| 摘要 |
A method for determining a property of formations surrounding an earth borehole being drilled with a drill bit at the end of a drill string, using drilling fluid that flows downward through the drill string, exits through the drill bit, and returns toward the earth' s surface in the annulus between the drill string and the periphery of the borehole, including the following steps: obtaining, downhole near the drill bit, a pre-bit sample of the mud in the drill string as it approaches the drill bit; obtaining, downhole near the drill bit, a post-bit sample of the mud in the annulus, entrained with drilled earth formation, after its egression fro m the drill bit; implementing pre-bit measurements on the pre-bit sample; implementing post-b it measurements on the post-bit sample; and determining a property of the formations from th e post-bit measurements and the pre-bit measurements.
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