APPLICATIONS OF THERMAL MULTIGATE DECAY PULSED NEUTRON LOGS IN UNUSUAL DOWNHOLE LOGGING ENVIRONMENTS

1985 ◽  
Vol 25 (1) ◽  
pp. 265
Author(s):  
Sami O. Ajam ◽  
V.E. Rahal
Keyword(s):  
Gamma Rays ◽  
Cross Sections ◽  
Gamma Ray ◽  
Decay Curve ◽  
Drill Pipe ◽  
Paper Briefly ◽  
Gamma Ray Detectors ◽  
Porosity Ratio ◽  
Pulsed Neutron ◽  
Capture Cross Sections

The Thermal Multigate Decay (TMD) logging system utilizes a pulsed 14 Mev generator and two gamma ray detectors to obtain measurements of the capture cross sections of downhole formations. The composite decay curve from both formation and borehole capture gamma rays is detected, and is separated into the two individual components : sigma formation and sigma borehole. The resulting sigma formation measurement is only minimally affected by borehole conditions, especially in cased wells.In addition to sigma formation and sigma borehole, the TMD system generates a dual-spaced porosity ratio and several other parameters which provide information on log quality, borehole parameters, and tool stability. These features can be used to assist the log analyst in understanding the down- hole borehole environment as well as formation characteristics. Under appropriate conditions, the TMD log can also provide production logging information relating to fluid movement in or near the wellbore.The paper briefly reviews the TMD logging system, after which it concentrates on log examples in unusual borehole conditions : logs run across intervals where borehole conditions change; logs run in air filled boreholes; logs run in badly washed out boreholes; logs run through stuck drill pipe/ collars; logs run in flowing wells. The supplemental TMD curves in these situations identify the presence of gravel packs and packers, changes in borehole fluid salinity, possible communication between zones, and water and oil producing perforations. Gas in the borehole can also be clearly differentiated from gas in the formation.

scholarly journals Partial and total thermal neutron capture cross sections for non-destructive assay and transmutation monitoring of 99Tc

2002 ◽  
Vol 90 (8) ◽  
Author(s):  
G. L. Molnár ◽  
T. Belgya ◽  
Zs. Révay ◽  
Syed M. Qaim
Keyword(s):  
Gamma Rays ◽  
Cross Sections ◽  
Neutron Capture ◽  
Gamma Ray ◽  
Cold Neutron ◽  
Production Cross ◽  
Radioactive Product ◽  
Non Destructive ◽  
Decay Gamma ◽  
Capture Cross Sections

SummaryAccurate partial gamma-ray production cross sections were determined for the prompt and radioactive product decay gamma rays following cold neutron capture in

Physical Properties of Shales and Possible Origin of High Pressures

1980 ◽  
Vol 20 (05) ◽  
pp. 341-348 ◽  
Author(s):  
William C. Pritchett
Keyword(s):  
High Pressure ◽  
Cross Sections ◽  
Neutron Capture ◽  
Gamma Ray ◽  
Gulf Coast ◽  
Capture Cross ◽  
Neutron Lifetime ◽  
Ray Density ◽  
Depth Of Investigation ◽  
Capture Cross Sections

Introduction Laboratory and borehole measurements of shale properties may be unreliable because of modification during or after drilling or coring. The borehole gravimeter is an ideal tool for measuring the bulk density of thick shale units because of its great depth of investigation and negligible sensitivity to shale in the vicinity of the borehole, which may have been modified in drilling. By contrast, the scatter gamma ray density log has an extremely shallow depth of investigation and its response may be dominated by modified shale surrounding a borehole. A comparison of bulk densities measured by these two methods in both sands and shales was made in three U.S. gulf coast wells. In all three wells the two methods yielded comparable densities for the sands. But in two wells, which were drilled with fresh muds, the density log yielded shale bulk densities significantly less than those shown by the borehole gravimeter. These data indicate that shale adjacent to the borehole in these two wells had been modified by drilling and the modified shale densities had been reduced significantly. In the well drilled with a saline mud, bulk densities from the two methods were in close agreement in both sands and shales, which indicates that shales adjacent to the borehole in this well were not modified significantly. High-pressure shales are particularly susceptible to modification during drilling since they are relatively permeabble and soft. Sometimes they even flow. Density log data in high-pressure shales are unreliable due to probable shale modification. Unfortunately, we have no borehole gravimeter data in high. pressure shales and, therefore, no reliable measurements of bulk densities in their natural state. The best data available for studying high-pressure shales are some neutron lifetime logs. The effective depth of investigation of the neutron lifetime log is considerably greater than that of the scatter gamma ray density log.1,2 Therefore, neutron lifetime log measurements should be affected much less by any modified shale near the borehole than would measurements made with a density log. Neutron lifetime logs show a progressive decrease in macroscopic neutron capture cross section with increasing depth for U.S. gulf coast shales with normal pore pressures. This decrease in neutron capture cross section is the result of increased compaction of shales with depth. If high-pressure shales are shales that were not compacted normally with increasing depth of burial, then they should have physical properties comparable with relatively uncompacted shales at much shallower depths of a few thousand feet (1000 to 1500 m). In particular, they should have high neutron capture cross sections as compared with normally pressured shales at slightly shallower depths. However, our logs show neutron capture cross sections for U.S. gulf coast high-pressure shales that range from normal to less than normal for their depths. These data indicate that these high-pressure shales are not shales that were never compacted. The data are consistent with an alternate hypothesis for the generation of high pore pressures in shales.

scholarly journals Measurement of ke V-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of 143,145,146Nd

1999 ◽  
Vol 36 (10) ◽  
pp. 855-864 ◽  
Author(s):  
Teerasak VEERAPASPONG ◽  
Masayuki IGASHIRA ◽  
Satoshi MIZUNO ◽  
Jun-ichi HORI ◽  
Toshiro OHSAKI
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Gamma Ray ◽  
Capture Cross ◽  
Capture Cross Sections

NEUTRON CAPTURE GAMMA RAYS FROM LITHIUM, BORON, AND NITROGEN

1957 ◽  
Vol 35 (12) ◽  
pp. 1347-1360 ◽  
Author(s):  
G. A. Bartholomew ◽  
P. J. Campion
Keyword(s):  
Thermal Neutron ◽  
Gamma Rays ◽  
Cross Sections ◽  
Neutron Capture ◽  
Radiative Capture ◽  
Capture Cross ◽  
Γ Rays ◽  
Capture Cross Sections

The neutron capture γ-rays from Li7, B11, and N15 have been studied. In Li7 γ-rays are observed at 7.26 ± 0.03 Mev. and 6.78 ± 0.05 Mev. In B11 six γ-rays are detected. The spectrum is consistent with J = 7/2 + for the capturing state. In N15 six previously unreported γ-rays are detected. Estimates of thermal neutron radiative capture cross sections are: Li6, 0.028 ± 0.008 b.; B10, 0.5 ± 0.2 b.; and N14, 0.08 ± 0.02 b.

scholarly journals Measurements of keV-neutron capture cross sections and capture gamma-ray spectra of105Pd

2014 ◽  
Vol 51 (5) ◽  
pp. 671-680
Author(s):  
Kazushi Terada ◽  
Taihei Matsuhashi ◽  
Masayuki Igashira ◽  
Tatsuya Katabuchi
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Gamma Ray ◽  
Capture Cross ◽  
Capture Cross Sections

scholarly journals Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of140Ce and141Pr

2000 ◽  
Vol 37 (9) ◽  
pp. 740-749 ◽  
Author(s):  
Suhe HARNOOD ◽  
Masayuki IGASHIRA ◽  
Tetsuro MATSUMOTO ◽  
Satoshi MIZUNO ◽  
Toshiro OHSAKI
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Gamma Ray ◽  
Capture Cross ◽  
Capture Cross Sections

Quantitative interpretation of pulsed neutron capture logs: Part 2 — Inversion of measurements in thinly bedded formations

Geophysics ◽  
2011 ◽  
Vol 76 (3) ◽  
pp. E95-E103 ◽  
Author(s):  
Jordan G. Mimoun ◽  
Carlos Torres-Verdín ◽  
William E. Preeg
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Inversion Method ◽  
Layer By Layer ◽  
Cpu Time ◽  
Inversion Procedure ◽  
Bed Thickness ◽  
Definition Of ◽  
Pulsed Neutron ◽  
Capture Cross Sections

We have developed an inversion method to reduce shoulder-bed effects on pulsed neutron capture (PNC) logs for estimating layer-by-layer-capture cross sections Σ. The method is based on a previously developed rapid approximation of PNC logs. Tests performed on synthetic examples that include a variety of lithology, saturating-fluid, and bed-thickness configurations confirm the efficiency, reliability, and stability of the inversion procedure. Inversion consistently improves the vertical resolution and Σ definition of PNC logs across beds thinner than 45 cm. Our fast, iterative algorithm inverts Σ logs in seconds of CPU time and is therefore suitable for joint petrophysical interpretation with other open- and cased-hole logs.

scholarly journals Nuclear Structure Investigations of some Medium-Weight Isotopes

2021 ◽  
Author(s):  
◽  
Gavin Wallace
Keyword(s):  
Nuclear Structure ◽  
Beta Decay ◽  
Cross Section ◽  
Gamma Rays ◽  
Half Life ◽  
Decay Scheme ◽  
Gamma Ray ◽  
Calculated Cross Section ◽  
Beta Spectrum ◽  
Gamma Ray Detectors

<p>This thesis describes the methods and results of investigations made to determine the decay schemes of three short-lived isotopes 112Ag, 114Ag and 116Ag. A total of 76 gamma-rays was observed with a Ge(Li) detector in the gamma-radiation which follows the Beta-decay of 112Ag to levels of 112Cd. gamma- gamma coincidence and angular correlation measurements were made with Ge(Li)-NaI(T1) and NaI(T1)-NaI(T1) systems. A decay scheme consistent with the present data is proposed. Cross sections for the reactions 112Cd(n,p)112Ag and 115In(n, alpha)112Ag were measured, and the half-life of the 112Ag decay was found to be 3.14 plus-minus 0.01 hr. The decay scheme of 114Ag was studied with Ge(Li) gamma-ray detectors and plastic Beta-ray detectors. 9 of the 11 gamma-rays observed in the decay were incorporated into 114Cd level structure previously determined by conversion electron measurements on the 113Cd(n,gamma)114Cd reaction. The endpoint energy of the Beta-decay was determined as 4.90 plus-minus 0.26 MeV; no branching was evident in the Beta-spectrum. A decay scheme is proposed for which the Beta-branching was deduced from the measured gamma-ray yield and a calculated cross section value for the 114Cd(n,p)114Ag reaction. The 114Ag half-life was determined as 4.52 plus-minus 0.03 sec; a search for a previously reported isomeric state of 114Ag was unsuccessful. Ge(Li) and NaI(T1) gamma-ray detectors were used to study the direct and coincidence spectra that result from the decay of 116Ag, the half-life of which was found to be 2.50 plus-minus 0.02 min. 53 gamma-rays were observed from this decay. The Beta-branching to the 17 excited states of 116Cd in the proposed decay scheme was derived from the measured gamma-ray yield and a calculated cross section value for the 116Cd(n,p)Ag reaction. Spin and parity assignments for ihe energy levels of 116Cd are made. An investigation of the applicability of two collective models to nuclear structure typical of the Cd nuclei studied demonstrated that one of the models was misleading when applied to vibrational nuclei. A potential function was developed in the other model to extend the investigation to include a study of the transition between extremes of collective motion. This was used to examine the correspondence between nuclear level schemes representative of rotational and vibrational excitations.</p>

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