PITTSBURGH – The Utica/Point Pleasant shales have been compared favorably to the Eagle Ford play in South Texas. However, the Point Pleasant, especially, which runs from eastern Ohio to northwestern Pennsylvania, has several unique geological features that could make it one of the top domestic producers – if not the top producer.

The geological features for the Point Pleasant shale include higher resistivity than other shales, very thin limestone interbedding, and very low water saturation of only 10%, explained Kent Bowker, president, Bowker Petroleum and its partner, Sierra Buckeye LLC, at Hart Energy’s DUG East Conference in Pittsburgh on Nov. 14.

“I think the very thin limestone beds are important to flow rates. Permeability of the limestone is greater than 10 millidarcies,” he said. “This is kind of amazing. These numbers don’t sound like shale numbers. One sample has porosity of 13.7%. That is a huge amount of porosity created by the fractures in the limestone. These form mini-pathways in the Point Pleasant. The permeability results in very high flow rates from the Point Pleasant.

“Those little, tiny, 2-cm to 3-cm thick limestone layers act as nice horizontal permeability layers that can connect the vertical hydraulic fractures creating a matrix. Very high flow rates have been reported. I think the permeability mechanism within those limestone layers helps add to the deliverability of the wells. There is nothing I’ve seen like that in other shale plays I’ve been involved in,” he continued.

“Since we’re dealing with a very old Ordovician system, the precursor organic matter is completely different. For instance, the oil doesn’t fluoresce because of the chemical nature of the precursor organic matter. It doesn’t even smell. It kind of freaks you out,” he laughed.

Another unusual feature of the shale is “horizontal extrusion fractures that may be an indication of original overpressure,” said Dr. Joel Walls, director, technical resources, unconventional reservoirs, Ingrain Inc. “There is significant porosity development inside the organic material with its inversion ratio somewhere around 40%. The organic content by volume is anywhere from 2% to 8%.

“Samples we’ve examined along with porosity-permeability results were on a par with the lower Eagle Ford, even though those two formations are very different in geological age. There are some differences in mineralogy and lithology as well. I don’t want to make too much of that analogy, but at least in terms of reservoir quality there are some definite similarities,” he continued.

Ralph Williams, president, Reservoir Visualization Inc., pointed out that the Utica shale runs from St. Louis, Mo., to New York, where the Utica shale outcrops in Utica, N.Y., and the Marcellus outcrops in Marcellus, N.Y., and from Tennessee into New York and Canada.

“What continues to amaze me is the megascopic features of the Ordovician system, which the Utica is part of. In the northeastern US, we can see the entire west side of the basin in our well control. We look at geobodies, net sands and net shale to see where the positions are and infer if it is a delta, carbonate bank, or paleoridge like we saw in the Marcellus. We see an extra-wide areal extent of control that we don’t see in a lot of plays,” he added.

Bowker noted that operators don’t get much water back from horizontal play. “There is very little water recovered from the fracs in the Point Pleasant. You don’t get much water back from any shale plays. The lower the amount of water, the better the shale is. My understanding is that very little water recovered from fracs in the Point Pleasant. We’re dealing with a very dry reservoir.”

By putting the water into the hydraulic fractures and letting it sit, the shale is imbibing the water and not filling in the pores. The clay wants the water. After 60 to 90 days, the water is imbibed into the crystalline structure of the clay itself.
“Do I have any proof this? No, but I’m a geologist and I don’t need any proof,” he laughed. “That’s what I think is going on. The water is not harmful to the rock.”

Contact the author, Scott Weeden, at sweeden@hartenergy.com.