Realtimenews@SPE: Fiber Optics Shines Light on Temperatures in Heavy Oil Producer
by Matt Varhaug
Mon, Oct 2, 2006 15:43 GMT

SAN ANTONIO, Texas - In Canada, high-viscosity bitumen is being successfully extracted from heavy oil sands using a specialized pair of wells drilled by Total E&P Canada.

These wells, known as SAGD or steam-assisted gravity drainage wells, have been placed horizontally through the McMurray Formation in Joslyn Field, Alberta.

SAGD wells are paired together, with a horizontal wellbore for steam injection placed above the lower, producer wellbore. Temperature monitoring is critical to the success of this steam-injection project.

Speaking at the 2006 Society of Petroleum Engineers (SPE) Annual Technical Conference and Exhibition, Schlumberger engineer Brent Brough described the characteristics and capabilities of a permanent fiber optic monitoring system installed in the producer well. This distributed temperature system (DTS) provides temperature readouts along each meter of the wellbore. "DTS measurements allowed the operator to estimate flow distribution of bitumen and water along the length of the producing interval," Brough said.

The SAGD method requires injection of steam into the upper horizontal well, thus heating the surrounding formation and reducing the viscosity of the bitumen. The bitumen and condensed steam then flow by gravity down into the producer well that is located 5 m below the injector, from which they are pumped to the surface.

Fiber Optics

The DTS was installed in a quarter-inch steel tube inserted inside a coiled tubing string in the well. Optical fiber is pumped into this quarter-inch tube, which runs along the length of the reservoir interval of the horizontal producer well. A pulse of laser light is sent down the length of optical fiber, and temperature-dependant components of its backscatter are processed at the surface to obtain temperature measurements. Temperature variations track fluid movement into the wellbore.

Prior to extracting fluids from the lower well, steam was injected into both wells for several months, heating the bitumen between the injector and producer wells. Later, the DTS instrument string and a pump were installed in the lower producer well. With steam injection continuing in the upper well, production was obtained through the lower well. DTS was instrumental in understanding well performance in these heavy oil sands, Brough explained.

He added, "injector-producer temperature, which dictates the bitumen viscosity, was found to be the main parameter controlling flow in the injector-producer region."

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Reference:
Krawchuk P, Beshry MA, Brown GA and Brough B: "Predicting the flow distribution on Total E&P Canada's Joslyn project horizontal SAGD producing wells using permanently installed fiber optic monitoring," paper SPE 102159 presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, September 24–27, 2006.

*Mark of Schlumberger

© 2006 Schlumberger Limited.