Originally posted by soficrow
As I understand it, water is pumped in when oil and gas are extracted, at least. The reason for replacing the material with water is structural.
Water is not being used to replace oil, or gases. Water is used as a conductor for the data being transmitted to surface equiptment in rigs, data is
being sent in pulses by the MWD (Measurement While Drilling) tool with some of the most advanced technology used right now, and to flush out the
sediment from the borehole as the bit drills through the formation.
The mixed water with mud is forced down through the pipes and recycled reaching the surface to the mud pits, where the chips of rock and other pieces
of the drilled formation is separated from the mud/water by the shale shaker, then the mixed water/mud is again forced down the borehole, and the
process keeps being repeated.
Water also helps to maintain stability of the formation in the borehole as it is being drilled, otherwise the formation will become brittle and
collapse. The mixed solution of water and mud also depends on the formation being drilled, and the solution needed for the water/mud that will be
used is decided normally by one of the mud engineers. This mixed solution can change throughout the drilling process.
When the kicking point is reached, when they are about to start the curve to drill from vertical to horizontal, which is the way that is drilled in
most of the Northwest of the U.S., the end of that curve is the casing point. Which is the first section of the hole being drilled. When the casing
point is reached, casing is lowered and cemented to maintain better stability in that section of the borehole.
When the horizontal section is reached, the geologist gets together with the MWD and the directional driller throughout that section of drilling to
find out which way they have to drill to reach TD.
There are several ways to drill for oil/gas, water is not always used, and usually the water is mixed with mud, the composition of that mix is
determined by the Geologist or mud engineer. It depends on the formation being drilled and some other factors.
There are several steps that are made in order to drill for oil/gas. After all the data is retrieved and TD (Total Depth) is reached, a well
completion crew plugs the hole, after the rig is moved out of the area, a decision based on the data recieved is made on whether to make production
from that well, or to leave it plugged and abandon it.
BTW, drilling does not cause earthquakes, that is a myth to the best of my knowledge.
It is a bit more complicated than that, but pretty much that sums it up.
[edit on 16-1-2007 by Muaddib]