Appalachian Basin’s Marcellus – the new target
Another Shale Making Seismic Waves
If you feel bad because you failed to lay claim to a piece of the action early on in the high-flying Barnett Shale play in Texas, stop living in the past.
There’s a whole new shale play kicking off in the northeastern part of the United States that has industry analysts, operators and others all abuzz.
Some folks say eventually it might overshadow the Barnett in productivity.
It’s the Marcellus shale member of the Devonian black shales, and it spans a distance of approximately 600 miles, trending northeastward from West Virginia all the way into New York.
By comparison, the Barnett has a linear extent totaling about 120 miles.
“This is an unconventional play with a huge area to it,” said AAPG member and current Distinguished Lecturer Terry Engelder, a Pennsylvania State University geosciences professor who has studied the Devonian black shales in the Appalachian Basin for 30 years.
“It’s the size of this shale that’s continuous that makes this a very unique resource in terms of potential,” he said.
In fact, the play likely will increase the Potential Gas Committee’s probable resource numbers by 50 TCF, according to Engelder.
“Probable resources are associated with known fields and are the most assured of potential supplies,” he noted. “This is not a proven reserve, but when you compare it to American proved reserves of 200 TCF, this is 25 percent.
“Compared to technically recoverable reserves, it’s still 10 percent.”
Hot Off the Press
If this is all news to you, you’re not alone.
It was a December press release listing results from a pilot horizontal well program implemented by veteran Marcellus player Range Resources that put a spotlight on this shale’s significant productive potential.
The company reported initial test rates between 1.4 and 4.7 Mcf/d for five horizontal wells it drilled to the Marcellus in Pennsylvania, capturing the attention of a host of folks, including financial analysts and media-types.
“You always got a good gas kick drilling through the Marcellus, but no one could ever complete it and make it productive,” said Rodney Waller, senior vice president and chief compliance officer at Range. “This was over a 10 to 15-year period.
“Almost three years ago, we brought a slick water frac out of the Barnett-type of completion and did that on a vertical well and got a good initial rate, good production curve, et cetera, which gave us encouragement to move forward.”
Following a couple of other verticals, the company drilled a horizontal well, which didn’t perform competently yet showed inclining rather than declining production after several months.
“It told us, hey, there may be gas here, but the way in which you completed the well is probably not the optimum way,” Waller said. “There’s a very large section there – and like in the Barnett just as everywhere, where you put the horizontal, how you put it in, how you lay it in is very critically important.”
Waller noted there wasn’t excessive interest in the Marcellus until maybe 12 months ago.
“It was Range and maybe one other company looking at it,” he said. “This thing started getting legs under it after we started announcing bigger wells.”
It’s all about the fractures in the rock – and how you tap into them.
“The Marcellus has two sets of vertical fractures, or joints - the J1 and the J2,” said Engelder, who authored a paper in 1985 predicting that the Appalachian Basin could contain a well-developed set of natural hydraulic fractures. “Later, natural hydraulic fracturing in the basin was confirmed in a series of papers by myself and co-authors.
“In the Marcellus, the east-northeast trending J1s are more dense, more closely spaced and are cross-cut by the less well-developed, northwest-trending J2 joints,” Engelder noted.
“Operators can drill horizontal wells to the north-northwest, or south-southeast and cross and drain a whole bunch of the densely developed J1s,” he said, “which, because they are so planar, may be difficult to detect using conventional borehole imaging techniques.
“As explained in my 2006 GEOLOGY paper, the J1 joints are oriented the same throughout the basin, which is key to success of the play.
“Still another key is that this is a dual porosity reservoir,” Engelder said, “where the fractures will be drained rapidly and the matrix will be drained more slowly.
“It’s the matrix that really carries a lot of the gas – both free gas and adsorbed gas,” he noted. “The key is to connect the matrix porosity to the wellbore, and it’s the density of the J1 fractures that allows this connection to be the most effective and why the Marcellus is really going to work as a horizontal play.”
Evidence of the Marcellus shale can be found in the eastern U.S. drilling activity (above) that already is taking place in the Appalachian Basin, and along the shores of Lake Erie (below) south of Buffalo, N.Y.
Photos courtesy of Range Resources (above), Gary Lash
Different Strokes for Different Folks
Other Devonian shale reservoirs, such as the Huron, are present in the region, but the deeper Marcellus is higher pressured with more gas-in-place, according to Waller, particularly in Pennsylvania where the Marcellus is the dominant Devonian shale member.
Pinning down specific targets in the play is no easy task.
“We’re seeing different applications in different places, and we think the Marcellus will be prospective on a multiple play basis just as in the Barnett,” Waller said. “There are wet gas areas, dry gas areas, more geologically complex areas.
“You have all those types of areas that could be prospective,” Waller said, “so everyone is trying to home in on one specific area – but there are going to be multiple areas that are prospective.
“There’s a whole variety, and there are players who have drilled both horizontal and vertical wells in the Marcellus that are very good.”
In fact, Atlas Energy Resources reported in November that it had completed 10 vertical wells as commercial producers out of 13 verticals drilled. The remaining three wells were on schedule to be fractured and completed.
The wells are in southwestern Pennsylvania where the Marcellus is approximately 8,000 feet deep.
Mum’s the Word
Not surprisingly, there’s intense competition for acreage in this play – meaning most companies are close-mouthed and trying to maneuver under the radar.
A lack of available public information makes this effort even more challenging.
Technology and “understanding the shale” are the keys to success in the Appalachian.
Photo courtesy of Range Resources
“In Pennsylvania, there’s no regular log repository, and that’s one of the barriers to entry,” Waller said. “You have to have published papers, regional stuff, unless you’ve actually traded logs.”
After acquiring the leases, boning up on the vagaries of the fractured Marcellus and coming up with a drilling strategy, the players may have to wait in line to drill a well.
“There are currently only four, maybe six rigs in Appalachia that can drill horizontal wells,” Waller said, “and we have two or three of them.
“There’s also a scarcity of pump services, coil tubing, drilling equipment because most of the equipment in Appalachia is geared toward shallow drilling, gas supplies for utilities, et cetera.”
Throwing a Dart
Because the play kicked off on such a large scale geographically, operators will have to burn more midnight oil than usual to pinpoint a niche area.
“If you look at shale plays like the Barnett, Woodford, Fayetteville, they all started in a very finite, small area and expanded out,” Waller noted. “This is the first where the thing is happening over a 15- to 20-county area.
“It’s scattered through Pennsylvania because everyone has a little bit different interpretation as to where the most prospective shale may be in view of their past experience with other shales.”
Being four years into the play, Range enjoyed the luxury of applying a strategy different from the many new folks trying to establish a foothold in the play.
“We’ve been in the play long enough, we decided the key is to get a large amount of acreage throughout all prospective areas,” Waller noted. “That way no matter how quickly the play develops and the success people have, we have 10,000 or maybe 30,000 acres somewhere close to anything else that may be developed.”
For those operators who drilled vertical wells through the Marcellus over the years and experienced nothing more from the usual gas kick, opportunity appears to be knocking.
Indeed, it’s time to hone knowledge about this cracked rock and perhaps re-enter those verticals to apply different completion technology or take them horizontal with the goal of tapping into a cluster of fractures.
“Technology and understanding this shale are going to be the key components as to how to drill wells,” Waller said, “and how good the productivity is.”