Environmental impact, drilling fluids

Chromium lignosulfonates are the biggest contributions to heavy metals in drilling fluids. Although studies have shown minimal environmental impact, substitutes exist that can result in lower chromium levels in muds. The less used chromium lignites (trivalent chromium complexes) are similar in character and performance with less chromium. Nonchromium substitutes are effective in many situations. Typical total chromium levels in muds are 100-1000 mg/1. 

Synthetic-based muds are mineral oil muds in which the oil phase has been replaced with a synthetic fluid, such as ether, ester, PAO, or linear alkylbenzene, and are available from major mud companies. The mud selection process is based on the mud s technical performance, environmental impact, and financial impact. Synthetic muds are expensive. Two factors influence the direct cost unit or per-barrel cost and mud losses. Synthetic muds are the technical equivalent of oil-based muds when drilling intermediate hole sections. They are technically superior to all water-based systems when drilling reactive shales in directional wells. However, with efficient solids-control equipment, optimized drilling, and good housekeeping practices, the cost of the synthetic mud can be brought to a level comparable with oil-based mud [1308]. 

Neff, J.M., McKelvie, S. and Ayers, R.C. Jr (2000) Environmental Impacts of Synthetic Based Drilling Fluids, report prepared for MMS by Robert Ayers 8c Associates, US Department of the Interior, Minerals Management Service, Gulf of Mexico OCS... 

Friedheim, J.E. and Pantermuehl, R.M. (1993) Superior performance with minimal environmental impact a novel non-aqueous drilling fluid. SPE 25753 SPE/IADC Drilling Conference 23-25 February 1993, Amsterdam. Society of Petroleum Engineers, Richardson, TX, pp. 713-726. 

Norman, M Ross, S., McEwen, G. and GetlifF, J. (2002) Minimizing environmental impacts and maximizing hole stability - the significance of drilling with synthetic fluids in New Zealand. New Zealand Petroleum Conference Proceedings 24—27 February 2002. 

There is increasingly a fifth function that must be met, namely, to minimize the environmental impact of the drilling fluid and the drilled... 

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