Real-Life Decision Making
R.D. Drake, an Oklahoma-based oil-drilling consultant, says there's
an easy way to understand hydrostatic pressure.
"Go out in your front yard with a garden hose turned on and push it into
the ground," he said. "Keep backing the hose up and pushing it deeper into
the ground. You're drilling, basically.
"Once you're down 10 feet or so, turn the hose off," he continued.
"What'll happen is your hose will get stuck."
As a drill bit goes into the ground, the earth, fluids and rock around
it are pushing to fill the hole it made. To counter this, the drill bit has
fluid called "mud" pumped through it like the end of a water hose. This makes
counter-pressure to keep the hole open. This is called hydrostatic
pressure.
Jim Chenoweth, an instructor at the Well Control School in Hardey, Louisiana,
says that as a driller adds fluid to the hole, he knows that he should be
getting about the same amount of fluid back at the surface.
However, what if there's more fluid emerging from the drill hole than
is being put into the hole? Now you have a potentially dangerous situation
called a "kick."
Remember why you're drilling: for petroleum that people will burn
for energy. That other fluid filling the hole could be natural gas and oil,
an explosive combination building pressure in a sealed hole where you're
running a drill and creating friction.
But that other fluid seeping into the hole could also be water. In addition,
the pressure difference between what you're adding to the hole and what's
coming back could be very minimal.
Chenoweth says the petroleum company you're drilling for is paying
around $60,000 a day to lease the drilling rig. It doesn't get breaks
for downtime if you "kill," or shut off, the drill.
Should you shut off the drill and get "blowout preventers" in place, knowing
it'll take several hours to get the drill going again? Or should you
wait until an engineer has had time to examine the fluid coming to the surface
to find out if it's really oil or natural gas seeping into the hole?
What do you do?