37 Drilling of oil and gas wells; consultancy, information and advisory services relating to drilling of oil and gas wells; pumping and extraction of oil; drilling and extraction of gas; consultancy, information and advisory services relating to pumping and extraction of oil; consultancy, information and advisory services relating to drilling and extraction of gas; construction of structures for the production, shipping, transportation, storage of oil and gas, namely, oil processing plants, gas processing plants, oil pipelines, gas pipelines, oil wells, gas wells, oil tanks, gas tanks, oil separators, gas separators, oil rigs, gas rigs, oil platforms and gas platforms; consultancy, information and advisory services relating to construction of structures including oil plants, gas plants, oil pipelines and gas pipelines for the production, shipping, transportation and storage of oil and gas; repair and maintenance of oil and gas plants; consultancy, information and advisory services relating to repair and maintenance of oil and gas plants; repair and maintenance of oil pipelines and gas pipelines; consultancy, information and advisory services relating to repair and maintenance of oil pipeline and gas pipelines; repair or maintenance of oil and gas plants, namely, repair or maintenance of oil wells, gas wells, oil tanks, gas tanks, oil separators, gas separators, oil rigs, gas rigs, oil platforms and gas platforms associated with oil and gas processing; consultancy, information and advisory services relating to repair and maintenance of oil and gas plants, and drilling of oil and gas wells; drilling of natural resources, namely, oil and natural gas drilling; drilling of wells; construction of chemical plants; repair and maintenance of chemical plants; check and inspection services in the course of construction of underground tanks and buried piping; repair works of underground tanks and buried piping; clearance work, being cleaning of ground pollution; advisory services relating to clearance work, being cleaning of ground pollution