How is coupling and packer works in an oilwel?

hey Kelvin..Well an oil well is one example but the same application takes place on other things as well .even a kitchen faucet has a coupling and packing to maintain the leaks..Here is how it works...Oil of course is a fluid but even a fluid has a viscosity based on its atomic structure. When you see an oil well pumping (that's the large rocking device on the surface) it has a rod which goes into the ground though a small head sampler tube ..On the top of the tube is a compression coupling that holds the "pony" rod in place and also squeezes the packing material against the polished rod so that if oil rides up the pumping rod it doesn't just collect on the ground around the well head. The coupling in some cases is a split ring type and the packing is a jute rope impregnated with carbon and other lubricants. the split ring has a cap that forces the jute down into the lands which are swaged. When you tighten the bolts the packing gland is forced in and against the rod making a very tight seal. Well there ya go from the E..