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Permalink Reply by HJ on January 23, 2013 at 5:23pm

Almost all of the horizontal Utica well bores are drilled approximately 30 degrees "off of north and south".

If you are explaining it to others perhaps the easiest way to help them visualize it is to tell them that if the center of a clock face is the well pad, wells are drilled either to the 11:00 or the 5:00 position on the clock face (it just happens that each of the numbers on a clock face is 30 degrees from the next).

If you go to the ODNR website and work your way to the completions reports you can find well plats among the links at the bottom of the report. Occasionally a well bore will deviate a few degrees plus or minus from 30 degrees in order to fit into the available acreage.

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Permalink Reply by Jack Straw on January 23, 2013 at 5:40pm

 

They drill in azimuths that will encounter the mazimum number of naturally occuring joints (fractures) in the formation. They do this to take advantage of these fractures (as pre-existing avenues of hydrocarbon migration into the borehole).

This jointing tends to be ENE-WSW; so you want to drill at 90 degrees to the azimuth of the primary jointing inorder to encounter the maximum number of these joints. (To avoid confusion, I find it easier to make a "back of the envelope" diagram.)

To accomplish this, they drill roughly NNW (and the opposite SSE).

This azimuth will potentially vary a bit going from South to North; as the axis/azimuth of the (orthoganal) primary jointing changes a bit.

If you consult the Well Plat for a Marcellus Well that was recently posted by Todd Smith in this Discussion:

 http://gomarcellusshale.com/forum/topics/organic-rich-shale-thickne...

you will note that this well was to be drilled at an azimuth of S 23 deg. E. (an azimuth of SSE (157 deg.)). 

 

From a pad, you can anticipate wells will be drilled to the NNW and to SSE (plus or minus a bit to account for local variation in the azimuth of jointing). In a nutshell, the reasons are due to Tectonics/Geology.

 

Hope that this was not too confusing.

 

JS

 

 

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Permalink Reply by Robert Bond on January 24, 2013 at 2:23am

I thank you both for the information!

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