Reservoir Samples Research Articles

Miniaturized Pathogen Detection System Using Magnetic Nanoparticles and Microfluidics Technology

Rapid detection of a biological agent is essential to anticipate a threat to the protection of biodiversity and ecosystems. Our goal is to miniaturize a magnetic pathogen detection system in order to fabricate an efficient and portable system. The detection device is based on flat, multilayer coils associated with microfluidic structures to detect magnetic nanoparticles linked to pathogen agents. One type of immunological diagnosis is based on the measurement of the magnetic sensitivity of magnetic nanoparticles (MNPs), which are markers connected to pathogens. This method of analysis involves the coupling of antibodies or antigen proteins with MNPs. Among the available magnetic techniques, the frequency mixing method has a definite advantage by making it possible to quantify MNPs. An external magnetic field composed of a low- and a high-frequency field is applied to the sample reservoir. Then, the response signal is measured and analyzed. In this paper, magnetic microcoils are implemented on a multilayer Printed Circuit Board (PCB), and a microfluidics microstructure is designed in connection with the planar coils. Simulation software, COMSOL version 5.3, provides an analytical perspective to choose the number of turns in magnetic coils and to understand the effects of changing the shape and dimensions of the microfluidics microstructure.

New Insights into the Understanding of High-Pressure Air Injection (HPAI): The Role of the Different Chemical Reactions

High-pressure air injection (HPAI) is an enhanced oil recovery process in which compressed air is injected into deep, light oil reservoirs, with the expectation that the oxygen in the injected air will react with a fraction of the reservoir oil at an elevated temperature to produce carbon dioxide. The different chemical reactions taking place can be grouped into oxygen addition, thermal cracking, oxygen-induced cracking, and bond scission reactions. The latter reactions involve the combustion of a flammable vapor as well as the combustion of solid fuel, commonly known as “coke”. Since stable peak temperatures observed during HPAI experiments are typically below 300 °C, it has been suggested that thermal cracking and combustion of solid fuel may not be important reaction mechanisms for the process. The objective of this work is to assess the validity of that hypothesis. Therefore, this study makes use of different oxidation and combustion HPAI experiments, which were performed on two different light oil reservoir samples. Modeling of those tests indicate that thermal cracking is not an important reaction mechanism during HPAI and can potentially be ignored. The work also suggests that the main fuel consumed by the process is a flammable vapor generated by the chemical reactions. This represents a shift from the original in situ combustion paradigm, which is based on the combustion of coke.

تصميم نظام غمر المياه لحقل الدفا النفطي

Currently, water-flooding is responsible for a big portion of world oil production. The vertical sweep efficiency and the areal coverage each of these requires careful sampling to get represented reservoir rock and fluid properties measures of reservoir heterogeneity, Economically, a pilot is a desirable tool for studying oil recovery performance on reservoir sample and then scaled up to yield the performance to be expected from field performance. Defa field was produced since 1968 with good oil flow rate reaching 200,000 BOPD but during the life of the field, the production decreased to 50,000 BOPD in 2001. So, this study was conducted to increase oil production by add some energy to the reservoir to increase average reservoir pressure and try to maintain it to initial pressure and to increase displacement and sweep efficiency. The water flooding design was implemented in sector model in the Defa field using five spots pattern. The study was performed by using Excel and Water Drive software to achieve a good water flooding design. When comparing the results obtained from two calculation methods, the minimum error was equal 0.03 percent and the maximum error was around 12 percent. So, the results were acceptable and the process was recommended to the Defa-field. Keywords: Water flooding; Software; Fractional Flow, Break through.

A Method for Optimizing Production Layer Regrouping Based on a Genetic Algorithm

As waterflooding multi-layer reservoirs reach the high-water-cut stage, inter-layer conflicts become increasingly serious, leading to a worsening development effect over time. Production layer regrouping is an effective approach for resolving inter-layer conflicts and improving waterflooding efficiency. At the current stage, there are limitations to most of the methods of production layer regrouping. This article proposes a smart method for optimizing the layer regroup plan based on a genetic algorithm. Comprehensively considering various factors that affect the regroup of layers, such as layer thickness, porosity, permeability, remaining oil saturation, remaining reserves, recovery ratio, water cut, etc., based on the combination principle of “smaller intra-group variance and larger inter-group variance of each influencing factor are expected”, a genetic algorithm is used to calculate the fitness value of the initial combination schemes, and the advantageous schemes with higher fitness values are selected as the basis of the next generation. Then, crossover and mutation operations are performed on those advantageous schemes to generate new schemes. Through continuous selection and evolution, until the global optimal solution with the highest fitness value is found, the optimal combination scheme is determined. Comparative analysis with numerical simulation results demonstrates the reliability of this intelligent method, with an increased oil recovery of 4.34% for the sample reservoir. Unlike selecting a preferable plan from a limited number of predefined combination schemes, this method is an automatic optimization to solve the optimal solution of the problem. It improves both efficiency and accuracy as compared to conventional reservoir engineering methods, numerical simulation methods, and most mathematical methods, thus providing effective guidance for EOR strategies of waterflooding reservoirs in the high-water-cut stage.

Pannonibacter tanglangensis sp. nov., a New Species Isolated from Pond Sediment.

Two bacterial strains (XCT-34T and XCT-53) isolated from sediment samples of an artificial freshwater reservoir were analyzed using a polyphasic approach. The two isolates are aerobic, Gram-stain-negative, oxidase-negative, catalase-positive, motile with polar flagella, rod-shaped, and approximately 1.4-3.4 × 0.4-0.9μm in size. Phylogenetic analyses based on 16S rRNA gene and whole-genome sequences showed that the two strains formed a distinct branch within the evolutionary radiation of the genus Pannonibacter, closest to Pannonibacter carbonis Q4.6T (KCTC 52466). Furthermore, lower than threshold average nucleotide identity values (ANI, 85.7-86.4%) and digital DNA-DNA hybridization values (dDDH, 22.3-30.5%) of the two strains compared to the nearest type strains also confirmed that they represented a novel species. Genomic analyses, including annotation of the KEGG pathways, prediction of the secondary metabolism biosynthetic gene clusters and PHI phenotypes, supported functional inference and differentiation of the strains from the closely related taxa. Results of chemotaxonomic and physiological studies revealed that their distinct phenotypic characteristics distinguished them from existing Pannonibacter species. Thus, the two strains are considered to represent a novel species of Pannonibacter, for which the name of Pannonibacter tanglangensis sp. nov. is proposed, with XCT-34T (= KCTC 82332T = GDMCC 1.1947T) as the respective type strain.

Research on the influence of dynamic contact angle of mercury meniscus on the interpretation of rock pore throat radius in mercury intrusion experiments

Addressing the lack of measurement methods for dynamic contact angles of mercury meniscus in mercury intrusion porosimetry experiments and the unclear understanding of the impact of dynamic contact angles on the interpretation of pore throat radius in rocks, a new type of closed mercury intrusion characteristic curve (O-R curve) is constructed utilizing the withdrawal curve O and the secondary injection curve R obtained from the experiments. Based on the excellent wetting and de-wetting correlation characteristics at the equal mercury saturation points on this curve, a method for measuring the dynamic contact angles of mercury meniscus (O-R loop method) is established. Taking the Chang 63 tight oil reservoir samples from the Nanliang Oilfield in the Ordos Basin of China as an example, this method is applied to investigate the dynamic contact angles of mercury meniscus in mercury intrusion porosimetry experiments and the impact on the interpretation of pore throat radius in rocks. The results indicate that the dynamic contact angles of mercury meniscus changes significantly during the experiments, which cannot be ignored. And the smaller pore throats lead to more severe deformation of mercury meniscus, resulting in higher wetting resistance coefficients and hysteresis angles. Calculations reveal that the pore throat radius interpreted using the modified Washburn equation (which adopts dynamic contact angles) are generally larger than those interpreted using the conventional Washburn equation (which adopts static contact angles), with relative errors ranging from 12.2% to 54.7%. The smaller the pore throats, the larger the relative errors. The analysis shows that the conventional Washburn equation significantly underestimates the reservoir pore throat radius due to the neglect of the dynamic contact angle, while the modified Washburn equation provides more accurate interpretation. Overall, this research provides a method for calculating the dynamic contact angle in mercury intrusion porosimetry experiments and has important reference significance for the accurate interpretation of rock pore throat radius.

Continual learning approaches to hand–eye calibration in robots

This study addresses the problem of hand–eye calibration in robotic systems by developing Continual Learning (CL)-based approaches. Traditionally, robots require explicit models to transfer knowledge from camera observations to their hands or base. However, this poses limitations, as the hand–eye calibration parameters are typically valid only for the current camera configuration. We, therefore, propose a flexible and autonomous hand–eye calibration system that can adapt to changes in camera pose over time. Three CL-based approaches are introduced: the naive CL approach, the reservoir rehearsal approach, and the hybrid approach combining reservoir sampling with new data evaluation. The naive CL approach suffers from catastrophic forgetting, while the reservoir rehearsal approach mitigates this issue by sampling uniformly from past data. The hybrid approach further enhances performance by incorporating reservoir sampling and assessing new data for novelty. Experiments conducted in simulated and real-world environments demonstrate that the CL-based approaches, except for the naive approach, achieve competitive performance compared to traditional batch learning-based methods. This suggests that treating hand–eye calibration as a time sequence problem enables the extension of the learned space without complete retraining. The adaptability of the CL-based approaches facilitates accommodating changes in camera pose, leading to an improved hand–eye calibration system.

Validation of a New Liquid Asymmetric-Electrode Plasma Optical Emission Spectroscopy (LAEP-OES) Method for Measurement of Total Mercury in Tuna.

Mercury intake is caused by eating seafood, such as tuna and other predatory fish species. To reduce the health risks of mercury intake, it is necessary to continuously measure and monitor mercury concentrations at fish farms and markets. We have developed a compact system that can detect multiple heavy metals by liquid asymmetric-electrode plasma optical emission spectroscopy (LAEP-OES). The validity of the LAEP-OES method for total mercury levels was evaluated using standard solutions, certified substances, and specimens of bluefin tuna and other fish species. All specimens were dissolved in 4 M lithium hydroxide solution and then dispensed into a sample reservoir well of the single-use measurement reagent pack. Total mercury levels were automatically measured within 15 min of placement into the dedicated equipment. A total of 102 fish specimens, classified into 10 fish species, were evaluated using the new method and the results were compared to those obtained from validated analytical methods. LOD (0.02 mg/kg), LOQ (0.07 mg/kg), repeatability (4.0%), intermediate precision (9.8%), and trueness (recoveries 107%) of the proposed method were within satisfactory limits for total mercury levels in fish. Additionally, when using various fish species, the method had a strong positive correlation with the results of cold-vapor atomic absorption spectrometry (CV-AAS, the official method) with Spearman rs = 0.984. The LAEP-OES method can be used for measuring total mercury levels in bluefin tuna. Total mercury measurement using this new method has the potential to be applied to other fish species. Total mercury levels in fish were measured using our unique analysis system. Pacific bluefin tuna, southern bluefin tuna, and Atlantic bluefin tuna distributed in the Japanese market were analyzed for total mercury in their wild and farmed fish varieties.

Study of Pore–Throat Structure in Tight Triassic Sandstone: A Case Study on the Late Triassic Yanchang Formation, Southwestern Ordos Basin, China

In order to better understand pore–throat structure characteristics, the coupling relationship between micropore–throat structure and macro reservoir quality and influencing factors caused by authigenic minerals were studied. Petrographic analyses, scanning electron microscopy (SEM), pressure-controlled mercury injection (PMI), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) were performed on a suite of tight reservoir samples from the Chang 8 Member of the Upper Triassic Yanchang Formation in the southwestern Ordos Basin, China. The results show that the pore–throat sizes obtained with the combination of PMI and NMR methods varied from nano- to microscale, revealing pore–throat sizes ranging from 0.001 μm to 70 μm, and showing that pore–throats with a radius larger than 1.0 μm are rare. Larger pore–throats with good connectivity (>rapex) account for a smaller part of the total pore volume, ranging from approximately 7.58% to 38.90% with an average of 22.77%, but account for more than 80% of contributions to permeability. The effective movable fluid porosity (φemp) measured by NMR, ranging from approximately 0.10% to 7.07% with an average of 2.56%, had a positive contribution to permeability. The contents of chlorite occurrence state, other than illite, are beneficial to pore–throat preservation. A new reservoir evaluation scheme of the Chang 8 reservoir is established. These research results provide a theoretical basis for the evaluation and development of tight sandstone oil and gas exploration.

Reservoir Sampling over Joins

Sampling over joins is a fundamental task in large-scale data analytics. Instead of computing the full join results, which could be massive, a uniform sample of the join results would suffice for many purposes, such as answering analytical queries or training machine learning models. In this paper, we study the problem of how to maintain a random sample over joins while the tuples are streaming in. Without the join, this problem can be solved by some simple and classical reservoir sampling algorithms. However, the join operator makes the problem significantly harder, as the join size can be polynomially larger than the input. We present a new algorithm for this problem that achieves a near-linear complexity. The key technical components are a generalized reservoir sampling algorithm that supports a predicate, and a dynamic index for sampling over joins. We also conduct extensive experiments on both graph and relational data over various join queries, and the experimental results demonstrate significant performance improvement over the state of the art.

Cryosphere and land cover influence on stream water quality in Central Asia's glacierized catchments

This work helps address recent calls for systematic water quality assessment in Central Asia and considers how nutrient and salinity sources, and transport, affect water quality along the continuum from the cryosphere to the lowland plains. Spatial and, for the first time, temporal variations in stream water pH, temperature, electrical conductivity, and nitrate and phosphate concentrations are presented for four catchments (485–13,500 km2), all with glaciers and major urban areas. The catchments studied were: Kaskelen (Kazakhstan), Ala-Archa (Kyrgyzstan), Chirchik (Uzbekistan) and the Kofarnihon (Tajikistan). Measurements were made in cryosphere, stream water, groundwater, reservoir and lake samples over a 22-month period at fortnightly intervals from 35 sites. The results highlight that glacier, permafrost and rock glacier outflows were primary and secondary nitrate sources (>1 mg N L−1) to the headwaters, and there were major increases in salinity and nitrate concentrations where rivers receive inputs from agriculture and settlements. Overall, the water quality complied with national and World Health Organization standards, however there were pollution hot-spots with shallow urban groundwaters contaminated with nitrate (>11 mg N L−1) and stream electrical conductivity above 800 μS cm−1 in some agricultural areas indicative of high salinity. Phosphate concentrations were generally low (<0.06 mg P L−1) throughout the catchments, though elevated (>0.2 mg P L−1) in urban areas due to effluent contamination. A melt water dilution effect along the main river channels was discernible, in the electrical conductivity and nitrate concentration seasonal dynamics, 100 s of km from the headwaters. Thus, the input of relatively clean water from the cryosphere is an important regulator of main channel water quality in the urban and farmed lowland plains adjacent to the Tien Shan and Pamir. Improved sewage treatment is needed in urban areas.

Quantitative characterization of 3D pore structures and percolation characteristics in bioturbated reservoir media based on X-ray micro-CT: a case study of the Neogene Sanya Formation in the Qiongdongnan Basin, Northern South China Sea

Organisms alter the primary texture of sediments, leading to alteration in petrophysical properties mediated by a textural and mineralogical contrast between burrow-fill and sediment host, which affects reservoir properties and fluid flow characteristics. In this article, in order to understand the microscopic pore structure and flow state of fluids in microscopic pores of bioturbated reservoirs, Ophiomorpha-bearing bioturbated reservoirs in the Neogene Sanya Formation of the Qiongdongnan Basin in the northern South China Sea were selected to research. Micro-CT was applied to scan selected core plugs, and a 3D pore structure model was established. The geometric characteristics of the microscopic pore structure were quantitatively and visually characterized by a modified maximal ball algorithm, and connectivity analysis of the pore structure was carried out. Numerical simulations of the percolation characteristics of the analyzed bioturbated reservoir samples were performed using digital core software (Avizo) and multi-physics field simulation software (Comsol). The results show that: (1) 3D pore structures reveal that pore volume, pore area, pore equivalent radius, throat area, throat equivalent radius and throat length have a large distribution range; among them, the pore volume has the largest distribution range, which can vary by six orders of magnitude, indicating that the pore size distribution of the bioturbated reservoir is uneven and has strong heterogeneous characteristics; (2) the connected pore structure is very complex, and as the equivalent radius of connected pore increases, the coordination number also gradually increases, the better the connectivity. Numerical percolation simulation results also suggested that larger connected pore space plays a key role in the effective permeability of the reservoir. This study has important implications for analyzing the modification effect of bioturbation on oil and gas reservoirs, and enhancing production and recovery in the study area.

Characteristics of inclusions in chang 7 member and shale oil accumulation stages in Zhijing-Ansai area, Ordos Basin.

In order to further clarify the shale oil accumulation period of the Chang 7 member of the Mesozoic Triassic Yanchang Formation in the Zhijing-Ansai area of the central Ordos Basin, Using fluid inclusion petrography analysis, microscopic temperature measurement, salinity analysis and fluorescence spectrum analysis methods, combined with the burial history-thermal history recovery in the area, the oil and gas accumulation period of the Chang 7 member of the Yanchang Formation in the Zhijing-Ansai area was comprehensively analyzed. Sixteen shale oil reservoir samples of the Mesozoic Triassic Yanchang Formation in seven typical wells in the study area were selected.The results show that the fluid inclusions in the Chang 7 member of Yanchang Formation can be divided into two stages. The first stage inclusions mainly develop liquid hydrocarbon inclusions and a large number of associated brine inclusions, which are mainly beaded in fracture-filled quartz and fracture-filled calcite. The fluorescence color is blue and blue-green, and the homogenization temperature of the associated brine inclusions is between 90-110°C. The second stage inclusions are mainly gas-liquid two-phase hydrocarbon inclusions, gas inclusions and asphalt inclusions. Most of them are distributed in the fracture-filled quartz, and the temperature of the associated brine inclusions is between 120-130°C. Fluid inclusions in Chang 7 member of the Yanchang Formation can be divided into two stages. The CO2 inclusions and high temperature inclusions in the Chang 7 member of the Yanchang Formation are mainly derived from deep volcanic activity in the crust.

Epidemiological Situation on Cholera in the Russian Federation in 2023 and Forecast for 2024

The paper presents an analysis and assessment of risks of complication of epidemiological situation regarding cholera in the Russian Federation and a forecast for 2024. It briefly characterizes the dynamics of the epidemic process around the world during the last decade (2013–2022). The forecast of cholera importation into the Russian Federation, due to activity of the epidemic process in endemic countries, has been confirmed. In 2023, two cases of cholera importation from India were reported. It was established that the toxigenic strains isolated from patients belonged to the currently dominant in the world “post-Haitian” group, including in India and Bangladesh, with the genotype ctxB7 tcpACIRS rtxA4a VSP-IIΔ0495-0512. Furthermore, non-toxigenic Vibrio cholerae O1 strains were isolated from samples of biological material from persons arriving from India, containing preCTX prophage and distinct from the strain (ctxAB– tcpAEТ–) isolated from a patient with acute intestinal infection (Zaporozhye Region, Melitopol). Nontoxigenic NAG vibrios were isolated from 13 patients with acute intestinal infections, which is 1.9 times more than in 2022. Regardless of importations, a strain of V. cholerae O1 (ctxB1+tcpAEТ) of the “pre-Haitian” group was isolated from a water sample of a surface reservoir. 52 non-toxigenic V. сholerae O1 strains were found on the territory of 11 constituent entities of the Russian Federation, which is 18.9 % more than in 2022. In 2024, epidemiological risks of cholera importation from endemic countries to any administrative territory of the Russian Federation remain. The risks of epidemic manifestations of cholera are especially high in the territories of the constituent entities of the Russian Federation which are under ongoing emergency, due to migration processes, and the impact of other risk-forming factors that contribute to an increase in the degree of contact of the population with water bodies contaminated with cholera vibrios. If epidemic foci of cholera are to emerge in a neighboring country, there will be a high probability of spread of this infection in the stated constituent entities of the Russian Federation and in other territories of southern Russia. In the absence of epidemic manifestations of cholera, the possibility of occasional detection of toxigenic O1 serogroup strains in water samples due to unidentified introductions from cholera-affected areas cannot be ruled out.

B-Detection: Runtime Reliability Anomaly Detection for MEC Services With Boosting LSTM Autoencoder

By pushing computing resources from the cloud to the network edge close to mobile users, mobile edge computing (MEC) enables low latency for a wide variety of applications. Nevertheless, in dynamic MEC systems, MEC services are challenged by the risks of runtime reliability anomalies. Detecting runtime reliability anomalies for MEC services is challenging yet critical to ensuring the stability of MEC systems. The effectiveness of existing anomaly detection methods suffers from poor performance when handling MEC services' large-volume, continuous, and volatile reliability streaming data. The key is to identify significant changes in the distribution of MEC services' current reliability streaming data compared with their historical performance. Inspired by concept drift, this paper proposes B-Detection, a boosting Long Short-Term Memory (LSTM) Autoencoder for detecting MEC services' runtime reliability anomalies based on distribution dissimilarity evaluation. B-Detection employs a deep learning method named LSTM Autoencoder to characterize the MEC services' historical reliability data distribution. To cope with the challenge of modeling complex distribution characteristics of MEC services' historical reliability streaming data and guarantee the real-time performance of B-Detection, we enhance LSTM Autoencoder with a weight-based reservoir sampling technique and an LSTM boosting algorithm. The reconstruction loss of the trained LSTM Autoencoder model is estimated for the up-to-date reliability streaming data, and the result is used to infer MEC services' runtime reliability anomalies. The performance of B-Detection is verified through a series of experiments conducted on a real-world dataset.

Sanding phenomena vulnerability observations due to CO2 injection at the Air Benakat reservoir in South Sumatera

Carbon sequestration using carbon capture storage (CCS) is one of the most important operational activities in the oil and gas industry to reduce greenhouse gas emissions and increase hydrocarbon production. Carbon Capture Utilization & Storage (CCUS) can be utilized for both enhancing oil recovery (CO2-EOR), as well as gas recovery (CO2-EGR) by injecting CO2 into the reservoir. However, the CO2 injection into reservoir rock can raise potential sanding problems in both injection and production wells. The phenomena of sanding may be induced dominantly due to carbonic acid injection in the reservoir. The reaction between CO2 and water will form carbonic acid in the reservoir, which can cause the dissolution of rock minerals, especially carbonate cementation (such as calcite and dolomite). We have investigated the sanding effect when CO2 was injected into the reservoir using several laboratory-scale measurements and observations on the Air Benakat reservoir sample in South Sumatera. The sanding vulnerability was measured by observing pore structure, changes in elastic properties, and rock strength through Rock Physics and Rock Mechanics measurements. XRD analysis showed the presence of CaMg(CO3)2 (dolomite) minerals in the Air Benakat sandstone sample, which resulted in the possibility of a chemical reaction of the sample, either matrix or pores. The pore structure dissolution was detected from microscale images when the rock was injected with CO2 dissolved in brine water. The changes in rock’s pores due to the dissolution process were also clearly observed from measurements of the changes in rock mass during the injection process of carbonic acid fluid into rock samples from time-to-time measurement.

A threshold of 100 or more colony-forming units on the anesthesia machine predicts bacterial pathogen detection: a retrospective laboratory-based analysis.

Preventing the spread of pathogens in the anesthesia work area reduces surgical site infections. Improved cleaning reduces the percentage of anesthesia machine samples with ≥ 100 colony-forming units (CFU) per surface area sampled. Targeting a threshold of < 100CFU when cleaning anesthesia machines may be associated with a lower prevalence of bacterial pathogens. We hypothesized that anesthesia work area reservoir samples returning < 100CFU would have a low (< 5%) prevalence ofpathogens. In this retrospective cohort study of bacterial count data from nine hospitals, obtained between 2017 and 2022, anesthesia attending and assistants' hands, patient skin sites (nares, axilla, and groin), and anesthesia machine (adjustable pressure-limiting valve and agent dials) reservoirs were sampled at case start and at case end. The patient intravenous stopcock set was sampled at case end. The isolation of ≥ 1CFU of Staphylococcus aureus, methicillin-resistant Staphylococcusaureus, Enterococcus, vancomycin-resistant Enterococcus, gram-negative (i.e., Klebsiella, Acinetobacter, Pseudomonas, and Enterobacter spp.) or coagulase-negative Staphylococcus was compared for reservoir samples returning ≥ 100CFU vs those returning < 100CFU. Bacterial pathogens were isolated from 24% (7,601/31,783) of reservoir samples, 93% (98/105) of operating rooms, and 83% (2,170/2,616) of cases. The ratio of total pathogen isolates to total CFU was < 0.0003%. Anesthesia machine reservoirs returned ≥ 100CFU for 44% (2,262/5,150) of cases. Twenty-three percent of samples returning ≥ 100CFU were positive for ≥ 1 bacterial pathogen (521/2,262; 99% lower confidence limit, 22%) vs 3% of samples returning < 100CFU (96/2,888; 99% upper limit, 4%). Anesthesia machine reservoir samples returning < 100CFU were associated with negligible pathogen detection. This threshold can be used for assessment of terminal, routine, and between-case cleaning of the anesthesia machine and equipment. Such feedback may be useful because the 44% prevalence of ≥ 100CFU was comparable to the 46% (25/54) reported earlier from an unrelated hospital.

Geochemistry of Liquid Hydrocarbons and Natural Gases Combined with 1D Basin Modeling of the Oligocene Shale Source Rock System in the Offshore Nile Delta, Egypt.

The current study aims to integrate the geochemical characteristics of the Oligocene shale source rock system, oil, condensate, and natural gas samples in the Oligocene sandstone reservoirs from three exploration wells located in the offshore Nile Delta, East Mediterranean Sea, using organic geochemistry and a 1D basin modeling scheme. The Tineh shales exhibit total organic carbon values ranging between 0.90 and 1.89 wt %, along with hydrogen index values in the range of 54-240 mg hydrocarbon/g rock. The geochemical characterization suggests that the shale intervals of the Oligocene Tineh Formation contain type II-III and type III kerogens and, thereby, could be regarded as promising oil- and gas-prone source rocks with high contributions of gas generation potential. The study also reconstructs the 1D thermal and burial history models, showing that the Oligocene Tineh source rock system is in the main oil and wet gas generation phases from the late Miocene to the present time. The simulated basin models reveal the transformation (TR) of 10-50% kerogen to oil during the late Miocene-early Pliocene period and that the Oligocene Tineh source rock system has larger oil generation and expulsion competency, with a TR value of up to 65% during the early Pliocene-Pleistocene time period. The thermogenic gas was also formed during this time and continued to the present day. This study also investigated the presence of oil and condensate in the Oligocene sandstone reservoir samples and revealed that they were generated from mature source rock, ranging from moderately to highly mature stages. This source rock unit was deposited in fluvial to fluvial-deltaic environments under oxic mixed organic conditions and accumulated during the Tertiary time, as evidenced by the presence of the oleanane biomarker dating indicator. The molecular and isotope compositions of natural gases revealed that most of the natural gases in the Oligocene sandstone reservoir are mainly thermogenic methane gases that were generated from mainly mixed organic matter. The thermogenic methane gases were formed mainly from secondary cracking of oil and gas, with small contributions of primary kerogen cracking. The properties of natural gases together with oil and condensate in the Oligocene reservoir rocks suggest that most of the thermogenic methane gases and associated liquid hydrocarbons are derived primarily from the Oligocene shale source rock system and formed by primary kerogen cracking and secondary oil and oil/gas cracking in different thermal maturity stages. Therefore, the Oligocene Tineh Formation can be regarded as self-source generation and self-reservoir rock; hence, an intensive oil exploration and production program can be recommended whenever the Tineh source rock system is is well developed and deeply buried.

Employing Statistical Algorithms and Clustering Techniques to Assess Lithological Facies for Identifying Optimal Reservoir Rocks: A Case Study of the Mansouri Oilfields, SW Iran

The crucial parameters influencing drilling operations, reservoir production behavior, and well completion are lithology and reservoir rock. This study identified optimal reservoir rocks and facies in 280 core samples from a drilled well in the Asmari reservoir of the Mansouri field in SW Iran to determine the number of hydraulic flow units. Reservoir samples were prepared, and their porosity and permeability were determined by measuring devices. The flow zone index (FZI) was calculated for each sample using MATLAB software; then, a histogram analysis was performed on the logarithmic data of the FZI, and the number of hydraulic flow units was determined based on the obtained normal distributions. Electrical facies were determined based on artificial neural network (ANN) and multi-resolution graph-based clustering (MRGC) approaches. Five electrical facies with dissimilar reservoir conditions and lithological compositions were ultimately specified. Based on described lithofacies, shale and sandstone in zones three and five demonstrated elevated reservoir quality. This study aimed to determine the Asmari reservoir’s porous medium’s flowing fluid according to the C-mean fuzzy logic method. Furthermore, the third and fourth flow units in the Asmari Formation have the best flow units with high reservoir quality and permeability due to determining the siliceous–clastic facies of the rock units and log data. Outcomes could be corresponded to the flow unit determination in further nearby wellbores without cores.

Improving the prediction of elemental sulfur solubility in sour gas mixtures by modifying cubic equations of state

So far, several correlations have been developed to forecast the solubility of sulfur in various mixtures of acid gases with different concentrations of hydrogen sulfide. These correlations are correlative methods requiring experimental sulfur solubility data to tune their model parameters. Besides, correlative methods have many restrictions and are useable only for a limited range of operating conditions. Another approach for predicting sulfur solubility is applying equations of state. The predictive ability of equations of state has made them a powerful tool to more accurately perform the equilibrium phase calculations of acid gas mixtures in a vaster operating range. The major problem of the equations of state is the inaccurate characterization of their parameters for elemental sulfur due to its chemical complexity. In this study, the performance of three cubic equations of state is evaluated for forecasting the solubility of elemental sulfur in different acid gas mixtures. The main idea which is supposed to be put forward for rectifying defects of cubic equations of state is to model the trend of errors propagated in predicting the solubility of sulfur. Indeed, the effect of sulfur chemical reactions is ignored, and a generalized correction function is developed to compensate for deviations arising from the simplification assumptions. Subsequently, the results predicted by modified equations of state are compared to experimental sulfur solubility data and previously existing methods. Finally, a case study is performed on a sour gas reservoir sample to predict precipitation P-T curve and to calculate sulfur solubility changes with the pressure and temperature reduction throughout the gas well. Predicted results revealed the proposed correction function could significantly decrease the solubility calculations obtained from the modified equations of state under 5.6%, which is a good achievement compared to their original versions.