Nuclear Techniques ›› 2018, Vol. 41 ›› Issue (8): 80406-080406.doi: 10.11889/j.0253-3219.2018.hjs.41.080406

• NUCLEAR ELECTRONICS AND INSTRUMENTATION • Previous Articles     Next Articles

Formation density affects and corrections in pulsed neutron porosity logging

WANG Hu1, WU Wensheng1, WANG Hongwei2, REN Liwei2, GE Yunlong1, DONG Duo1, WANG Ruigang1, HE Liuqiong1   

  1. 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China;
    2. Daqing Branch, China Petroleum Group Logging Co., Ltd., Daqing 163412, China
  • Received:2017-10-19 Revised:2018-03-21 Online:2018-08-10 Published:2018-08-15
  • Supported by:
    Supported by National Natural Science Foundation of China (No.41304095)

Abstract: [Background] The inelastic scattering reaction between neutron and formation element in pulsed neutron porosity logging can not be neglected. Compared to chemical source, the influences of lithology and density on the measurement of hydrogen index increase, so the measured apparent porosity may be affected.[Purpose] This study aims to investigate the formation density influence and corresponding correction method.[Methods] First of all, the relationship of slowing-down length of neutrons in the infinite homogeneous formation between bulk density and hydrogen index was deduced, and numerical simulation was performed. Then the correlation between the quotient of counting rate after correction of formation density and the hydrogen index of the formation was obtained. Finally, the quotients of far detector counting rate and near detector counting rate were used to correct the formation density, and the result of the experiment was analyzed.[Results] The relation between the bulk density corrected count ratio and hydrogen index was obtained, and the sensitiveness of pulsed neutron porosity logging got improved.[Conclusions] Correcting count ratio of near detector and far detector with bulk density by means of numerical simulation can reduce the influence of bulk density, enhance the detection sensitivity of porosity and reduce the influence of lithology and shale effect.

Key words: Neutron porosity log, Bulk density, Hydrogen index, Sensitivity

CLC Number: 

  • TL99