Could Barnett Shale drilling be cause...

Could Barnett Shale drilling be cause for Texas earthquakes?

There are 8 comments on the KHOU-TV Houston story from Jun 8, 2009, titled Could Barnett Shale drilling be cause for Texas earthquakes?. In it, KHOU-TV Houston reports that:

Before last week there had never been an earthquake in Cleburne. In the past six days the Johnson County town has been shaken by three earthquakes.

Join the discussion below, or Read more at KHOU-TV Houston.

Brenda Wolinski

Dallas, TX

#1 Jun 11, 2009
I m sure it is from drilling... but they ve been drilling for oil for years in TX same as for gas... and we ve been having small quakes forever in Texas... just not enough to notice really..
Tom

Dallas, TX

#2 Jun 12, 2009
This gas is supposed to be trapped in the shale. They drill in such a way as to crack the shale so it releases the gas, I think. Anyone out there who can explain how they actually get the gas.
nope

United States

#3 Jun 29, 2009
The gas is under pressure and seeps out

“WEATHER is not CLIMATE”

Since: Jun 08

Pasadena, TX

#4 Jun 30, 2009
The gas is in Shale in two ways...
- it is in the micropores, the very small void spaces within the shale,
- it is adsorbed or absorbed on to the organic bits in the shale.

The big problem with Shale, unlike many sandstones, is that the porosity (the little void spaces) aren't connected well at all to each other. That means that even if you drilled into the rock, little gas would normally flow. So what they do is run in with fluid or sometimes a gas and pump it into the rock under extremely high pressure. This is an artificial fracturing of the rock (called a "frac") and causes the rock to crack. The crack network is the pathway that the gas uses to get to the wellbore.

The first gas to move is the matrix gas (the stuff in the little holes). As the rock starts to feel the pressure difference between it and the surface, the "sorbed" gas breaks free from the organic material in the shale.

In most cases only a small amount of the gas in the shale is ever able to flow. Often only about a quarter of the gas that is in the rock will be produced.
Loverman

Venice, CA

#5 Aug 6, 2009
There could be a correlation to the quakes and oil/gas drilling. There are such things as domino effects, which can occur when there is displacement, as what happens with drilling, thus producing an effect much farther down into the crust. The buildup happens at a very quick time, perhaps, due to the emptied gas, some other liquid seeps upward to replace where the oil/gas was, due to pressure. Strain would cause an earthquake, when you factor in that perhaps the gas/oil was there in that particular area for a reason after all, stablizing the landscape. Hopefully some new fault isn't forming in this region, due to our gas pumping, oil sucking ways, caused by geologic displacement?
Newbie

AOL

#6 Aug 6, 2009
Nacho Man and Loverman, your posts are very interesting. I've often wondered if there was a correlation between the drilling and earth quakes.
gas field worker

Azle, TX

#7 Aug 7, 2009
okay heres my take on the whole thing... i honestly dont think it has anything to do with the "drilling" per say, i think it has to do with the fracking... i mean think about it, when they frack the wells, they are taking out the gas and replacing it all with a water and sand mixture, right, well the thing is, when they do this, the wated is sucked up by the ground, or the walls of the "gas pocket" then the sand is left there, just damp sand, which i sont think is taking up all the room that the gas was filling... so if you think about it, the water is soaked up, and the pocket then falls into itself, causing not only that pocket to fall in, but also the ground around it to move, which in turn causes somewhat of a domino effect on the rest of the surrounding dirt, mud, or whatever else there is... im no geologist, but thats just how i see how things in the gas field are working... just my own opinion...

“WEATHER is not CLIMATE”

Since: Jun 08

Calgary, Canada

#8 Aug 11, 2009
Shale gas is entirely different from conventional buoyancy related trapping. There is no "replacement" of gas in the system as the nanopermeability does not allow flow of any fluid very far very fast. Without fracturing, it takes thousands of years to move a molecule of gas or water through the shale. Gas is not replaced by anything. The water that is injected in the frac is immediately withdrawn and while the sand is extra material, it hold the fractures open. The gas that is produced is replaced by nothing. The pressure of the reservoir is reduced and the gas in place expands. Sorbed gas components are freed and gas produces to the surface through the well bore.

The whole premise of unconventional gas is that it does not require the a water drive mechanism. Even if it did, there are no domino effect that would be felt tens of miles deeper. The gas production elements described well by other posters apply to conventional reservoirs and not shale gas reservoirs.

The entire Gulf coast is fault ridden. The weight of the sediments have been causing and moving growth faults for undreds of millions of years. The N. Texas earthquakes are related to something other than the relatively shallow shale gas drilling.

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