Saturday, May 3, 2008

Basic Drilling Concepts: Bit and Mud

Drill Bit: Drilling Engineer optimizes design by picking the best bit for the work. Different formation requires different type of bit usage. The most important parameter is cost per meter, a DE must be able to minimize cost per meter to maximize the cost effectiveness.

Once cuttings (chipped formation from bit cutting action) are produced, it is necessary to 'clean the hole' (transport cuttings to surface). The use of 'mud' (drilling fluid) is essential to: transport cuttings, keep the bit cool (the deeper it is, the higher the temperature. heat is also generated from rotation and vibration), softens the formation to make drilling easier and lubricates the well to ease 'casing running' (installing tubulars in drilled well).

The circulation system starts from 'mud pits' where mud is mixed (mud has different ingredients and chemicals to behave according to a DE's design in terms of viscosity, weight, gel strength and others). Mud is pumped using big pumps called mud pumps (wow what a technical term) and circulated up the derrick (in the stand pipe), down the top drive, into the ID (inner diameter) of the drill pipe, out the bit, up the annulus, back to the pits.

KMC or Kota Mineral Chemicals is one of the best local companies providing this product. The company is owned by Scomi and is now known as Scomi OilTools. The other big mud company is MI Swaco. MI is partly owned by Schlumberger and Smith International.


bats said...

mate, couple of questions..

1. does the 'mud' leave the drilling infra? from the diagram, it appears to do so... what happens to it?

2. what about all the debris from the drilling, like rocks below the seabed, etc? what happens to them?

again, another good read.

opcharlie said...

thanks for your interest bro.

mud is circulated in a complete cycle - regulation does not allow for it to be released. there are two main types of muds, one is water-based and the other is oil-based. After mud exits the "annulus" (space between drill pipe and hole), it will enter a series of filtration system called "shaker" and then through a centrifuge and then back to the pits. The big chunks of cuttings will be filtered by the shakers and either backloaded into drums and shipped to shore or you-know-where-it's-dumped-to. I'll talk more about it in my next post - thanks for reading!

opcharlie said...

Let me add on - mud can be released to the environment under certain conditions only and they vary depending on which government.