Crop and animal production, hunting and related service activities, Growing of non-perennial crops, Service activities incidental to oil and gas extraction excluding surveying [This class includes oil and gas field service activities provided on a fee or contract basis, including: directional drilling; `spudding in`; derrick building; repairing and dismantling; cementing oil and gas well casings; pumping wells; and other service activities. Oil and gas field exploration and geo-physical, geological and seismic surveying are classified in class 7421 (Architectural and engineering activities and related technical consultancy)] (01120)