What's new in exploration

	Vol. 226 No. 7
PERRY A. FISCHER, EDITOR

Interesting conferences. I do not know if it was due to high oil and gas prices, Calgary’s spectacular weather, the summer solstice or what, but this year’s AAPG show was the most upbeat that I have ever seen. Attendance, at 7,748, was the highest in 19 years. While the show featured the typical oilfield geology subjects, there were many off-oilfield topics such as CO₂ sequestration, and wind and fuel cell energy. But the surprise was the overwhelming interest in Martian geology. For these presentations, the crowd spilled well into the halls, with everyone craning their necks to catch a glimpse of the dozens of spectacular images from the two Martian Rovers. 

Doug Strickland, exploration manager for Wolverine Gas & Oil, gave an interesting talk on the Utah Covenant field discovery, which I discussed in last month’s column. My reserves estimate of 100,000 bbl was clearly way too low. Unfortunately, the correct number is supposedly not known. Strickland stated that he does indeed believe it to be a “billion barrel province, ” and the field has “285 million barrels of oil in place.” Although two wells now online are producing about 800 bopd each, when completed, he expects production from the field to reach 10,000 bopd. A “sketch on the napkin” guess shows that, a 5,000 bpd average, extended over 20 years, would yield 37 million bbl. However, when asked directly, he simply stated that, since the company was private and not bound by SEC rules, “I honestly have no idea what that (proved reserves) number would be.”

Immediately preceding the AAPG show was the long-awaited Hedburg Research Conference on Origin of Petroleum. The conference accomplished part of its goal of “an exchange of ideas,” but not the part about “keeping an open mind.” At one point, I thought that some speakers might get physical.

Scrunched into one day instead of the two days originally planned, a lot got left on the cutting room floor. I was a bit disappointed, because the “freak” fields and required freak migration pathways were barely touched on. “They can all be explained conventionally,” one speaker said to me. “Yes, of course,” was my reply, “But the oddest of them would require a rather convoluted explanation.”

There was time for only one of the “combination” hypotheses. This involves upwelling methane, which was created from water-rock reactions (serpentinization – a well-known process). This gas, in turn, reacts with organics in rocks such as shales to yield all of the biomarkers, source rocks and migration paths that we see in the biological theory.

The bio folks often used the success of the business case to prove their point. I can’t buy into that, because the search for oil first involves finding reservoir quality rock – rock with high porosity and high permeability, such as sandstone, followed by a thick sealing layer, like shale. Metamorphic or igneous rock is not usually drilled in, because the chance of finding reservoir quality rock and seal is greatly reduced, while drilling costs are increased. Thus, the business case skews the data toward sedimentary rock.

The best evidence for the high-C end, that is, the oil portion of hydrocarbon generation, remains the peculiar set of molecules (biomarkers) that can sometimes be traced back to a high-organic-content shale or carbonate source rock. On the low-C end, that is, methane, it gets a bit tricky, since both sides agree that there exists at least some abiogenic methane.

It would be great to try this conference again, only next time focused more on the exceptions, the oddities, together with a much longer panel session and the ability to bring a few PowerPoint slides so that anyone in the audience (there were about 75) could illustrate a point. There might need to be referees and “bouncers,” just in case the discussion got completely out of hand. But I doubt that this conference will happen again, especially since Michel Halbouty, one of the original backers of the conference, has passed on. The folks on both (actually, three) sides of this argument are not idiots – far from it. They just like to think of each other that way.

Martian methane, take two. In this column in January 2005, I talked about the fact that three independent teams had arrived at a conclusion that there was too much methane in the Martian atmosphere, such that it must be surface derived. One of the scientists even suggested it was probably biologically sourced.

“Not so fast,” say geologists Chris Oze and Mukul Sharma of Dartmouth College, New Hampshire. The methane could easily be produced by the same serpentinization process that occurs on Earth. When olivine is heated under pressure, it reacts with water and carbon dioxide to create methane, leaving the mineral serpentine behind. The geologists believe that the necessary conditions exist just a couple of miles beneath the surface.

The pair calculated that the process would consume about 80,000 mt of olivine each year. To generate methane at the same rate over the planet’s 4.5-billion-year lifetime would require a global, 20-in. (50-cm) thick layer of olivine. That would be just one millionth of the mass of the planet. Their calculation is published online in Geophysical Research Letters.

It is certain that the red planet has green olivine. The mineral is found in Martian meteorites, and has been spotted by both the Mars rover Opportunity and NASA’s orbiting probe, Mars Global Surveyor. The extent of one particular olivine surface outcrop is now thought to be the size of Cuba.

A Mars probe, slated for launch in 2010, will measure carbon isotopes in methane, which could prove that bacteria are the source.

What a voyage. Twenty-eight years ago, the Voyager I spacecraft left our solar system. Last month, it was agreed that it has now passed to where the Sun’s influence ends and the solar wind crashes into the thin gas between stars. This heliosphere extends from the Sun to distance of 8.7 billion miles. From that point on, the solar wind and other solar effects drop off relatively quickly, and the Sun looks just like any other star.

Voyager’s plutonium power supply will allow it to continue sending us data for the next 15 years or so, assuming that it isn’t killed sooner by budget cutters. So, new data will continue to add to our knowledge of what lies beyond the influence of our Sun.

Whatever happens, congratulations to all of us. We are no longer just interplanetary travelers. We have now become interstellar explorationists.