Do we REALLY need to be worrying about where we’re going to find those pesky BTU’s that power our planet? Can we get rid of the angst engendered when we read about rising population counts and start thinking “HOW are all those folks gonna get their lights turned on?” Will access to energy cease to be the cause of political instability and wars?? Well, maybe…
Gas hydrates may be the answer.
Often called fire ice, gas hydrates are formed under conditions of high pressure and/or cold temperature, and have three different crystallographic structures. Think of them as a methane molecule
surrounded by 34, 46, or 136 water molecules in a cage like structure.
They are found onshore in permafrost regions (Artic) below about 600’ and in the deep ocean margins, where both cold water temperatures and the pressure of deep water columns cause them to form.
The map at the beginning of this blog shows places where gas hydrates have either been sampled or inferred to exist. It’s pretty obvious that they are predominantly found on ocean margins, but also in deep fresh water lakes (Lake Baikal) and, importantly to the US, in the deeper parts of the Gulf of Mexico. The graphic below give us an idea of the extent and viability of this as a potential resource
So what’s the potential?
Consider that estimates of the amount of Original Gas In Place [ which is not the same as recoverable gas] for the Marcellus play is 1500 TCF (trillion cubic feet). Low estimates for global gas hydrate volumes are 100,000 TCF, and high estimates place it around 5,000,000 TCF. These numbers translate to anywhere from 67 to 3333 Marcellus plays available to be exploited.
BP estimated that worldwide consumption of gas in 2012 was 116 TCF. If the numbers above are to be believed , there is enough gas in gas hydrates to meet this demand for anywhere between 860 to 43,000 YEARS…other estimates would even place the worldwide in-seabed resource at a sufficient size to meet over 2,000,000 years of current consumption.
These are big, big numbers that have piqued the interest of countries that are not blessed with an abundance of national fossil fuel energy resources—like Japan, and even China. The Japanese have successfully drilled to and produced gas hydrates in the Nankai trough (2012)[water depth 3300’, drilled section in seabed 1000’]. This results are absolutely vital to our understanding of whether these gas hydrates are an add to the world’s energy balance, or whether they are a pipe dream.
How do we develop gas hydrates?
Production of gas hydrates requires either the lowering of confining pressure or increasing their temperature. When either of these things occur, the gas will begin to disassociate from its cage structure, and do so very rapidly, expanding to nearly 140 times its original volume.
Given that these gas hydrates are found in the upper 1000’ of the sea bed—which is predominantly silty but may have debris fan (turbidite) sands, they will have hydrostatic pressure of the ocean loading them, but NOT the typical rock overburden pressures that you would find at 10,000-20,000’. So it’s not really known how completely a well targeting them could drain the resource.
Flow test results from the Japanese well were about 700 MCF(thousand cubic feet)/day, with a total cumulative volumes of 4200 MCF over a six day test [https://www.netl.doe.gov/File%20Library/Research/Oil-Gas/methane%20hydrates/MHNews_2013_October.pdf.] No doubt this was a highly controlled, highly choked and very cautiously done flow test. There’s no data regarding what the final flowing pressures were, so there’s no way of knowing whether there was pressure drop and therefore no sense of effective drainage.
This is highly important information, because these reserves cannot be economically developed under free market conditions given the offshore drilling and infrastructure costs UNLESS they ultimately can produce large volumes of gas—or unless they are supported by state subsidies.
There is concern that given the rapid pressure buildup inherent in the disassociation of gas from its water “cage”, drilling hazard mitigation will require large engineering safety costs. But the industry has already drilled into and through gas hydrates on its way to deeper oil reservoirs, and the apparently incident-free Japanese test shows that it can be done in both drilling and production modes.
There is also concern that poorly handled drilling practices could cause what are called geohazard releases of methane into the oceans—mudslides, slope adjustment etc.—that could release large amounts of methane into the oceans and potentially release the disassociated methane into the atmosphere, thereby exacerbating global warming.
Although the research is still young on this topic, several side scan sonar images would indicate that once methane is released into the water column it will dissipate. The image below is from Lake Baikal at -600’.
And this image is from a Shell Oil presentation by Craig Shipp, PhD
There’s an enormous error bar in the data that estimates the size of the potential resource. Identifying gas hydrates can sometimes be done seismically (identifying a BSR-bottom seismic reflector-which occurs at the base of the gas hydrate). This is not always present, however, so estimates of location and therefore resource base await a lot more data. And the engineering “best practices” rule book has not yet been written.
The future of gas hydrates
But the actual production of gas hydrates has been demonstrated to be feasible. Given US shale gas resources identified in the Barnett, Marcellus and other plays, don’t expect to see gas hydrates in the news in the very near future for US producers. But the pace of their development and adoption may go screaming forward for nations-like Japan, India and others—that have determined that it’s very much in their strategic national interest to develop alternatives to geopolitically vulnerable imports.
What do you think? Will anyone take the vanguard and lead on gas hydrates in the near future? Leave a comment below.
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