From hot rocks to frozen gas
An ‘Unconventional Convention’
In keeping with the theme to “Deliver the Conventional: Pursue the Unconventional,” this year’s AAPG Annual Convention in San Antonio will offer ample opportunities to get up to speed on the latest happenings in the realm of unconventional resources.
In fact, an entire forum is dedicated to this topic.
The EMD-sponsored event – Future of Unconventional Resource Plays – will convene the afternoon of Tuesday, April 22.
“The main focus at the forum is to take an overview of the importance of what the unconventional resources have been and what they will be in the future, and discuss the technologies that will be used to help exploit these resources,” said Andrew Scott, forum chair and past president of EMD.
“With unconventionals, the key is finding the key to unlock the lock that will let you exploit the resource,” he said.
“With each resource, you have to find that one key trick to make it happen.”
Australia’s Hot Rocks
It’s commonplace these days to hear about coalbed methane, oil shales, gas shales, tight gas and such.
But there are other lower-profile unconventional resources, and they can tend to be somewhat exotic.
Look at hot rocks, for example.
Australia’s hot rock and hydrothermal resources have the potential to fuel competitively-priced, emission free, renewable baseload power for centuries, according to AAPG member Barry Goldstein. His scheduled presentation at the forum, “Australia Hot Rocks – Glow With the Flow,” will take a look at the status of these resources.
Goldstein, with the minerals and energy division of Department of Primary Industries and Resources of South Australia in Adelaide, noted that companies are targeting geothermal energy resources in Australia that fall into two categories:
- Hydrothermal resources in relatively hot sedimentary basins.
- Hot rocks.
If your prospecting milieu is confined to soft sediments – or mud, as some folks say – in areas like the U.S. Gulf Coast, hot rocks understandably are not on your radar screen. Hot rock systems are ordinarily associated with granites that contain extraordinarily high concentrations of naturally radioactive elements.
The radioactive decay of these elements over millions of years generates heat that becomes trapped when the granite is buried by insulating sediments, according to Geoscience Australia, which is the national agency for geoscience research and geospatial information.
The agency noted the hot rock system must be fractured to achieve fluid flow necessary for heat transfer. Liquid is pumped down an injection well and traverses the fracture network where it’s heated by the rock prior to returning to the surface in a production well where its extreme heat is transferred to a secondary fluid.
‘World’s Largest Energy Resource’
Another intriguing yet untapped unconventional resource – gas hydrates – might be said to occupy a position in the unconventional resource spectrum that’s a one-eighty from hot rocks.
The building blocks of a gas hydrate, which is a crystalline solid, consist of a gas molecule surrounded by a cage of water molecules, according to the U.S. Geological Survey. In fact, it looks much like water ice.
These gas hydrates occur naturally both in Arctic regions and marine sediments – and they hold enormous promise as an energy source.
“The potential for gas hydrates worldwide has been stated to be equal to, if not greater than, the energy potential stored in all the known gas, oil and coal resources in the world,” said member Tim Collett, who will talk about gas hydrates at the AAPG forum.
Collett’s presentation is provocatively titled “Gas Hydrates: The World’s Largest Energy Resource – But Should I Care!”
“That potential (of gas hydrates) is a strong statement,” Collett said, “but the problem we have is that none of it’s been produced yet.
“Basically the issue is how producible are gas hydrates themselves,” he said, “and that is the focus of ongoing research. We have a large known amount of hydrocarbons within gas hydrates, but understanding how it would contribute to the energy mix is totally unknown.”
Some of the new gas hydrate projects implemented over the last decade – and especially the last few years – include international projects designed to assess the resource potential of hydrates and to actually test the producibility, according to Collett.
“The ground is shifting before us,” he said. “Our knowledge base about the hydrates, both the geological occurrence and producibility, is growing very rapidly right now.”
Familiar (Shale Gas) Territory
Hot rocks and gas hydrates in particular may be all the more tantalizing because of their esoteric nature, but the more familiar unconventionals, such as shale gas, still exude panache in many cases.
For instance, on-site activity itself is a bit unconventional in at least one area of the popular Barnett shale play in Texas.
Recognizing that a primo chunk of this prolific shale sits beneath the Dallas-Fort Worth International Airport (DFW), Chesapeake Energy inked an agreement with the powers-that-be to acquire a 3-D seismic survey over the vast expanse of DFW. The last of the data were acquired in March 2007, and a big-time drilling program is well under way.
AAPG member Larry Lunardi, vice president of geophysics at Chesapeake in Oklahoma City, will provide AAPG forum attendees an overview of this activity and more during his presentation: “Unconventional Seismic – Hazard Mapping for Shale Gas Plays.”
He’ll describe how Chesapeake is using seismic in the many different shale plays the company is pursuing.
“In most cases, what it boils down to is figuring a way to produce a very detailed hazard map for the horizontal drilling programs we have going in all these plays,” Lunardi said.
“It turned out to be very significant that we had that map (at DFW),” he noted.
“In this part of the Barnett, we don’t have to worry so much about karst features, but you do have to worry about deep seated faults.”
Chesapeake has drilled and completed more than 40 wells at DFW, and more are in the works.
“We have four conventional rigs running, and one very unusual specialty rig with a 100-foot mast on it,” Lunardi said. “You can put that rig right in the flight path of a landing aircraft and not interfere with the communications or line-of-sight for the pilots.
“We’re drilling right in the vicinity of runways. I visited one of the rigs a couple of months ago, and it’s a bit unnerving when standing on a rig floor and you hear a 737 come roaring by,” he said. “The 3-D was just as entertaining.”
Horizontal wells can sit up close to the edge of the runway and then drill right under the runway providing almost unlimited opportunity for hydrocarbon recovery.
“There’s no part of the airport we think we won’t be able to reach with our horizontal wells given the pad sites the airport has been approving,” Lunardi said.