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Great Bear uses airborne mapping tool Says that LIDAR surveying saves money and improves decision making by providing high-resolution surface detail at a modest cost Alan Bailey Petroleum News
In the interests of having detailed information at its fingertips about its surface acreage, Great Bear Petroleum has been conducting airborne LIDAR surveys over its North Slope oil and gas leases. The company carried out surveys of this type in the summers of 2012 and 2014 and has an eventual aim of covering its entire North Slope acreage, Pat Galvin, Great Bear's vice president of external affairs and deputy general counsel, told the Alaska Forum on the Environment on Feb. 12. The survey data provide highly detailed surface topography maps for the planning and permitting of exploration and development projects. (see map)
Great Bear is engaged in an exploration project in state land south of Prudhoe Bay, seeking to test the potential for producing oil from North Slope oil source rocks while also seeking more conventional oil and gas development opportunities.
University of Texas The company has been conducting its LIDAR surveys in conjunction with the University of Texas Bureau of Economic Geology, Galvin said. The university group, which has a close affiliation with Great Bear through Ed Duncan, the company’s president and CEO, was looking for applications for the testing of LIDAR technology, to try out the technique in different practical scenarios - Duncan saw an opportunity to apply the technology in Great Bear’s North Slope operations, Galvin said.
By timing the reflections from an object of laser-emitted light pulses, LIDAR technology enables the distance between the LIDAR equipment and the target object to be measured with high precision. A LIDAR airborne survey involves carrying LIDAR equipment in the belly of an aircraft, with a laser beam directed vertically downwards and reflecting off the ground surface below. Through the use of GPS and inertial measurement technology in the aircraft to track the aircraft’s position with astounding accuracy, LIDAR generated data can be converted into precise depictions of the land surface that the aircraft is overflying.
Two colors Great Bear, for its surveys, uses two laser systems, one emitting red light and one emitting green light, Galvin said. The red light reflects off water, thus providing data about the elevations of the water surfaces of tundra lakes. The green light penetrates the water and reflects off the lake bottoms. Thus, in combination, the two systems enable the collection of detailed lake bathymetry, Galvin explained.
To achieve the high levels of accuracy in continuously measuring the aircraft’s position during a survey, Great Bear has supplemented satellite GPS data with the use of a small ground-based GPS station, mounted on a tripod.
The region of Great Bear’s North Slope oil and gas leases is almost flat, but the LIDAR surveys have sufficient precision to illuminate small changes in topography, all but invisible from the ground but potentially important in exploration and development planning. The company conducted its 2012 survey concurrently with its drilling operations near the Dalton Highway - a LIDAR generated image of the surface topography around the drilling site clearly depicts the well pad, where the rig mat surface was only about a foot above the surrounding tundra. That survey also involved the shooting of aerial photographs from the survey aircraft, with the possibility of merging the digital photographic images with the LIDAR data during the data processing of the survey results, Galvin said.
Rapid surveying Great Bear sees LIDAR surveying as a very cost effective means of gathering information about areas targeted for exploration and possible future development. In fact, the acquisition of surface information is one of the biggest time hurdles in a development project, Galvin said. He contrasted a land based lake survey that Great Bear conducted in 2011 with the results of a LIDAR survey conducted in 2014. The land based survey, involving the helicopter deployment of a field crew equipped with a boat, resulted in the acquisition of bathymetric data for about 25 lakes, Galvin said. By contrast, the LIDAR survey was able to collect precision data for about 5,500 lakes, he said.
An overlap between the 2011 surface survey and the 2014 LIDAR survey has enabled Great Bear to ground truth the LIDAR lake bathymetry results. There was about a 99 percent correlation between the data from the two surveys, Galvin said. Topographic data gathered during seismic surveying has also confirmed the accuracy of the LIDAR results, he said.
Various uses Great Bear is exploring various ways in which its LIDAR data might be used.
The data has already proved its worth in improving the efficiency with which the company could plan an ice road for drilling operations being conducted this winter. Detailed knowledge gleaned about lake bathymetry also helps in planning water supplies for ice road construction. And the detailed regional mapping of lake hydrology will be tremendously helpful in development planning, the company thinks. The company is also working with ASRC Energy Services to try using the LIDAR data to extrapolate the results of the surface delineation and characterization of wetland areas, Galvin said.
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