765 ILCS 525/1
It is hereby declared to be the law of the State of Illinois that the grant in an oil and gas lease or contract to a lessee or operator of the right or power, in substance, to explore for and remove all oil and gas from any lands in the State of Illinois, in the absence of an express provision to the contrary therein contained, includes the right of the lessee, or his heirs or assigns, to do what a prudent operator using reasonable diligence, would do having in mind the best interests of the lessor and lessee, in producing and removing oil and gas, and includes the use of practices and methods employed by the oil and gas industry, including the injection of air, gas, water and other fluids into the productive formations or strata, and cycling and recycling of gas, when done upon the authority of and under the rules, regulations and orders of the Department of Natural Resources.
765 ILCS 525/1