How to Quantify the Crude?

Expert Says Measuring Methane May Help Determine Size of Gulf Spill

Dr. David Valentine
Paul Wellman (file)

Two days ago, Santa Barbara’s Dr. David Valentine published a theoretical technique he thinks will help the United States determine how much oil has seeped into the Gulf of Mexico since BP’s drilling rig exploded and sank over a month ago. In an opinion article featured on May 23 in the British journal Nature, the UCSB earth scientist explains that 40 percent of the leaking petroleum’s mass is methane gas and, because methane dissolves uniformly in water and the tools exist to accurately measure it, calculating the amount of gas now in the ocean may be the best way to gauge how large the oil slick is and where it’s headed.

Valentine, who’s an expert on the behavior of oil and methane in the ocean and has published several authoritative papers on the subject, writes, “Although methane from surface-vessel spills or shallow-water blowouts escapes into the air, I expect that the vast majority of methane making the long trip to the sea surface from a deep-water spill would dissolve.”

While BP has tried over the weeks to plug the geysering gash in the seabed with a number of ultimately-failed techniques, company officials have struggled to come up with a definitive figure of how much oil is, and has been, escaping into the ocean on a daily basis. Publicized numbers have varied widely — as few as 1,000 barrels per day to as many as 100,000 barrels per day — and, thus far, no private or federal agency has been able to put its finger on an amount with any certainty. The latest release rate being thrown around is 5,000 barrels per day but that piece of data and all others, said Valentine, is based only on inherently inaccurate and highly variable visual, spot, and satellite observations.

In his article, Valentine points out that knowing exactly how much oil has been spilled will help predict ecological impacts, determine current and future mop-up efforts, and allow scientists to compare this incident to others. He also brings up the U.S. Pollution Act of 1990 that, as he writes, “requires the completion of natural-resource damage assessment to determine liability, and the quantity spilled is a factor in damage assessment models.” In short, states Valentine, pinpointing a number will help answer the question that’s been on everyone’s mind: “How big of an environmental disaster is this?”

In a call to action, aimed at the US government, BP and Deepwater Horizon representatives, as well as the international community, Valentine suggests that a fleet of research vessels begin to map methane plumes as soon as possible. Confident that the equipment is available, in-country, and up to the task — “The US academic research fleet alone has a dozen vessels capable of such work,” he writes — Valentine wants to first get a sense of the size and shape of the plumes by tracking water flow with “drifting profiling floats” coupled with additional spot analyses in real time.

Once that’s done, he argues, a two-vessel mission should set out to “ensure the plumes are quantified as comprehensively as possible.” Ships could be easily equipped with sensors that, dragged through the water, would quickly measure methane in different areas at different depths. This gameplan, Valentine writes, would at least provide a lower limit on how much oil is flowing. “Measures of methane-plume movement could also be used to estimate the rate of the spill,” he says. But, Valentine asserts, it must be done soon before the plumes start to disperse.

And the cost, he estimates at “a few million dollars or less,” is negligible compared to the possible benefits of properly studying what he says “is likely to be the worst oil spill in U.S. history.” BP has reportedly spent $450 million on its containment and cleanup efforts so far, and some say the company may have to spend close to $2 billion by the time it’s all over.

According to the Los Angeles Times, Valentine recently pitched his idea to officials involved in the spill and received a positive response. There is no word yet, however, if any of them will act on it.


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