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Drilling and Production Under Special Conditions: Technical Issues Relating to Oil and Gas Operations in Potash, Trona and Coal Beds

W. Greg Hazlett, Basic Oil & Gas Geology and Technology for Lawyers and Other Non-Technical Personnel (2001)

The issues surrounding multiple mineral development are complex and involve numerous entities. Certain regulatory and legal decisions, however, should be based on sound science and engineering. When oil and gas operations are in or around subsurface mines, development of both resources will result in some interference. Either the mines and wells will have to be kept some specific distance apart, or the wells will need to be left in subsidence pillars to protect the wellbore. If the oil and gas company can't place wells in certain locations, oil and gas will be wasted. If the miners can't mine through or near an oil or gas field, or have to leave overly large pillars or buffer zones, unmined mineral will be wasted. The primary technical concern in these cases is safety. How close can a producing, shut-in, or plugged and abandoned well be to a mine and still be safe? Once the appropriate well to mine offset is determined, decisions regarding waste can be made more accurately.

The answers to the safety questions are case specific due to differences in types of oil and gas reservoirs and wellbores, mining techniques, and the characteristics of the geologic formations being mined. Several technical questions need to be answered. If a wellbore leaks, is the pressure inside the wellbore greater or less than the pressure outside in the formation being mined? If the pressure in