<|im_start|>user
Based on the above passage name some of the companies which specialize in large-scale construction of the infrastructure to support oil field exploitation. Display the results in a comma separated format.

Context:
An oil field is an area of accumulation of liquid oil underground in multiple (potentially linked) reservoirs, trapped as it rises by impermeable rock formations. In industrial terms, an oil field implies that there is economic benefit worthy of commercial attention. Oil fields themselves may extend up to several hundred kilometers across the surface, meaning that extraction efforts can be large and spread out across the area. In addition to extraction equipment, there may be exploratory wells probing the edges to find more reservoir area, pipelines to transport the oil elsewhere, and support facilities.

Oil fields can occur anywhere that the geology of the underlying rock allows, meaning that certain fields can be far away from civilization, including at sea. Creating an operation at an oil field can be a logistically complex undertaking, as it involves not only the equipment associated with extraction and transportation, but infrastructure such as roads and housing for workers. This infrastructure has to be designed with the lifespan of the oil field in mind, as production can last many years. 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 to support oil field exploitation.<|im_end|>
<|im_start|>assistant
Hill International, Bechtel, Esso, Weatherford International, Schlumberger Limited, Baker Hughes, Halliburton<|im_end|>
