Thus, the typical oil field resembles a small, self-contained town in the midst of a landscape dotted with drilling rigs and/or the pump jacks, which are known as "nodding donkeys" because of their bobbing arm. Several companies, such as Hill International, Bechtel, Esso, Weatherford International, Schlumberger Limited, Baker Hughes and Halliburton, have organizations that specialize in the large-scale construction of the infrastructure and providing specialized services required to operate a field profitably