The Huntsman Field (Nebraska, USA) produced 28 billion cubic feet of gas prior to conversion to gas storage in 1963. In 1968, the West Engelland gas field was discovered adjacent to the Huntsman Field. It had a much lower reservoir pressure than the initial pressure at Huntsman, which implied some type of pressure connection.
West Engelland was then developed and by the early 1980s had produced five times more gas than the original gas-in-place. Meanwhile the Huntsman gas storage field was experiencing some significant unexplained reductions in reservoir pressure, which eventually were attributed to tilting of the gas-water contact, allowing gas to flow from Huntsman to West Engelland.
Not surprisingly, this led to a lawsuit and an out-of-court settlement in 1985 to compensate the Huntsman operator for the storage gas that was siphoned to West Engelland. The figure below shows the relationship between the two fields and demonstrates how we can mistakenly conclude that separate geological structures are hydraulically isolated.
