Ground penetrating radar surveys of peatlands for oilfield pipelines in Canada

Abstract

Placement of buried pipelines in thick peat deposits is difficult because of the low bearing strength and high water content of the material for support of heavy construction equipment. Previously, ground penetrating radar (GPR) has been used to assess thickness and volume of peat as a fuel resource and horticultural material in Scandinavia and Canada. To our knowledge, GPR has not been applied to the site assessment and placement of pipelines crossing peatlands. Field experiments were conducted in the Mitsue oilfield operated by Chevron Canada Resources Ltd., located immediately southeast of Lesser Slave Lake in north-central Alberta Province, Canada. Surficial deposits consist of Holocene, linear, sandy beach ridges separated by peatlands underlain by sand. Several GPR surveys assessed the thickness of the peat along two oil pipeline right-of-ways. Results show the peat-sand contact as irregular and undulating, ranging from 0 to 3.7 m deep. Each survey, 460 and 550 m long, was completed in two hours. Such results from 1 m station spacings (sampling interval) can considerably reduce the uncertainties in planning and placement of oil, gas, and water pipelines crossing peatlands. Results indicate that thickness variations of peat can be detected more effectively in terms of quality of results, lower cost, and less time with GPR than with a peat probe or by coring.