Natural Gamma Activity Research Articles

К вопросу о методике литолого-петрофизических исследований каменного материала (в процессе бурения нефтегазовых скважин)

This article discussessome aspects of the methodology for preparingsludge andcoresamples for lithological and petrophysicalstudies. Methods for obtainingrockmaterial(sludge,core) are described interms of determiningthemoment of openingthereservoir layer,tyingthecore in depth, and sampling the sludge. A sludge collector has been proposed that makes it possible to obtain sludge of overall fractions washed from the drilling fluid. The effectiveness of the harmonic analysis method, which takes into account the lithology of the studied section and changes in drilling parameters to optimize the frequency of sludge sampling during drilling, is shown. A system for placing sludge sampling points has been justified to increase the information content of the study of well sections. An analysis of the actual material on the connection of sludge to formations using natural gamma activity in wells drilled in the conditions of the Saratov Volga region was carried out. The distribution of the residual values of the burial depths according to thesludge and well logging allowed us toconclude that in the vast majority (> 75%) ofcases, the binding ofsludge during geological testing iscarried out withsatisfactory accuracy. The implementation ofsome elements of the above described interpretation techniques is shown using the example of one of the wells located in the northwestern part of the near-shore zone of the Caspian basin.

Predicting 2D geotechnical parameter fields in near-surface sedimentary environments

Abstract For a detailed characterization of near-surface environments, geophysical techniques are increasingly used to support more conventional point-based techniques such as borehole and direct-push logging. Because the underlying parameter relations are often complex, site-specific, or even poorly understood, a remaining challenging task is to link the geophysical parameter models to the actual geotechnical target parameters measured only at selected points. We propose a workflow based on nonparametric regression to establish functional relationships between jointly inverted geophysical parameters and selected geotechnical parameters as measured, for example, by different borehole and direct-push tools. To illustrate our workflow, we present field data collected to characterize a near-surface sedimentary environment. Our field data base includes crosshole ground penetrating radar (GPR), seismic P-, and S-wave data sets collected between 25 m deep boreholes penetrating sand- and gravel dominated sediments. Furthermore, different typical borehole and direct-push logs are available. We perform a global joint inversion of traveltimes extracted from the crosshole geophysical data using a recently proposed approach based on particle swarm optimization. Our inversion strategy allows for generating consistent models of GPR, P-wave, and S-wave velocities including an appraisal of uncertainties. We analyze the observed complex relationships between geophysical velocities and target parameter logs using the alternating conditional expectation (ACE) algorithm. This nonparametric statistical tool allows us to perform multivariate regression analysis without assuming a specific functional relation between the variables. We are able to explain selected target parameters such as characteristic grain size values or natural gamma activity by our inverted geophysical data and to extrapolate these parameters to the inter-borehole plane covered by our crosshole experiments. We conclude that the ACE algorithm is a powerful tool to analyze a multivariate petrophysical data base and to develop an understanding of how a multi-parameter geophysical model can be linked and translated to selected geotechnical parameters.

Determination of Th, U and K contamination in materials used in a low background detector by nuclear measures

In a low background detector high contamination of U, Th and K in the materials used couldn't be accepted. All materials furnished should be tested and measures optioned have a sensibility of 10−11−10−12g/g. Such measures need an adequate irradiation time and flux. An optimum cooling time and other parameters should be optimised in order to reach the goal. Analysis are made by Neutron Activation Analysis (NAA) while analysis of the natural gamma activity are made by long time measures in a low background detector.

Negative correlation between porosity and hydraulic conductivity in sand-and-gravel aquifers at Cape Cod, Massachusetts, USA

Although it may be intuitive to think of the hydraulic conductivity K of unconsolidated, coarse-grained sediments as increasing monotonically with increasing porosity Φ, studies have documented a negative correlation between these two parameters under certain grain-size distributions and packing arrangements. This is confirmed at two sites on Cape Cod, Massachusetts, USA, where groundwater investigations were conducted in sand-and-gravel aquifers specifically to examine the interdependency of several aquifer properties using measurements from four geophysical well logs. Along with K and Φ, the electrical resistivity R 0 and the natural gamma activity γ of saturated deposits were determined as functions of depth. Qualitative examination of results from the first site implies a negative correlation between K and Φ that is substantiated by a rigorous multivariate analysis of log data collected from the second site. A principal components analysis describes an over-determined system of inversion equations, with approximately 92% of the cumulative proportion of the total variance being accounted for by only three of the four eigenvectors. A subsequent R-mode factor analysis projects directional trends among the four variables ( K, Φ, R 0 and γ), and a negative correlation between K and Φ emerges as the primary result.

Natural gamma-ray activity compared to geotechnical and environmental characteristics of near surface marine sediments

The main purpose of the present study is to investigate the use of natural gamma activity as a measure of geotechnical properties such as density, porosity, water content and shear strength of near surface marine sediments. Natural gamma activity data were acquired under in situ conditions at two locations in the Arkona basin of the Baltic Sea. Sedimentological parameters were determined at intervals of 10 cm in three gravity cores taken near the geophysical locations. The values of natural gamma radioactivity ranged from 5 API at the sea floor to 75 API at approximately 5 m below sea floor. High correlation coefficients (up to ±0.79) were observed between natural gamma radioactivity and silt and clay content, wet bulk density, porosity, water content and shear strength. Moreover, most of the correlations were tested as significant by using the Student's t-test of significance. Since the intensity of natural gamma activity is proportional to the mass of radioactive substance (in this case, clay minerals), the increase of natural gamma activity in near surface marine sediments may be related to compaction processes. During compaction (cementation is not considered), as porosity is reduced, there would be an increase in the amount of clay minerals for the same volume of unconsolidated sediment, causing an increase in the natural gamma activity.

Petrophysical characterisation of parna using ground and downhole geophysics at Marinna, central New South Wales

Parna, an aeolian sediment of dominantly clay size, forms a significant component of the regolith developed in western New South Wales. These materials blanket parts of the contemporary landscape and, in places, they form surficial deposits in excess of 8 m thick. Recent studies have suggested that parna constitutes a significant store and source of soluble salts, hence its significance to land management. This paper describes the mineralogical and petrophysical characteristics of parna, making specific reference to materials adjacent to a recognised parna section at Marinna, near Junee, which is located in the Murrumbidgee catchment. Rising water tables and dryland salinity have been identified as major concerns to the overall health of this catchment. Therefore information on the distribution and movement of salt within the upper reaches of this catchment is important, as is the role of parna in controlling these dynamics. Results from multiparameter borehole geophysical studies indicate that parna is characterised by sub-horizontal variations in conductivity and natural gamma activity. These properties are attributed to contrasts in the porosity and permeability of these materials and to variations in their composition. Significant vertical conductivity contrasts have been noted between parna and underlying saprolite, with the results from EC1:5 measurements and downhole induction logs suggesting that conductivity is primarily controlled by textural variations rather than the soluble salt and moisture content of these materials. Ground electromagnetic surveys (EM31) suggest that areas covered by parna may exhibit marked lateral variations in average conductivity attributable to differences in the thickness and proportion of parna in these materials.

About the spectral composition of natural gamma activity

About the spectral composition of natural gamma activity

Results from Surface and Borehole Geophysical Investigations During Deep Gas Drilling in Siljan Impact Structure: ABSTRACT

Seismic data reveal high-amplitude subhorizontal reflections in the crystalline rock of the Siljan impact structure in Sweden. Pre-drilling geophysical investigations, included gravity, magnetics, VLF and magnetotelluric surveys. By using vertical seismic profiling (VSP), the depth in the borehole has been related directly to times on the seismic sections and ensures that reflections are real. All of the surface investigations indicate the Siljan Ring area to be a geophysically anomalous region. A composite log, which includes the standard logs run in most boreholes, shows both gradual and abrupt changes in the amount of natural gamma activity, sonic velocity, and resistivity of the rock. The discrepancy between the maximum caloper reading and the minimum reading on the four-arm caloper log gives a clear indication of the anisotropic horizontal stress conditions present in the rock. The resulting elliptical and rugose hole caused several compilations both in data acquisition and processing. The micro electric scanner tool (FMS) display shows the configuration of the individual fractures within fracture zones. Current studies using the geochemical tool string, consisting of the NGS, GST, and AACT tools will help evaluate the chemical composition of the rock.

The problem of the age of radioactive mineralization in the singhbhum shear zone, india

The age of smoky quartz was determined by measurement of thermoluminescence, comparing the value with that for quartz subjected to laboratory gamma radiation and using measured natural gamma activity to estimate duration of exposure. The average age, 940 + or - 160 million years is believed to be more reliable than Pb/U and Pb/Th ages of 439-518 m.y. because of evidence for isotope fractionation.

The Use of Natural Gamma Activity to Measure the Composition of Pork and Lamb Samplesa

SUMMARYThe gamma activity of 20 pork and 15 lamb samples, varying over a wide range in composition and each weighing 38 lb, was used to predict their chemical composition in terms of percentage of water, fat, and protein. All correlations between the estimated potassium content of the samples and the sample components were highly significant. However, the standard errors of the regression equations indicated that none of the relationships between the chemical components of the lamb samples and their potassium content were close enough to be of practical significance. The results on the pork samples seemed more promising. The standard errors suggest that chemical analysis should be used when accurate results are required or when the range in composition is small. However, advances in instrumentation may increase the accuracy of the K‐40 method. Some of the difficulties in applying the method to the measurement of meat composition are discussed.

APPLICATIONS OF NATURAL GAMMA ACTIVITY MEASUREMENTS TO MEATa

APPLICATIONS OF NATURAL GAMMA ACTIVITY MEASUREMENTS TO MEAT^a

Spectral Gamma-Ray Logging

Published in Petroleum Transactions, AIME, Vol. 207, 1956, pages 30–35. Abstract The introduction of the scintillation counter into field use for gamma-ray well logging has provided a new tool with special utility for the determination of natural radioactivity of sediments. Previous subsurface gamma-ray measurements have indicated only the total amount of radioactivity of the sediments. With the scintillation counter, the relative amounts of the elements which emit gamma radiation can be determined. Sediments logged included 35 zones in wells located in the Texas Gulf Coast, East Texas, and West Texas. Although the data obtained from measurements made to date are not sufficient to evaluate the possibilities of spectral logging, it appears likely that spectral measurements will yield information of geologic value. Introduction Although variations in the natural radioactivity of sediments were recognized as early as 1909, the application of such variations to borehole logging was not made until almost 30 years later. A group of Russian workers in the early 1930's were successful in making crude measurements of natural gamma activity in an oil well borehole. The first practical gamma-ray logging system was developed by Howell and Frosch in 1939. Induced radioactivity, or neutron, logging appeared soon after the introduction of gamma-ray logging. After early work had demonstrated the potentialities of radioactivity logging, development of sensitive and stable logging equipment for field use followed, so that neutron and natural gamma logs are now run routinely and have proved to be extremely valuable in characterizing subsurface formations.