Low Gamma-ray Research Articles

Effect of FBG Fiber Dosimeter Division in Sensing Capability for Low Radiation Doses

ر A fiber Bragg grating (FBG) as a dosimeter is developed in this simulation study (based on Optisystem 21 software) by dividing its region into five individual regions. The division includes the same properties for all regions, which is a standard SiO2 optical fiber material. In dosimeters, it is convenient to introduce dopants to increase the fiber sensitivity. The new design accepts dopants and can work without such a dopant. Measurements for sensing deflected signals from the FBG sensor confirmed increased sensitivity for low-rate radiation doses in comparison to one bulk region in a traditional fiber dosimeter. The sensitivity of this dosimeter is based on both the FWHM line shape function and the amplitude of the deflected signals. The FBG dosimeter sensor can respond to low-dose radiation in a noticeable manner according to the type of applied simulated effect. Dosimeter body division for multi-regions gives rise to sensitivity in comparison to the traditional bulk region. The measured FWHM from the line-shape function for overall observed signals fluctuates from 0.374 MHz under applied temperature, stress x, y, z, and strain to 0.358, 0.373, 0.3733, 0.368, and 0.3737 MHz, respectively. While this range follows different fitting functions: Sin, Exp.Decay, SinSqu., Exp.Decay3, and GaussAmpl. For last effects, according to measured effect. The same measurements were carried out for signal amplitude variation, with these effects giving a variety of relationships indicating their existing contribution. Results confirmed an efficient tool for use in sensing for low x-ray and gamma ray radiation dose applications versus traditional bulk FBG sensor type.

Optimizing reservoir characterization: insights from integrated data analysis

The Onshore Hydrocarbon prospectivity of the Niger Delta X-field is examined through the integration of 3D seismic and recorded information from well log data. Probable reservoirs of hydrocarbon-bearing were delineated to tackle the non-uniqueness in the identification of hydrocarbon quantity of concern. Three significant faulting patterns or systems were delineated and their architectural attributes depict a typical Niger Delta embedded anticlinal structural pattern. The study field exhibited both synthetic and antithetic structures, hence only fault on delineated reservoirs was used for structural modeling. All well locations were sited within the fault-supported synthetic and anticlinal structures and the static characteristics within the well coordinates were analyzed through petrophysical assessment. Depicted reservoir sands show low gamma ray readings, low volume of shale, considerate hydrocarbon saturation and low water saturation. The established petrophysical models showed a better net-to-gross (NTG) ratio, for the entire delineated reservoir units. This has contributed to the assessment of hydrocarbon-bearing reservoir units before employing the strategy for field development scenario, in order to eliminate dry hole drilling campaign. These will contribute to the reduction of operational costs, having delineated the accurate geometry and petrophysical model of hydrocarbon reservoir units.

On the response of the CR-39 NTD to low doses of gamma rays using optical and photoluminescence spectroscopy

In this work, the response of the CR-39 nuclear track detector (NTD) exposed to different low doses of gamma rays was investigated using UV–Vis and photoluminescence spectroscopy. Five NTDs of CR-39 were irradiated with low gamma-ray doses ranging from 10 to 120 kGy using a60Co source. The dose of gamma rays correlates with red shift in the absorption spectra of a gamma-irradiated CR-39 detector. As the gamma dose increases, the indirect and direct energy band gaps, as well as Urbach energy, decrease gradually. However, the decrease in the indirect optical band gap is greater than the decrease in the direct band gap. The observed spectra of the CR-39 detector after being irradiated with different doses of γ-rays showed an acceptable variation in photoluminescence (PL) emission spectra generated by a well-defined excitation wavelength of 290 nm. Starting at 45 kGy dose, the integrated area of the photoluminescence peak increases and tends to saturate, whereas the photoluminescence peak height is linearly correlated with the gamma dose with high sensitivity, which is 53.1 ± 6.3 CPS. kGy−1. According to the current findings, photoluminescence (PL) spectroscopy has a greater sensitivity than UV–Vis spectroscopy for measuring the response of the CR-39 detector to gamma rays in the dose range of 10–120 kGy. The results reflected a potential possibility of using the CR-39 detector in dosimetric applications of low gamma ray doses through the high resolution achieved by photoluminescence (PL) and UV–Vis spectroscopy.

Fracture stratigraphy in oil-rich shale of the Upper Xiaganchaigou Formation (upper Eocene), western Qaidam Basin

Natural fractures in wells from oil-rich shale of the Upper Xiaganchaigou Formation in Qaidam Basin, the largest Cenozoic sedimentary basin in the Tibetan Plateau, vary systematically by stratigraphic position, allowing reconstruction of fracture generation processes during regional tectonic deformation. Compacted fractures, layer-bounded fractures, and low-angle (or bed-parallel) fractures were widely identified in oil-rich shale cores obtained from vertical wells. The layer-bounded fractures can be subdivided into two sets: one prevalent in light-colored (low gamma-ray) stiff layers and arrested by dark-colored (high gamma-ray) compliant layers, the other set primarily confined to the dark-colored compliant layers. The strikes of layer-bounded fractures, revealed by horizontal well FMI logs, are dominantly N60°-80°E and N10°-30°E within the light and dark intervals respectively. These strikes are consistent with natural hydraulic fracturing of the light layers during the Oligocene and the dark layers during the Middle Miocene-Holocene, based on a regional anticlockwise rotation of the compressional strain orientation. The abutment of layer-bounded fractures against low-angle (or bed-parallel) fractures in dark layers implies that the low-angle fractures were hydraulically fractured under a vertical least compressive stress during the Early Miocene, which produced the most intense tectonic compression. Layer-bounded fractures generally remain unmineralized in the dark layers but were mineralized in the light layers, suggesting that fractures confined in light layers would not decrease the sealing capacity of the shale oil system and fractures confined in dark layers can increase the pore space of shale oil storage. The Oligocene and Early Miocene fractures represented mechanical flaws that affected the initiation of Middle Miocene-Holocene fractures, implying that all natural fractures may alter hydraulic fracture stimulations to some extent.

تقييم الأداء الديناميكي لتكوين الحواز في حوض مرزق بليبيا كما يستدل عليه بتقنية التفسير السريع.

The evaluating of the Hawaz reservoir in the Murzuq basin based on the well recording data available for twelve exploratory were provided for this study. These records data have been examined through employing some cross-plots and use their outputs for controlling the interactive petrophysics software in order to identify the lithological constituents and fluid saturation parameters.The litho-saturation cross-plot indicated that the Hawaz Formation consists of sandstones with few shale.The Hawaz formation officially subdivided intoeight horizons, namely H1–H8. Horizons (H4 and H5) are the main reservoirs in Hawaz formation as all readings indicate its high resistivity, with positive differentiation between its different curves, high porosity, and low gamma ray. BVW min technology is introduced the fast method depends on calculating the minimum total water volume so that the reservoir is considered to contain irreducible water, meaning that water will not be produced with the oil. The value of BVW min was 0.05, meaning that any range for which the product of porosity multiplied by water saturation (Φ.SW) is greater than that value is excluded from any detailed calculations.Also, calculate the minimum value of electrical resistance (Rtmin=140ῼm) for oil production zones, where zones with electrical resistivity less than that value are excluded. Keywords: Hawaz Formation, H field of NC186, petrophysical parameters, well logging.

Effect of Gamma Irradiation on Embryogenic Calli of Rice and Subsequent Shoot and Regeneration

This study was carried out during May 2021 to January 2022 at the Tissue Culture Laboratory of Biotechnology Division, Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh, Bangladesh for callus induction and regeneration ability of plantlet from low doses irradiated embryogenic calli of Binadhan-13 and BR5 (Dulabhog). The effect of low gamma rays such as 4, 6 and 8 Gy were observed in vitro shoot, root and plantlet formation. Two different incubation conditions such as light and dark incubation were maintained. Between two varieties, Binadhan-13 showed the highest ability of callus induction in both conditions. Callus induction was significantly higher under dark condition (77.14%) than light condition (67.14%) ‍at 21 days. Data revealed that gamma rays affect both shoot and root regeneration ability of embryogenic callus. Shoot regeneration ability was the highest at 4 Gy in Binadhan-13 (60%) and gradually decreased with the increased doses of gamma rays. Among the treatments, shoot regeneration ability (60% in Binadhan-13 and 50% in BR5) was higher at 4 Gy dose of gamma ray followed by 6 Gy where shoot regeneration ability was 55% and 45% in Binadhan-13 and BR5 respectively. In root induction, the highest root induction ability (80%) was observed in the cultivar Binadhan-13 at control condition. Like shoot regeneration, 4 Gy gamma ray showed better root induction in both the varieties (70% in Binadhan-13, 60% in BR5). The in vitro regenerated plantlets from irradiated embryogenic calli were successfully transferred to soil in pots. The regeneration protocol could be further used for varietal improvement of rice varieties using nuclear technique (60Co gamma ray). Bangladesh J. Nuclear Agric, 37(2): 29-42, 2023

Post-stack seismic inversion through probabilistic neural networks and deep forward neural networks

Seismic inversion, a nonlinear, non-unique-solution, and human-prone error problem, seeks the optimal solution in multivariate space, a task that AI algorithms perform better. So, inversion with AI becomes appropriate to extract information from post-stack data. A probabilistic neural network (PNN) and deep feedforward neural network (DFNN) inverted seismic data using multiattributes, and their results were compared with those provided by a model-based inversion (MBI). Applied to a post-stack volume of the Frontier Formation at the Teapot-Dome field, Wyoming-USA, the three methods provided porosity volumes (ϕ), gamma rays (GR), and Lamé impedances (µρ, λρ). The comparison between well-logs and the provided volumes revealed a reliable PNN prediction, while DFNN achieved the best geologically correlated parameter sections and a less reliable MBI prediction. The geomorphological time-slice analysis discriminated high ϕ-µρ areas and low GR–λρ areas, geologically interpreted as a deltaic environment, with distributary channels and beachfront lobes subject to the action of the tides, which agrees with the well-log interpretation and the basin geological evolution. The results enhanced the stacked section’s importance by the geological information contained, which would contribute to reducing the prospecting risk. Finally, PNN and DFNN encouraging results reaffirm their best searching-in-multivariate space ability.

Exploring one giga electronvolt cosmic gamma rays with a Cherenkov plenoscope capable of recording atmospheric light fields, Part 1: Optics

Detecting cosmic gamma rays at high rates is the key to time-resolve the acceleration of particles within some of the most powerful events in the universe. Time-resolving the emission of gamma rays from merging celestial bodies, apparently random bursts of gamma rays, recurring novas in binary systems, flaring jets from active galactic nuclei, clocking pulsars, and many more became a critical contribution to astronomy. For good timing on account of high rates, we would ideally collect the naturally more abundant, low energetic gamma rays in the domain of one giga electronvolt in large areas. Satellites detect low energetic gamma rays but only in small collecting areas. Cherenkov telescopes have large collecting areas but can only detect the rare, high energetic gamma rays. To detect gamma rays with lower energies, Cherenkov-telescopes need to increase in precision and size. But when we push the concept of the –far/tele– seeing Cherenkov telescope accordingly, the telescope’s physical limits show more clearly. The narrower depth-of-field of larger mirrors, the aberrations of mirrors, and the deformations of mirrors and mechanics all blur the telescope’s image. To overcome these limits, we propose to record the –full/plenum– Cherenkov-light field of an atmospheric shower, i.e. recording the directions and impacts of each individual Cherenkov photon simultaneously, with a novel class of instrument. This novel Cherenkov plenoscope can turn a narrow depth-of-field into the perception of depth, can compensate aberrations, and can tolerate deformations. We design a Cherenkov plenoscope to explore timing by detecting low energetic gamma rays in large areas.

Effect of Location and Shielding on Gamma Radiation Background in Low Level Gamma Ray Spectrometry

Effect of Location and Shielding on Gamma Radiation Background in Low Level Gamma Ray Spectrometry

An investigation of the state changes of PSR J2021+4026 and the Vela pulsar

ABSTRACT We report on long-term evolution of gamma-ray flux and spin-down rate of two bright gamma-ray pulsars, PSR J2021+4026 and Vela (PSR J0835−4510). PSR J2021+4026 shows repeated state changes in gamma-ray flux and spin-down rate. We report two new state changes, a first one from a low gamma-ray flux to a high flux that occurred around MJD 58910, and a second one from high to low flux that occurred around MJD 59510. We find that the flux changes associated with these two state changes are smaller than those determined in the previous events, and the waiting time of the new state change from the high gamma-ray flux to low gamma-ray flux is significantly shorter than previous events. Since the waiting time-scale of the quasi-periodic state changes of PSR J2021+4026 is similar to the waiting time-scale of the glitch events of the Vela pulsar, we search for the state change of the gamma-ray emission of the Vela pulsar to investigate the possibility that the glitching process is the trigger of the state change of PSR J2021+4026. For the Vela pulsar, the flux of the radio pulses briefly decreased around the 2016 glitch, suggesting that the glitch may have affected the structure of the magnetosphere. Nevertheless, we could not find any significant change of the gamma-ray emission properties using 15 yr of Fermi-LAT data. Overall, it seems inconclusive that a glitch-like process similar to that occurred to the Vela pulsar triggers the structure change of the global magnetosphere and causes state changes of PSR J2021+4026. Further and deep investigations to clarify the mechanism of the mode change for PSR J2021+4026 are required.

FRACTURING LIQUID DESIGN AND ECONOMIC ANALYSIS FOR LOW PERMEABILITY AND HIGH TEMPERATURE

Mirabelle 01 M01 well is a developed-stage well which has undergone drilling since February 2020 until May 3th 2020. It has 13000 ft depth and dominated with sandstone layers and some shaly inserts. This well is a high temperature (300 F), low permeability (0.5-5 mD) and porosity well which casues hydraulic fracturing should be done in this well. Aim: to carry out fluid fracturing design analysis by considering additional materials and economics. The perforation in this well divided into 2 perforations, first perforation has been 297 ft long and located at 12143 ft-12440 ft of well depth. The second perforation has been 45 ft in length and is located at 12,730 ft-12,685 ft of well depth. Payzone of this well is dominated by sandstone which is determined from the low gamma ray data. This Mirabelle 01 M01 well has high resistivity due to the resistivity log. Water mix used for the formation is a neutral water mix but still has several negative ions with corrosive properties such as SO42- and Cl-. Acid inhibitors are needed to remove these ions and prevent corrosive to be happened. Scale inhibitors are also needed to be added to prevent scale formation caused by Mg2+ ions which are contained in the mix water. From the average pressure calculation, the closure pressure was found about 7914.67 psi. The young modulus found from 8-10 Mpsi which indicates that the formation has high stiffness. The base of the fracturing fluid used is low price water-base fluid with guar gum polymer which can produce hydroxypropilguar (HPG) that don't ruin the formation even if the formation is in the high temperature. Borate ions are used to be crosslinker agents that binds metal ions with polymers. To split polymers molecules, sodium salt from the peroxydisulphate is used to be the gel breaker.

Feasibility study of optical imaging of the boron-dose distribution by a liquid scintillator in a clinical boron neutron capture therapy field.

Evaluation of the boron dose is essential for boron neutron capture therapy (BNCT). Nevertheless, a direct evaluation method for the boron-dose distribution has not yet been established in the clinical BNCT field. To date, even in quality assurance (QA) measurements, the boron dose has been indirectly evaluated from the thermal neutron flux measured using the activation method with gold foil or wire and an assumed boron concentration in the QA procedure. Recently, we successfully conducted optical imaging of the boron-dose distribution using a cooled charge-coupled device (CCD) camera and a boron-added liquid scintillator at the E-3 port facility of the Kyoto University Research Reactor (KUR), which supplies an almost pure thermal neutron beam with very low gamma-ray contamination. However, in a clinical accelerator-based BNCT facility, there is a concern that the boron-dose distribution may not be accurately extracted because the unwanted luminescence intensity, which is irrelevant to the boron dose is expected to increase owing to the contamination of fast neutrons and gamma rays. The purpose of this research was to study the validity of a newly proposed method using a boron-added liquid scintillator and a cooled CCD camera to directly observe the boron-dose distribution in a clinical accelerator-based BNCT field. A liquid scintillator phantom with 10 B was prepared by filling a small quartz glass container with a commercial liquid scintillator and boron-containing material (trimethyl borate); its natural boron concentration was 1wt%. Luminescence images of the boron-neutron capture reaction were obtained in a water tank at several different depths using a CCD camera. The contribution of background luminescence, mainly due to gamma rays, was removed by subtracting the luminescence images obtained using another sole liquid scintillator phantom (natural boron concentration of 0wt%) at each corresponding depth, and a depth profile of the boron dose with several discrete points was obtained. The obtained depth profile was compared with that of calculated boron dose, and those of thermal neutron flux which were experimentally measured or calculated using a Monte Carlo code. The depth profile evaluated from the subtracted images indicated reasonable agreement with the calculated boron-dose profile and thermal neutron flux profiles, except for the shallow region. This discrepancy is thought to be due to the contribution of light reflected from the tank wall. The simulation results also demonstrated that the thermal neutron flux would be severely perturbed by the 10 B-containing phantom if a relatively larger container was used to evaluate a wide range of boron-dose distributions in a single shot. This indicates a trade-off between the luminescence intensity of the 10 B-added phantom and its perturbation effect on the thermal neutron flux. Although a partial discrepancy was observed, the validity of the newly proposed boron-dose evaluation method using liquid-scintillator phantoms with and without 10 B was experimentally confirmed in the neutron field of an accelerator-based clinical BNCT facility. However, this study has some limitations, including the trade-off problem stated above. Therefore, further studies are required to address these limitations.

Mineralogical Modeling and Petrophysical Properties of the Barra Velha Formation, Santos Basin, Brazil

The Santos Basin, offshore Brazil, has the most significant petroleum carbonate reservoir province in South America. The presalt carbonates reservoirs of the Barra Velha Formation (BVF) present a complex mineralogic distribution and heterogeneous physical properties, making it challenging to construct a reliable mineralogical model. Understanding rock mineralogy is important to petroleum prospects and the study of porous media, besides calibrating seismic facies. In this paper, we present a mineralogical inversion procedure to model reservoir and nonreservoir intervals within the BVF in a presalt field applying multicomponent inversion. The uppermost 15 to 28 m of the BVF, known as “Lula Fingers,” present higher values of gamma ray when compared with deeper intervals and are characterized by high modeled dolomite contents. Below the Lula Fingers region, the Upper BVF can be divided into BVF100 (top), which is characterized by low gamma ray values just above the BVF200 (bottom). They are formed mainly by shrub and spherulite-rich in-situ facies with fewer clay and Mg-clays contents, which are often replaced by dolomite and quartz. The bottom part of Upper BVF (BVF200) presents a microporous Mg-clay-rich interval, mainly in the structural flanks region, or a macroporous Mg-clay-poor interval, mainly in high levels. The present model fits well with the stratigraphic interval and allows a better understanding of the mineralogical distribution over the entire BVF100 and BVF200, particularly the lateral mineralogical variability in regions with structural highs and flanks.

Feasibility of neutron coincidence counting for spent TRISO fuel

High-temperature gas reactors rely on TRIstructural-ISOtropic (TRISO) fuel for enhanced fission product retention. Accurate fuel characterization would improve monitoring of efficient fuel usage and accountability. We developed a new neutron multiplicity counter (NMC) based on boron coated straw (BCS) detectors and used it in coincidence mode for 235U assay in TRISO fuel. In this work, we demonstrate that a high-efficiency version of the NMC encompassing 396 straws is able to estimate the 235U in used TRISO-fueled pebbles or compacts with a relative uncertainty below 2.5% in 100s. We performed neutronics and fuel depletion calculation of the HTR-10 pebble bed reactor to estimate the neutron and gamma-ray source strengths of used TRISO-fueled pebbles with burnup between 9 and 90GWd/t. Then, we measured a gamma-ray intrinsic efficiency of 10−12 at an exposure rate of 340.87R/h. The low gamma-ray sensitivity and high neutron detection efficiency enable the inspection of used fuel.

Characteristics of Permian igneous rocks and their petroleum geology implications in the northern part of central Sichuan, Sichuan Basin, China

Based on data from cores, cuttings, thin sections, and logging and seismic activities, the lithofacies, geophysical response, and spatial distribution characteristics of the Permian igneous rocks in the northern part of central Sichuan were analyzed and summarized. Furthermore, the eruption and filling processes of the igneous rocks were restored, and the hydrocarbon geologic significance of the volcanic eruption events was investigated. The results reveal that the igneous rocks in this area are volcanic overflow facies and sedimentary facies, with volcanic lava and pyroclastic rocks developed. Only one eruption cycle occurred vertically. The igneous rocks exhibit low natural gamma ray, low acoustic, high compensation neutron logging, high density, and high resistivity logging values. The seismic responses are characterized by multiaxial, flexural, and upward arching. The plane distribution shape is an inverted U, with a nearly east–west linear distribution. The igneous rocks in the area were emplaced via a fissure eruption along the basement faults in the early Longtan. The eruption-filling process can be roughly divided into four stages: the deposition of the Maokou Formation, the geomorphological embryonic stage, the geomorphological differentiation stage, and the volcanic eruption and filling stage. The underdevelopment of primary pores and the lack of dissolution in the later stage led to poor igneous reservoir performance, which limits the igneous reservoir hydrocarbon exploration prospect. However, the early faulting activity resulted in the differentiation of the Maokou Formation sedimentary and karst landforms. The thermodynamic conditions created by the later eruption of the igneous rocks, sufficient Mg2+ sources, and favorable geomorphological units laid a good foundation for the development of the dolomite reservoirs in the Maokou Formation. Among them, the karst slopes and highland areas of the Maokou Formation along the two sides of the strip of igneous rocks are dominant areas for the development of the dolomite reservoirs in the Maokou Formation.

Preparation and experimental estimation of radiation shielding properties of novel epoxy reinforced with Sb2O3 and PbO

Abstract The present work aims to fabricate new inexpensive epoxy-based composites with a concentration described by the formula (90 − x)epoxy + 10Sb2O3 + xPbO, where x = 5, 10, 15, and 20 wt%. The impacts of the substitution of epoxy by PbO on the composite density and radiation shielding properties of the fabricated composites were studied. The density of the fabricated composites varied between 1.30 and 1.49 g·cm−3, enriching the PbO concentration. Utilizing the narrow beam transmission method, the linear attenuation coefficient (LAC) of the fabricated composites was measured using the NaI (Tl) detector as well as radioactive sources Am-241 and Cs-137. The LAC increased by 84% and 18% at gamma-ray energy of 0.059 and 0.662 MeV, when the PbO concentration raised between 5 and 20 wt%, respectively. Then the transmission rate and half-value layer of the fabricated composites were reduced by raising the PbO concentration. Therefore, the fabricated composite has good shielding properties in the low gamma-ray energy interval to be suitable for medical applications and low radioactive waste container constructions.

Petrophysical Properties and Reservoir Assessment of Mishrif Formation in Eridu oil field, Southern Iraq

This study is achieved in the local area of the Eridu oil field, where the Mishrif Formation is considered the main productive reservoir. The Mishrif Formation was deposited during the Cretaceous period in the secondary sedimentary cycle (Cenomanian-Early Turonian as a part of the Wasia Group, a carbonate succession widespread throughout the Arabian Plate. The Mishrif Formation already have been evaluated in terms of depositional environments and their diagenetic processes. Here, it will test the previous conclusions with petrophysical properties delineated by using well logging. The results show there is a fully matching with two reservoir units (MA and MB). Dissolution and primary porosity are responsible for forming a variety of large porosity types. These porosity types have preserved the hydrocarbons in commercial quantities. MA and MB reservoir units show low gamma ray and high to moderate total and effective porosities values. The water saturation Sw in the upper unit (MA) is very high in generally to become water-bearing zone. This appears in all studied wells except in the E-NE part, characterized by patches area of moderate water saturation. In contrast, the lower unit (MB) is characterized by high values of hydrocarbon saturation (Sh) except for some areas in the middle of the studied field. Cap rocks (CR1 and CR2) represents rock unit with low porosity and permeability due to the main components of these units. It contains lime mudstone with log response of this cap rocks indicates high gamma-ray peak value. Compaction and dolomitization are responsible for low porosity and permeability in this type of rock unit.

Integrating seismic attributes and rock physics for delineating Pliocene reservoir in Disouq field, Nile Delta, Egypt

The Nile Delta is known as the most prolific gas province in North Africa. Gas exploration and production were the main targets over decades in the Nile Delta. The integration of petrophysical analysis, seismic interpretation, and seismic attributes could indicate the presence of gas in Disouq field, which is located in Nile Delta, Egypt. Well log data showed that the reservoir is classified into three zones (A, B, and C). These zones are characterized by low gamma ray (around 35%), with relatively high porosity (around 29%) and low water saturation (36–38%). Structural and stratigraphic interpretation was conducted in order to investigate the extension and geometry of the reservoir, in addition to the faults affecting the study area. The reservoir is represented by a channel of Pliocene age, characterized by the low impedance sand saturated by gas. Near and far offset data show the gas effect. There is an increase of the negative amplitude from near to far offset. The amplitude map and structural contours match well and show good conformance. Seismic attributes including surface attributes and “Red Green Blue/colour blending” help in delineating the extent and geometry of the reservoir, in addition to the possible prospect. Finally, the volume of original gas in place was estimated what showed that the study area is of great economic interest.

Radiation-induced attenuation in aluminum- and aluminum-thulium-doped optical fibers.

Gamma-ray-induced attenuation in Al-doped and Al/Tm-co-doped optical fibers is investigated in the visible and near-infrared domain up to 1Gy. The behavior of radiation-induced attenuation (RIA) regarding dose and dose rate is discussed. Our results reveal high sensitivities for both types of fibers at low gamma ray doses and also reveal that Al/Tm fibers are very promising at original interrogation wavelengths for dosimetry applications.

Integrating facies analysis and geostatistical methods in an onshore oil field using petrophysical groups

Reservoir facies studies are of great importance in different stages of exploration and development of hydrocarbon fields. We have aimed to generate a reservoir facies model for the Asmari Formation in an onshore oil field located in southwest Iran. Input data for electrofacies (EF) clustering algorithms are used, which include gamma-ray (GR), density (RHOB), porosity, and sonic logs from four wells. We obtain the petrophysical group (PG) and EF class using core drill data (mercury injection capillary pressure) and well-logs analysis. The integration of PGs and log EF significantly decreases the uncertainty in reservoir modeling, which alternatively enhances field development decisions. We compare the multiresolution graph-based clustering (MRGC) and k-means clustering methods. EF clustering results find nine EF classes. We delineate high-quality reservoirs based on lower GR, RHOB, and high-porosity logs. Next, we use the clustering results in the static reservoir modeling process, using the sequential index simulation and indicator kriging methods. The comparison between the facies obtained models and existing drilling core data finds that the absolute percentage error of the MRGC algorithm is less than that of the k-means algorithm. The results obtained by this study can provide useful information for the development of hydrocarbon exploration plans in the studied oil field.