Low-temperature Reservoir Research Articles

Investigation of air-cooled condenser’s operating parameters in modern thermal power plant

Air-cooled condensers in thermal power plants have recently become increasingly popular. Besides all the advantages they have, like no demands for water supply on the plant site and no need for taking care of environmental regulations, they also have some serious disadvantages. One of the biggest disadvantages air-cooled condensers do have is precisely the nature of the Earth?s atmosphere being their low temperature reservoir. Low density and low heat capacity of the air as the cooling medium combined with extremely stochastic behavior of the atmosphere itself put some serious challenges in front of the air-cooled condenser?s proper and steady functioning. In this paper, the operating parameters of the air-cooled condenser in the chosen thermal power plant were investigated to gain a clearer insight into the influence of the atmospheric changes on its entropy generation and consequently on its efficiency. Also, the acquired results were further proposed as a starting point for potential optimization of the process inside the device.

Effect of Crosslinker Types on Temporary Plugging Performance of Degradable Preformed Particle Gels for Unconventional Petroleum Reservoir Development

Temporary plugging agents (TPAs) have been widely used in unconventional petroleum reservoirs to increase the stimulated reservoir volume and generate an easier flow of oil and gas into the production well. The properties of particle-gel-based TPAs include a straightforward injection procedure, excellent deformation, strong plugging strength, and total self-degradation. This study prepared degradable preformed particle gel (DPPG) samples polymerized by two types of crosslinkers (i.e., alcohol ester and alkenoic acid ester) for low-temperature (less than 40 °C) reservoirs. The effects of different crosslinkers in the DPPG compositions on the temporary plugging performance were investigated. Infrared spectrum analysis, differential calorimetry scanning evaluation, static particle gel swelling and degradation performance assessment experiments, and dynamic temporary plugging performance tests were all employed. The results showed that the swelling ratio of DPPGs prepared by the crosslinker containing alcohol ester was larger than that of alkenoate acid ester, but the degradation rate was slower. Among them, when the amount of crosslinker was 0.01 g, the swelling ratio of DPPG prepared using the alcohol ester crosslinker was as high as 40 times, and the complete degradation time could be regulated between 80 and 360 h. When the type of crosslinker was the same, the influence of its molecular weight also significantly affected the performance of the particle gel. The plugging strength of DPPG prepared by different crosslinkers in cores was as high as 20 MPa. The DPPG prepared from the alcohol ester crosslinker caused less damage to the core after being self-degraded and was used as an ideal crosslinker. Infrared spectroscopy and differential scanning calorimetry analysis at the molecular level verified that different types of crosslinkers had apparent effects on the chemical structure stability of the DPPG. In this paper, the influence of the type of crosslinker on the performance of the DPPG was studied, which provides a new idea and theoretical basis for developing a particle gel-based TPA system with programmed self-degradation time at low temperatures.

Numerical Simulation of the Proppant Settlement in SC-CO2 Sand-Carrying Fluid in Fracturing Fractures

Supercritical CO2 fracturing has unique advantages for improving unconventional reservoir recovery. Supercritical CO2 can penetrate deep into the reservoir and increase reservoir reform volume, and it is less damaging to reservoir and easy to flow back. However, when the supercritical CO2 flows as the sand-carrying fluid in the fracture, the settlement of the proppant is still worth studying. Based on the study of supercritical CO2 density and viscosity properties, assuming that the reservoir has been pressed out of the vertical crack by injecting prepad fluid, the proppant characteristics in sand-carrying fluid under different conditions were studied by numerical simulation. After the analysis, the proppant accumulation and backflow will occur at the end of the crack. Large sand diameters, high fluid flow rates, high sand concentrations, high reservoir temperatures, and low reservoir pressures can help to shorten deposition time, and the small particle size, high fluid flow rate, low sand concentration, low reservoir temperature, and high reservoir pressure can help increase the uniformity of sand deposition. Shortening the sand deposition time can help to complete the fracturing efficiently, and increasing the deposition uniformity can improve the fracture conductivity. This article has studied the proppant settling and crack formation characteristics. It is hoped that this study can provide theoretical support for field fracturing and provide theoretical assistance to relevant researchers.

Experimental Study on the Performance Analysis of Vapour Compression Refrigeration Test Rig with and without Phase Change Materials

The performance of heat transfer is the essential area of research in the field of thermal engineering. For the process of heat transfer, there are numbers of refrigerants which used in domestic refrigeration to transfer the heat from low-temperature reservoir to high-temperature reservoir. The vapour compression refrigeration technology has made a great improvement over a few decades in the form of the efficiency of cycle through significant efforts of thermal engineers and manufacturers. The modification of the cycle should be investigated to enhance the efficiency of the system. In this paper, the experimental study is conducted to predict the comparison between the Simple VCR with and without Phase change materials such as potassium chloride solution, Ethylene Glycol. Hence the proposed system could be a new option for performance improvement of a VCR system by enhancing heat transfer of the evaporator with the help of Phase Change Materials.

Degradable preformed particle gel as temporary plugging agent for low-temperature unconventional petroleum reservoirs: Effect of molecular weight of the cross-linking agent

The development of unconventional petroleum resources has gradually become an important succession for increasing oil production. However, the efficient development of this type of reservoir is paying more and more attention to the application of temporary plugging agents. The use of temporary plugging agents can further expand the stimulated reservoir volume (SRV) and facilitate the flow of oil and gas to the bottom of the well. Particle-gels used as temporary plugging agents have the characteristics of the simple injection process, good deformation, high plugging strength, and complete self-degradation performance, which has been widely applied in recent years. In this paper, five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared. In addition, infrared spectroscopy analysis, differential calorimetry scanning (DSC) analysis, static particle gel swelling and degradation performance evaluation experiments, and dynamic temporary plugging performance experiments in cores were used to study the influence mechanism of the cross-linking agent molecular weight ( M w ) of the DPPG molecule on its temporary plugging performance. Results show that as the molecular weight of the cross-linking agent (at 0.01 g) in the DPPG molecule decreases from 1000 to 200 Daltons, the fewer cross-linking sites of DPPG, the looser the microscopic three-dimensional mesh structure formed, and the swelling ratio is increased from seven to 33 times. However, the complete degradation time increases from 40 to 210 min. Moreover, the DSC scanning results confirmed that the larger the molecular weight of the cross-linking agent, the worse it is chemical stability and the more prone it to self-degradation. The DPPG particle samples have good temporary plugging performance in reservoir cores. The DPPG prepared by the cross-linking agent with smaller molecular weight has a smaller expansion ratio, higher gel strength, and greater plugging strength in the core. Moreover, the degraded DPPG is less damaging to the cores. However, its slower degradation rate takes a slightly longer time to reach complete degradation. The results of this paper can provide new ideas and a theoretical basis for the development of particle gel-based temporary plugging agents (TPA) with controllable degradation time in low-temperature reservoirs. It can help to expand further the application range of existing DPPG reservoir conditions.

Experimental Realization of a Quantum Refrigerator Driven by Indefinite Causal Orders.

Indefinite causal order (ICO) is playing a key role in recent quantum technologies. Here, we experimentally study quantum thermodynamics driven by ICO on nuclear spins using the nuclear magnetic resonance system. We realize the ICO of two thermalizing channels to exhibit how the mechanism works, and show that the working substance can be cooled or heated albeit it undergoes thermal contacts with reservoirs of the same temperature. Moreover, we construct a single cycle of the ICO refrigerator based on the Maxwell's demon mechanism, and evaluate its performance by measuring the work consumption and the heat energy extracted from the low-temperature reservoir. Unlike classical refrigerators in which the coefficient of performance (COP) is perversely higher the closer the temperature of the high-temperature and low-temperature reservoirs are to each other, the ICO refrigerator's COP is always bounded to small values due to the nonunit success probability in projecting the ancillary qubit to the preferable subspace. To enhance the COP, we propose and experimentally demonstrate a general framework based on the density matrix exponentiation (DME) approach, as an extension to the ICO refrigeration. The COP is observed to be enhanced by more than 3 times with the DME approach. Our Letter demonstrates a new way for nonclassical heat exchange, and paves the way towards construction of quantum refrigerators on a quantum system.

Gelling Behavior of PAM/Phenolic Crosslinked Gel and Its Profile Control in a Low-Temperature and High-Salinity Reservoir.

Gel conformance control technology is widely used in moderate and high temperature reservoirs. However, there are few studies on shallow low-temperature and high-salinity reservoirs. The difficulties are that it is difficult to crosslink at low temperatures and with poor stability at high salt concentrations. Therefore, the PHRO gel was developed, which was composed of gelatinizing agent (polyacrylamide), crosslinking agents (hexamethylenetetramine and resorcinol) and crosslinking promoting agent (oxalic acid). The PHRO could form high-strength gels in both deionized water and high-concentration salinity solutions (NaCl, KCl, CaCl2 and MgCl2). The observation of the microstructure of PHRO gel shows that a strong “stem—leaf”-shaped three-dimensional network structure is formed in deionized water, and the network structure is still intact in high-concentration salt solution. The results show that PHRO has good salt resistance properties and is suitable for conformance control of low-temperature and high-salinity reservoirs.

Accelerated low-temperature oxidation for sand consolidation and production control

Sand production that occurs in poorly consolidated oil and gas reservoirs causes many serious operational problems. Industry experts have used both chemical and mechanical sand control techniques to overcome this challenge; however, these techniques have various technical and economic limitations. For example, a technique that employed in-situ low-temperature oxidation (LTO) of an asphaltic solution saturating the near-wellbore area helped increase the formation's compressive strength while retaining its permeability; however, this technique was time-consuming at low reservoir temperatures. This study employed thermochemicals to preheat the sand and thereby accelerate the LTO reaction and shorten the consolidation process. First, small packs of loose sand saturated with an asphaltic solution were oxidized via external heating until consolidation. The optimal conditions involved continuous airflow for 6 h at 180 °C, which produced consolidated sand with a compressive strength exceeding 12.4 MPa. Second, a similar but insulated saturated sand pack was flooded with several pore volumes of thermochemicals, which raised its temperature from 75 °C to 188 °C; this was followed by 6 h of air injection. The consolidated sand had a compressive strength of 10.27 MPa and showed excellent stability against acid and crude oil floods as well as prolonged soaking in toluene.This study demonstrated the potential of using thermochemicals for the in situ heating of the wellbore area to elevated temperatures for sand consolidation. By shortening the treatment time, the thermochemicals improved the cost-effectiveness of sand consolidation via LTO without adversely affecting the consolidation quality.

The Use of Equipment for the Study of Phase Changes to Determine the Conditions of Precipitation of Inorganic Sediments in Geothermal Waters

In Poland, there are low-temperature geothermal reservoirs that can be used for various purposes in many regions of the country. Low-temperature deposits of geothermal waters are common and occur much more frequently than high-temperature deposits. They contain water with temperatures lower than 150 °C. Their temperature normally ranges from 20 to 90 °C. Achieving a state of equilibrium depends on many factors, including the kinetics of reactions between the individual components of the system, temperature, reactivity of reservoir rock, concentration of chemical components in the water and the time the water remains in contact with the rock. Therefore, this article presents the possibility of checking the conditions of precipitation of inorganic sediments in geothermal waters with the use of PVT equipment. Tests were carried out with the use of geothermal waters under given dynamic conditions (pressure, temperature and flow). This paper confirms the suitability of using the equipment for PVT (device for the study of phase changes) testing in order to determine the conditions for the precipitation of inorganic sediments in geothermal projects. Tests on the precipitation of solid sediments in geothermal waters were carried out. A result of the research is the adaptation of the equipment for PVT testing in order to determine the conditions for the precipitation of inorganic deposits in geothermal waters. As a result, different capillary blocking times were obtained depending on the measurement conditions (e.g., for P = 40 bar, T = 120 °C and q = 1 cm3/min, the blocking start time was 10.8 min). The authors found that solid sludge inhibitors, as well as other chemicals used, including paraffin inhibitors, must be periodically adjusted to prevent precipitation in geothermal waters.

Lithium-rich geothermal brines in Europe: An up-date about geochemical characteristics and implications for potential Li resources

Lithium (Li) is a strategic metal - especially for batteries in electric vehicles - for which worldwide demand is constantly increasing. Presently, several investigations are examining if a part of lithium could be extracted from deep European geothermal fluids. Among the data from geothermal and hydrocarbon wells found in the literature review carried out by BRGM and EIFER, only six areas stand out with deep fluids containing high Li concentrations from 125 to 480 mg/l in Italy, Germany, France and the United-Kingdom. Except the UK fluid, which has a relatively low salinity (TDS = 19 g/l) and reservoir temperature (around 52 °C), these deep Li-rich fluids are Na-Cl brines (TDS ≥ 56 g/l) with high concentrations of Na (> 18 g/l) and Cl (> 25 g/l) and high temperatures (≥ 120 °C and up to 380 °C in Italy). If high TDS and temperature values seem to be key factors for triggering high Li concentrations in such fluids, these two factors alone cannot be sufficient. Indeed, our study confirms that Li concentrations not only depend on temperature and fluid salinity, but also on the type of reservoir rock and its mineralogical constituents, as demonstrated by the good results obtained using two different Na-Li thermometric relationships existing in the literature. One fits well with the brines from low to high temperature (120–250 °C) reservoirs in deep tectonic sedimentary basins over a crystalline basement (France, Germany) and the other with the fluids from ultra-high temperature (≥ 300 °C) reservoirs in volcano-sedimentary environment (Italy). If the high chloride concentrations values in these brines mainly depend on the fluid origin (evaporated seawater or freshwater, halite dissolution, primary neutralization fluids or parent-geothermal fluids in high-temperature and -pressure volcanic environments, water mixing, etc.), the other aqueous major species are mostly controlled by hydrothermal water-rock interaction processes. At these temperatures (≥ 120 °C), the fluid-rock interaction processes are generally dominated by plagioclase and K-feldspar dissolution, followed by albitization of these minerals, dissolution of white micas and biotite, precipitation of illite, and chloritization. According to the two Na-Li thermometric relationships, existing mineralogical and isotopic data, this study suggests that the main sources of Li are white micas and biotite dissolution. Among the European areas, it shows that the Upper Rhine Graben (URG) along the French/German border is probably the most promising zone. For the URG geothermal brines, the main source and control of lithium, at about 225 °C, at reservoir depth, is probably the up to 450-m-thick micaceous continental sandstone of Triassic Buntsandstein. A minor contribution from the granite basement can also not be excluded. Though the Li concentration values of these brines (≥ 150 mg/l) seem to be favourable for geothermal Li exploitation, it is essential to make an as accurate as possible estimate of the Li resource of these brines, design the Li extraction process, and examine the economic conditions of its exploitation.

Microbial Community Composition in Thermal Waters from the Lindian Geothermal Field (Songliao Basin, North-Eastern China)

Geothermal systems represent discrete and relatively homogenous habitats for extremophiles; investigation into the microbial community is key to revealing the geochemical environment and the geochemical evolution of fluids in geothermal reservoirs. The reservoir of the Lindian geothermal field in Northeast China, is highly reducing and rich in methane, but the pathways of methane generation and the related microbial community structure are still unclear. In this research, five thermal water samples were collected and tested, and the microbial community structure and diversity were analyzed. The results show that in the sandstone reservoir belonging to the low-temperature (reservoir temperature < 90°C) brackish water (total dissolved solids concentration between 1000 and 10,000 mg/L) environment, the richness of the microbial community is relatively high. The microbial community structure is different from other geothermal systems reported but similar to that of oilfields, which may be related to the highly reducing geochemical environment with abundant organic matter. According to the analysis of archaeal function, the biogas production in the Lindian geothermal field is dominated by hydrogen nutrition type methane production, while the H2 reducing methylamine type methane production is secondary, and results of Pearson correlation show that the archaeal communities are more strongly correlated to physicochemical factors than the bacterial communities.

Structural controls on sandstone compaction within the anticline crest and flank: An example from the Xihu Sag, East China Sea Basin

The tight sandstones of the fourth (E3h4) and fifth (E3h5) members of the Oligocene Huagang (E3h) Formation in the Xihu Sag of the East China Sea Basin are feldspar lithic quartzose, which are ideal for the investigation of compaction. Based on routine core analysis, petrology, fluid inclusions, and compaction numerical simulation, this study investigated the compaction characteristics, porosity evolution, and high-value porosity area of tight sandstone on a structural anticline two-dimensional (2D) profile. The textural characteristics of the sandstones are moderately well sorted and are generally subangular-subrounded. The E3h4 and E3h5 sandstones on the crest of the anticline develop primary intergranular pores, whereas these sandstones on the flank develop a small amount of primary intergranular pores. The contact types between quartz grains on the anticline crest were mainly tangential, long, and concavo-convex contacts, whereas the contact types between quartz grains on the flank were primarily long, concavo-convex, and sutured contacts. The duration age of the mechanical compaction (MEC) porosity loss of sandy conglomerate (SC), fine-grained sandstone (FS), and medium-grained sandstone (MS) in the E3h4 and E3h5 members ranged from 27 Ma to 7 Ma. The onset of the chemical compaction (CHC) of the E3h4 and E3h5 sandstones were between 10.2 Ma and 10.6 Ma, respectively. Based on similar grain size, mineral composition, and sorting, the degree of the MEC of the E3h4 and E3h5 sandstones on the crest of the anticline is less than that of the flank due to burial depth. The distribution ranges of the MEC porosity loss were 21.92%–26.02% and 22.31%–26.43% for the E3h4 on the anticline crest and flank and 26.74%–27.26% for the E3h5 on the flank, respectively. By integrating similar burial time and clay minerals, the degree of the CHC of the E3h4 and E3h5 sandstones on the crest of the anticline is less than that of the flank due to reservoir temperature. The distribution ranges of the CHC porosity loss were 0.41%–1.05% and 0.44%–1.02% for the E3h4 on the anticline crest and flank and 0.48%–0.91% for the E3h5 on the flank, respectively. During the Late Miocene Longjing movement, the CHC porosity loss ranged from 0.15% to 0.4%. The study results show that the sandstone with porosity between 9% and 11% is distributed sporadically in E3h4 and E3h5, whereas the sandstone with porosity between 6% and 9% is distributed in contiguous pieces. The formation of high-value porosity areas is mainly due to the coarser grain size, shallower burial depth, chlorite coat, underdeveloped illite, lower reservoir temperature, and slight overpressure.

Application of low temperature fracturing fluid system in oil reservoir – A breakthrough approach

Fracturing fluid formulation is crucial for successful hydraulic fracturing, especially in low-temperature reservoirs. Low-temperature Indian reservoirs are fractured with borate-based fluids. Temperature, pH, shear history, and cross linker-polymer bond affect fracturing fluid stability. Optimization of breaker and cross linker is crucial for gel stability to carry proppant deep into the formation and smooth post-job flow from low-temperature reservoirs. Without a proper breaker, earlier fracturing operations used linear gel compositions, compromising flow return. These formulations restrict high-concentration proppant use. Many studies were conducted to optimize the breaker-complexes for smooth flow back in simulated reservoir conditions. These formulations feature an in-house developed breaker that works well for low-temperature reservoirs (near ambient to 55 °C). This paper covers newly created low temperature fracturing fluid formulations, lab studies and successful field implementations.

Analysis on the Formation of Water/Oil Emulsion System of High Water-cut Crude Oil and Its Profile and Flooding Effect

In view of the limitations of modulated flooding technology in low permeability high temperature reservoirs, the water/oil emulsion with the effect of expanding sweep volume and its influence on the effect of modulated flooding were studied. Under the condition of high water content (80% water content), the dispersion system formed by emulsifier 55# and crude oil is mainly water/oil emulsion. At the same time, the influence of surfactant type, water content, temperature and other factors on the formation of water/oil emulsion system was investigated, and the influence of emulsion properties on the effect of displacement was analyzed. The low permeability core experiment shows that the emulsifier with the effect of expanding sweep volume can improve the oil recovery by 17.93% on the basis of water flooding, which is obviously higher than that of polymer flooding. At the same time, emulsifier has good temperature resistance, which is of great significance for enhancing oil recovery in high temperature and low permeability water drive reservoirs.

Повышение технологической эффективности глушения скважин с использованием инновационных технологий

Introduction. The article considers the issue of assessing the technological efficiency of the well killing process, taking into account changes in the reservoir properties of the productive formation when using various compositions of process fluids. Innovative technologies are presented that are used when killing wells in various mining and geological conditions to block the bottomhole formation zone. Materials and methods of research. The study is based on a summary of many years of experience in the field of creation and practical use of process fluids for killing wells and on the results of theoretical, laboratory, bench studies of killing fluids and blocking compositions, performed in specialized scientific laboratories using specialized laboratory equipment according to standard methods for the oil and gas industry. Research results and discussion. The compositions of process fluids are presented, which are easily removed when inducing inflow from the formation, and which allow to provide the required pressure at the bottomhole, as well as to maintain the reservoir properties of the productive formation and prevent its damage. The results of killing wells with the use of various compositions of process fluids with high stability, low filtration, in a wide range of adjustable density and rheological properties, which allow creating the necessary repression on the formation and performing various operations in the well, are considered. The article also provides information on the analytical studies carried out within the framework of the given problem. The results made it possible to draw conclusions regarding the use of various types of fluids for killing oil, gas, gas condensate wells under conditions of abnormally low reservoir pressures and elevated reservoir temperatures. Consideration is given to the liquids with an acidsoluble condensable solid phase, the formation of which in solution is due to the occurrence of physicochemical processes between its components; biopolymer-based liquids containing various fillers and functional additives; viscoelastic compositions reinforced with solid-state lamellar and fibrous particles of organic and mineral origin (for example, bridging additive brand «OM-2C») based on commercially available polymer reagent «Binar»; emulsion-type kill fluids containing surfactants and a hydrocarbon phase. The main rheological and technological parameters, as well as the properties of the proposed process fluids for killing wells, are described. Сonclusions. Based on the study, it was determined that the most promising technology for killing wells under conditions of abnormally low formation pressures is the technology of preliminary blocking of the bottomhole formation zone using special compositions of process fluids with controlled rheological parameters, taking into account the characteristics of the formation, technologically applicable in special climatic conditions with low negative temperatures. It has also been established that ensuring high efficiency of repair work is impossible without performing theoretical calculations and laboratory studies with modeling the process of blocking the bottomhole zone during well killing and subsequent development.

Разнообразие психрофильных бактерий и их биотехнологический потенциал (обзор)

Psychrophilic bacteria are a large group of microorganisms that prevail in low-temperature ecosystems. Psychrophilic bacteria have undergone a number of adaptations that help them exist in such conditions. One of such adaptations is the use of enzymes with a high specific activity at low temperatures. Such enzymes are usually called “cold-active.” These enzymes have potential applications in biotechnology and industry. In our review, we considered individual genera of psychrophilic bacteria, current global trends in the study of cold-active enzymes, their applications, and place in industrial biotechnology. Thus, the main goal of this study was to explore the diversity of psychrophilic bacteria, as well as opportunities of their application in biotechnology. The natural ecological sites of psychrophiles are numerous and varied. Psychrophiles form a permanent microflora of eternal cold regions, polar regions and oceans. Bacteria belonging to this group are found in soil, water or associated with plants and animals. An important site for psychrophilic microorganisms is a low-temperature water reservoir. At present, many new genera of psychrophiles and psychrotrophs have been derived from the bottom sediments and sea waters of the Arctic and Antarctic and described. Psychrophilic microorganisms are found in caves and in ancient ice crystal structures. The latter testifies to the very possibility of the super-long anabiosis phenomenon, as well as vital capacity preservation without division for a long period of time. Psychrophiles do not have a single form, they belong to at least several phylogenetic groups. Psychrophilic forms are found among the representatives of a large number of genera. There are no common physiological and biochemical parameters typical of psychrophilic bacteria. They comprise rods, cocci, vibrios, gram-negative and gram-positive bacteria, bacteria that produce and do not produce spores, strict aerobes, facultative and strict anaerobes. We lay greater emphasis on the diversity of psychrophilic bacteria capable of producing industrially important enzymes. The review considers bacteria belonging to the genera Vibrio and Aliivibrio, Pseudomonas, Achromobacter, Arthrobacter, Pseudoalteromonas, Bacillus, Clostridium, Micrococcus, Psychrobacter, Psychromonas, Flavobacterium, and psychrophilic methanotrophic microorganisms. These bacteria enzymes are used in agriculture, biotechnology, pharmaceuticals and household chemicals, as well as other sectors of the national economy. Psychrophilic bacteria produce a chemical compound that can be used in medicine. For example, Pseudomonas antarctica contains a cluster of genes encoding microcin B, R-type pyocins, adenosylcobalamin, and pyrroloquinoline quinone. Thus, P. antarctica has antibiotic activity. Psychrobacter proteolyticus also has an antineoplastic action and secrets an extracellular cold-adapted metalloproteinase being able to inhibit the space-occupying process. Cold-active metalloproteinases are also widely used as detergents, in currying, food sector and molecular biology. The immunogenic Pal conformable protein was derived from the psychrophilic strain of The representatives of the genus Arthrobacter capable of metabolizing diuron and petroleum products have an important property. A. agilis produces a red pigment, a bacterioruberin-type carotenoid being interesting as an antioxidant. A. psychrochitiniphilus is promising for cleaning water areas, oil-polluted coastlines, as it decomposes oil and petroleum products. Flavobacterium limicola is a potential source of cold-active protease. This bacterium is characterized by an increase in protease secretion as temperature decreases. Thus, F. limicola can be used in environmental biotransformations and bioremediations. The psychrophilic bacteria of the genus Bacillus are the participants of active studies. Their cold-active enzymes have a high potential in various areas of biomedicine, immunology, decontamination, and various industrial applications. The antifreeze proteins of psychrophilic Clostridia are considered a promising biotechnological product for use in medicine, food, beauty products, fuel, and other industries. This study reviews literary sources and indicates that at present obligate and facultative psychrophiles (psychrotrophs) and their cold-active enzymes are of scientific interest throughout the world. A significant part of the research is focused on a general understanding of the distribution of psychrophilic bacteria and a local study of enzymatic activity. A further study of psychrophilic microorganisms producing enzymes at low temperatures will reveal new ways for the development of biotechnologies in various sectors of the national economy. The paper contains 94 References. The Authors declare no conflict of interest.

Four-terminal hybrid driven refrigerator based on three coupled quantum dots

In this paper, a four-terminal hybrid driven refrigerator model with three capacitively coupled quantum dots is proposed, which can be driven by the energy current injected from the highest temperature thermal reservoir and the power input to achieve the refrigeration of the low temperature reservoir. Based on the master equation we derive the expressions for charge current and heat current between three quantum dots and thermal reservoirs in the weak/strong capacitive coupling case, respectively. We numerically analyze the thermodynamic performance characteristics of the refrigerator between the cooling rate and the coefficient of performance, and the main performance parameters of the refrigerator are optimized under the condition of the maximum cooling rate. Finally, we compare the performance of this refrigerator in the strong capacitive coupling case with that in the weak capacitive coupling case.

Estimation of Electric Potential of X Geothermal Field Using Monte Carlo Method

Field X is a marginal geothermal field located in the province of Maluku, Indonesia. An assessment of reservoir characteristics needs to be carried out to determine the appropriate field development method. The purpose of this study is to evaluate the electrical potential that can be generated from Field X. The Monte Carlo method is used to estimate the usable electric potential. The sensitivity of the parameters of generation time, initial temperature, and final temperature was carried out to get a wider picture. Based on the simulation results obtained a proportional relationship between reservoir temperature and electric potential. Higher reservoir temperatures can be obtained by drilling deeper wells. The most probable estimate (P50) of the electric potential of Field X is in the range of 0.141 – 0.248 MWe. An increase in the initial reservoir temperature of 15 oC causes an average increase of 16% MWe. Due to the relatively low reservoir temperature, low temperature geothermal binary power generation should be applied for field development.

Hydrochemical characterization of geothermal and non-geothermal waters from Wadi Fatima, western Saudi Arabia

The present study was conducted in the Wadi Fatima catchment in western Saudi Arabia with the primary objective of finding the major hydrochemical differences among geothermal and non-geothermal groundwater samples. Based on the dissolved-silica content of 124 groundwater samples, the chalcedony geothermometer with no steam loss was used to classify them as geothermal or non-geothermal. The mean total dissolved solids (TDS) of the non-geothermal and geothermal samples were 1254 mg/L and 4389 mg/L, respectively. The high TDS of the geothermal samples can be attributed to the higher temperature of circulation leading to a greater degree of mineral dissolution, as well as the mixing of fresh, shallow groundwater with deeper saline water, as can be seen on Piper and Durov plots. Silicate weathering is the primary hydrochemical process active in the area. Based on the saturation indices of commonly dissolved mineral phases, the geothermal water samples showed higher saturation. Using chalcedony geothermometer can be an effective tool for classifying groundwater from low-temperature reservoirs as geothermal and non-geothermal. Further groundwater facies analysis, ionic relationships, and saturation indices can be employed to determine hydrochemical characteristics of these two different types of waters.

The structure of the sedimentary complex of the Middle and South Caspian depressions (Azerbaijan sector)

The high degree of knowledge of the upper horizons of the sedimentary cover of the Middle and South Caspian depressions, given an insufficient increase in hydrocarbon reserves, leads to the need for a detailed approach to the search for oil and gas deposits in deep-seated sediments (over 6 km). During the geological interpretation of new highly informative seismic data, as well as data of deep drilling and petrological core studies, there were revealed obvious shortcomings in the concepts of the origin and evolution of the Middle and South Caspian depressions. These ideas misinterpret evolution, especially the South Caspian Basin, which is characterized by a number of unique features: very thick sedimentary cover (up to 22 km), extremely high sedimentation rate, low heat flow and reservoir temperatures, abnormally high pore and reservoir pressures, high clay content of the section, etc. The main purpose of the study was to elucidate the regional structure and features of the dissection of the sedimentary cover of the Middle and South Caspian depressions, the conditions of occurrence and distribution of facies and thicknesses of individual complexes of deposits.
 The paper analyzes the results of some previous studies of the geological structure of the Middle and South Caspian depressions based on the data of deep seismic sounding, seismological and gravimetric observations. We consider the main conclusions of these studies, about the geological structure of the sedimentary complex of the region’s, very outdated and subject to revision.
 The results of seismic stratigraphic analysis of seismic data allowed the authors to identify new data about the tectonic structure and express a completely different point of view regarding the structure of the sedimentary cover in the region.
 The work also touches on the issue associated with the tectonics of the region and the alleged subduction zone here.