发明名称 |
Methods and apparatus for determining error in formation parameter determinations |
摘要 |
Methods and apparatus for generating an error bar (variance) log for a formation parameter are disclosed. According to the method, acoustic waveforms are detected at a plurality (M) of detectors which are a function of a source signal which has interacted with the formation and noise, and the detected waveforms are sampled and processed in order to obtain a semblance or a normalized mean square error. Using the semblance or the NMSE which is related to the semblance, a signal to noise ratio 2E/N0 can be found by recognizing that the semblance function has a non-central beta distribution whose mean is a function of the signal to noise ratio 2E/N0, the time-bandwidth product N, and M. The signal to noise ratio is then used to find the Cramer-Rao lower bound which is taken as an estimate of the variance. An error bar log is formed by repeating these steps at a plurality of locations along the borehole. The method of the invention can be used in conjunction with both attenuating and non-attenuating waves. The apparatus of the invention relates closely to the method.
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申请公布号 |
US5661696(A) |
申请公布日期 |
1997.08.26 |
申请号 |
US19950514412 |
申请日期 |
1995.08.11 |
申请人 |
SCHLUMBERGER TECHNOLOGY CORPORATION |
发明人 |
KIMBALL, CHRISTOPHER K.;SCHEIBNER, DAVID J. |
分类号 |
G01V1/44;G01V1/48;(IPC1-7):G01V1/40;G01V1/28 |
主分类号 |
G01V1/44 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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