Natural Gamma Ray Research Articles

Evaluation of the Gas Content of Coal Reservoirs with Geophysical Logging in Weibei Coalbed Methane Field, Southeastern Ordos Basin, China

Gas content is one of the most important factors in the process of exploration and development of coalbed methane (CBM). The relationships between gas content and characteristics of geophysical logs have been evaluated for the No. 5 coal seam in Weibei CBM field. It is found that the main well loggings that have good responses for gas contents are the compensating density, natural gamma-ray, compensating neutron, natural spontaneous potential and acoustic. A theoretical model was proposed to calculate the gas content by using these well logging data and as well as the burial depth. The calculated gas contents fits well with the measured data with a small relative-error of 0.38-5.05%. In the model, both tectonic movement intensity and the gas accumulation were taken into consideration. Key words: Coalbed methane, Weibei coalfield, Ordos Basin, Gas content, Geophysical logging

Estimation of <i>In Situ</i> Stresses by Using Hydraulic Fracturing and Welllogging Data in Shizhuangnan Coalbed Methane Field

This paper focuses on the research of the vertical and regional distributions of stress characteristics in the Shizhuangnan coalbed methane field, southeastern Ordos basin. The minimum and maximum horizontal stresses were firstly calculated by the breakdown pressure, closure pressure and tensile strength of the fracturing data of key wells. Then the calculated results are compared with the results calculated from the natural gamma-ray, density and acoustic logging data and Anderson’s Model. Based on the comparison, the residual stress in the Anderson’s Model is corrected. By adding the residual stress data in the Anderson’s Model, the modified model can be well used for evaluating the stress characteristics in the area with complex structure types. Finally, the distribution of stress characteristics in the Shizhuangnan coalbed methane field were evaluated by using the modified Anderson model.

Routine Surveys for Gamma-Ray Background Characterization

In gamma-ray spectroscopy and imaging, the natural gamma-ray background can significantly reduce detection sensitivity, especially when the source is weak and the background varies substantially. This project aims to systematically measure and characterize the spatial and temporal variations of the background in order to assess their impact on detection sensitivity and specificity for homeland security applications. An extensive survey of typical backgrounds found in the San Francisco bay area was performed, and initial measurement results are presented here.

Using support vector regression to estimate sonic log distributions: A case study from the Anadarko Basin, Oklahoma

Abstract In petroleum industry, the compressional acoustic or sonic log (DT) is commonly used as a predictor because its capabilities respond to changes in porosity or compaction which, in turn, are further used to estimate formation (sonic) porosity, to map abnormal pore-fluid pressure, or to carry out petrophysical studies. Despite its intrinsic capabilities, the sonic log is not routinely recorded in during well logging. We propose using a method belonging to the class of supervised machine learning algorithms — Support Vector Regression (SVR) — to synthesize missing compressional acoustic or sonic (DT) logs when only common logs (e.g., natural gamma ray—GR, or deep resistivity—REID) are available. Our approach involves three steps: (1) supervised training of the model; (2) confirmation and validation of the model by blind-testing the results in wells containing both the predictor (GR, REID) and the target (DT) values used in the supervised training; and (3) application of the predicted model to wells containing the predictor data and obtaining the synthetic (simulated) DT log. SVR methodology offers two advantages over traditional deterministic methods: strong nonlinear approximation capabilities and good generalization effectiveness. These result from the use of kernel functions and from the structural risk minimization principle behind SVR. Unlike linear regression techniques, SVR does not overpredict mean values and thereby preserves original data variability. SVR also deals greatly with uncertainty associated with the data, the immense size of the data and the diversity of the data type. A case study from the Anadarko Basin, Oklahoma, about estimating the presence of abnormally pressurized pore-fluid zones by using synthesized DT values, is presented. The results are promising and encouraging.

Astronomical Dating of the Middle Miocene Hanjiang Formation in the Pearl River Mouth Basin, South China Sea

AbstractThe Hanjiang Formation of Langhian age (middle Miocene) in the Pearl River Mouth Basin (PRMB), South China Sea consists of deltaic siliciclastic and neritic shelf carbonate rhythmic alternations, which form one of the potential reservoirs of the basin. To improve stratigraphic resolutions for hydrocarbon prospecting and exploration in the basin, the present study undertakes spectral analysis of high‐resolution natural gamma‐ray (NGR) well‐logging record to determine the dominant frequency components and test whether Milankovitch orbital signals are recorded in rhythmic successions. Analytical results indicate the orbital cycles of precession (∼19 ka and ∼23 ka), obliquity (∼41 ka), and eccentricity (∼100 ka and ∼405 ka), which provide the strong evidence for astronomically driven climate changes in the rhythmic alternation successions. Within biochronological constraint, a high‐resolution astronomical timescale was constructed through the astronomical tuning of the NGR record to recent astronomically calculated variation of Earth's orbit. The astronomically tuned timescale can be applied to calculate astronomical ages for the geological events and bioevents recognized throughout the period. The first downhole occurrences of foraminifers Globorotalia peripheroronda and Globigerinoides sicanus are dated at 14.546 Ma and 14.919 Ma, respectively, which are slightly different from earlier estimates in the South China Sea. When compared with the global sea‐level change chart, the astronomical estimate for the sequences recognized based on microfossil distributions have the same end time but the different initiation time. This is probably due to the local or regional tectonic activities superimposed on eustatic rise which postponed the effect of global sea‐level rising. Astronomical timescale also resolves the depositional evolution history for the Langhian Stage (middle Miocene) with a variation that strongly resembles that of Earth's orbital eccentricity predicted from 13.65 Ma to 15.97 Ma. We infer that the main factor controlling the variability of the sedimentation rate in the Hanjiang Formation is related to the ∼405‐ka‐period eccentricity.

The Application of Committee Machine With Intelligent Systems to the Prediction of Permeability From Petrographic Image Analysis and Well Logs Data: A Case Study From the South Pars Gas Field, South Iran

Permeability is the ability of porous rock to transmit fluids. An accurate knowledge of reservoir permeability is necessary for reservoir management and development. This study presents an improved model based on the integration of petrographic data, conventional logs, and intelligent systems to predict permeability. Petrographic image analysis was employed to measure the optical porosity, pore types, pore morphologies, mineralogy, amount of cement, and type of texture. Available conventional log measurements include bulk density, neutron porosity, and natural gamma ray. The permeability was first predicted using the individual intelligent systems including a neural network (NN), a fuzzy logic (FL), and a neuro-fuzzy (NF) model. Afterwards, two types of committee machine with intelligent systems (CMIS) were used to combine the permeability values calculated from the individual intelligent systems: simple averaging and weighted averaging. In the weighted averaging, a genetic algorithm model was employed to obtain the optimal contribution of each expert. The results show that both of the CMIS performed better than NN, FL, and NF models acting alone.

Characteristics of Milankovitch Cycles in the Mid‐Permian Liangshan and Qixia Formations of the Sichuan Basin—Examples from Well‐Long17 and Well‐Wujia1

AbstractThe Liangshan and Qixia formations in the Sichuan Basin of central China were formed in the earlier middle Permian. Based on outcrop observation of the Changjianggou section at Shangsi, Guangyuan region and 3rd‐order sequence division in typical drillings, one‐dimensional spectrum analysis has been used to choose the better curve between the natural gamma ray spectrometry log(ln (Th/K)) in Well‐Long17 and the gamma ray log(GR) in Well‐Wujia1, respectively, for identifying Milankovitch cycles in Sequence PSQ1 which comprises the Liangshan and Qixia formations, and then to identify the variation in the Milankovitch cycle sequences. On this basis, the system tract and 4th‐order sequence interfaces in Sequence PSQ1 were found via two‐dimensional spectral analysis and digital filtering. Finally, a high‐frequency sequence division program was established. Among these cycles, long eccentricity (413.0 ka) and short eccentricity (123.0 ka) are the most unambiguous, and they are separately the major control factors in forming 4th‐order (parasequence sets) and 5th‐order (parasequences) sequences, with the average thicknesses corresponding to the main cycles being 11.47 m and 3.32 m in Well‐Long17, and 14.21 m and 3.79 m in Well‐Wujia1, respectively. In other words, the deposition rate in the beach subfacies is faster than that of the inner ramp facies. The ln(Th/K) curve is more sensitive than the GR as the index of relatively ancient water depth in carbonate deposition. One‐dimensional spectrum analysis of ln(Th/K) curve could distinguish the Milankovitch cycle sequences that arose from the Precession cycle (20.90 ka), with a much higher credibility. Sequence PSQ1 in Well‐Long17 contains 10 4th‐order sequences, and the growth span of Sequence PSQ1 consisting of the Liangshan and Qixia formations is about 4.13 Ma. The single deposition thickness of the long eccentricity cycle sequence has the characteristics of thinning and then thickening in the two‐dimensional spectrum, which could be used to identify the system tract interface of the 3rd‐order sequence. The precession sequence thickness remains stationary. As a result, the early deposition rate in the mid‐Permian of the Sichuan basin was very slow, remaining nearly stationary, and this reflects a sustained depositional environment. Whole‐rock carbon and oxygen isotope curves could also prove this point Milankovitch cycle sequence studies provide a basis for paleoenvironmental analysis and, as such, can be used to analyze ancient climate change, calculate deposition rate and deposition time, and carry out fine isochronous stratigraphic correlation.

Astrochronology of the Early Turonian–Early Campanian terrestrial succession in the Songliao Basin, northeastern China and its implication for long-period behavior of the Solar System

The first complete Early Turonian–Early Campanian lacustrine succession has been recovered from the SK-I south (SK-Is) borehole in the Songliao Basin (SLB), northeastern China. We conducted a detailed cyclostratigraphic study of natural gamma-ray (GR) log, thorium (Th) log, and magnetic susceptibility (MS) data from this core. Spectral analysis of the upper Quantou Formation (K2q3+4), Qingshankou Formation (K2qn), Yaojia Formation (K2y), and lower Nenjiang Formation (K2n1+2) reveals a hierarchy of meter- to decameter-scale cycling in the data. The wavelength ratios of the cycles in these stratigraphic units are ~20:5:2:1, corresponding with those of Milankovitch cycle periods of 405kyr (long eccentricity):100kyr (short eccentricity):37kyr (obliquity):20kyr (precession), indicating astronomical control on sedimentation. An astronomical time scale (ATS) was established by tuning interpreted 405kyr cycles to a 405kyr orbital eccentricity target curve, and to four SIMS U–Pb zircon radioisotope ages. This ‘absolute’ ATS provides precise numerical ages for stratigraphic boundaries, biozones, geological and geophysical events, and serves as a basis for correlation of strata and events between marine and terrestrial systems. The ages of the C33r/C34n geomagnetic polarity boundary in K2n2 and three short reversal events in K2y are estimated as 83.633Ma, 84.819–84.862Ma, 84.982–85.092Ma and 85.240–85.629Ma, respectively. Long-period amplitude modulations in the obliquity and eccentricity bands of the 405-kyr-tuned GR-Th series provide strong evidence that long-period orbital forcing influenced climate change and depositional processes in the SLB. The extracted amplitude modulations provide evidence that the orbits of Earth and Mars were not in secular resonance, and were undergoing chaotic interactions during this time, although the modulations do not match those of recent astronomical models.

Characteristics of the fault-related rocks, fault zones and the principal slip zone in the Wenchuan Earthquake Fault Scientific Drilling Project Hole-1 (WFSD-1)

Scientific drilling in active faults after a large earthquake is ideal to study earthquake mechanisms. The Wenchuan earthquake Fault Scientific Drilling project (WFSD) is an extremely rapid response to the 2008 Ms 8.0 Wenchuan earthquake, which happened along the Longmenshan fault, eastern margin of the Tibetan Plateau. In order to better understand the fault mechanism and the physical and chemical characteristics of the rocks, the WFSD project will eventually drill 5 boreholes along the two main faults. This paper focuses on the first hole (WFSD-1), which started just 178days after the earthquake, down to a final depth of 1201.15m. Petrological and structural analyses of the cores allowed the identification of fault-related rocks in the Yingxiu–Beichuan fault (fault gouge, cataclasite, and fault breccia), and the Principle Slip Zone (PSZ) location of the Wenchuan earthquake was determined.We found 12 fault zones in the entire core profile, with at least 10, including the Yingxiu–Beichuan fault zone, with a multiple cores structure and minimum width of ~100m. The co-seismic slip plane of the Wenchuan earthquake at depth (corresponding to the Yingxiu–Beichuan fault zone at the outcrop), as well as its PSZ, was expected to be located at the bottom of the fault zone (at 759m-depth). Instead, it was found at ~590m-depth with 1cm-wide fresh fault gouge, as determined by logging data such as temperature, natural gamma ray, p-wave velocity and resistivity, combined with the fresh appearance, magnetic susceptibility, and microstructure of the gouge. The Wenchuan earthquake slip plane has a dip angle of ~65°, showing the high-angle thrust feature. The distribution of fault gouge with several meters thick, the location of the Wenchuan earthquake's PSZ and the thickness of fresh gouge all imply a correlation between the width of the fault zone and the number of seismic events.

Potential of natural gamma-ray spectrometry for mapping and environmental monitoring of black-sandbeach deposits on the Northern coast of Sinai, Egypt

The concentrations and distributions of naturally occurring radioactive materials were studied with the aim of detecting and mapping radioactive anomalies as well as monitoring the environment for black-sand beach deposits in Northern Sinai, Egypt. For this purpose, ground gamma-ray spectrometric surveys were conducted using a portable GS-512 spectrometer, with an NaI (Tl) detector, on an area 77.5 km(2) in surface area located between the cities of Rafah and Elareish on the Mediterranean Sea coast. The results revealed that the black-sand beach deposits could be differentiated according to their total-count (TC) radioactivity into five normally distributed interpreted radiometric lithologic (IRL) units denoted by U1, U2, U3, U4 and U5. The computed characteristic TC radiometric statistics of these five IRL units range from 4.67 to 9.96 Ur for their individual arithmetic means. The computed arithmetic means for the three radioelements K, eU and eTh reach 0.46 %, 2.25 and 6.17 ppm, respectively for the whole study area. Monitoring the environmental effects of radioelement concentrations on the study area showed that the mean natural equivalent radiation dose rate from the terrestrial gamma-radiation of the whole area attains 0.33 mSv y(-1). This average value remains on the safe side and within the maximum permissible safe radiation dose (<1.0 mSv y(-1)) without harm to the individual, except at three scattered points reaching more than these values. Some of the local inhabitants in the region sometimes use black sands as a building material. Consequently, they are not recommended for use as building materials, because the inhabitants will, then, receive a relatively high radioactive dose generated mainly by monazite and zircon minerals, two of the main constituents of black sands.

Automated interpretation of nuclear and electrical well loggings for basalt characterization (case study from southern Syria)

Nuclear well logging, including natural gamma ray, density and neutron-porosity techniques are used with electrical well logging of long and short normal techniques in order to characterize the large extended basaltic areas in southern Syria. Four kinds of basalt have been identified: hard massive basalt, hard basalt, pyroclastic basalt and the alteration basalt products, clay, based on a statistical analysis approach with the threshold concept. The statistical conditions for such basalt characterization have been programmed in the present research to automatically interpret the well logging data for establishing and predicting the lithological cross-section of the studied well. A specific computer program has been written in Delphi for such purposes. The program is flexible and it can be used for other well logging applications by changing the statistical conditions and the well logging parameters. The program has been successfully tested on the Kodanah well logging data in southern Syria.

Monte-Carlo Simulation of Response Functions for Natural Gamma-Rays in LaBr3 Detector System with Complex Borehole Configurations

Usually, there are several methods, e.g. experiment, interpolation experiment-based, analytic function, and Monte-Carlo simulation, to calculate the response functions in LaBr3(Ce) detectors. In logging applications, the experiment-based methods cannot be adopted because of their limitations. Analytic function has the advantage of fast calculating speed, but it is very difficult to take into account many effects that occur in practical applications. On the contrary, Monte-Carlo simulation can deal with physical and geometric configurations very tactfully. It has a distinct advantage for calculating the functions with complex configurations in borehole. A new application of LaBr3(Ce) detector is in natural gamma-rays borehole spectrometer for uranium well logging. Calculation of response functions must consider a series of physical and geometric factors under complex logging conditions, including earth formations and its relevant parameters, different energies, material and thickness of the casings, the fluid between the two tubes, and relative position of the LaBr3(Ce) crystal to steel ingot at the front of logging tube. The present work establishes Monte-Carlo simulation models for the above-mentioned situations, and then performs calculations for main gamma-rays from natural radio-elements series. The response functions can offer experimental directions for the design of borehole detection system, and provide technique basis and basic data for spectral analysis of natural gamma-rays, and for sourceless calibration in uranium quantitative interpretation.

Mid-Ludfordian coeval carbon isotope, natural gamma ray and magnetic susceptibility excursions in the Mielnik IG-1 borehole (Eastern Poland)—Dustiness as a possible link between global climate and the Silurian carbon isotope record

The graptolite-bearing upper Silurian succession of the Mielnik IG-1 borehole (eastern Poland) represents a periplatform setting on a neritic carbonate platform located on the palaeocontinent of Baltica and records widely recorded positive mid-Ludfordian Carbon Isotope Excursion (CIE). The initial increase of δ13C values occurs in the uppermost part of the Neocucullograptus kozlowskii Zone whereas pronounced increase and maximal values (+6.74‰) are noted in the N. kozlowskii–Pseudomonoclimacis latilobus interzone (Pristiograptus dubius bloom interval). The thickness–time relation in the section indicates that the main, initial shift in carbon isotope ratio (of 2.7‰) occurred over a very short time, estimated to be around 4000years, and is coeval with a rapid initiation of deposition of rock-forming, silt-sized detrital dolomite and quartz. The CIE decline is interpreted as steeper than in inner shelf sections, and is coincident with a flooding event in the Ps. latilobus–Slovinograptus balticus Zone; whereas the end of the excursion is coeval with the next flooding surface marked by the Ps. Latilobus–Uncinatograptus acer graptolite assemblage. Combined SGR (Spectral Gamma Ray), facies, and faunal records during the CIE suggest prolonged sea-level lowstand conditions. The abundant detrital material (‘dolomite siltstone facies’), occurring exclusively in the CIE interval, is noted in microfacies as well as in the geophysics record—as pronounced negative excursions in total natural gamma ray and magnetic susceptibility, both resulting from dilution by diamagnetic and low-radioactivity minerals. The perfectly sorted, vertically equally-sized silt material contains unique, constant and low diversified grain assemblage (euhedral dolomite, quartz, minute ooids)—suggesting its provenance exclusively from the shallower and/or emerged parts of the carbonate platform interior. The spot findings of graptolites and nautiloids along with delicate parallel lamination of sediments indicates relatively deep environment, with absence of traction processes. These features, along with the lack of dolomite detritus in accompanying redeposited carbonates, suggest its derivation by wind. With regard to the earlier noted presence of aeolian detritus in the middle Ludfordian, we suggest dustiness as a plausible driving force of the CIE. In the hypothesis proposed, bioavailable Fe-bearing dust inflow in concert with antiestuarine circulation on shelfs, caused nutrient (N:P ratio) disturbances, resulting in methanogenesis in surface layer of the seas. The surface layer methanogenesis should resulting in bathymetric gradient of isotope fractionation, what is consistent with the CIE record. Coincidence of sea-level lowstand, low-latitude aridity, and gustiness of the global climate, are in accordance with the hypothetical short-lived glaciation in mid-Ludfordian time.

A preliminary study on the potential of the geothermal resources around the Gulf of Suez, Egypt

The Gulf of Suez is characterized by the presence of many hot springs and deep thermal wells scattered around its coastal areas. So it is considered one of the promised geothermal areas in Egypt. In this study, the main emphasis is to investigate the geothermal potential around the Gulf of Suez using the available logging and geothermometer datasets. The temperature profiles and well logging data of some hot springs and deep wells around or within the coastal area of the Gulf of Suez are used in this study. The temperature profiles are analyzed and some important thermophysical properties are estimated (geothermal gradient, thermal conductivity, heat flow, and specific heat capacity). Such analysis revealed that a medium to high geothermal gradient (22.0–30°C/Km) is given for the Gulf of Suez as a whole, with some spots of much higher gradient in the order of 35.0–44°C/Km (Ras Fanar and Hammam Faraun areas). The compiled thermal plots show that the thick evaporites and rock salt lithology, which is a major constituent in this area, attain the highest thermal conductivity (>3.10 W/m/K) and heat flow (>90 mW/m2) and the lowest specific heat capacity (<0.30 J/kg/K). The available gamma ray and the natural gamma ray spectroscopy logs are used to conduct a radioactive-based heat generation study using the characteristic radioactive nature of some elements like; 238U, 235U, 232Th, and of the isotope of 40K. A good linearity is observed between the heat production (A in microwatt per cubic meter) and the gamma ray (API) along a wide range of datasets (0–150 API) in all wells. The heat production factor increases in the carbonate lithology (up to 3.20 μW/m3) and is proportional to the shale volume. A geothermometer-based study is used to estimate the subsurface formation temperature and heat flow from the geochemical analysis of some water samples collected from the studied hot springs. The estimated thermal parameters are in harmony with the regional thermal regime concluded form logging data. A thermal basin growth study, in relation to the clay diagenesis is conducted concerning the thermal effects that take place with depth giving rise to another clay mineral (illite). Furthermore, a number of 2D thermal–burial history diagrams are constructed for the complied sections of some of the studied areas to show the vertical distribution of the estimated petrothermal properties. A reserve evaluation study is carried out to estimate the economic geothermal capacity of these hot springs to be used as alternative clean source for possible energy production (electricity) and other low-temperature purposes.

Testing Research of Slurry Water Concentration Based on Natural Gamma-Ray Attenuation Method

The slurry water concentration measurement device based on the natural gamma-rays attenuation method was designed in this paper; this natural gamma-ray is taken from a special kind of sand beach, which contains thorium. A number of experiments were made in the laboratory. The natural gamma-rays attenuation rules were obtained when it passing through the different concentration of the slurry water. The attenuation rules of natural gamma-ray passing through different concentration of slurry water were proved in theory and in tests. This provides reliable criterion for design of slurry water concentration detector.

Study on the Regularity of the Natural Gamma-Rays Attenuation in the Slurry Water

Gamma-ray density meter has been widely used in coal preparation plant to detect the concentration of the slurry water, but it require annual inspection, approval, and the protection of the radioactive sources causes a lot of inconvenience to the coal preparation plant. In this paper a natural mineral sand beach has been chosen as radioactive sources, which contains thorium. An experimental device has been designed to detect the concentration of the slurry water, the natural gamma-rays attenuation rules were obtained after lots of experiments in the laboratory when it passing through the different concentration of the slurry water, and the rules were proved in theory and in tests. This provides reliable basis for design of slurry water concentration measurement device.

Geophysical logging and magnetic susceptibility studies on the Dababiya Quarry Corehole, Dababiya Natural Park, southern Nile Valley, Egypt

Following the designation of a GSSP for the Paleocene/Eocene boundary in the Dababiya Quarry section in the southern Nile Valley of Egypt a continuously cored well was drilled in the hope of recovering better preserved lithologies and microfossils than in nearby outcrops. The well was continuously cored from the lower part of the El Mahmiya Member of the Esna Shale and penetrated the Dababiya Quarry Beds, El Hanadi Member of the Esna Shale, Tarawan Chalk and Dakhla Shale to a total depth of 140 m. Geophysical logging included Natural Gamma Ray (GR), Single-Point Resistivity (PR), Self-Potential (SP), and Resistivity, Short Normal (SN) and Long Normal (LN). Magnetic susceptibility was also measured. The Paleocene/Eocene and Cretaceous/Paleogene (K/P) boundaries. were recorded as sharp peaks on all logs particularly the GR and PR, and in the magnetic susceptibility log. Accordingly, in addition to the paleontological and lithological studies, the two boundaries are well delineated/characterized from the geophysical logging and magnetic susceptibility logs. This paper presents a brief description and discussion of the logging and magnetic susceptibility characteristics of the subsurface sequences encountered in the Dababiya Quarry Corehole (DQC).

Fractal analysis based on the continuous wavelet transform and lithofacies classification from well-logs data using the self-organizing map neural network

The main goal of this paper is to show that the fractal analysis based on the continuous wavelet transform is not able to improve lithofacies classification using the self-organizing map (SOM) neural network model from well-logs data. The proposed idea consists to inject many inputs in SOM neural network machines and to choose the best map. These inputs are: data set 1: the five raw well-logs data which are: the gamma ray, density, neutron porosity, photoelectric absorption coefficient and sonic well-log; data set 2: the estimated Holder exponents using the continuous wavelet transform of the data set 1; data set 3: data set 1 and the three radioactive elements concentrations; data set 4: the estimated Holder exponents of the data set 1 and the Holder exponents of the radioactive elements concentrations; data set 5: the estimated Holder exponents of the data set 1 and the three radioactive elements concentrations logs. Application of the proposed idea at two boreholes located in the Algerian Sahara shows that the Holder exponents estimated with the continuous wavelet transform as an input of the SOM neural network are not able to give geological details. However, the raw well-logs as an input give more details and precision especially when they are enhanced with the natural gamma ray spectrometry data.

Identifying Parasequence Sets Boundaries by Using Well Logging Data

Logging data, as representations of lithology and physical properties of stratum, hold abundant information related to sedimentary cycles with high vertical resolution. The use of various methods to extract and analyze corresponding information will greatly promote the quantitative level in the study of stratum sequence. SP mirror (spontaneous potential), the ratio of sand and mud, CN (neutron)-GR (natural gamma ray) curve overlay technique and wavelet analyses were comprehensively analyzed in this paper. Application in X block of Algeria that it has a great effect and is a good tool in the parasequence sets study. Continuously improve the level of utilization of logging data, full logging data in sequence stratigraphic analysis of the role and scope of application will be beneficial for the development of sequence stratigraphy.

Evaluation of Naturally Occurring Radioactive Materials (NORMs) in Inorganic and Organic Oilfield Scales from the Middle East

The distribution of natural nuclide gamma-ray activities and their respective annual effective dose rates, produced by potassium-40 (⁴⁰K), uranium-238 (²³⁸U), thorium-232 (²³²Th), and radium-226 (²²⁶Ra), were determined for 14 oilfield scale samples from the Middle East. Accumulated radioactive materials concentrate in tubing and surface equipment, and workers at equipment-cleaning facilities and naturally occurring radioactive materials (NORMs) disposal facilities are the population most at risk for exposure to NORM radiation. Gamma-spectra analysis indicated that photo-gamma lines represent the parents of 10 radioactive nuclides: ²³⁴Th, plutonium-239, actinium-228, ²²⁶Ra, lead-212 (²¹²Pb), ²¹⁴Pb, thallium-238 (²⁰⁸Tl), bismuth-212 (²¹²Bi), ²¹⁴Bi, and ⁴⁰K. These nuclides represent the daughters of the natural radioactive series ²³⁸U and ²³²Th with ⁴⁰K as well. The mean activity concentration of ²³⁸U, ²³²Th, and ⁴⁰K were found to be 25.8 ± 11.6, 18.3 ± 8.1, and 4487.2 ± 2.5% Bq kg⁻¹ (average values for 14 samples), respectively. The annual effective dose rates and the absorbed doses in air, both indoor and outdoor, for the samples were obtained as well. The results can be used to assess the respective hazard on workers in the field and represent a basis for revisiting current engineering practices.