Replies to This Discussion

Permalink Reply by P.G. on August 7, 2011 at 11:32

Speaking of rigs, don't they have to be located away from section lines by so many feet?

If one subtracts that amount of land (set back)  around the circumference of a section , how much of the section  (acres) or percent will never get drained?

• ▶ Reply

Permalink Reply by Skip Peel - Mineral Consultant on August 7, 2011 at 12:42

The perforation point in the well bore has to be set back from the unit boundary lines, not the rig (surface location).

• ▶ Reply

Permalink Reply by P.G. on August 7, 2011 at 15:22

Oh okay...but say in a township, if all sections got drilled...how much land would not get drained due to the setbacks?

• ▶ Reply

Permalink Reply by Skip Peel - Mineral Consultant on August 7, 2011 at 15:48

Theoretically about a sixty foot wide band being 30' on both sides of a unit boundary based on fracture propagation of 300' from the well bore.  I have not seen any statement by an operator regarding the shale that is not produced because of the setbacks meant to avoid drainage across unit lines.  EnCana for one may think that their cross unit lateral design will allow for full  drainage.  If it does, I think they will announce it.  If that is the case, more operators may wish to amend units to allow for that development design.  I say "may" because it would certainly be controversial.

• ▶ Reply

Permalink Reply by Les Bamburg on August 7, 2011 at 16:27

PG, generally it is believed that 100% of the acreage would be drained assuming sections are developed on an 80 acre spacing.

• ▶ Reply

Permalink Reply by Les Bamburg on August 7, 2011 at 16:24

PG, perforations have to be at least 330 ft from section lines so it is possible that no areas are left unproduced. 

• ▶ Reply

Permalink Reply by P.G. on August 7, 2011 at 16:58

Just trying to wrap my mind around this...so if the well bore bottom were to be no closer than 330 feet from a section line, the perforations would actually reach out and drain right up to the section lines then?

For some reason I had a image of a grid all the way around a section that couldn't get drilled...I didn't think about the fracking cracking the shale within that grid..

• ▶ Reply

Permalink Reply by Les Bamburg on August 7, 2011 at 18:36

PG, it is the fractures that extend from the lateral/perforations that drain the additional area.  The concern is that the fractures do not fully extend north and south to the section line from a north/south lateral.  Of course there is some drainage of the rock matrix beyond the extent of the fractures.  There are less concerns/issues with fractures extending east and west perpendicular from the lateral.  

• ▶ Reply

Permalink Reply by P.G. on August 8, 2011 at 1:43

Could it be possible for a second well fracked pretty close to the first to re-pressurize the first well?

• ▶ Reply

Permalink Reply by Les Bamburg on August 8, 2011 at 1:48

PG, unlikely since the immediate area of the shale formation will be partially depeleted (depressured) due to the natural gas production of the first well.  In fact, that is the reason operators want to avoid lateral spacing being too close creating uneconomic wells.

• ▶ Reply

Permalink Reply by P.G. on August 8, 2011 at 12:08

That would put things back to leaving some shale left un-fracked (unharvested) as a buffer if not to allow a new well from seeping into an older de-pressurized well. If two wells were fracked close to a section line (one in one section, the other in another section) then it could possibly siphon ng from one section over to another section if one well had a lower pressure from it's decline. The mineral owners of that second well would be losing ng to the mineral owners of the older well in the other section. If the same driller drilled both wells, what he lost on one could be recovered on the other..right? A driller wouldn't do something like that on purpose if he had more profitable leases in one section than he had in the other would he?

• ▶ Reply

Permalink Reply by Les Bamburg on August 8, 2011 at 14:38

PG, there is some area between adjacent wells that is unfrac'ed on an 80 acre spacing that is drained thru the rock matrix by adjacent well.  The distance gas can flow thru the rock is matrix is limited and that is the reason operators have selected 80 acre spacing and the State requires the 330 ft distance from the section boundaries.  This avoids concerns with drainage across section/unit boundaries.

 

An operator's selection of well spacing is driven by optimizing the economic recovery of natural gas resources.  

• ▶ Reply