Businesses providing oil industry service activities support the exploration, drilling and production of crude oil, and often natural gas. Their work may include geological and geophysical surveys, seismic data collection, site assessment and technical advice to help identify and evaluate underground reserves. Some companies supply specialist personnel, equipment and materials for onshore or offshore operations. Services can also cover drilling and well construction, well testing, maintenance, inspection, repair and intervention, as well as the installation and operation of production equipment. Other activities include handling fluids and waste generated during drilling, managing logistics and providing engineering or safety support. These businesses generally work for exploration and production operators and contractors; they do not usually extract oil themselves, refine it into fuels or sell it to consumers.