As to where our industry is heading, I believe this message from a very red state means even more than what comes out of a purple state,
http://bigstory.ap.org/article/7599f55f480a4e61b08b630af2d05e02/oklahoma-oil-gas-regulators-order-changes-after-earthquakes
Oklahoma oil, gas regulators order changes after earthquakes
By TIM TALLEY Jan. 5, 2016 1:13 AM EST
OKLAHOMA CITY (AP) — The state commission that regulates Oklahoma's oil and natural gas industry ordered some injection well operators to reduce wastewater disposal volumes on Monday after at least a dozen earthquakes hit an area north of Oklahoma City in less than a week.
The Oklahoma Corporation Commission said it was implementing a plan that affects five wastewater injection wells operating within 10 miles of the center of earthquake activity near Edmond, a northeast suburb of Oklahoma City. Among the recent quakes to hit the area was a 4.2 magnitude temblor on New Year's Day that caused minor damage but no injuries.
"We are working with researchers on the entire area of the state involved in the latest seismic activity to plot out where we should go from here," Oil and Gas Conservation Division Director Tim Baker said, adding that responding to the swarm of earthquakes in the region was an ongoing process.
Oklahoma has become one of the most earthquake-prone areas in the world, with the number of quakes magnitude 3.0 or greater skyrocketing from a few dozen in 2012 to more than 800 in 2015. Many of the earthquakes are occurring in swarms in areas where injection wells pump salty wastewater — a byproduct of oil and gas production — deep into the earth.
George Choy, a U.S. Geological Survey seismologist in Denver, said studies indicate that earthquakes in certain areas have been induced by wastewater disposal. About 200 million barrels was disposed in the state each month in 2015, he said.
"Ceasing activity or slowing it down would be a prudent measure," Choy said. "The science here is still developing. What we need to know is more about the geology, more about the existence of faults."
At least three earthquakes were recorded Monday in the Stillwater area, about 50 miles northeast of Edmond. The largest was a magnitude 3.2 quake, according to the U.S. Geological Survey. Baker said his agency also was looking at the new seismic activity.
The response plan announced Monday calls for one well located 3.5 miles from the center of earthquake activity near Edmond to reduce disposal volumes by 50 percent and four other located between six and 10 miles away by 25 percent. Other wells within 15 miles of the activity will conduct reservoir pressure testing.
Compliance with the plan is voluntary at this point, though none of the operators have raised objections. The commission said the operator of the well closest to the earthquake activity, Pedestal Oil Company Inc., has agreed to suspend operations entirely to assist the agency's research effort.
My question to you geologists on this forum:
We all know that the earth is not some static rock but continuously moves. This means that earthquakes always occur, so someone who is against fraccing can always find an 'earthquake' conveniently whenever he wishes to advance an agenda.
How do we differentiate typical 'earthquakes' from an atypical 'earthquake'? I am implying that a quality indicator is used, not just a quantity (more earthquakes) indicator.
It is unlikely that the disposal wells are inducing faults, only that they are facilitating movement along existing faults. Clusters of earthquakes in the vicinity of disposal facilities and which intensify with increased fluid disposal would appear to have a relationship with that disposal and, if in an area with little other seismic activity, would appear to be atypical.
Note: This isn't fraccing, which is a transient event designed to fracture the rock in a producing formation by inducing pressure, but saltwater disposal. Frac fluids are pumped into the well bore at high pressures to break the rock at depth, but only for a short time. Frac fluid and pressure are recovered and relieved, respectively by production, and the fracturing limited and ideally more intense over a smaller area and thickness to more efficiently produce oil and gas which would otherwise be trapped and isolated in unconnected pore space.
Saltwater disposal (via an injection well) is the disposal of production water by injecting it into a formation with the porosity and permeability to absorb fluid volumes, and the pressure of injection commonly exceeds the natural formation pressure found in virgin reservoir in that formation.
(A formation being a layer of rock of similar characteristics and type extensive enough to be mapped).
The injection is facilitated by the pressure exerted by a column of fluid in the disposal well exerting more pressure at the depth of the reservoir than that natural virgin reservoir pressure, so the fluid in the well bore flows into the formation. As that happens, the top of the fluid drops in the wellbore, and it is, in turn, replaced by the addition of more salt water, keeping the process going. Without actually having to pump anything at high pressure (unlike fraccing), a disposal well relies on the density of the salt water to exert pressure down hole. This way, a lot of production fluid can be put back into the earth, without having a disposal problem on the surface, and without high pressure pumps and other specialized equipment. That fluid, as it is introduced to the disposal reservoir increases pressure in the pore spaces in the formation the disposed fluids are entering, that effect most intense near the well bore and tapering off (all other things being equal) as you go away from the wellbore. Eventually, following the properties of physics and without barriers in the formation to flow, that pressure will tend to equalize.
If the fluid comes into contact with natural fractures or faults, it will enter any pore space along them, and increase the fluid pressure there just like any other porosity it can enter. It is believed that that may be enough to overcome the friction between the rock on different sides of the fault, and if there is stress built up, movement can occur, producing an earthquake.
Note that compliance in this is voluntary, and at this point willing. The good thing about this is that no one is assuming that the earthquakes in this instance are the result of saltwater disposal, and the reduction in disposal volumes could afford the opportunity to either show a correlation or connection between disposal volumes and earthquake activity or the lack of that connection.
If there is no connection, then the relief of seismic stress is natural and there is no effect, but something else is causing the clusters of activity. I'll leave it up to the seismologists to assess whether that is cause for concern.
It is theoretically possible to increase fluid pressure along an existing fault to the point where that fluid in effect lubricates the fault and stress (already existing) is relieved.
That might not be a bad thing, as the alternative is to allow greater stresses to build along the fault until an earthquake occurs without that increase in pore pressure, which could be more severe because the stress would be higher. The other side of that coin is that as that stress is being relieved in one place, it may be accumulating somewhere else, or that may be just old tectonic stress, accumulated through structural deformation.
A spin off may be the ability to research relieving stress along a fault in a series of (somewhat) controlled milder events versus just sitting and waiting for 'the big one'. The implications for such research could be phenomenal on a global level, keeping in mind the caveat that no two geological situations are exactly alike.
