High Quality Content by WIKIPEDIA articles! Well control is the technique used in oil and gas operations such as drilling, well workover, and well completions to maintaining the fluid column hydrostatic pressure and formation pressure to prevent influx of formation fluids into the wellbore. This technique involves the estimation of formation fluid pressures, the strength of the subsurface formations and the use of casing and mud density to offset those pressures in a predictable fashion. Understanding of pressure and pressure relationships are very important in well control.