The writer suggests that a method is available to Gulf Coast operators for detecting the proximity of high-pressure fluid reservoirs in drill holes. The presence of high background gas and high trip gas, together with lower than normal shale density, has been reported by mud logging companies to signify the proximity of a high-pressure fluid reservoir. The writer found that low-density shales are not necessarily accompanied by background gas or trip gas, or even low resistivities on electric logs, but that a minimum increase of 200 percent in the shale penetration rate indicates that a high-pressure reservoir is nearby.

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