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Seeing The Light

Using fibre-optic technology to improve recoveries
[Print Article: November 2010, by Richard Macedo] The unconventional gas revolution is in full swing thanks in large part to the inventiveness and ingenuity of horizontal drilling and multi-stage fracture stimulation.

Despite these advances, the slide in gas prices implores producers to continue finding ways to improve productive capability and reduce costs in these technically challenging reservoirs. This is fostering a drive by many in the industry to target technologies that have minimal development costs but will produce immediate rewards.

In tight gas and shale gas plays, for example, optimizing downhole operations and maximizing the amount of gas flowing to surface means increased profitability. To help achieve this, a clearer picture of the reservoir is needed. Some major companies have been using existing fibre-optic technologies and adapting them for this purpose.

The result is a more powerful downhole flashlight, so to speak, that's allowing them to make better decisions during completion operations.

Royal Dutch Shell has been employing a strategy of using these fibre-optic systems in its operations including the Deep Basin and Groundbirch. The latter, located in British Columbia, is a top growth area for the company. There, Shell is producing natural gas from a reservoir of tight sandstone, siltstone and shale at a depth of about 2,500 metres. The company is currently producing enough gas to supply more than 400,000 typical homes for one year.

During the summer, Shell announced a collaboration for the use of QinetiQ's OptaSense fibre-optic Distributed Acoustic Sensing (DAS) system. QinetiQ is a United Kingdom-based company that provides technical advice to customers, including aerospace, defence and security markets.

The technology will provide an ability to use standard telecom fibre-optic cable to detect, discriminate and locate acoustic events during wellbore operations beyond what is currently available. This will allow for design and execution improvements that can boost recoveries and lower costs.

The collaboration agreement between Shell and QinetiQ is a culmination of 18 months of jointly working on the technology through several successful field trials in Canada. Shell is working toward using this optical sensing system based on QinetiQ's existing OptaSense DAS technology initially in onshore field development and exploration.

Shell officials say that the technology has the potential to deliver significant value in the near-term and, because of its wide potential application area, it can also be the catalyst for improvements to managing assets across its lifecycle, from exploration to successful operation.

The technology could also benefit hydraulic fracturing operations of tight gas and shale gas reservoirs, an increasingly important aspect of the company's business.

"By analyzing back reflected light in an effective way, OptaSense is able to turn that fibre into an acoustic sensing array such that every several metres of that fibre acts as a microphone," says Vianney Koelman, Shell's team leader of in-well technology research and development, based in Houston. "It has to do with disturbances in the coherence of the back-scattered light you can use to pick up acoustic signals."

The OptaSense DAS system incorporates some of the latest developments in fibre-optic sensing technology along with sophisticated signal and data processing techniques.

"Our aim is to deliver a suite of novel real-time decision-making tools into the industry," adds David Hill, QinetiQ's technical director for OptaSense.

Shell staff was the first to recognize the potential breakthrough innovation of applying QinetiQ's DAS technology (currently used for onshore pipeline monitoring) during the first field trial in February 2009. Given that most of this technology is in use today in the defence and security industries, Shell expects a relatively low development risk.

"For Shell, this fits with our overall fibre-optic R&D program," Koelman says.

The technology helps complete the picture downhole, which lets the company make better decisions in the critical time during completion operations to improve production.

Mathieu Molenaar, a production engineer and sensor expert with Shell Canada in Calgary, says that the goal behind this is to improve wellbore monitoring for flow and hydraulic fracturing, adding that when company officials came across OptaSense they thought it could work for reservoir monitoring.

"We have monitored wells in different locations, different configurations and different formations," Molenaar says. "We've got thousands of hours of recorded measurements downhole, which resulted in many terabytes of data.

"When developing tight and shale gas via hydraulic fracturing, it's important to optimize operations downhole. More data can help with production versus cost decisions. It illuminates your wellbore," Molenaar adds. "You can see a more complete picture of what is happening in your wellbore. The same is true when you start to produce the wellbore; it helps tell us more precisely where production is coming from."

The company has tested the technology in its Canadian shale and tight gas plays in both vertical and horizontal wells.

"I think the technical advance is that the information we're getting is clearer," Molenaar says. "We have other downhole measurements but DAS is a valuable addition to the temperature-based monitoring that we're used to."

While the technology is helpful in tight gas and shale gas reservoirs, it has broader applicability, he notes.

"Some of our requirements go much further than what you usually require for pipeline or perimeter protection. It's opening completely new avenues in terms of downhole sensing," Koelman says. "Integration with other fibre-optic technologies, such as combining the acoustic measurements with the temperature measurements, is an enabler to more robust interpretation."

The company, meanwhile, has other fibre-optic R&D projects on the go with different technology providers.

Shell and Petroleum Geo-Services (PGS ) earlier announced a collaboration to develop an ultra-high channel count fibre-optic seismic sensing system. Higher channel counts with high-quality sensors recover more seismic energy and help cancel noise. The improved resolution and imaging translate into better exploration decisions.

PGS offers a broad range of products including seismic and electromagnetic services, data acquisition, processing, reservoir analysis/interpretation and multi-client library data. The company helps producers find oil and gas reserves offshore worldwide. It was founded in Norway in 1991.

Shell intends to use this optical sensing system -- based on PGS's existing fibre-optic technology -- for onshore exploration as well as reservoir monitoring. It will enable scalability far beyond what is currently available.

The collaboration was aided by Shell technologists who first recognized the potential breakthrough innovation of applying PGS's underlying OptoSeis technology for onshore seismic.

In offshore applications, OptoSeis is operational down to 3,000-metre water depths and the system offers a more cost-effective alternative to electrical systems. Each durable sensor station contains three axis optical accelerometers and a hydrophone, which is designed for optimum performance and reliability.

Using these existing technologies is a way to offer technological solutions quickly and efficiently, according to Shell. Like OptaSense, given that most of this technology is in existence today, the company expects low development risk.

"We find the quality of seismic data on land inadequate for exploration purposes and also for reservoir monitoring," Wim Walk, Shell's manager of geophysical measurement technologies, noted during a conference call announcing the collaboration with PGS . "We really want to make a big step forward in improving that quality.

"By using PGS's technology, we can make a step forward in improving the quality of seismic data on land without making the logistics and without making some of the issues around deploying the system cost-or effort-inhibitive."

Continuing the move toward fibre-optic technology, Calgarybased Pure Energy Services earlier this year announced a deal with Fotech Solutions Inc. for the exclusive use of Fotech's patented fibre-optic DAS technology in well completion applications in Canada and the use of the DAS technology as a preferred partner for well completion applications in the United States.

The DAS technology will be jointly marketed by Pure and Fotech in Canada and the U.S. under the name Purelight. Fotech is a British-based developer of fibre-optic based acoustic monitoring systems.

The initial field testing of DAS technology has demonstrated that this technology will provide oil and natural gas development and production customers with critical, previously unattainable, downhole production data.

The technology has been operated successfully on oil and natural gas test wells in both Canada and south of the border. It's expected that data gathered using the DAS technology will allow customers to better understand reservoir flow characteristics and assist in the development of critical operating decisions and plans for the exploitation and production of oil and natural gas reservoirs.

The DAS technology is expected to have significant application in both vertical and horizontal well completions by assisting in the establishment of accurate production flow rates and data from different completed zones or stages in vertical and horizontal multi-zone completions. It's also anticipated that the technology will have application in the monitoring of permanent oil and natural gas installations, such as steam-assisted gravity drainage wells. •


Jaryl Strong, Shell Energy, Tel: (713) 241-3488, Email: [email protected]

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