Linear iterative refinement method for the rapid simulation of borehole nuclear measurements: Part 2 — High-angle and horizontal wells

Geophysics ◽  
2010 ◽  
Vol 75 (2) ◽  
pp. E79-E90 ◽  
Author(s):  
Alberto Mendoza ◽  
Carlos Torres-Verdín ◽  
Bill Preeg
Keyword(s):  
Monte Carlo ◽  
Iterative Refinement ◽  
High Angle ◽  
Density Measurements ◽  
Spatial Properties ◽  
Refinement Method ◽  
Geometric Factors ◽  
Neutron Porosity ◽  
New Research ◽  
Water Saturated

Based on previous research, we developed and successfully tested a new linear iterative refinement method to rapidly simulate borehole nuclear measurements acquired in vertical wells. The approximation considers 2D spatial properties of Monte Carlo-derived flux-sensitivity functions (FSFs) to simulate neutron and density measurements. Based on new research, we implemented the linear iterative refinement method with explicit 3D spatial properties of FSFs to approximate nuclear borehole measurements acquired in high-angle and horizontal (HA/HZ) wells. We used generic neutron and density tools that are close to commercial tool designs to construct 3D FSFs in the proximity of a bed boundary between layers of contrasting petrophysical properties. Likewise, to benchmark the approximation, we consider adjacent layers of 5% and 30% porosity water-saturated sandstone. For the case of neutron measurements, variations of azimuthal geometric factors are as large as 20° and 57° for the near and far detectors, respectively. Variations in the radial length of investigation (J-factors) are as large as [Formula: see text] for near and far detectors. In the case of density measurements, radial and azimuthal geometric factors are approximately invariant. Linear iterative refinement approximations yield errors in the simulated neutron porosity ranging from 1.6% to 4.3% with respect to Monte Carlo-simulated logs in wells deviating from 60° to 85° from the vertical.

Linear iterative refinement method for the rapid simulation of borehole nuclear measurements: Part I — Vertical wells

Geophysics ◽  
2010 ◽  
Vol 75 (1) ◽  
pp. E9-E29 ◽  
Author(s):  
Alberto Mendoza ◽  
Carlos Torres-Verdín ◽  
Bill Preeg
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Numerical Technique ◽  
Integral Form ◽  
Computer Time ◽  
Iterative Refinement ◽  
Detector Response ◽  
Layer By Layer ◽  
Response Factors ◽  
Refinement Method

As a result of its high numerical accuracy and versatility to include complex tool configurations and arbitrary spatial distributions of material properties, the Monte Carlo method is the foremost numerical technique used to simulate borehole nuclear measurements. Although recent advances in computer technology have considerably reduced the computer time required by Monte Carlo simulations of borehole nuclear measurements, the efficiency of the method is still not sufficient for estimation of layer-by-layer properties or combined quantitative interpretation with other borehole measurements. We develop and successfully test a new linear iterative refinement method to simulate nuclear borehole measurements accurately and rapidly. The approximation stems from Monte Carlo-derived geometric response factors, referred to as flux sensitivity functions (FSFs), for specific density and neutron-tool configurations. Our procedure first invokes the integral representation of Boltzmann’s transport equation to describe the detector response from the flux of particles emitted by the radioactive source. Subsequently, we use theMonte Carlo N-particle (MCNP) code to calculate the associated detector response function and the particle flux included in the integral form of Boltzmann’s equation. The linear iterative refinement method accounts for variations of the response functions attributable to local perturbations when numerically simulating neutron and density porosity logs. We quantify variations in the FSFs of neutron and density measurements from borehole environmental effects and spatial variations of formation properties. Simulations performed with the new approximations yield errors in the simulated value of density of less than [Formula: see text] with respect to Monte Carlo-simulated logs. Moreover, for the case of radial geometric factor of density, we observe a maximum shift of [Formula: see text] at 90% of the total sensitivity as a result of realistic variations of formation density. For radial variation of neutron properties (migration length), the maximum change in the radial length of investigation is [Formula: see text]. Neutron porosity values simulated with the new approximation differ by less than 10% from Monte Carlo simulations. The approximations enable the simulation of borehole nuclear measurements in seconds of CPU time compared to several hours with MCNP.

Electron density study of KNiF3 by the vacuum-camera-imaging plate method

1999 ◽  
Vol 55 (6) ◽  
pp. 917-922 ◽  
Author(s):  
Elizabeth A. Zhurova ◽  
Vladimir V. Zhurov ◽  
Kiyoaki Tanaka
Keyword(s):  
Electron Density ◽  
Oblique Incidence ◽  
Scintillation Counter ◽  
Imaging Plate ◽  
High Angle ◽  
Plate Method ◽  
Density Measurements ◽  
Camera Imaging ◽  
Density Study

The electron density measurements of KNiF3, nickel potassium trifluoride, by the vacuum-camera-imaging plate (VCIP) method and using a four-circle diffractometer with scintillation counter, are performed and compared. In the IP (imaging plate) case evacuation allowed the background around peaks to be reduced 50 times, which significantly increased the accuracy of the data, especially for high-angle reflections. A new VIIPP program for visualizing and integration of IP data was designed to treat the data, in which the correction for oblique incidence was applied. The resulting electron density reproduces all the features of the accurate conventional measurement.

scholarly journals The outer disk of the classical Be star ψ Per

2016 ◽  
Vol 12 (S329) ◽  
pp. 414-414
Author(s):  
Robert Klement ◽  
Alex C. Carciofi ◽  
Thomas Rivinius ◽  
Lynn D. Matthews ◽  
Richard Ignace ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Density Measurements ◽  
Outer Disk ◽  
Disk Size ◽  
Gaussian Fit ◽  
Be Star ◽  
Best Fit ◽  
Striking Contrast

AbstractTo this date ψ Per is the only classical Be star that was angularly resolved in radio (by the VLA at λ = 2 cm). Gaussian fit to the azimuthally averaged visibility data indicates a disk size (FWHM) of ~500 stellar radii (Dougherty & Taylor 1992). Recently, we obtained new multi-band cm flux density measurements of ψ Per from the enhanced VLA. We modeled the observed spectral energy distribution (SED) covering the interval from ultraviolet to radio using the Monte Carlo radiative transfer code HDUST (Carciofi & Bjorkman 2006). An SED turndown, that occurs between far-IR and radio wavelengths, is explained by a truncated viscous decretion disk (VDD), although the shallow slope of the radio SED suggests that the disk is not simply cut off, as is assumed in our model. The best-fit size of a truncated disk derived from the modeling of the radio SED is 100+5−15 stellar radii, which is in striking contrast with the result of Dougherty & Taylor (1992). The reasons for this discrepancy are under investigation.

scholarly journals Analysis of geometric factors for an X-ray fluorescence analyzer designed via the Monte Carlo method

2016 ◽  
Vol 61 ◽  
pp. 01008
Author(s):  
Hefan Liu ◽  
Hong Tian ◽  
Laidong Zhou ◽  
Zihang Zhou ◽  
Fengxia Huang ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
X Ray ◽  
The Monte Carlo Method ◽  
Geometric Factors ◽  
Fluorescence Analyzer

Electron-beam spreading in thin foils at 40keV

1983 ◽  
Vol 41 ◽  
pp. 370-371
Author(s):  
T.A. Stephenson ◽  
M.H. Loretto ◽  
I.P. Jones ◽  
P. Augustus
Keyword(s):  
Monte Carlo ◽  
Single Crystal ◽  
Cross Sections ◽  
Single Crystal Silicon ◽  
Orientation Dependence ◽  
High Angle ◽  
Crystal Silicon ◽  
Beam Spreading ◽  
Monte Carlo Calculations ◽  
Thin Foils

Experiments have been performed to determine the effects of thickness, and crystallinity on beam spreading in thin foils. The experimental technique consists of measuring an incident and exit electron probe size as shown in Fig. 1. Beam spreading is defined as the difference between these two quantities. Results were compared with Monte Carlo calculations.Beam spreading experiments in single crystal silicon oriented positive of a 440 reflection have shown that the experimental measurements are adequately described by Monte Carlo calculations using Doyle and Turner elastic scattering cross-sections (Fig.2). The addition of an inelastic component via the Bethe continuous loss approximation produces an insignificant change. Adjustment for the generation and scattering of fast secondary electrons is reserved for future work.Two experiments were performed to elucidate the effects of crystallinity. The first involved single crystal silicon in which exit grobe size measurgments were performed with diffracting conditions s=+0.0027Å-1 and s=-0.0034Å-1 from 220 (Table 1). Since beam spreading is dependent on high angle scattering, these results are qualitatively consistent with the orientation dependence of high angle diffuse scattering.

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