. Bulletin. with a rotary if proper observation and care ismade during the drilling. Hard rock, hard shell, sand (hard orsoft), shale and gumbo, can usually be detected by watching theway the engine runs, the action of the rotary table, the tune of themud pump, and the way the bit wears. There are many examples where formations can be detected by theway they drill. In the Caddo oil field, Louisiana, the Nacatoch sandusually drills very hard, wears out many bits and drills quitedifferently from the formations immediately above and drillers of that area can tell when they reach the Na
. Bulletin. with a rotary if proper observation and care ismade during the drilling. Hard rock, hard shell, sand (hard orsoft), shale and gumbo, can usually be detected by watching theway the engine runs, the action of the rotary table, the tune of themud pump, and the way the bit wears. There are many examples where formations can be detected by theway they drill. In the Caddo oil field, Louisiana, the Nacatoch sandusually drills very hard, wears out many bits and drills quitedifferently from the formations immediately above and drillers of that area can tell when they reach the Nacatochsand. In other areas a hard limestone shell causes the rotarydrill stem to jiunp and catch, and in this limestone the drill willmake hole slowly. Again, gumbo will cause the bit to ball up,necessitating an occasional spudding to clean the bit. Where suchformations are persistent over a considerable area, they are of ma-terial aid in the correlation of rotary logs. BUREAU OF MINES BULLETIN 195 PLATE II. IMPROVISED ROTARY CORE BARREL.(Courtesy of W. W. Scott.)
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
