Gas Is Where You Find It

In early 1974 my company started a program of exploration for shallow gas. Wells were drilled in areas in which previous drilling had either ignored or failed to find the gas. Case histories are briefly described, and the logs presented and discussed, on five successful gas wells. Two examples illustrate the use of the neutron log for finding shallow gas, when combination of the commonly used induction and sonic logs, only, probably would have failed to indicate the gas sands. The third well was a successful gas discovery, but more by luck than judgment. It should provide food for thought for those in the exploration business. The fourth case again involves discovery by chance rather than design. A gas sand was so shallow that it was covered by the surface casing. A fortuitously run neutron lifetime log found it. The fifth example is a case in which the induction log failed to record anywhere near true resistivity in a productive gas sand, possibly due to "annulus effect". "Local knowledge"was the clincher in this discovery.