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In rotary drilling, drilling fluids are essential to lubricate the drill bit and circulate the drill cuttings to the surface. It is well documented that oil-based drilling muds (OBMs, sometimes referred to as non-aqueous drilling fluids or NADFs) have several advantages over their water-based counterparts. OBMs have a higher natural lubricity, making them suitable for challenging drilling operations. Also, OBMs are less reactive with clays and shales, thereby preventing hole enlargement, resulting in smaller overall waste volumes. However, OBMs must be carefully handled and treated prior to disposal due to their potential negative environ-mental effects.

There are a number of options available to treat and dispose of OBM drilling wastes (for example, land spreading and land filling), however the cost of handling and disposing of drilling waste is in-creasing. The drilling industry is now turning to novel approaches for the treatment and disposal of drilling wastes in order to meet more stringent environmental guidelines.

Supercritical fluid extraction (SFE) is an extraction technique that uses substances at or above their critical pressure and temperature as solvents. In the vicinity of the critical point, the liquid and vapor phases of the substance merge, producing a fluid with gas-like diffusivity and viscosity and liquid-like density. These properties provide for favorable mass transfer of soluble waste components (i.e. hydrocarbons) from solid matrices to the bulk supercritical fluid. The density of the fluid is defined by the pressure and temperature; small changes in processing conditions can fine-tune the solvating power of the fluid.

The of OBM drilling waste treatment http://www.kosun.us/drilling-waste-management/ using SFE has proved to be a quite effective method. Long before a patent by eppig et al. detailed a system suitable for the removal of organic contaminants from inorganic matrices. This patent specifically lists the treatment of oil contaminated drill cuttings as an application of the technology, and indicates that propane, Freon and carbon dioxide would be suitable supercritical fluids for this purpose.