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Victoria University Antarctic Research Expedition Science and Logistics Reports 1998-99: VUWAE 43

2.9 Drill Site Environmental Audit

2.9 Drill Site Environmental Audit

Fuel, oils and lubricants.

No fuel spills during transfer of drums from Aalener sledges to refuelling Hagglund sledge and pumping into Generator, Drill Rig and Science Lab holding tanks. JP8 and Mogas Herman Nelson hot air machines were refuelled at the equipment pumped from a 209 litre drum and plastic Jerry cans.

Waste oils, primarily from routine generator and drill rig oil changes stored in a 209 litre drum in the Italian tent.

Minor hydraulic connector leaks on the rig floor were captured in the underslung tarpaulin and fluid transferred to a waste oil drum. This tarpaulin could be improved by getting a new one cut to position beneath the rig floor and so it would interfere less with tidal monitoring page break attached to the sea riser.

Explosives.

Twenty four Anzomex P explosive primers (0.5 kg each.) with detonators were fired beneath the sea ice for the Vertical Seismic Profiling experiment on 30 November. Seal observations in the drill site area were made daily from the shift change helicopters and seals investigated if within 2 km of the drill site. Lone seals were noted on 10 November 1.4 and 1 km North West of the drill site but they had left after two days. A single seal was noted on 23 November 0.6+ km south of the drill rig and remained less than 24 hours. All seals did not have ice holes when investigated and were transient. No seals were observed in the drill site area on the 7 days leading up to the VSP experiment.

A explosive cutter was used to sever the sea riser casing at the sea floor in 178 m of water on 01 December.

Chemicals.

Up to 2 litres of food grade glycol was used in gas detection system. Most of this was recovered on decommissioning the site and consigned to the waste oil containers. No chemical consumables are used in the laboratory operations. The radioactive sources installed in the core logging equipment and used during down-hole logging were used routinely without incident and transported from the drill site after use.

Drilling Cuttings

Sediment recovered from the drill fluid by centrifuge and sediment rich sea water from the Laboratory core cutting saws and sink was dumped on the sea ice 50 m west of the Lab. Some cuttings and minor spilled drill fluid from the centrifuge were returned directly to the sea via the sea ice access holes.

Sea Floor Impact

Drill fluids and cuttings and grout (cement) reached the sea floor during the riser installation to 6.25 m bsf, coring ahead with HQ to 57.5 m bsf and a second riser installation to 13 m bsf. After the second riser installation no drill fluid or cuttings were observed with the submarine video that exited the annulus around the riser at the sea floor. A flat cone of cuttings and cement was created on the sea floor that was less than 5 m in diameter and 0.6 m high with an approximate volume of 1.25 cubic metres.

During this phase of riser installation and HQ coring ahead a volume of 300 cubic metres of drill fluid was used comprising 17.5 tonnes of biodegradable dry mud products that was dispersed into the sea water at the sea floor. Cementing the riser used 2.2 tonnes of dry cement to mix 1.1 cubic metres of grout that was distributed in the annulus around the riser to a depth of 13 m bsf and in the sea floor cuttings. Drill fluids used after installation of the riser and sealing at the sea floor annulus were not observed exiting the sea floor in the video system field of view and were presumed to be lost to the formation.

Drill Fluids CRP-2/2A

Total drill fluids used: 600 cubic metres (38 tonnes of biodegradable dry products or inert mineral products [mica and barytes).

Total cement fluid grout 1.385 cubic metres (2.64 tonnes of dry product).

Casing and hole completion

HQ casing (with barrel assembly later drilled out) was cemented at 199.3 m bsf. This casing was cut off around 70? m bsf [confirm with drilling manager's report] leaving approximately 130m of casing cemented in the well. The cut off HQ casing was with- drawn to expose the formation above 70? m bsf for down hole logging but immediately bridged at the 25 m and probably collapsed down to the casing cut off.

The hole was sealed above 25 m bsf with 165 litres of grout on December 1?

The sea riser casing was cut off about 1-1.5 m bsf leaving approximately 12.5 m of casing page break cemented below the sea floor.

Drill Fluid spillage.

Spills were minor in 1998. This is not a environmental problem as this material comprises sea water and biodegradable products. In the colder part of the season spills on the sea ice surface froze and were shovelled up and either dumped through the ice hole or taken to the surface dumping area or reused if the product was clean. The problem is that later in the season when ice temperatures have warmed the saline enriched fluid is corrosive on and penetrates the sea ice causing premature weakening of the sea ice structure. We should consider ways to capture/divert spilt drill fluid in the cellar floor area to maintain the integrity of the ice directly under the drill rig.