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Ervironmental friendly drilling fluid management offshore Norway.

Torleiv Bilstad, B. Jensen, Martin Toft

Vol. 31, no. 2 (2014), s. 191-196, [1]

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Types and amount of fluids utilized when drilling a well determine to which extent the drilled cuttings are legally considered hazardous waste. The main categories of drilling fluids are oil based (OBM), water based (WBM) and synthetic based mud (SBM). The purpose of adding fluids to the drilling operations is to cool and lubricate the drill bit, to stabilize the well bore, to control subsurface pressure, to control formation pressure, to control well stability. to control corrosion, and to carry cuttings to the surface. Historically, cuttings from drilling sub-surface wells have been depositeddirectly from the platform to the seabed. However, environmental laws and regulations for the Norwegian offshore sector prohibit such practice when the oil on cutting exceeds 1 % by weight. Re-injection of cuttings as a slurry into subsurface formations is still practiced. Due to migration, leaks, re-entering of slurry onto the seabed, and collapsing formations this disposal method is on a decline. Transport of oily cuttings to shore for final treatment is the preferred Norwegian practice. However, cutting treatment on platforms is also continuousl yevaluated. For logistics and cost reasons, as well as health, safety and environmental (HSE) and working environment reasons, emphasis is put on offshore waste minimization, reuse and recycle.Ten onshore locations in Norway are currently receiving cuttings for further treatment and fluid recovery. The treated cuttings are for the most part disposed in landfills.