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Chemical-based monitor warns of rising levels of well water
Unwanted inflows of water are the single most important factor causing production problems for oil companies. A company such as Statoil alone produces enough water to fill a 350 000 tonne tanker every day. Much of this water could be replaced by saleable oil if measures to prevent water from flowing into the wells were implemented.
Information about just where water flows into wells is a fundamental requirement for planning such measures. At current oil prices, even a one per cent increase in Norwegian oil production would be worth NOK4b/y (E0.5b/y).
‘Chemical intelligence’
Howevera solution might now be at hand. Statoil has just started producing from a well that makes use of a new ‘chemical intelligence’ technique that monitors unwanted inflows of water.
The equipment being used in the project was supplied by Trondheim-based ResMana small start-up company set up by the Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology (Sintef).
ResMan is the result of extensive research jointly carried out by Sintef and the Norwegian Institute of Energy Technology.
It has taken about a year to develop the prototype that has just been installed on the Urd field in the Norwegian Sea. Scientists believe that it will offer operating companies completely new possibilities for well control.
ResMan md Fridtjof Nyhavn outlined the problems caused by water in wells: “When oil is producedall the fluids in the reservoirincluding the waterstart to move.
“Water in movement can have a planned positive functionbecause it can force the oil to move in the direction of the wellsthus increasing production.
“But there is still a great deal of uncertainty regarding just how water moves through a reservoirand it often flows into production wells where it mixes with the other fluids. The result may be a reduction in saleable productionand in the worst caseserious well problems and operational shutdown.”
“We decided to test this technology on Urd as we regard it as an extremely useful tool for the future” noted Statoil’s Sigurd Hundsnes.
The ResMan system consists of a number of plastic staves that are installed in the well in the production zone (Fig.1). The staves are doped with tracers unique to each section of the well and are liberated if the plastic staves are surrounded by water. As long as there is only oil in the well the tracers will not be liberated.
It is this liberation of tracers – controlled by condition and environmental conditions – that is described as ‘chemical intelligence’. Measurements using chemical intelligence can be made without having to send any sort of cabling down the well.
Once it has been fully developedthe ResMan system will provide information about what is flowingwhereand in what quantities. This will apply not only at the interface between reservoir and wellbut also internally in complex well completions.
“The pilot tests on Statoil’s field are extremely important for us” says ResMan’s director of development Anne Dalager Dyrli. “We have demonstrated the system in the laboratory under conditions similar to well conditionsand we have produced sufficient plastic staves at full scale to meet the needs of a complete well.
“All of these stepsup to installation in a wellhave taken place without any problems worth mentioning. The fact that production is now under way according to plan on the field shows that the ResMan system in the well situation has no negative effects on production and that the downhole parts of the system are functioning properly.
The measurements (topside aspect) will be demonstrated in the event of a subsequent water breakthrough.”
Renewables-based syngas
Anyone who has overheated vegetable oil or sweet syrup knows that neither oil nor sugar evaporate. The oil smokes and turns brownwhile the sugar turns black. Both leave a nasty film of carbon on the cookware.
Now a University of Minnesota team in the US has invented a ‘reactive flash volatilisation process’ that heats oil and sugar about a million times faster than you can in your kitchen. This produces hydrogen and carbon monoxidea mixture called synthesis gasor syngasbecause it is used to make chemicals and fuelsincluding gasoline.
The new process works 10–100 times faster than current technologywith no input of fossil fuels and in reactors at least 10 times smaller than current models. The work could significantly improve the efficiency of fuel production from renewable energy sources.
“It’s a way to take cheapworthless biomass and turn it into useful fuels and chemicals” said team leader Lanny Schmidta Regents professor of chemical engineering and materials science at the university. “Potentiallythe biomass could be used cooking oil or even products from cow manureyard clippingscornstalks or trees.”
Biodiesel
One up-and-coming fuel is biodieselwhich is produced from soy oil. Currentlythe key step in conversion of the oil to biodiesel requires the addition of methanola fossil fuel. The new process skips the biodiesel step and turns oil straight into hydrogen and carbon monoxide gases by heating it to about 1000°C.
About 70percent of the hydrogen in the oil is converted to hydrogen gas. Similarlyusing a nearly saturated solution of glucose in waterthe process heats the sugar so fast that ittoobreaks up into syngas instead of its usual products: carbon and water.
A difficulty in turning plant material into usable fuels has been breaking down the chemical bonds in cellulose – the material that gives plant cell walls their stiffness – to liberate simple sugars that can be fermented into ethanol or turned into other fuels. That requires special enzymes and lots of time. But the high heat of the new process breaks those bonds with easemeaning cellulose and similar plant materials can possibly be used as feedstocks.
Schmidt and his university colleaguesgraduate students James SalgeBrady Dreyer and Paul Dauenhauerhave produced a pound of synthesis gas in a day using their small-scale reactor.
Here’s how the new process works: the oil and sugar water are sprayed as fine droplets from an automotive fuel injector through a tube onto a
ceramic disc made of a catalyst material – the elements rhodium and cerium – that guides the break-up of the feedstock molecules toward the production of syngas and away from water and carbon ‘gunk’.
Because the catalytic disc is porousthe syngas passes through it and is collected downstream in the tube. No external heat is neededbecause the chemical reactions that produce syngas release enough heat to break up subsequent molecules of oil or sugar.
“The secret is ultrafast flash volatilisation” said Schmidt. “It happens here because we vapourise the fuel and mix it with oxygen before it sees the catalyst so it doesn’t burn to char. This is potentially 100 times faster than what is currently available to make syngas and hydrogen.”
Schmidt came to US national attention in February 2004 when a team he headed invented a similar apparatus to produce hydrogen from ethanol.
