"The skunk at the picnic"......Marcellus Shale "Fault Lines"

 

What`s the story about faults found in the Marcellus Shale layer?  Are they always bad or sometimes good?  Do they make an area unsuitable for drilling & development now and forever, or are there strategies to overcome them?  Are faults common or found only in certain areas and why?   Is there a Pennsylvania map showing where these faults are located?   How do gas companies overcome the presence of faults?   Can they simply drill from another direction?  Has anyone had a unit or well plan cancelled because of the discovery of faults?   Wouldn`t a gas company investigate an interested area for faults before signing new leases or plan for a unit?  Does finding a fault mean that an specific area can not be developed?                               Is a fault the "skunk at the picnic" for landowners and lease owners ?

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Permalink Reply by Brian on August 29, 2011 at 12:55am

I have heard that partially why they do the seismic testing is to find the fault lines of the area.  It does not deem the area "unusable", the production company would more than likely choose to drill at or near the fault line, and then have the lateral portion of the well go out and away from the fault line.  This helps to prevent unexpected/unpredictable frac propagation.  

Trying to avoid the lateral portion of the well from crossing one of these fault lines could possibly help to contain the fractures.  This is what i have been told.  It makes sense to a point.  Maybe there are others out there that have some better first hand experience at this that could give a better answer...

Permalink Reply by Area Man on August 29, 2011 at 1:32am

In general, you want to avoid faults to avoid uncertainty.

There are a few issues when you cross a fault: (1) you may exist your target section while drilling, (2) they may direct your frac energy out of zone.

If you are drilling a lateral section and cross a fault, if the offset is enough you may find yourself out of your target.  If that happens, you have to scramble to figure out where you are and how to turn your bit to correct and get back, all the while spending money on the rig and drilling through rock that likely isn't going to produce.

As well, when you come across faults/fractures that you didn't account for, when you pump your frac job your water and energy may follow these faults and go where you don't want them to.  Please note, this doesn't mean we are suddenly fraccing up into an acquifer (for example) but it does mean you likely wasted money on a frac job that doesn't fracture your target.

 

So, yes seismic is a good tool to help map out fault zones - then we can adjust accordingly.

And no, faults do not make an area unusable, but it may delay development until the area is understood better.

 

Hope that helps!

Permalink Reply by craig on August 29, 2011 at 5:07am

Area Man,

Thank you for an informed reply. We need more folks informed on these subjects to post here to help offset some of the speculation. I see you have been a member and watching the boards here for sometime. I am glad to see you getting involved and posting.

 

Permalink Reply by Area Man on August 29, 2011 at 8:00am

Yeah, I'm a lurker - I try to chime in where I can but I work for a big company so I have to stick to the science and less of the opinion.

 

Cheers!

Permalink Reply by craig on August 29, 2011 at 8:39am

I'm sure you may be limited in what you say as well.... Science is much more preferred here, I believe.

 

0jw0dsu4txfuvPermalink Reply by 0jw0dsu4txfuv on August 29, 2011 at 1:32pm

Area Man,

I apprecaite your comments. Beware. I answered a few and got hammered. Mostly the people are real nice.

Permalink Reply by Area Man on August 29, 2011 at 1:40pm

Ha, I know - saw those posts too and almost responded but that's exactly where I can't chime in!

Permalink Reply by farmgas on August 29, 2011 at 12:44pm

 

These are all great replies...thanks!   How common are faults?   Is this normal operating procedure for the gas company to maneuver around faults?   Is there a map of Pennsylvania fault lines or do the O&G companies keep this information to themselves?    With all the excitement about leasing...is the discovery of faults a major concern?  The "skunk at the picnic"....

Permalink Reply by Area Man on August 29, 2011 at 1:46pm

A state map?  Well, they're certainly out there but faults come in all sizes/offsets.  From the perspective of the entire state, it would be a blob covering virtually everywhere.  You gotta remember, its not just laterally but also vertically - that is, faults don't continue from the surface to the core.  They are finite and only some will offset the Marcellus (for instance), while many others may be in your area but are much deeper or more shallow.

It is definitely normal procedure to avoid faults until they are better understood - sometimes they can help production by accessing more natural fractures, allowing more gas/oil to flow.  However, in general they are detrimental so we want to stay clear but either way it's important to know where they are concentrated.

Faults are VERY ubiquitous – definitely not the skunk at the picnic, but as I said if an area tends to be more fractured then anticipated an operator may gather more data before continuing an all ahead full program.

Permalink Reply by Jim Litwinowicz on August 29, 2011 at 2:16pm
I'm gonna guess that faults are more common as you get nearer the ridges of the Appalachians. There have to be fewer as you go west and get into Ohio.
Permalink Reply by Patrick DeBerry on August 29, 2011 at 2:39pm
Faults are quite common and occur randomly across the Appalachian Basin. There is no "secret map" showing where these faults lie. That's why the drillers often do several 3D seismic tests before they invest the 2-3 million dollars required before the first gas comes out of the ground. They also use the results of these tests to "steer" the bit through the layers of shale that tend undulate. I have been told that a drilling pad will often be moved just a short distance so that the vertical portion of the wellbore goes into the fault and then the horizontal "legs" pass through the shale uninterupted. The cost of these detailed seismic tests is quite expensive and the results are usually proprietary.
Permalink Reply by farmgas on August 30, 2011 at 12:43am
Patrick...so, once a fault is known to exist, and as you described, not all is lost.  Just relocate the well pad.   Makes sense!   Are there still problems, though, of available acreage for the gas company to use for this adjustment.   They may have to acquire additional leases to modify their plan, right?   If they are limited to available acreage then they may have to cancell their plans for developing that area...is that a possible scenario?

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