RE: Scott/ MJ13 Sep 2022 08:41
Smasher... "get the correct balance" about sums it up. They need to maintain control of the well using the hydrostatic pressure created by the drilling mud. The mud characteristics such as weight, viscosity and general components (barite mainly) are infinitely variable and are continually adjusted during the drilling process as the well deepens and different well characteristics are encountered. The general idea is to keep the hydrostatic head pressure just above the formation pressure to prevent formation fluids entering the well bore. The heavier the mud, the greater hydrostatic head. But its not just as easy as whacking up the weight and job done, too much mud weight can fracture the un-cased well sections and cause the mud to disappear into the formation--this is not good as it can fairly quickly reduce the hydrostatic head-cos the mud is depleted and then the well can become out of control as the pressure wants to blow everything up the drill stem and annulus towards the rig floor---enter the BOP, exit the roughnecks.
They add different chemicals inc oil to the mud to maintain low viscosity and high mud weight so far as possible . Heavy mud with high viscosity increases friction down the hole and can cause the drill pipe to become stuck in the well.- especially if the driller has to stop rotation for some reason and then it becomes difficult for the drive motors to overcome the resistance of the drill string against the heavy mud. So yes--- a correct balance is essential. I did this stuff a lifetime ago in the N Sea, it is but a vague memory and I am not pretending to be any kind of expert so pls check/confirm for yourself. I am now involved in building, testing and commissioning a £500m addition to Europe's largest LNG importation terminal and surrounded by enough gas to supply about 20% of the UK demand. It's a tricky business and we have to continually satisfy the regulators about safety, integrity, layers of protection, engineering standards, earthquakes, terrorist attacks, keeping the local community informed and 'at bay'. Basically, all the stuff facing TXP but in a different jurisdiction. Anyhow-soap box moment over. Where's the Sp heading short term--that's what I want to know.:)