Time sequence design method for collecting double pulse neutron gamma spectrums

Abstract

The invention discloses a time sequence design method for collecting double pulse neutron gamma spectrums, which solves the technical problems that only a gamma energy spectrum or a gamma time spectrum can be collected in a down-hole process in the conventional pulse neutron saturation logging technique, the measurement of two physical parameters cannot be completed simultaneously, the saturation can be determined by means of other materials such as porosity and the like. A complete measurement period of the double pulse neutron gamma spectrums comprises three time slices: a C / O measurement time slice, a neutron service life measurement time slice and a background gamma energy spectrum measurement time slice, totally 40000 mus. By designing a double pulse emission and measurement time sequence, the inelastic dispersion can be measured by making use of the repeatedly emitted neutrons of a narrow pulse and the gamma energy spectrum can be seized, the gamma time spectrum can be also measured by making use of the emitted neutrons of a wide pulse, and as two parameters are obtained simultaneously in the same measurement at the same depth point, the uncertain factors are reduced, and the measurement accuracy is improved.

Description

technical field [0001] The invention relates to the technical field of oil and gas well logging, in particular to a timing design for collecting pulsed neutron gamma spectrum. Background technique [0002] It is of great significance to accurately grasp the production situation of oil layers and the distribution of remaining oil in the process of oilfield development. At present, pulsed neutron saturation logging technology at home and abroad includes C / O energy spectrum logging technology and neutron lifetime logging technology. Among them, the timing design of C / O energy spectrum logging is to use the D-T neutron generator with a pulse width of 10μs, 20μs or 40μs to emit neutrons in one working cycle, and have inelastic scattering, elastic scattering, capture, Activate the isokuclear reaction, use the scintillation crystal gamma detector to detect the inelastic scattering and capture energy spectra respectively within the pulse width and the subsequent time period, and ca...

AI Technical Summary

Problems solved by technology

However, the current pulsed neutron saturation logging technology can only collect gamma energy spectrum or gamma time spectrum in one downhole process, and cannot complete the measurement of the two physical parameters at the same time. The saturation needs to be determined by other data such as porosity. In the absence of porosity, saturation cannot be determined

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