Drilling fluid technology in ice sheets: Hydrostatic pressure and borehole closure considerations

The drilling of deep boreholes in ice sheets requires that the hole is filled by a liquid to compensate the ice-overburden pressure. Density is the most important drilling fluid property, so the hydrostatic pressure of the fluid column should be sufficient to prevent closure of the borehole. However, it is impossible to prevent borehole closure at all, because the upper part of glaciers contains a lot of air inclusions and the density of...