Search

In an attempt to characterize a reservoir in a field, importance is given to living models as it serves critical function in estimating if the reservoir under study is economically viable. Having a good knowledge of electrical response to reservoir rocks is important in characterizing and modeling the behavior of fluids at the subsurface. In this study, core plugs extracted from core barrels in a Niger Delta oil field were analyzed in the laboratory in order to determine the electrical properties of the samples and their relationship with each other and formation fluid. This was achieved by using a brine of a known concentration for simulation of core plugs. Results obtained show that for the unconsolidated sandstone, Formation resistivity factor increases with an increase in confining pressure. This characteristic depends on the porosity of the Formation and type of fluid present. Resistivity values in a reservoir will increase with an increase in capillary pressure and decrease with water saturation. The decrease in cementation exponent increases the rate of permeability in reservoir sand. However, resistivity values decrease with clay presence in reservoir sand.

An analysis was made of the development of sections of the D3ps formation of the Devonian terrigenous sequence of the Shkapovsky field, with a share of contact zones of more than 78%, which showed that the exploitation of deposits by vertical and deviated wells is unprofitable. Studies show that the development of reserves at the facility occurs along highly permeable interlayers located in the plantar. The construction of sectoral geological and hydrodynamic models showed a detailed distribution of residual oil reserves by area and section in areas with low production values. When analyzing the parameters of the operation of wells with horizontal completion, it was found that the selection of mobile oil reserves localized in a volume limited by the plane of the initial oil-water contact and the surface formed by the rise of the oil-water contact when pulling the water cone to the wells with horizontal completion is comparable with the period of reaching a water cut of 95%. The volumetric method was used to calculate the moving oil reserves in the area of ​​water cone formation. It is recommended to drill wells with horizontal completion as an effective method of additional production of residual oil reserves in fields with similar geological and physical conditions.

he most important element concerning efficiency and safety of developing mineral deposits is the consideration of the main structural features of the rock massif. The paper considers methodological issues of the GPR sensing application to study the internal structure of rocks. GPR surveys have been performed on a working bench of the Zhelezny mine, Kovdorsky GOK. Initially, the sensing has been performed by longitudinal profiling of the rock mass in its natural state to the depth of 20 m in combination with a telemetric survey of rock fracturing in the borehole located on the profile. Then the borehole was completely flooded with water, and GPR sensing studies have being repeated after 15, 30 and 60 minutes simultaneously with the registration of a decrease in the water level in the borehole. The GPR study results have been analysed in order to identify the effect of rocks' water-saturation on the recorded electromagnetic characteristics, and to determine the relationship of structural disturbance of rocks and their dielectric constant before and after water-saturation. It has been revealed that rock water saturation is an indicator that allows for more contrasting detection of rock disturbance zones due to the relatively insignificant difference in dielectric constant in the undisturbed and disturbed dry rock massif. The rock disturbance in an open pit slope has been estimated by GPR sensing, using water-filled borehole for contrast of measurements. The assessment has shown that water-saturated, porous, permeable, fractured rocks have higher dielectric constant values than dry / monolithic, weakly fractured rocks that have lower dielectric values permeability. It has been established that due to the water-saturation of rocks changes in the values of dielectric constant increased twice, and amounted to 0.6 units, while before saturation these changes were only 0.3 units, i. e. were two times lower. In order to substantiate the assessment of rock disturbance by GPR sensing, a comparative analysis has been made of GPR data and void of rocks in the vicinity of the borehole calculated on the basis of the filtration coefficient. The analysis has shown that the dielectric constant increases with increasing voids in the rock and, accordingly, with increasing water-saturation

Predicting reservoir parameters accurately is of great significance in petroleum exploration and development. In this paper, we propose a reservoir parameter prediction method named a fusional temporal convolutional network (FTCN). Specifically, we first analyze the relationship between logging curves and reservoir parameters. Then, we build a temporal convolutional network and design a fusion module to improve the prediction results in curve inflection points, which integrates characteristics of the shallow convolution layer and the deep temporal convolution network. Finally, we conduct experiments on real logging datasets. The results indicate that compared with the baseline method, the mean square errors of FTCN are reduced by 0.23, 0.24 and 0.25 in predicting porosity, permeability, and water saturation, respectively, which shows that our method is more consistent with the actual reservoir geological conditions. Our innovation is that we propose a new reservoir parameter prediction method and introduce the fusion module in the model innovatively. Our main contribution is that this method can well predict reservoir parameters even when there are great changes in formation properties. Our research work can provide a reference for reservoir analysis, which is conducive to logging interpreters’ efforts to analyze rock strata and identify oil and gas resources.

Threshold pressure gradient (TPG) is a key parameter determining the pore-scale fluid dynamics. In tight gas reservoirs, both gas and water exist in the porous rock, and the existing water can be divided into irreducible and movable water. However, how movable water saturation will influence TPG has not yet been investigated. Therefore herein, nuclear magnetic resonance (NMR) and high-pressure mercury intrusion (HPMI) experiments were performed to determine pore-scale water distribution, movable water saturation, and pore throat distribution in the core plugs. Subsequently, the air bubble method was used to measure TPG as a function of movable water saturation and permeability inside tight gas core plugs, finding that TPG increased from 0.01 MPa/m to 0.25 MPa/m with the movable saturation increased from 2% to 35%. Finally, a semi-empirical model was derived to describe the correlation between TPG, movable water saturation, and permeability, which performed better than previous models in the literature. These insights will advance the fundamental understanding of TPG in tight gas reservoirs and provide useful guidance on tight gas reservoirs development.

It is commonly assumed that dry and saturated sands exhibit similar cone resistance–relative density relationships. Some studies pointed out that partial saturation and calcareous sands with considerable fines content are potential factors affecting these relationships. However, there is experimental evidence in Shaqour Bull Eng Geol Environ 66:59-70, (2006) that clean uncemented quartz sand may exhibit lower cone resistance in saturated conditions. The present study aims on contributing towards better understanding the effect of water saturation on cone resistance in sand. For this purpose, Ticino sand samples were prepared dry and saturated in a calibration chamber and cone penetration tests were performed over a wide range of relative densities and at two consolidation stresses. Overall, it was observed that dry and saturated samples exhibited similar cone resistances. Only slightly higher cone resistances were observed for dry samples at the lower consolidation stress. Two anomalous samples, which were tested dry at medium relative density, were found to exhibit way higher cone resistances than expected from published cone resistance–relative density relationships. The Young's modulus was observed to be proportional to cone resistance and independent of whether a sample was tested dry or saturated, being therefore considered as more robust soil property for cone resistance relationships. [ABSTRACT FROM AUTHOR]

The electrical conductivity of porous dielectric materials saturated with water is usually determined by the bulk water conduction. However, the unsaturated state can be affected by a water film covering the unsaturated grain surface. Thus far, a few studies have been conducted on the study of the electrical conductivity with respect to water film covering the grain surface. In this study, the electrical conductivities of the Shirasu porous glass with three different uniform pore sizes (1.0, 0.5, and 0.2 μ m ) soaked in various NaCl solutions (0.001, 0.01, and 0.1 mol L - 1 ) were measured using an impedance meter while being dried at different water saturations. The resulting complex conductivities were fitted by a three-component Cole–Cole model to obtain Cole–Cole parameters. The conductivity values in these parameters were compared with the calculated conductivity values using tortuosities of surface and bulk conduction obtained from two different circuit models. The parallel model of bulk and surface water conduction could not reproduce accurate experimental results; however, the parallel plus series model, including the series connection of water film and bulk water around the meniscus, produced better results. This new model is expected to provide an improved quantitative evaluation of the electrical conductivity of unsaturated porous materials. Article Highlights: Electrical conductivity of the Shirasu porous glass at different water saturations was measured. The relationship between tortuosity of bulk and surface, and water saturation was obtained. A new model was proposed for explaining experimental results. [ABSTRACT FROM AUTHOR]

This article is devoted to integral analysis of physicomechanical properties of surface soils peculiar to Akkain, Kok Tobe and Shymbulak landslides of Trans-Ili Alatau located in close vicinity to city borders and in Almaty. While analyzing previous landslides of this region, the authors determined three main reasons of landslide occurrence on these mountain slopes: water saturation of surface subsoils during spring rainfalls, technogenic and gravitational reasons. It has been concluded that in many cases landslides occur due to water saturation of subsoils. It is proposed to consider landslide subsoils as two-phase medium. Algorithm of prediction of reduced physicomechanical properties of two-phase subsoil is summarized. Actual predictions are carried out using the proposed procedure and algorithms. The obtained results for certain types of loose subsoils, such as sandy clay, various loams and clays, are summarized in tables which are required for deep study of landslide occurrence in water saturated subsoils of these slopes on the basis of strain--stress states. [ABSTRACT FROM AUTHOR]

Summary: The change of the geometry of the flow field plate will affect the distribution of reaction gas and further change the reaction rate inside the cell. This article uses computational fluid dynamics as a research method to observe the improvement of fuel cell performance of different channel geometries. In the single‐channel simulation, channel of different shapes has very limited influence on current density, but it will change the water saturation, especially near the outlet of the channel. In this research, the performance of a variable waveform flow field plate is relatively better. This will be conducive to the promotion and application of proton‐exchange membrane fuel cells in real life. [ABSTRACT FROM AUTHOR]

Water saturation (Sw) is a vital parameter in the evaluation of hydrocarbon reservoir. Realistic estimation of Sw in shale reservoir is a challenging problem because of the presence of significant clay minerals and organic matter. The present study aims to estimate Sw of organic-rich Cambay Shale, Jambusar–Broach block, Cambay Basin, India, using an effective methodology and improved equation (TOC–clay equation), considering the appropriate corrections to counter the effect of clay minerals and organic matter in modifying resistivity. Advanced log like Litho-scanner has been utilized for the continuous estimation of clay content and total organic carbon (TOC), required for the estimation of Sw. Elemental capture spectroscopy and support vector regression were also applied for evaluation of clay content and TOC in one well where Litho-scanner log is not available. To investigate the effectiveness and applicability of the TOC–clay equation, results of Sw estimated from this equation and various other models have been compared with core Sw for a well. The analysis indicates that Sw derived from TOC–clay equation is having the closest agreement to core Sw data with an average absolute percentage error of 7.9% and coefficient of correlation 0.95. For other models, average absolute errors are significantly higher (16.8–32.7%). The application of TOC–clay equation will be useful for evaluation of the Cambay Shale reservoir. In addition, the resistivity-based TOC–clay equation used in this study is simple with a practical approach; it can be applied easily and efficiently for any organic-rich shale reservoir elsewhere. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental investigations of the propagation of shock waves in media made up of sand and of glass balls with volume content of liquid in the pore space from 0 to 100%. It has been established that gas microbubbles on the surface of dispersed particles in the case of complete saturation of the porous medium with water exert a great infl uence on the propagation velocity of waves. [ABSTRACT FROM AUTHOR]

In an attempt to reduce the errors and uncertainties associated with predicting reservoir properties for static modeling, seismic inversion was integrated with artificial neural network for improved porosity and water saturation prediction in the undrilled prospective area of the study field, where hydrocarbon presence had been confirmed. Two supervised neural network techniques (MLFN and PNN) were adopted in the feasibility study performed to predict reservoir properties, using P-impedance volumes generated from model-based inversion process as the major secondary constraint parameter. Results of the feasibility study for predicted porosity with PNN gave a better result than MLFN, when correlated with well porosity, with a correlation coefficient of 0.96 and 0.69, respectively. Validation of the prediction revealed a cross-validation correlation of 0.88 and 0.26, respectively, for both techniques, when a random transfer function derived from a given well is applied on other well locations. Prediction of water saturation using PNN also gave a better result than MLFN with correlation coefficient of 0.97 and 0.57 and cross-validation correlation coefficient of 0.89 and 0.3, respectively. Hence, PNN technique was adopted to predict both reservoir properties in the field. The porosity and water saturation predicted from seismic in the prospective area were 24–30% and 20–30%, respectively. This indicates the presence of good quality hydrocarbon bearing sand within the prospective region of the studied reservoir. As such, the results from the integrated techniques can be relied upon to predict and populate static models with very good representative subsurface reservoir properties for reserves estimation before and after drilling wells in the prospective zone of reservoirs. [ABSTRACT FROM AUTHOR]

(1) Background: The study was undertaken to evaluate the surface characteristics, microhardness, and color stability of PEEK materials related to water saturation and in vitro aging. (2) Methods: Custom specimens of unmodified and modified PEEK CAD/CAM materials were investigated: BioHPP, a ceramic reinforced PEEK, and Finoframe PEEK and Juvora medical PEEK, 100% PEEK materials. Forty-eight plates were sectioned in rectangular slices. The specimens were immersed in distilled water at 37 °C for a period of 28 days, and then subjected to aging by thermal cycling (10,000 cycles). Surface roughness was measured with a contact profilometer; nanosurface topographic characterization was made by Atomic Force Microscopy; Vickers hardness measurements were performed with a micro-hardness tester; color changes were calculated. All registrations were made before immersion in water and then subsequently once a week for 4 weeks, and after thermocycling. (3) Results: The studied reinforced and unfilled PEEK materials reached water saturation after the first week of immersion, without significant differences between them. The most affected from this point of view was the reinforced PEEK material. Thermocycling induces a significant increase inmicroroughness, without significant differences between the studied materials. In relation to the nanosurface topography and roughness, the reinforced PEEK material was the least modified by aging. The color changes after 4 weeks of water immersion and one year of simulated in vitro aging ranged from extremely slight to slight, for all materials. (4) Conclusions: Water absorption was associated with a decrease in microhardness. Surface characteristics are affected by water immersion and thermocycling. Perceivable or marked color changes of the materials were not detected during the study.

A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or the risk of forest fire. A membrane-based humidity sensor (MHS) can measure the relative humidity (RH) as an average value in such heterogeneous substrates via its sensitive tubular silicone membrane. This RH corresponds to the moisture-dependent water potential of the substrate. For humid conditions in soil, however, the RH is already larger than 98% and hence is insensitively correlated with the water potential. For such conditions, a step-like response of the MHS was found, which occurs if the silicone membrane is wetted with water. This appears to correspond to oversaturated water vapor and must be attributed to a phase-dependent sorption mechanism of the membrane. This effect allows the expansion of the range of applications of the MHS in the detection of liquid water, such as in dew point detection. Based on this, the dependency of the measurement signal on the mean water saturation in a substrate along the tubular membrane is demonstrated. A comparison of the measurement signal with an internal reference signal according to the MHS measurement principle makes it possible to distinguish this new, saturation-dependent measurement scale from the one used for RH measurement.

The contribution of natural lignocellulosic fibers to the reduction in wear damage in polymer resins is of interest, especially when two of these fibers can combine their respective effects. Wear properties of hybrid kenaf/banana epoxy composites have been investigated using three different total amount of fibers, 20, 30 and 40 wt.%, at loading forces up to 30 N and to sliding distances of up to 75 m. This demonstrated that the introduction of the highest level of fibers proved the most suitable for consistency of results and containment of wear with increasing load, as was also found from the morphological evaluation of wear degradation using scanning electron microscopy (SEM). Subsequently, tensile, flexural and impact properties of as-received and post-water-saturation hybrid composites were examined. The tests revealed a limited reduction in tensile and flexural strength, not exceeding 10% of the initial values, which were very high compared to similar materials, almost reaching 140 MPa for tensile strength and exceeding 170 MPa for flexural strength. In contrast, a higher standard deviation of values was found for impact strength, although the decrease in average values was only slightly above 10%. The results suggest the availability of these hybrids for wear-resisting applications in high-moisture environments, and the even more limited water absorption conferred by banana fibers added to kenaf ones.

The use of a solar architecture system is a feasible way to reduce the energy consumption of a building. The system also has important significance to the “Dual-carbon” plan. In this study, the heat transfer characteristics of a photo-thermal roof were analyzed in hot summer and cold winter zones; a model to calculate insulation performance was established. In the summer climate, the thermal performances of the photo-thermal roof and an ordinary roof were explored through experiments and simulations. The results showed that the heat transfer and temperature of the photo-thermal roof were lower than those of the ordinary roof. Heat transfer through a photo-thermal roof can be changed by adjusting the water flow of collectors. The water saturation of insulation materials is an important factor that affects the insulation performance of a roof. Compared with the ordinary roof, the change in water saturation was shown to have less impact on the insulation performance of the photo-thermal roof. The water saturation increased from 0 to 30%, while the heat transfer per unit area of the photo-thermal roof only increased by 0.9 W/m2; 97.3% lower than that of the ordinary roof. The effect of reducing the insulation material thickness was less for the photo-thermal roof than for the ordinary roof. When the insulation material thickness was reduced from 100 mm to 0 mm, the average temperature in the indoor non-working area reached 38.5 °C and 27.1 °C in the ordinary roof and the photo-thermal roof, respectively. The insulation thickness of the photo-thermal roof had little effect on the indoor air temperature. The research results provide a reference for the roof energy-saving design of new buildings and the roof energy-saving transformation of existing buildings.

Accurately measuring wettability is of the utmost importance because it influences several reservoir parameters while also impacting reservoir potential, recovery, development, and management plan. As such, this study proposes a new formulated mathematical model based on the correlation between the Amott-USBM wettability measurement and field NMR T2LM log. The exponential relationship based on the existence of immiscible fluids in the pore space had a correlation coefficient of 0.95. Earlier studies on laboratory core wettability measurements using T2 distribution as a function of increasing water saturation were modified to include T2LM field data. Based on the trends observed, water-wet and oil-wet conditions were qualitatively identified. Using the mean T2LM for the intervals of interest and the formulated mathematical formula, the various wetting conditions in existence were quantitatively measured. Results of this agreed with the various core wettability measurements used to develop the mathematical equation. The results expressed the validity of the mathematical equation to characterise wettability at the field scale. With the cost of running NMR logs not favourable, and hence not always run, a deep ensemble super learner was employed to establish a relationship between NMR T2LM and wireline logs. This model is based on the architecture of a deep learning model and the theoretical background of ensemble models due to their reported superiority. The super learner was developed using nine ensemble models as base learners. The performance of nine ensemble models was compared to the deep ensemble super learner. Based on the RMSE, R2, MAE, MAPD and MPD the deep ensemble super learner greatly outperformed the base learners. This indicates that the deep ensemble super learner can be used to predict NMR T2LM in the field. By applying the methodology and mathematical formula proposed in this study, the wettability of reservoirs can be accurately characterised as illustrated in the field deployment.

The estimation of rock petrophysical parameters is an essential matter to characterize any reservoir. This research deals with the evaluation of effective porosity (Pe), shale volume (Vsh) and water saturation (Sw) of reservoirs at Kumait and Dujalia fields, which were analyzed from well log and seismic data. The absolute acoustic impedance (AI) and relative acoustic impedance (RAI) were derived from a model which is based on the inversion of seismic 3-D post-stack data. NahrUmr formation’s sand reservoirs are identified by the RAI section of the study area. Nahr Umr sand-2 unit in Kumait field is the main reservoir; its delineation depends on the available well logs and AI sections information. The results of well logging interpretation showed a decrease of Sw and Vsh and an increase of effective porosity in the oil reservoir area, which coincides with the decrease of AI values. The existence of the water reservoir in Du-2 well revealed a convergence of the results of AI and effective porosity with those of Kumait wells, along with and some differential results of Sw and Vsh values that may be related to changes in lithology and fluid density. [ABSTRACT FROM AUTHOR]

Water accelerates the deformation and failure of rock and hence deteriorates the stability of rock structures on and under the ground. However, most of the previous studies examined the mechanical properties of rocks in air-dried and water-saturated conditions or the effect of water saturation on compressive strength. In this study, Brazilian tension tests were conducted with tuff, sandstone, and andesite in seven water saturation conditions between almost completely dried and water saturated. These conditions were controlled by varying the time the specimens were submerged in water and then dried. The test results showed that the Brazilian tensile strength of the tuff and the sandstone increases with a decrease of water saturation and then tends to be constant in very low water saturation conditions. In contrast, the Brazilian tensile strength of the andesite consistently increased with a decrease of water saturation. This trend for each of the rocks was also observed in the Young's modulus estimated from the loaddisplacement curves in the Brazilian tension tests as well as the uniaxial compressive strength obtained in the previous studies. The applicability of the Hertz contact theory to the Brazilian tension tests with these rocks in various water saturation conditions was validated by comparing the estimated and measured Young's modulus and by relating the Young's modulus and the strength. The results in this study are helpful for estimating the strength and Young's modulus of rocks in various water saturation conditions and for assessing the stability of underground structures. [ABSTRACT FROM AUTHOR]

Foam injection is a promising solution for control of mobility in oil and gas field exploration and development, including enhanced oil recovery, matrix-acidization treatments, contaminated-aquifer remediation and gas leakage prevention. This study presents a numerical investigation of foam behavior in a porous medium. Fractional flow method is applied to describe steady-state foam displacement in the entrance region. In this model, foam flow for the cases of excluding and including capillary pressure and for two types of gas, nitrogen (N2) and carbon dioxide (CO2) are investigated. Effects of pertinent parameters are also verified. Results indicate that the foam texture strongly governs foam flow in porous media. Required entrance region may be quite different for foam texture to accede local equilibrium, depending on the case and physical properties that are used. According to the fact that the aim of foaming of injected gas is to reduce gas mobility, results show that CO2 is a more proper injecting gas than N2. There are also some ideas presented here on improvement in foam displacement process. This study will provide an insight into future laboratory research and development of full-field foam flow in a porous medium. [ABSTRACT FROM AUTHOR]

A comparison was conducted between two wells, Kt-1and Kt-2, in Kumait and two wells, Du-1and Du-2, in Dujaila oil fields that belong to Mishrif formation, southern Iraq. Seismic inversion method was employed to detect oil and water reservoirs. The comparison included the behavior of acoustic impedance (AI) of fluids and the lithology with related petrophysical properties. The values of water saturation, Shale volume (Vsh), and effective porosity were compared between the AI, two fluid reservoirs. It was found that the AI value for the oil reservoir unit is relatively low to medium, whereas it was relatively medium for the water reservoir. Effective porosity value showed, in general, an increase in the oil reservoir and a slightly decrease in the water reservoir. The Vsh and water saturation (Sw) values of the oil reservoir unit were in general lower than those in the water reservoir, which indicates the presence of hydrocarbons accumulation. The lithology and porosity are the main factors affecting the acoustic impedance values. Despite the small difference in density between oil and water, these two fluids still show perceptible variation in their properties. [ABSTRACT FROM AUTHOR]

Water saturation is a key parameter in evaluating oil and gas reservoirs and calculating OIIP and GIIP for petroleum fields. The late Cretaceous Bahariya reservoir contains variable amounts of clay minerals. Bore hole logs are affected with those clay minerals particularly the density and resistivity logs. Several methods are acknowledged to determine the true water saturation from well logs in shaley sand reservoirs. Each method assumes a sort of corrections to amount of shale distributed in the reservoir. The scope of this petrophysical study is to integrate core analysis and bore hole logs to investigate the characteristics of water saturation in the Bahariya reservoirs. Comparison between most of the significant shaley sand methods is presented in this research. Reservoir lithology and mineralogy are explained by Elan-model while bore hole images are used for fine-tuning the electrofacies. Siltstone, shaley sand and clean sandstones are the main electrofacies that is characterizing the Bahariya reservoir rocks. For accurate saturation results, some core samples have been used for validating the log-derived water saturation. Dean stark and cation exchange capacity experiments are integrated with bore hole logs to calculate the error in water saturation for each method for best calibration. The successful integration between logs and core measurements led to convenient log evaluation and accurate understanding for the Bahariya reservoir in the prospective part of Abu Gharadig basin. [ABSTRACT FROM AUTHOR]

The determination of the formation water saturation, Sw, is a continuous process throughout the life of the fields. Multiple water saturation models are developed to increase the accuracy of calculating this critical parameter for both open-hole and cased-hole wells. All current open-hole water saturation models require prior knowledge of some field parameters namely; formation water resistivity, Rw, clay volume, Vc and rock electrical properties (m, n). It is normally assumed that those reservoir parameters as either constant for the entire reservoir section or change by zones. This is obviously an impractical assumption especially for the (m) and (n) parameters. Also, when a reservoir is under water injection for enhanced oil recovery, the water salinity may change throughout the reservoir, based on the distribution of the reservoir permeability and the salinity of the injected water, resulting in a variable Rw. This case represents a real challenge to the existing water saturation models. In this paper, a methodology to determine water saturation without the need for prior knowledge of the formation water resistivity or the rock electrical properties is developed. This approach is a generalization of the Passey total organic carbon, TOC, model which is developed to determine the organic richness of the unconventional reservoirs. The scientific basis of the method, the modification required to be applied in conventional reservoirs, the proof of concept using forward modeled cases and actual field applications in sandstone and carbonate reservoirs are performed to examine the theoretical and the practical applications of the methodology. Excellent results are obtained and discussed. [ABSTRACT FROM AUTHOR]

Berau Basin is assessed to have same potential in clastic sediments with Mesozoic and Paleozoic ages, where reservoirs and source rocks are similar to productive areas of hydrocarbons in Northwest Shield Australia. This study aims to identify the hydrocarbon prospect zones and potential rocks zones using petrophysical parameters, such as shale volume, porosity, water saturation and permeability. Petrophysical analysis of reservoir and source rock are carried out on three wells located in the Berau Basin, namely DI-1, DI-2 and DI-3 in Kembelangan and Tipuma Formation. Qualitative analysis shows that there are 4 reservoir rock zones and 4 source rock zones from thorough analysis of these three wells. Based on quantitative analysis of DI-1 well, it has an average shale volume (Vsh) 9.253%, effective porosity (PHIE) 20.68%, water saturation (Sw) 93.3% and permeability (k) 55.69 mD. DI-2 well’s average shale volume, effective porosity, water saturation and permeability values are 29.16%, 2.97%, 67.9% and 0.05 mD, respectively. In DI-3 well, average shale volume, effective porosity, water saturation and permeability values are 6.205%, 19.36%, 80.2% and 242.05 mD, respectively. From the reservoir zone of these three wells in Kembelangan Formation, there are no show any hydrocarbon prospect.

This article deals with the study of the initial water saturation effect of a porous medium on the oil recovery factor using a water-based nanosuspension. The initial water saturation of the porous medium in the computations varied within the range from 0 to 90%. The nanoparticle SiO2 concentration varied from 0 to 1 wt%. The particle sizes were equal to 5, 18, 22, and 50 nm. Experimentally measured wetting angles and the interfacial tension coefficient depending on the concentration and size of nanoparticles were used in computations. A mathematical model was developed, describing the transfer and diffusion of nanoparticles within the aqueous phase during immiscible displacement of oil by nanosuspension from a porous medium. Using the developed model, a systematic computational study of the effect of the initial water saturation of the core micromodel on the oil recovery factor using nanosuspension was carried out. It was revealed that with an increase in the initial water saturation, the oil recovery factor monotonically decreased in the case of displacement both by water and nanosuspension. It was shown that with an increase in the concentration of nanoparticles and a decrease in their size, the oil recovery factor increased. At that, the relative increase in the recovery factor had a maximum at an initial water saturation equal to 60%.

Abstract In this study, the effect of initial water saturation on the oil recovery for carbonate rocks is investigated using spontaneous imbibition experiments. The experiments are performed using 20 times diluted sea water as imbibing fluid and the sea water as initial water. In addition, the impact of pH and Ca2+, Mg2+, Na+, and K+ cations concentration change of imbibing fluid are investigated during tests. These results help to identify the active cations in the wettability alteration process of carbonate rocks during the low-salinity water injection. A mechanism is proposed to describe the effect of initial water saturation on the oil recovery by low-salinity water injection. The impact of initial water saturation on the wettability alteration might be positive or negative depending on its value and the rock permeability. The comparison of divalent cations concentrations shows that the minimum adsorption of Ca2+ and maximum desorption of Mg2+ lead to maximum oil recovery of spontaneous imbibition. The results confirm that three cations of Ca2+, Mg2+, and Na+ are active for wettability alteration of carbonate rocks in the presence of sea water as initial water and diluted sea as imbibing fluid, whilst the amounts of potassium remain constant.

It is known that the rock strength increases with an increase in loading rate. Many studies on the loadingrate dependence of rock strength have been performed under two environments, namely water-saturated and airdried conditions, and the loading-rate dependence has not been investigated well under the conditions of various water saturations observed in situ rock masses. In addition, the quantitative relation between the loading-rate dependence and water saturation has not been examined. In this study, the uniaxial compression test of Sanjome andesite under various water saturations was carried out and the dependence of the strength on the loading rate and water saturation was investigated. The test was performed with alternating two loading rates and the strength corresponding to each loading rate was determined from a single specimen. The test results show that the strength increase with a ten-fold increase in loading rate is almost the same under various water saturations and that the strength increases with a decrease in water saturation. Based on the test results, the theory to explain the dependence of the strength on the loading rate and water saturation was suggested. The variation in the strength was discussed to validate the theory.

Abstract Reservoir characterization is an important phase in oil and gas field development, which takes place during the appraisal phase of either a green field or a brown field upon which further development options are considered. Water saturation is a very important parameter in the general description of the reservoir as well as equity determination and dynamic modelling. Numerous equations have been developed which have been used to determine water saturation, but calculated water saturation values have been inconsistent with the saturation values determined from core analysis. This is generally due to their inability to account for the varying distribution of shale in the reservoir and the often incorrectness of their underlying assumptions. The major aim of this research is to develop a model which can be used to determine water saturation values using data from well logs; also, to compare the developed model with other existing models used in the oil and gas industry, using data from core analysis and well logs as the input data; and then finally, to discuss the results of the comparison, using the core-derived saturation values as the bench mark. The model is based on a parallel resistivity model, which is based on the assumption that the conductivity of the sandstone term and the shale term exist in parallel in the shaly-sand reservoir. The shale term in the reservoir of the model is based on the assumption that the clay-bound electrons do not move in the same conductivity path as the sandstone electrons. The shale conductivity term is based on the bound water saturation and the bound water resistivity. The modelled equation was compared in two scenarios using well log data and core data from two different reservoirs, and the model showed consistency in predicting the average water saturation in both reservoirs. The results of the comparison were positive for the modelled equation, as it gave coherent results in both comparison scenarios and matched reasonably the average water saturation of the selected reservoirs. This developed model can serve as an accurate means of determining water saturation in reservoirs, especially for reservoirs with similar characteristics as the selected reservoirs in this research.

This paper aims to investigate the water saturation effects on the thermal infrared radiation (IRR) characteristics of rock materials during deformation and fracturing processes. Three kinds of rocks, namely sandstone, granite, and marble, were adopted for tests. Uniaxial compression tests were carried out on oven-dried and water-saturated rock samples. The evolution of IRR temperature on rock surface was monitored and recorded with the aid of an infrared thermographic camera. Test results show that the IRR temperature of saturated samples is apparently higher than that of dry ones subjected to the same axial stress. After water saturation, the heating rate in elastic deformation phase, the IRR temperature increment at peak stress, and the IRR temperature on the new-formed fracture surface have a significant growth compared to dry condition. These indicate that the presence of water facilitates the release of thermal energy. The sensitivities of the heating rates in elastic deformation phase to water saturation are very distinct for the three rocks. This is possibly resulted from the mineral composition of rock types, especially the proportion of calcite and swelling clay minerals. The IRR temperature increment at peak stress for rock not only depends on the moisture condition, but is also relevant to the uniaxial compressive strength. [ABSTRACT FROM AUTHOR]

An unexpected surface subsidence in Mexico City on 19 May 2015 prompted a detailed geophysical investigation of the three‐dimensional structure of a collapsed‐soil mine located in a section of the Chapultepec Park in the vicinity of an artificial lake. As revealed from past geological explorations, the subsoil at the site consists of volcano‐sedimentary materials that were quarried in the mid‐20th century; subsequently, during the construction of the park, most of those mines had been only partially rehabilitated, with a potential risk of land subsidence. Near‐surface imaging techniques based on ambient seismic noise as well as microgravimetry, electrical resistivity tomography, shallow seismic refraction methods were evaluated for their applicability to characterize the structure of the collapsed mine. Tomography images computed using ambient‐noise array data characterized the extent of the underground mine showing high‐velocity anomaly, while results from microgravimetry and electrical resistivity tomography analyses indicated the structure through weak contrasts in gravity and resistivity anomalies. Additionally, electrical resistivity tomography results also illustrated the saturated nature of the subsoil. While different methods exhibit different capabilities to constrain such a small spatial feature, the present study highlighted the scope of an integrated approach in confirming the existence of potential voids as well as to estimate soil‐subsidence hazard. In terms of operational convenience and rapid performance, the ambient noise tomography method proved to be a relatively efficient and economical reconnaissance tool for identifying 3D velocity contrasts in an urban environment. [ABSTRACT FROM AUTHOR]

Water flooding characteristic curve is an important method for estimate recoverable reserves of water flooding reservoir. But conventional water flooding characteristic curve may deviate out from a straight line and up-warping phenomenon at the high water-cut stage, thus the adaptability of the conventional water flooding characteristic curve is poor for water flooding reservoirs. An improved water flooding characteristic curve is proposed. Firstly, a new characterization equation for the relationship between water-oil relative permeability ratio and water saturation, considering the limit problem of water flooding. Based on this equation, the new water flooding characteristic curve is derived theoretically. A method based on equation transformation is proposed to determine the parameters in the new equation. The new method is deduced to suit the development laws at the high water-cut stage. And the conventional water flooding characteristic curve can be a special case of the new method at high recovery conditions. The application case shows that the error is only 0.4%. The new method is more accurate than the conventional model in predicting production performance and meet the needs of oilfield production. [ABSTRACT FROM AUTHOR]