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Neutron count in window
\tau = [\tau_1, \, \tau_2]
(1) |
N_{near}[\tau] = \int_{\tau_1}^{\tau_2} N_{near}(t) dt |
(2) |
N_{far}[\tau] = \int_{\tau_1}^{\tau_2} N_{far}(t) dt |
(3) |
N2F = \frac{ N_{near}[\tau]}{N_{far}[\tau]} |
Diffusion Correction
(4) |
\phi_N = N2F[\tau] + \Delta_{\tau}(\phi) |
(5) |
N_{near}(t) = N_{near}(0) \exp ( - t \, \Sigma_{near} ) |
(6) |
N_{far}(t) = N_{far}(0) \exp ( - t \, \Sigma_{far} ) |
Diffusion Correction
(7) |
\Sigma_{near} = \Sigma_{frm} + \Delta_{near}(\phi) |
(8) |
\Sigma_{far} = \Sigma_{frm} + \Delta_{far}(\phi) |
(9) |
\Sigma_{frm} = (1-\phi) \, \Sigma_m + \phi \, ( \Sigma_w \, s_w + \Sigma_o \, s_o +\Sigma_g \, s_g) |
(10) |
\Sigma_m = \sum_k \Sigma_k |
In case of two-component sandstone-shale model:
(11) |
\Sigma_m = (1-V_{sh}) \, \Sigma_{snd} + V_{sh} \, \Sigma_{sh} |
In case of two-component limestone-shale model:
(12) |
\Sigma_m = (1-V_{sh}) \, \Sigma_{lms} + V_{sh} \, \Sigma_{sh} |
CNT_NEAR, CNT_FAR, NPHI, SIGMA,
SPE162074 – Memory Pulsed Neutron-Neutron Logging