In last night’s Psych, an offshore oil rig turns out to be drilling on a fault line (secretly). This is assumed to be very dangerous, but the nature of the risk is never mentioned. Would it cause an earthquake or what?
IIRC (which I probably don’t) the issue isn’t Superman-like chaos, but oil leaking up around the bore hole (or whatever it’s called), e.g., environmental harm.
I have’t seen the TV show(?) in question, but it sounds as though the writer may have read news reports of the spectacular mud volcano in East Java that has flowed for more than two years, destroying roads, railways and at least one town, and has displaced thousands of people. Although generally thought to have been caused by the drilling of a poorly-engineered natural gas well, it may be that a large earthquake (not itself caused by the drilling, so far as anyone knows) in the region two days before the flow began was the major contributing factor.
Although the triggering of a seismic event by drilling is not entirely outside the realm of possibility, oil and gas wells are in fact drilled though faults all the time without triggering earthquakes or other disasters; in fact faulting is a very common structural feature of the fluid ‘traps’ that create oil and gas reservoirs to begin with. If tectonic stresses on the rocks are high, one can have significant borehole stability problems, but this usually affects only the drilling operation itself.
As an example, some years back when I worked as a mud logger, I was on site for several wells drilled in a highly seismically active area in Guatemala. We never triggered any earthquakes, but the stresses on the sedimentary rocks we were drilling though were sufficiently high that we had all kinds of stuck pipe problems due to ovalization of the borehole along the axes of the horizontal stresses.
In an old James Bond flick, A View To A Kill, water is pumped into drill holes along a fault line to set it off.
Is this what the OP had in mind?
Knowing what we know of human nature, if we knew of a way to trigger earthquakes, some one would have already done it - if only to show that he could.
“Mud logger”?
Drilling oil wells, you drill through faults pretty much all the time (ok depends where you are in the world and the types of traps). The worst part about drilling through a fault is it tends to confuse the geologist, who then start to wonder around the rig in a confused and geologically lost state.
Many wells and boreholes have been drilled in and around faults connected with earthquake zones. These bore holes have hydrophones and geophones installed along with pressure and temperature sensors. The purpose is to try and monitor the build up of stresses to understand and hopefully give some early warning of an earthquake.
During the act of drilling a hole, I really cannot see there being sufficient energy caused by the drilling to trigger an earthquake, and the small quantity of rock removed is very unlikely to affect the stability of the fault itself. Now if you were to start trying hydraulic fracturing (ie pumping bucket loads of water under pressure in an attempt to induce more fractures, who knows. My guess would be the amount of energy man can put into the system is negligible compared to the forces put in play by the plates moving around.)
Anyway as a more factual answer as to what happens when an oil well is drilled though a fault I offer the following. Well first off, I should explain that when a well is drilled, a drilling fluid is pumped down through the drill pipe, out the bit and back up the annular space between the hole and the drill pipe (the drill bit has a larger diameter then the pipe behind it). This fluid has several purposes, amongst which, it provides cooling for the bit, it transports all the cut up rock back to surface, and most importantly it provides a pressure balance against the formation pressure. As one drills deeper the hydrostatic pressure due to the column of fluid increases (just in the same way as the water pressure increases the deeper one goes in the ocean), this increase offsets the increasing pressure the rock is under. Matching the formation pressure is critical to the safety and success for a drilling operation, if you don’t you can find fluids in the formation flow into the well (known as a kick which can lead to a blowout (a very bad thing)), the rock may collapse in the well bore or if you over compensate for the formation pressure, you could end up fracturing the rock and loosing all the drilling fluid. The drilling fluid density, hence the pressure it exerts, can be adjusted by adding powdered barite, using salt saturated solutions, using weird cesium formate solutions, using synthetic oil based fluids and other magic snake oils. One thing they all have in common is they are not cheap.
Honest I do remember the question, which leads lesson to faults. A fault represents a break in the geological sequence of rocks. As you pass across a fault you may (not always) cross from one formation type which was deposited under certain conditions, to another. The stability and integrity of the rock may change, and most importantly it may be under a different pressure régime. This sudden change of stability and pressure may not be correctly balanced by the drilling fluid pressure, this imbalance may lead to several unpleased things happening.
So drilling through a fault can have some untoward effects in the drilling process,
-
The actual zone of the fault may have a fair amount of broken rubble which could cave into the bore hole, worst case it may lead to the drill string getting stuck in the hole, which is expensive.
-
You could loose circulation, basically the fault can be a fissure into which all the drilling fluid can drain. The loss of drilling fluid, whilst representing a cost, may also lead to a decrease in the pressure further up the hole as hydrostatic head is lost. The drop in well bore pressure may not correctly balance the formation pressures and so a kick may be induced, or well bore collapse
-
You enter into a new formation with a higher formation pressure. The drilling fluid pressure and the formation pressure are out of balance and the well bore may collapse, or if there are permeable and porous formations, formation fluids may be forced into the well bore resulting in a kick and a blowout.
-
A fault may also be a conduction path from deeper formations to shallower formations. This is a particular problem in gas basins. Basically a shallow formation in communication through a fault with a deeper gas bearing formation may become charged up to the same pressure as the deeper formation. Now this becomes a problem when one drills into the shallow formation expecting pressure of a few hundred psi, but in fact finding pressures of several thousand. Blowouts and chaos normally ensue.
-
As mentioned at the beginning, the geologist becomes geologically lost, the worst case is that one exits the drilling of the reservoir early, or does not encounter the reservoir at all. This could lead to cementing the well back up and trying again.
Anyway, drilling across faults happens a lot, sometimes there is no impact at all, sometimes it results in a junked well, and sometimes, thankfully rarely, it results in too much excitement.
A mud logger (aka sample catcher, data engineer) is someone who works on the rig typically employed by a service company contracted to the oil company.
They do two things (well 3 if you include the usual supply of coffee and a comfy sofa in the mud logging unit on the rig).
First off they collect and analyze the samples of rock that are circulated up the well bore with the drilling fluid. This acts as a first pass screening for the geologist, who will work with the mud loggers to put the drill bit on the geological map. This is largely being replaced by sensors close to the drill bit that measure the properties of the rock however sometimes legal requirmenst mandate the collection of samples, and sometimes there is no substiture for looking at the pebbles along with the dead bugs and pollen etc contained within.
The second thing the mud loggers do is to monitor the drilling progress through a range of sensors which tell us the rate of drilling, the amount of torque applied, etc. Whilst the driller monitors this on a minute by minute basis, the mud loggers provide a longer time frame analysis, which helps spot slowly developing problems, or used to improve the drilling process. They also provide a vital safety backup for monitoring the volumes of drilling fluid on the rig. Keeping track of the pit volumes is about the only way to effectively spot a kick and prevent a blowout, the mud loggers are the second pair of eyes behind the driller.
A lot of this data analysis is now being done back on dry land data centers, where the sensor data is streamed onto land via satellite and is available to many people.
The name comes from the fact tat they logged (measured) the drilling fluid which is know as drilling mud.
Couldn’t have said it better myself, NBC.
Someone watched the so-bad-it’s-good 10.5
Yep, I came in to say what NBC said, except for that mud logger bit.
I can certainly think of something that could be described as a “mud log”.