Academic literature on the topic 'Nuclear logging probes'

Developments in the field of well logging over the last 25 years are reviewed. Surface and borehole instrumentation have evolved significantly, taking advantage of modern digital and analog integrated circuits. Most open‐hole petroleum well logs are now recorded digitally. Digital logs are also frequently acquired in cased‐hole petroleum, mineral, and geotechnical applications. Nuclear well‐log measurements have become accepted and reliable. New measurements include borehole compensated density and neutron‐porosity, sidewall epithermal neutron‐porosity, and most recently litho‐density. The neutron decay log, developed early in the 25‐year period, has undergone a number of major improvements since its introduction. Probes which make spectral measurements of natural gamma‐ray emission, and gamma‐ray emission from neutron interactions with matter have also been developed. Resistivity measurements are now made with probes which combine three or more sensors each with different depths of investigation so that information about the borehole invasion profile can be acquired. Acoustic logging methods have expressed major developments and improvements. The compensated sonic measurement was introduced early in the period along with the cement bond logging method. Interest in measurement of shear‐wave velocity has produced new direct shear‐wave measurements as well as improved acoustic probes for full‐waveform acoustic logging. Other interesting or promising methods which have been developed or improved during the period include the borehole televiewer, the borehole gravimeter, and the nuclear magnetic resonance log. The digital computer provides powerful capabilities for well‐log analysis both at the well site and in the office. Analysis of complex sand‐shale and carbonate formations using two or more logs in a simultaneous solution of a litho‐porosity model is now routine. Powerful signal processing techniques are being applied to “deconvolve” well logs, to enhance or synthesize images of the wellbore, and to estimate or extract information from full‐waveform acoustic logs. While new or improved measurements have been introduced and log analysts now have access to powerful computers and graphic work stations, understanding of the petrophysical significance of the measurements lags behind the basic hardware measurement and interpretation technology.

Orano Mining has relied on Nuclear Measurement Laboratories for several years to estimate calibration factors for borehole radiometric probes. The total gamma count rate recorded with a NaI(Tl) scintillation detector (NGRS probe) is converted into equivalent uranium grade using a calibration coefficient in s-1.ppmU-1 units, estimated thanks to different calibration blocks ranging from 0 to 10,000 ppm of uranium, at Orano CIME calibration facility in Bessines, France. Recently, Orano Mining embarked on an update of its measurement means by associating gamma spectrometry directly in the wellbore. Therefore, Orano Mining has recently tested a CeBr3 probe designed and developed by ALT (Advanced Logic Technology) to qualify a patented borehole spectroscopic method based on energy bands recently developed by CEA and Orano. In this context, we have implemented a fine Monte Carlo modelling of this new probe in order to correct the calibration coefficients as a function of different parameters such as the drilling diameter, the presence of a casing, the density of the mineralization, the distance of the probe with respect to the well or casing walls, etc. In the present work, we have simulated the CeBr3 probe in the concrete calibration blocks of Orano CIME. The MCNP model of the probe has been validated through a comparison with experimental data. The calibration coefficient determined by simulation is 11.6 s-1.ppm -1 > 10 % in total gamma counting, which is in good agreement with the one measured in Bessines, i.e. 10.6 s-1.ppm -1. The calculation vs. experiment agreement is also satisfactory (i.e. within 10 %) for spectroscopic energy bands used to characterize the uranium grade in case of disequilibrium in the uranium chain, when total count rate does not apply. This method recently developed for samples and boreholes will be tested in future work with this new CeBr3 probe.

In order to improve the logging interpretation accuracy for complex oil and water layers developed in tight sandstone reservoirs, this study takes the Chang 8 member of the Yanchang Formation in the Huanxian area as the research object, and two new fluid identification methods were constructed based on nuclear magnetic resonance (NMR) logging and array acoustic logging. Firstly, the reservoir characteristics of physical properties and conductivity were studied in the research area, and the limitations of conventional logging methods in identifying complex oil and water layers were clarified. Then, the sensitive parameters for identifying different pore fluids were established by analyzing the relationship between NMR logging and array acoustic logging with different pore fluids. On this basis, the fluid identification plate, composed of movable fluid apparent diffusion coefficient and effective porosity difference (Da-Δφe) by NMR logging data of D9TWE3 observation mode, and the other fluid identification plate, composed of apparent bulk modulus of pore fluid and elastic parameter sensitive factor (Kf-Fac), were constructed, respectively. Finally, these two fluid identification methods were used for reservoir interpretation of actual logging data. This study shows that the two new fluid identification methods constructed by NMR logging and array acoustic logging can effectively eliminate the interference of rock skeleton on logging interpretation, which make them more effective in identifying complex oil and water layers than the conventional logging method. Additionally, the two methods have their own advantages and disadvantages when used separately for interpreting complex oil and water layers, and the comprehensive interpretation of the two methods provides a technical development direction for further improving the accuracy of logging the interpretation of complex oil and water layers.

Shale oil reservoirs differ from conventional reservoirs in several aspects, including the sedimentary model, accumulation mechanism, and reservoir characteristics, which pose significant challenges to their exploration and development. Therefore, identifying the location of optimal spots is crucial for the successful exploration and development of shale oil reservoirs. Mobility, particularly in low-permeability shale oil reservoirs with nano-scale pores, is a crucial petrophysical property that determines the development plan. However, two-dimensional nuclear magnetic resonance (2D-NMR) is expensive and has limited applicability, although it can estimate shale oil mobility. Hence, it is of great significance to find a precise method for evaluating shale oil mobility using conventional logging. In this paper, we propose a new method for assessing shale oil mobility based on free oil porosity derived from the difference in flowing porosity detected at different ranges of logging, utilizing the Maxwell conductivity model and conductivity efficiency theory. Our study shows that longitudinal-T2 (T1-T2) NMR logging can accurately evaluate the mobility of shale oil. This is demonstrated by comparing the processing results obtained from our proposed method with those from 2D-NMR and laboratory NMR experiments. The predicted results based on conventional well logs also show good agreement with experimental results, confirming the effectiveness and reliability of our new method. Our proposed method carries reference significance for evaluating shale oil reservoir quality.

The Pinghu Formation is a low permeability sandstone reservoir in the KQT Region, East China Sea. Its porosity ranges from 3.6 to 18.0%, and permeability is distributed from 0.5 to 251.19 mD. The relationship between porosity and permeability was poor due to strong heterogeneity. This led to the difficulty of quantitatively evaluating effective reservoirs and identifying pore fluids by using common methods. In this study, to effectively evaluate low permeability sandstones in the Pinghu Formation of KQT Region, pore structure was first characterized from nuclear magnetic resonance (NMR) logging based on piecewise function calibration (PFC) method. Effective formation classification criteria were established to indicate the “sweet spot”. Afterwards, several effective methods were proposed to calculate formation of petrophysical parameters, e.g., porosity, permeability, water saturation (Sw), irreducible water saturation (Swirr). Finally, two techniques, established based on the crossplots of mean value of apparent formation water resistivity (Rwam) versus variance of apparent formation water resistivity (Rwav)—Sw versus Swirr—were adopted to distinguish hydrocarbon-bearing formations from water saturated layers. Field applications in two different regions illustrated that the established methods and techniques were widely applicable. Computed petrophysical parameters matched well with core-derived results, and pore fluids were obviously identified. These methods were valuable in improving low permeability sandstone reservoirs characterization.

The Xihu Sag in the East China Sea Basin is located at the edge of the eastern Chinese continent and has great exploration potential. In recent years, the development of low-permeability and tight sandstone gas has become an important area of exploration and development in the Huagang Formation (E3h) of the Xihu Sag. The tight sandstone reservoir in the Xihu Sag is characterized by serious heterogeneity, high water saturation, low resistivity, and a complex gas–water relationship. Because of these characteristics of tight sandstone reservoirs, it is difficult to perform an evaluation of them. In this work, a bimodal Gaussian density function was constructed using the data of high-pressure mercury intrusion (HPMI) and nuclear magnetic resonance (NMR); this approach was used to analyze the pore structure parameters. The reservoirs were divided into four types using the fitting parameter η, and the rock electric parameters that correspond to different pore structures were quite different. When combined with the log response equation of η with acoustic interval transit time (AC), density (DEN), and natural gamma (GR) logging curves, an evaluation method of gas-bearing properties that was based on the characteristics of the pore structure was established. Compared with the water saturation test of the sealing core, it was found that the water saturation calculated by the classification of the pore structure was more accurate than that obtained by the conventional method, and the error was less than 8.35%, which proves that this method is feasible and effective. The findings of this study can help provide a better understanding of the distribution characteristics of gas and water in tight sandstone and provide help for tight gas exploration and development.

Dans les puits pétroliers, de nombreux outils fonctionnant sur différents principes physiques sont couramment utilisés pour l’acquisition de données. Cette thèse se concentre sur les sondes de diagraphies nucléaires actives, faisant intervenir une source neutronique ou gamma. Elles sont utilisées dans l'industrie pétrolière pour caractériser la géologie des puits et ont été initialement développées pour réaliser des mesures quantitatives en conditions puits ouvert où la sonde est en contact direct avec la formation rocheuse. Une fois le puits pétrolier foré, un tube en acier est installé puis cimenté, les sondes ne sont alors plus en contact avec la formation rocheuse et les mesures sont considérées comme qualitatives en raison de la complexité de la géométrie et de l'atténuation du signal.Avec la raréfaction des ressources en hydrocarbures, le nombre de projets d’explorations diminue chaque année. Les compagnies pétrolières ont de plus en plus de puits dont il faut maintenir les capacités de production et d’autres en fin de vie qu’il faut abandonner, ce qui passe systématiquement par des mesures. La quantité de diagraphies en configuration puits tubé tend donc fortement à augmenter et il devient nécessaire d’améliorer leur interprétation.La problématique industrielle est de pouvoir caractériser de manière quantitative, dans un domaine à forte hétérogénéité radiale, l’ensemble de tous les éléments du puits (e.g. les fluides, le tubage, le ciment) et pas uniquement les paramètres du réservoir rocheux. L’approche développée dans la thèse se base sur le concept des fonctions de sensibilité des sondes diagraphiques nucléaires, qui représentent la dépendance en 3D de la mesure aux éléments du modèle et sont obtenues par simulation Monte-Carlo. Du fait du nombre important de variables, une inversion multiphysique prenant en compte l’ensemble des mesures des différentes sondes nucléaires (de porosité par diffusion neutronique, de densité par diffusion gamma, de lithologie par activation neutron-gamma) est indispensable.La première étape de la thèse a permis de comparer les codes Monte-Carlo de transport de particules GEANT4 et MCNP pour des applications de Géosciences. Les résultats montrent un très bon accord pour la physique gamma-gamma, un bon accord pour la physique neutron-neutron mais des écarts significatifs pour la physique neutron-gamma pour laquelle MCNP semble plus pertinent.La deuxième étape de la thèse a permis de valider expérimentalement les simulations Monte Carlo et de concevoir une méthode de calcul des fonctions de sensibilité numériques spécifique au domaine des puits tubés. La validation se traduit par une comparaison entre les fonctions de sensibilité expérimentales mesurées en centre d’étalonnage et les fonctions de sensibilité numériques calculées avec deux méthodes différentes, l’une basée sur des importances spatiales estimées par MCNP, l’autre sur les lieux d’interaction obtenus avec GEANT4. Les résultats montrent un bon accord expérimental entre les profils de sensibilité radial et axial mesurés et calculés, ce qui valide le concept de fonction de sensibilité avec une préférence pour la méthode des lieux d’interaction qui présente un contraste radial plus importante entre les différents constituants du puits.La troisième étape de la thèse a consisté à faire l’interprétation géologique d’une zone réservoir d’un puits tubé avec les fonctions de sensibilité. Les diagraphies neutron-gamma et de porosité prédites grâce aux fonctions de sensibilité sont comparées à celles mesurées en puits. Un modèle de terrain optimal est obtenu par itération, montrant une bonne capacité des algorithmes de prédiction à reproduire quantitativement en configuration puits tubé ce type de diagraphies à condition de choisir un étalonnage pertinent
In petroleum wells, many tools operating on different physical principles are commonly used for data acquisition. This thesis focuses on actives nuclear logging probes involving a neutron or a gamma source. They are used in the oil industry to characterize the well geology and have been initially developed to realize quantitative measurements in open hole conditions where the probe is directly in contact with the rock formation. Once the petroleum well is drilled, a steel casing is installed and cemented, the probes are then no longer in contact with the rock formation and the measurements are considered qualitative due to the complexity of the geometry and the signal attenuation.With the hydrocarbon resources rarefaction, the number of explorations projects decease each year. Petroleum companies have more and more mature wells whose production capacities must be maintained and others at the end of their life which must be abandoned. Those phases require systematically logging measurements. The quantity of logs in cased-hole configuration tends to increase a lot and it becomes necessary to improve their interpretation.The industrial problematic is to characterize quantitatively, in a filed with strong radial heterogeneity, all the components the well (e.g. the fluids, the casing, the cement) and not just the rock reservoir parameters. The approach developed in the thesis is based on the concept of sensitivity function of nuclear logging probes, which represents the 3D dependency of the measurement to the model elements and are obtained by Monte-Carlo simulation. Due to the large number of unknowns, a multiphysical inversion considering the all the measurements of the different nuclear probes (porosity by neutron diffusion, density by gamma diffusion, lithology by neutron-gamma activation) is essential.The first part of the thesis allowed to compare the Monte-Carlo particles transport codes GEANT4 and MCNP for Geosciences applications. Results show a very good agreement for the gamma-gamma physics and a good agreement for the neutron-neutron physics but significant discrepancies for the neutron-gamma physics where MCNP seems to be more relevant.The second part of the thesis allowed to experimental validate Monte-Carlo simulations and to design a sensitivity function computation method specific for the cased-hole configuration. The validation is a comparison between the experimental sensitivity functions measured in calibration center and the numerical sensitivity functions computed using two different methods, the first one based on spatial importances estimated with MCNP and the second one based on interaction locations obtained with GEANT4. The results show good experimental agreement between the measured and calculated radial and axial sensitivity profiles, which validates the concept of sensitivity function with a preference for the interaction locations method which presents greater radial contrast between the different components of the well.The third part of the thesis consisted of making the geological interpretation of a reservoir zone of a cased hole well with sensitivity functions. The neutron-gamma and porosity logs predicted using the sensitivity functions are compared to the measured logs. An optimal earth model is obtained by iteration, showing a good capacity of the fast forward modeling algorithums to quantitatively reproduce the logs in cased-hole configuration providing that a relevant calibration is apply

Well logging was invented in 1927 by two French brothers—Conrad and Marcel Schlumberger—and has been rapidly developed and plays an important role in the oil and gas industry. Well logging is involved in the whole life cycle of a well from its starting point of drilling to its abandonment and therefore is involved in the whole life cycle of an oil field, from the first well to the last. There are many kinds of logging methods, with different capabilities to evaluate different kinds of reservoirs. This chapter summarizes a brief history of well logging, the elements of a logging unit, the development of wireline logging to logging while drilling, and the mainstream technology in well logging. The technological difficulties of conventional logging are outlined and nuclear magnetic resonance is introduced to solve these problems, from which two questions are answered: why nuclear magnetic resonance is needed and how nuclear magnetic resonance works.

A chemical reactor has been developed that takes only carbon dioxide, water and electricity as inputs and produces a mixture of methanol and water. The system includes an electrolyzer that splits water into oxygen and hydrogen; and data logging capabilities for four temperatures probes, two pressure probes and three flow rates. The methanol synthesis unit was run under a number of flow conditions to help characterize its operation. One day of continuous temperature, pressure and flow rate data from the reactor will be presented to illustrate the system robustness. Finally, synchronized flow, temperature, and pressure data will be presented for the system as it undergoes step changes in the synloop flow rate. The results show that the flow rate through the reactor strongly influences the reactor temperature, which, in turn, influences the rate of methanol production.

Subsurface characterization of fluid volumes is typically constrained and validated by core analytical fluid saturation measurement techniques (example Dean-Stark or Open Retort methodology). As production in resource plays has progressed over time, it has been noted that many of these methods have a large error when compared to production data. A large source of the error seems to be that water saturations in tight rocks have been consistently underestimated in the traditional laboratory measurement techniques. Operators need improved fluid saturation measurements to better constrain their log-based oil-in-place estimates and forward-looking production trends. The overall goal of this study is to test a new laboratory workflow for fluid saturation quantification. Recent advancements have led to an innovative methodology where a closed retort laboratory technique is applied to samples from lithological rock types in the Williston, Uinta and Denever-Julesburg (DJ) basins. This new technique is specifically designed to better quantify and validate water measurements throughout the tight rock analysis process, as well as improved oil recovery and built-in prediction. A comparison of standard crushed rock analysis employing Dean-Stark saturation methods is compared to the closed retort results and observations discussed. Results will also be compared against additional laboratory methods that validate the results such as geochemistry and nuclear magnetic resonance. Finally, open-hole wireline logs will be utilized to quantify the impact on total water saturation and the oil-in place estimates based on the improved accuracy of the closed retort technique.