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Permalink Reply by bungalow_steve on August 22, 2012 at 11:54am

The more dense and closely spaced natural shale fractures run NE to SW, so they want to intersect as many as possible by drilling perpendicular to them.

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Permalink Reply by Jack Straw on August 22, 2012 at 12:10pm

The reasons have to deal with geology; and the past geologic history of the area.

 

In the distant past, tectonic forces resulted in jointing (fracturing) of the subsurface rocks.

The primary (strongest) jointing (fracturing) was oriented in a NE-SW direction.

Perhaps you have observed jointing in bedrock surfaces exposed in such places as river beds.

 

To best exploit the shales, it is desirable to have the horizontal portion of the well bore encounter as many of these pre-existing joints (fractures) as possible. As existing zones of weakness, these joints are natural fractures that can be more easily widened and kept open through fracing and the introduction of proppants during the fracing process. Utilizing these pre-existing fractures allows for better well production.

 

To encounter as many joints in the rock as possible, the horizontal portion of the well bore is oriented at an azimuth at right angles to the azimuth (direction) of the existing jointing.

 

Since the primary jointing in PA & OH is oriented NE-SW, the horizontal well bores are preferentially oriented NW-SE.

 

Hope that this explains.

 

JS

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Permalink Reply by Donald on August 22, 2012 at 2:31pm

THANKS, THAT EXPLAINES IT IN A WAY I CAN UNDERSTAND. WAS NEVER QUITE SURE THE REASONING BEHIND IT . THANKS AGAIN.

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