annulus void pressure).
The well is logged (measuring equipment suspended down borehole) before running casing but once the final casing is run and cemented the well is completed and suspended whilst analysis of the cored samples are undertaken. The current estimated drilling time depends on the formations encountered but is currently estimated approximately 60 days.
Other Notes Relating to Drilling Phase:
Conductor sections are welded together and other casing is threaded to create an appropriate seal (gas tight seal where required).
The pressure determination test described in the Scoping Report and Application Documentation is no longer a part of the programme and would form part of a later scheme of work if the core samples prove to be of interest. Different equipment to that used in the drilling programme being required.
Once the well is drilled a mobile seismic survey from within the compound, will be undertaken using a VSP type vehicle (vibroseis) to help calibrate seismic data
IGas Drill Manager manages operation reporting to Well Engineering Director and there is an onsite Drilling Supervisor working to Borehole Regulations who is in charge of the site. Tool Pusher reports to the Drilling Supervisor. Other contractors, looking after mud, waste, directional drilling (keeping it vertical!), coring, logging and security. The drilling management team are very experienced in UK drilling operations and regulations.
Ideal scenario would be to move the drill rig from Tinker lane to Springs road on completion.