Density measurement method based on D-D controllable neutron source

Abstract

The invention belongs to the technical field of petroleum and natural gas exploration, and relates to a density measurement method based on a D-D controllable neutron source. The controllable neutronsource and a multi-detector system are adopted, the gamma energy spectrums and the thermal neutron energy spectrums at different positions are recorded through pulse and measurement time sequence design, and the relation between the near-far capture gamma counting ratio, the near-far thermal neutron counting ratio and the stratum density under different stratum conditions is studied; then, a stratum density calculation model is theoretically determined through an existing spectral analysis and data processing method, the obtained density calculation value is compared with a reference value, and the precision is enabled to meet the measurement requirement; stratum density measurement is achieved through combination of a pulse neutron source and multiple detectors, thus a complete set of D-Dcontrollable source density measurement method is established, the method is of great significance to development of a new generation of pulse neutron-gamma density logging instrument and effective elimination of harm of tritium elements in the instrument to human bodies and the environment, and a guarantee is provided for safe exploration of unconventional stratums.

Description

[0001] Technical field: [0002] The invention belongs to the technical field of petroleum and natural gas exploration, and relates to a density measurement method based on a D-D controllable neutron source. The D-D controllable neutron source is used to calculate formation density for well logging. [0003] Background technique: [0004] In recent years, it has become an inevitable trend in the development of nuclear logging to replace traditional chemical radioactive sources with controllable neutron sources for density logging. At present, D-T controllable neutron sources are widely used in well logging with controllable source density. For D-T source density logging, researchers at home and abroad have carried out various research work and achieved certain results. [0005] In the method of the controllable source density measurement that appears at home and abroad recently, adopt the D-T neutron source of 14Mev mostly, its measurement principle is to utilize non-elastic ga...

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Problems solved by technology

[0007] The purpose of the present invention is to solve the shortcomings of traditional density logging, to overcome the short life of the D-T controllable neutron source, the high cost, and the potential danger of using radioactive tritium targets, and to design a pulse sequence design based on the D-D controllable neutron source Methods of Measuring Formation Density

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