【国外标准】 Standard Guide for Conducting Borehole Geophysical Logging—Neutron

5.1 An appropriately developed, documented, and executed guide is essential for the proper collection and application of neutron logs. 5.2 The benefits of its use include improving selection of neutron logging methods and equipment; neutron log quality and reliability; usefulness of the neutron log data for subsequent display and interpretation. 5.3 This guide applies to commonly used neutron logging methods for geotechnical applications. 1.1 This guide is focused on the general procedures necessary to conduct neutron or neutron porosity (hereafter referred to as neutron) logging of boreholes, wells, access tubes, caissons, or shafts (hereafter referred to as boreholes) as commonly applied to geologic, engineering, groundwater and environmental (hereafter referred to as geotechnical) explorations. Neutron soil moisture measurements made using neutron moisture gauges, are excluded. Neutron logging for minerals or petroleum applications is excluded, along with neutron activation logs where gamma spectral detectors are used to characterize the induced gamma activity of minerals exposed to neutron radiation. 1.2 This guide defines a neutron log as a record of the rate at which thermal and epithermal neutrons are scattered back to one or more detectors located on a probe adjacent to a neutron source. 1.2.1 Induction logs are treated quantitatively and should be interpreted with other logs and data whenever possible. 1.2.2 Neutron logs are commonly used to: (1) delineate lithology, and (2) indicate the water-filled porosity of formations (see Fig. 1). Nc   =   corrected neutron log, N0   =   original neutron log, Csh   =   computed shale fraction based upon the gamma log position between the endpoints of 10 and 120 cps, and Φsh   =   estimate of shale non-effective porosity of about 40 % picked from intervals on the log where Φsh = 1.0.