Pressure: formation pressure increases with depth; pressure prediction plot is used to forecast pressure distribution along the well path; pore pressure is the pressure at which pore fluids leave the formation and influx into the well; fracture pressure is the pressure where the formation breaks down (the aim is to remain between these two former pressures); hydrostatic pressure is the pressure equivalent to the water column; over pressure is when the pressure is greater than that predicted for the depth (causes problems because of fluid influx); depleted zones are where the pressure is less than is should be for that depth (mainly caused by hydrocarbon production); pressure is usually managed using drilling mud