Drill cuttings are shards of rock resulting from deep sea drilling. The cuttings are created when the teeth of a drill bit cut through the seabed in order to bore a hole. These boreholes are used to access oil and gas deposits below.
The majority of cuttings taken from a bore hole are sand and shale. The total composition of the drill cuttings depends on the location of the drill and the type of sediment and rock encountered. Other cutting materials include barite, caustic soda KOH, potassium sulphate, sodium bicarbonate, and glycol.
Exploration drills use drilling fluids made of water-based muds to bore holes into the ground. These drilling fluids can be used for land and sea drills. Simple boreholes and can also be used to make wells. The drilling fluids are used to help keep the drill bit cool and clean while also helping to prevent formation fluids from entering the borehole.
The process of breaking up the rock and sediment to make the borehole puts drill cuttings into the drilling fluid. The cuttings are separated from the drilling fluid using shale shakers. Removing solids such as drill cuttings reduces drilling costs. Once clear of the cuttings, the drilling fluids flow back into the drilling fluid system.
After drill cuttings have been separated, the contractor must decide whether to dispose of the cuttings or make use of them. If cuttings can be used for some other purpose, the company may be able to generate income from them. Cuttings that need to be disposed will be a pure cost to the company. Many states and countries have rules outlining which cuttings can be reused and which must be eliminated. Those that are disposed of are usually placed in pre-dug pits adjacent to the drilling area.
Beneficial uses of drill cuttings include road spreading. Oil covered cuttings can be used on dirt roads in a similar manner to tar-chip surfacing. Treated cuttings of the right composition can be used as construction materials to make bricks, concrete, landfill covers, and asphalt.
There are also concerns about the environmental impact of drill cuttings. The primary concern relates to the impact on local marine life of dumping unwanted cuttings. Currently, an estimated 2.5 million metric tons of cuttings have been placed in the North Sea between Britain and Norway. In addition to smothering life on the seabed, the cuttings contain toxins stemming from the hydrocarbons they contain. Environmental groups and advisors have urged companies and nations to minimize discharges of drill cuttings.