Lithology affects and correction of neutron porosity logging using D-D source

Abstract

BackgroundIt is an inevitable trend in nuclear logging to use controllable source instead of isotopic neutron source for neutron porosity logging.PurposeThis study aims to improve the feasibility and measurement accuracy of controllable D-D source neutron porosity logging by analyzing, the influence of mud on D-D source neutron porosity logging.MethodsFirstly, the response of mudstone in neutron porosity logging of three sources (241Am-Be radioactive source, D-T source and D-D source) was compared and analyzed by Monte Carlo simulation method. Then, by changing the near and far source distance in D-D source neutron porosity logging, the source distance combination of D-D source was optimized to weaken the influence of shale by changing the source distance.ResultsAnalysis results show that the mudstone response characteristics of D-D source and 241Am-Be radioactive source are relatively close. When the source distance design of D-D source is closer to 241Am-Be, i.e., the source distance combination of 25~45 cm is adopted, the mudstone influence in D-D source neutron porosity logging shows the highest degree of proximity to that of 241Am-Be radioactive source.ConclusionsAlthough the change of source spacing combination can not make the mudstone response of D-D source and 241Am-Be radioactive source completely consistent or completely eliminate the influence of argillaceous matter, this high degree of convergence provides an idea for mudstone correction in D-D source neutron porosity logging and has certain application significance for the compatible substitution of radioactive sources in logging instruments in the future.

Keywords

• d-d source
• 241am-be source
• neutron porosity logging
• source distance combination
• argillaceous effect