Roto-Gro International Ltd RTGIF

RE:RE:RE:Refreshing

[Dirksidetrack]

Well, geologists would tell me mud man the average pore size in microns. With drilling engineers we work out concentrations of various sizes of calcium carbonate in the mud. Can go up to 60 pounds per barrel through most downhole tools if memory serves. Chicken grit is very dangerous to run through those tools because of the large, angular grain sizes packs off small diameters very quickly so we stay away from chicken grit.

About 4 times a day we run a PPT test or pore plugging test. It's a cylinder filled with mud heated to 250 F. At the bottom of the cylinder is a ceramic disk with pore throat diameter of a given micron size. For example if grologists say that the average pore diameter is 40 microns then I'd use a 40 micron ceramic disk. I put 1500 psi on the cylinder once the mud is heated up and open the bottom value so that filtrate from the mud is squeezed through the disk into a graduated cylinder for 30 minutes. If the mix of calcium carbonate is right then it almost immediately plugs up the pores in the disk and after about 30 minutes I'd collect maybe 2 ml of filtrate.

OK so we now know that the mix of calcium carbonate in the mud is blocking up the pores in the formation so it's like having casing in the hole. Little to no differential pressure pushing drill string against the well bore. Once you're stuck differentially you're very unlikely to get unstuck just jarring on it. You can read up on drilling jars if you don't know what they are. They're in every BHA that I've ever seen. A differential of say 300 psi is 300 pounds force per square inch of drill string contact surface area. Adds up to a lot of force pushing the drill string into the well bore walls. So specialty chemicals have to be pumped to eat the filter cake in the stuck zone to reduce the contact area of the drill string on the hole walls. We spot the chemicals and the driller starts jarring until the drill syring pops free. That's a quick summary.