June 1999 Vol. 220 No. 6  Production

Perry A. Fischer,  Engineering Editor

Gas hydrate production schemes; GOM goes fiber optic

Research into gas hydrate production is receiving a lot of attention lately, as noted in a companion report on page 21. Test wells have been drilled offshore Japan and onshore in the Canadian Arctic to research hydrate drilling and production. Production tests using simple depressurization were successfully carried out. While these resulted in substantial initial production, they soon stopped producing, as expected, due to the endothermic cooling that gas undergoes as it expands — the gas may eventually "refreeze."

The depressurization method involves horizontally drilling in the free gas zone just beneath a hydrate zone. As production of the free gas continues, the hydrates above become depressurized and decompose into free gas. This is already suspected, but not proven, to be the case with Russia’s Messoyakha gas field in Western Siberia. This field exhibits depressuring (from production) and repressuring (after shut-in) cycles. Such production pulsing may be a way to overcome the "refreezing" problem.

Another method for hydrate production may be to heat it. Whether steam flood or other energy-intensive heating results in sufficient net energy has yet to be proven, but Timothy Collet, a hydrate researcher with the U.S. Geological Survey, suggests initially placing hydrate wells near existing infrastructure, so that heat from produced well fluids could be used to dissociate the hydrates.

Professor Sasson at Texas A&M University has proposed a use for the reverse reaction: transforming natural gas into hydrates. Gas occupies less than 1/160 of its original volume when transformed into hydrate. Hydrate formation could be done in situ on the ocean floor, trapping vent gas from seafloor chimneys, or as a production method for remote gas fields. Once in a solid state, the hydrate could be towed from deep water to the shallow-water infrastructure and allowed to warm for production. Some research is focusing on hydrates as a safer, cheaper alternative to LNG conversion and transport. One Norwegian study concluded that it would cost 24% less to transport natural gas as hydrate, as opposed to LNG.

Although not related to E&P (except perhaps via Kyoto Protocol), investigation has been ongoing into what role, if any, hydrates play in climate change, especially ice ages. It seems that a change in ocean depth or temperature, regardless of the cause, would result in hydrate decomposition and release of massive amounts of natural gas into the atmosphere. What the effect would be is not known, but rest assured someone is trying to calculate it.

Perhaps the strangest hydrate horror, already well known to researchers and regular viewers of Unmysteries Solved, are hydrates’ proposed roles in unexplained ship disappearances, such as occur in the mythical Bermuda triangle (see http://woodshole.er.usgs.gov/project-pages/hydrates/bermuda.html). Seems some scientists actually tried to determine the likelihood that a mudslide or similar undersea event could suddenly expose a large area of hydrate, causing it depressurize and burst into gas. This in turn could cause the sea to "boil" and capsize a ship through extreme turbulence, or sink a ship outright through inadequate buoyancy.

Their conclusion? Although highly unlikely, it is possible. But heck, as any old salt that’s spent a lifetime at sea could tell you, some mighty strange things happen out there.

GOM fiber-optic network. Petrocom, already a major provider of satellite voice and data communications in the GOM, announced it would introduce the first fiber-optic communications transport in the Gulf. The system, a fiber-optical SONET ring, will connect Houston with New Orleans via a land and offshore network.

The system will provide offshore production platforms with high-speed internet access, video conferencing and virtual networks. In addition, increased bandwidth and a speed of 2.5 GB/s will allow for real-time data transmission from seismic operations, wireline and MWD operations. The system will triple the current volume of network capacity, equal to 32,000 simultaneous calls.

The increase in reliability, bandwidth and speed will enable more platform automation, monitoring and robotic capability, thus reducing the number of employees per platform.

Work will begin this month, first connecting several key deepwater platforms, and eventually connecting the rest with 1,200 mi of cable. The cable will be protected from heavy Gulf traffic by placement in decommissioned pipelines.

Gas-to-liquids project. The Department of Energy (DOE) said it would provide $2.5 million to the University of Alaska for development of new gas-to-liquids technology. Another $625,000 will come from private-sector cost sharing. The project’s aim is to make currently unmarketable gas, such as the vast reserves under the North Slope, sellable by shipping it through the Trans-Alaska Pipeline System, thereby extending TAPS at least 20 years.

Massachusetts Institute of Technology, the Univ. of Houston, the Univ. of Illinois-Chicago and the Univ. of Missouri-Rolla, as well as BP-Amoco will also share in the research. The team will conduct a 2-year research project to develop an "electroceramic membrane," a solid-state device that would separate oxygen from air and use it to convert natural gas to liquids.

Gas-to-liquids technology differs from LNG processing, wherein gas is cooled to a liquid. Gas-to-liquids technology chemically converts gas molecules by breaking them apart and re-combining them with oxygen to form a mixture called "synthesis gas." This gas in turn can be chemically converted into clean-burning transportation fuels and many valuable chemicals.

This is the second DOE research contract for development of a ceramic gas-to-liquids membrane. The first went to Air Products and Chemicals, Inc. in May 1997.

Factoid: Each decade, as much oil is discharged from natural seeps in the GOM as was spilled from the Exxon Valdez (Scientific American).

Copyright © 1999 World Oil
Copyright © 1999 Gulf Publishing Company