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So far, "there are few other meters available that can handle that range of temperatures," Geneau says. Without the meter, the company would have to take grab samples. That means using distillation analysis, he says, a labour-intensive process. "Typically, you don't get results until days after the sample is taken."
The Agar meter, on the other hand, samples production flow every three seconds, calculating the percentage of water in the flow stream. The meter, which works on the principle that water absorbs more energy than oil, measures the properties of the production fluids, typically oil and water. The difference in properties is then analyzed and translated to volumetric concentrations.
The meter is typically installed on the outflow from a test separator. Production flows from the well to the separator, where gas and liquids are separated. The liquids then flow to the Agar meter.
Tim Hewko, lead instrumentation technologist for Shell Canada, explains how the company narrowed the field of watercut meters. "Shell was involved in an evaluation of watercut analyzers in the spring of 2001. The result was that the Agar OW-201 was most suitable for the varying range of temperatures and salinity the meter would be exposed to."
Following the lab test, Shell decided to field-test the OW-201 meters. "They worked out well," Hewko says. Another meter, also able to withstand high temperatures, was initially in the running, but salinity issues made it unsuitable for Shell's application.
Marty Schlager, sales manager for Zirco Ltd., Agar's Canadian agent, says the meter corrects for changes in salinity, common in steam injection applications, and gives readings accurate to one percent over the full range of emulsions, from zero to 100%.
Hewko says Shell checked the accuracy of the Agar meters used at its Peace River complex by sampling manually, initially twice a day, and sending the samples to Calgary for analysis. "Between that analysis and the Agar reading, we were within two per cent consistently," he notes.
The company still samples outflow from the wells, but only once daily now. "I suspect in the future here we'll discontinue even the sampling program. We've pretty much proven that the meters are working."
Another producer injecting steam is EnCana Corporation, which began production of bitumen in 2001 at its steam-assisted gravity drainage operation at Foster Creek, Alberta. Bitumen produced at the site gets as hot as 180 degrees Celsius.
EnCana also chose the Agar OW-201 for the project. "We use it to determine basic sediment and water (BS&W) from well tests in our SAGD facility," says Kerry Shaw, production technologist at Foster Creek. "The BS&W is basically the water part of our oil production. When we test, we determine the rate the well is producing at, and use the analysis to determine what portion of that is water, so that we can figure how much oil we're producing."
"If the BS&W is changing, we may make changes in the production strategy of the well." Shaw says four Agar meters were installed in Foster Creek's commercial plant, and one in its pilot plant. The previous watercut units in the commercial plant were the older-generation Agar meter, ones that did not respond well to heat, Shaw explains.
"If we had a cold well, the thing would respond right on. If we put a hot well on it, initially it would respond well, but later on, the BS&W reading would start to drift off-scale." Those units have since been replaced.
As the new OW-201 units arrive onsite, each is calibrated. "The analyzer has two calibration curves — one for oil-continuous and one for water-continuous," Shaw says. Water with oil in it is considered to be in the water-continuous phase, while oil with water in it is in the oil-continuous phase.
"You have to calibrate it with your oil and your water. For us, the more important one is water, because our wells will probably be mostly in the water-continuous phase," Shaw says.
"When the emulsion is coming back, it's probably going to be greater than 50 or 60% water, versus say 30, 40% water. They use an energy absorption probe in the meter to tell it whether the emulsion is water- or oil-continuous. It works like a switch to tell it which calibration curve to use."
The real advance with the new meters is "that they're able to give us good numbers in our high-temperature range," he says. "We got one unit back (for the pilot) with its modifications and it worked very well, once it was field-calibrated.
"We've had our pilot meter running what I would say is good since before Christmas 2002. We actually just got our other four back after (Agar) made modifications to them." Because the latter units are only just back in service, Shaw is reluctant to offer an opinion until EnCana has completed the field calibrations and received more data.
"It usually comes down to a calibration. If we haven't done the field water-and-oil calibration correctly, then the meter seems to be out. After that, it's either going to work or it's not," he says.
"I have a lot of confidence in the (meter) at the pilot. It seems to be balancing against the battery." Shaw says operations staff has found that the readings from the manual samples and the meter are more consistent. "It's been like that since before Christmas."
Without the Agar meter, Shaw says the alternative would involve cooling "the sample down to below 100 degrees and take a manual or ‘grab sample' of the well, then do our conventional BS&W test. The problem with that is that it's a grabsample versus … the Agar meter, which is reading continuously."
In addition, when using grabsamples, he says the question arises whether the sample is representative of what the well is producing at the time. Sampling manually is also time-consuming and subjective. "It's a manually-determined number. The accuracy and repeatability of the number is always suspect."
Although the verdict is not yet in on Agar's redesigned watercut meter, Shaw is optimistic. "If these things work, they're going to tell us a lot of things we're guessing at now. They will be able to verify how a well responds at different operating parameters and what effect that has on BS&W. In the long term, that will give us better data to make decisions …."
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