发明名称 |
THERMAL NEUTRON POROSITY FROM NEUTRON SLOWING-DOWN LENGTH, FORMATION THERMAL NEUTRON CAPTURE CROSS SECTION, AND BULK DENSITY |
摘要 |
A method for determining at least one formation property calculated from neutron measurements acquired with a downhole tool includes emitting neutrons from a source in the tool into the formation, detecting neutrons with at least one detector in the downhole tool, calculating a first slowing-down length (L1) based on the detected neutrons, and deriving a second slowing-down length (L2) based on the first slowing-down length (L1). Further steps include deriving a correlation function for relating slowing-down lengths from a first tool to slowing-down lengths associated with a different source, wherein the correlation function depends on formation properties such as bulk density; and applying the correlation function to the slowing-down length of the first tool to derive the slowing-down length of the second tool. A method for determining a thermal neutron formation porosity based on a slowing-down length from epithermal neutron measurements from an electronic neutron source includes converting the slowing-down length into a computed neutron slowing-down length from thermal neutron measurements from a chemical neutron source, wherein the converting uses a correlation function that depends on formation bulk density; deriving a thermal neutron countrate ratio based on the computed neutron slowing-down length, wherein the deriving uses a function that depends on the formation bulk density and formation sigma; and computing the thermal neutron formation porosity from the thermal neutron countrate ratio.
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申请公布号 |
CA2696379(A1) |
申请公布日期 |
2009.02.26 |
申请号 |
CA20082696379 |
申请日期 |
2008.08.13 |
申请人 |
SCHLUMBERGER CANADA LIMITED |
发明人 |
FRICKE, SCOTT H.;ADOLPH, ROBERT A.;EVANS, MIKE |
分类号 |
G01V5/10 |
主分类号 |
G01V5/10 |
代理机构 |
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