From PLANT West: Into the wormhole
Exploring heavy oil's inner spaces.
Microsensor motes scan the empty spaces in oil resevoirs before drilling.
Energy producers in Canada could soon have a new set of eyes underground that will tap a lucrative network of ‘wormholes’ and boost oil production yields by more than 10%, thanks to a project originally destined to uncork the 25 billion barrels of heavy oil under the plains of northwestern Saskatchewan.
In November, microsensor motes were sent into a heavy oil reservoir at an undisclosed location (near Bonnyville, in Eastern Alberta) through an injection well and retrieved via a production well as part of a field trial conducted by the PI Innovation Centre. This joint venture involves the Canadian Petroleum Technology Research Centre (PTRC) and INCAS3, its Dutch-based partner and independent, non-profit research institute that developed the sensor motes.
PTRC, based in Regina, was established in 1998 by Natural Resources Canada, the Saskatchewan government, the University of Regina, and the Saskatchewan Research Council, to research and develop enhanced oil recovery and carbon storage methods. It’s headed by Malcolm Wilson, who says the sensors will help the province’s producers improve bitumen recovery rates.
INCAS3 performs industrial research projects led by doctoral students, postdoctoral researchers and senior scientists at its headquarters in Assen, The Netherlands. The venture is co-financed by the Dutch Ministry of Economic Affairs, the province of Drenthe, the European Fund for Regional Development and the Municipality of Assen.
“This is a breakthrough in terms of information technologies for energy producers,” says Wilson. “We’re marrying Canada’s knowledge of oil reservoirs and extraction methods with the Dutch high-tech sector. Microsensor technology will equip us with a lot more knowledge about extraction processes and make them as efficient as we can.
Saskatchewan’s oil production is second only to Alberta, accounting for 20% of Canada’s total natural resource output. Energy developments produced 157.7 million barrels in 2011 earning more than $12.7 billion. More than $5.1 billion was spent on exploration and development projects.
Saskatchewan’s heavy oil reservoirs are typically shallow resources under low pressure, which creates a need for an extraction process that uses sand to force oil to the surface. Unlike light crude found in Alberta’s oil sands, heavy oil can be extracted using conventional cold production methods (with or without enhanced recovery techniques using water, solvent and gas injection) or with heat (steam or hot water). Oil sands bitumen is extracted almost exclusively using heat and steam using techniques, such as steam-assisted gravity drainage (SAGD).
But heavy oil reservoirs in the Lloydminster-Kerrobert-Kindersley regions see only a 5% to 8% recovery rate using existing recovery methods such as CHOPS (cold heavy oil production with sand).
“We’re leaving 92% of this huge resource in the ground,” says Wilson. “That’s a significant issue.”
CHOPS involves a sand and oil mixture that’s extracted from the heavy oilfield, which leads to the creation of empty spaces or ‘wormholes’ in the reservoir. Cold production is a pressure driven process that transports both heavy oil and sand to the surface using a progressive cavity pump. Extraction creates high-pressure gradients in the reservoir causing failures in the unconsolidated sand matrix, which flows to the well and creates ‘wormholes.’
“If we know what these wormhole networks look like, we can pick and choose where to drill next,” says Wilson. “Knowing what’s happening below is critical.”
Wormholes cause reservoir pressure to fall below the bubble point, resulting in dissolved-gas coming out of solution to form foamy oil. They grow in a 3D radial pattern within the layers of an oil reservoir, forming an immense network of channels in unconsolidated sandstone that prevent pressurization of the reservoir and hamper the efficiency of oil production.
The microsensors, no more than 7 millimetres in diameter, travel through these wormholes and send individual signals back to 3D mapping software that paints a picture of the vast underground networks.
The PTRC believes if the oil industry can better characterize these reservoirs, it can improve extraction methods and boost yields by up to 20%, while lessening environmental effects by targeting oil supplies more efficiently. This will reduce water use in cold flow extraction processes, such as CHOPS.
“That means a lot more money into the economy, and possibly more energy efficient processes for getting hydrocarbons out of the ground,” says Wilson.
The project’s goal is to better understand the structure of the reservoirs, and if a network of wormholes exists, the sensors could provide details about their number, diameter, direction and location. Better targeting will lessen the amount of water needed to push into a well.
Wilson says the PTRC and INCAS3 face challenges related to the size of the sensors and how they handle conditions below the surface.
“We’ve got to figure how we get these things to do what we want them to do.”
Wilson says the next step is to analyze the test results and to set up a research program that moves to the next phase of trials, which will be aimed at establishing stronger communication levels between the sensors below and surface operations.
“Actually seeing and better understanding these wormholes will enable us to develop improved recovery techniques.”
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This article appears in the March/April edition of PLANT West.