'calvin grad' pid='44530' dateline='<a href="tel:1402157 Wrote:Explain we'll control and hole stability please
That's a lifetime career for some people. In simple terms drilling into the earth is an act of balancing earth stresses and pore pressures. From surface to TD the pressures and stresses are nonlinear. Petrophysicists make pore pressure/frac gradient predictions so drillers can design the mud and casing programs to get the well down. If the mud at any depth is too heavy or pump pressures are too high, you can unintentionally frac the mud into the earth (sometimes followed by a blowout). If it is too light, you can take a kick (i..e, the pressure exerted by the mud column is less than the pressure in the earth so the well starts flowing). This too will lead to a blowout if you don't re-establish well control. In some cases the mud can be too heavy and cause the drill pipe or casing to get stuck while running into the well. Also if mud pressures are too low there may not be enough stress exerted by the mud to keep the hole open. It will slough in. As I noted in another posting on this chain, the uncertainty in drilling is greatest in exploration wells. Ideally while drilling you want volume of mud pumped into a well = volume of mud that comes out - volume of the cuttings and fluids of the drilled section. Usually you have less mud coming out than going in due to seepage. Hope that helps. The Society of Petroleum Engineers has a great reference site where you can get much better definitions. Try this: http://petrowiki.spe.org/PetroWiki%3ACopyright