scholarly journals Study on the Mechanism of Water and Heat Transfer in Sandstone Geothermal System: A Case Study of Doublet Well

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 5) ◽  
Author(s):  
Jian Shen ◽  
Mingtao Chen ◽  
Shengtao Li ◽  
Zhenpeng Cui ◽  
Yilong Yuan ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Low Temperature ◽  
Flow Rate ◽  
Geothermal Energy ◽  
Injection Well ◽  
Geothermal System ◽  
Temperature Expansion ◽  
Well Spacing ◽  
Increased Risk ◽  
Thermal Breakthrough

Abstract The development of sandstone-type geothermal energy is an important part of the development of geothermal resources and has great significance in promoting environmental protection and energy structural transformation. In sandstone geothermal energy development, recharging is the main method to ensure bottom hole pressure. However, the pressure and temperature changes of sandstone reservoirs under recharge conditions have not been extensively studied. It is easy to ignore the hydraulic relationship between the production and the injection wells, which leads to an increased risk of thermal breakthrough. Therefore, a three-dimensional hydrothermal coupling model is established, and simulation studies of different flow rates, well lengths, and well spacings are completed in this paper. Here, we show the numerical simulation results. The low temperature expansion zone and hydrostatic pressure near the injection well increase with increasing flow rate, and the maximum expansion of the low temperature zone is about 350 m. The low temperature expansion area near the injection well has a small relationship with the well spacing, and the increase in hydrostatic pressure is proportional to the well spacing. As the length of the well increases, the increase in hydrostatic pressure near the injection well decreases, indicating that the injected water under the long well section easily enters the reservoir. When no thermal breakthrough occurs and the hydrostatic pressure drops significantly near the production well, it is recommended that the flow rate be controlled at approximately 20–25 L/s, the well spacing should be 600–800 m, and the well length should be greater than 100 m.

scholarly journals Performance of Multi-Well Exploitation and Reinjection in a Small-Scale Shallow Geothermal Reservoir in Huailai County

2021 ◽  
Vol 9 ◽  
Author(s):  
Wenzhen Yuan ◽  
Dailei Zhang ◽  
Yi Zhang ◽  
Jun Gao ◽  
Tongzhe Liu ◽  
...  
Keyword(s):  
Water Level ◽  
Geothermal Reservoir ◽  
Shallow Aquifer ◽  
Small Scale ◽  
Geothermal System ◽  
Geothermal Reservoirs ◽  
Well Spacing ◽  
Production Temperature ◽  
Thermal Breakthrough ◽  
Production Strategy

The sustainable development of a shallow aquifer geothermal reservoir is strongly affected by the reinjection–production strategy. However, the reinjection–production strategy optimization of a small-scale exploitation unit with tens of meters of well spacing is site specific and has not yet been fulfilled. This study numerically investigates sustainable heat extraction based on various reinjection–production strategies which were conducted in a single-phase aquitard–aquifer geothermal system in Huailai County, Hebei Province, China. The response of the water level and production temperature is mainly discussed. The numerical results show that production without reinjection induces the highest production temperature and also the water level drawdown. Although reinjection in a single doublet well system is conducive to the control of water level drawdown, the introduction of the thermal breakthrough problem causes a decrease in the production temperature. The thermal breakthrough and sustainability of geothermal reservoirs highly depend on the well spacing between the production and reinjection wells, especially for the small-scale field. Therefore, a large well spacing is suggested. A multi-well system facilitates the control of water level drawdown while bringing intensive well interference and thermal breakthrough. Large spacing between the production and reinjection wells is also the basic principle for the design of the multi-well system. A decrease in openhole length leads to an increase in the production temperature and output thermal power. An increase in the production rate affects the thermal breakthrough highly and shortens the lifetime of the geothermal system. Furthermore, the extracted thermal energy is highly affected by the reduction in the reinjection temperature. The results in this study can provide references to achieve sustainable geothermal exploitation in small-scale geothermal reservoirs.

Survival of mouse blastocysts after low-temperature preservation under high pressure

2004 ◽  
Vol 52 (4) ◽  
pp. 479-487 ◽  
Author(s):  
Cs. Pribenszky ◽  
M. Molnár ◽  
S. Cseh ◽  
L. Solti
Keyword(s):  
Phase Transition ◽  
Hydrostatic Pressure ◽  
Low Temperature ◽  
High Hydrostatic Pressure ◽  
Room Temperature ◽  
Freezing Point ◽  
Significant Loss ◽  
Embryo Cryopreservation ◽  
Subzero Temperatures ◽  
Survival Capacity

Cryoinjuries are almost inevitable during the freezing of embryos. The present study examines the possibility of using high hydrostatic pressure to reduce substantially the freezing point of the embryo-holding solution, in order to preserve embryos at subzero temperatures, thus avoiding all the disadvantages of freezing. The pressure of 210 MPa lowers the phase transition temperature of water to -21°C. According to the results of this study, embryos can survive in high hydrostatic pressure environment at room temperature; the time embryos spend under pressure without significant loss in their survival could be lengthened by gradual decompression. Pressurisation at 0°C significantly reduced the survival capacity of the embryos; gradual decompression had no beneficial effect on survival at that stage. Based on the findings, the use of the phenomena is not applicable in this form, since pressure and low temperature together proved to be lethal to the embryos in these experiments. The application of hydrostatic pressure in embryo cryopreservation requires more detailed research, although the experience gained in this study can be applied usefully in different circumstances.

Analytical solution for estimating the influence of a pre-existing ground water flow on a geothermal heat production-injection well system

2011 ◽  
Vol 2 (1) ◽  
pp. 13-17
Author(s):  
I. David ◽  
M. Visescu
Keyword(s):  
Ground Water ◽  
Water Flow ◽  
Geothermal Energy ◽  
Flow Direction ◽  
Energy Resource ◽  
Hot Water ◽  
Injection Well ◽  
Production Well ◽  
Ground Water Flow ◽  
The Earth

Abstract Geothermal energy source is the heat from the Earth, which ranges from the shallow ground (the upper 100 m of the Earth) to the hot water and hot rock which is a few thousand meters beneath the Earth's surface. In both cases the so-called open systems for geothermal energy resource exploitation consist of a groundwater production well to supply heat energy and an injection well to return the cooled water, from the heat pump after the thermal energy transfer, in the underground. In the paper an analytical method for a rapid estimation of the ground water flow direction effect on the coupled production well and injection well system will be proposed. The method will be illustrated with solutions and images for representative flow directions respect to the axis of the production/injection well system.

Sex differences in transaortic flow rate and association with all-cause mortality in patients with severe aortic stenosis

2021 ◽  
Author(s):  
Sahrai Saeed ◽  
Anastasia Vamvakidou ◽  
Spyridon Zidros ◽  
George Papasozomenos ◽  
Vegard Lysne ◽  
...  
Keyword(s):  
Sex Differences ◽  
Aortic Stenosis ◽  
Flow Rate ◽  
Cox Regression ◽  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Ventricular Ejection Fraction ◽  
Cox Regression Analysis ◽  
Increased Risk ◽  
All Cause Mortality

Abstract Aims It is not known whether transaortic flow rate (FR) in aortic stenosis (AS) differs between men and women, and whether the commonly used cut-off of 200 mL/s is prognostic in females. We aimed to explore sex differences in the determinants of FR, and determine the best sex-specific cut-offs for prediction of all-cause mortality. Methods and results Between 2010 and 2017, a total of 1564 symptomatic patients (mean age 76 ± 13 years, 51% men) with severe AS were prospectively included. Mean follow-up was 35 ± 22 months. The prevalence of cardiovascular disease was significantly higher in men than women (63% vs. 42%, P < 0.001). Men had higher left ventricular mass and lower left ventricular ejection fraction compared to women (both P < 0.001). Men were more likely to undergo an aortic valve intervention (AVI) (54% vs. 45%, P = 0.001), while the death rates were similar (42.0% in men and 40.6% in women, P = 0.580). A total of 779 (49.8%) patients underwent an AVI in which 145 (18.6%) died. In a multivariate Cox regression analysis, each 10 mL/s decrease in FR was associated with a 7% increase in hazard ratio (HR) for all-cause mortality (HR 1.07; 95% CI 1.03–1.11, P < 0.001). The best cut-off value of FR for prediction of all-cause mortality was 179 mL/s in women and 209 mL/s in men. Conclusion Transaortic FR was lower in women than men. In the group undergoing AVI, lower FR was associated with increased risk of all-cause mortality, and the optimal cut-off for prediction of all-cause mortality was lower in women than men.

scholarly journals Numerical Investigation on the Influence of Surface Flow Direction on the Heat Transfer Characteristics in a Granite Single Fracture

2021 ◽  
Vol 11 (2) ◽  
pp. 751
Author(s):  
Xuefeng Gao ◽  
Yanjun Zhang ◽  
Zhongjun Hu ◽  
Yibin Huang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Flow Direction ◽  
Heat Extraction ◽  
Geothermal System ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Heat Transfer Capacity

As fluid passes through the fracture of an enhanced geothermal system, the flow direction exhibits distinct angular relationships with the geometric profile of the rough fracture. This will inevitably affect the heat transfer characteristics in the fracture. Therefore, we established a hydro-thermal coupling model to study the influence of the fluid flow direction on the heat transfer characteristics of granite single fractures and the accuracy of the numerical model was verified by experiments. Results demonstrate a strong correlation between the distribution of the local heat transfer coefficient and the fracture morphology. A change in the flow direction is likely to alter the transfer coefficient value and does not affect the distribution characteristics along the flow path. Increasing injection flow rate has an enhanced effect. Although the heat transfer capacity in the fractured increases with the flow rate, a sharp decline in the heat extraction rate and the total heat transfer coefficient is also observed. Furthermore, the model with the smooth fracture surface in the flow direction exhibits a higher heat transfer capacity compared to that of the fracture model with varying roughness. This is attributed to the presence of fluid deflection and dominant channels.

Lowtemperature plasma generator for effective processing of materials

2021 ◽  
Vol 77 (5) ◽  
pp. 587-592
Author(s):  
M. Kh. Gadzhiev ◽  
A. S. Tyuftyaev ◽  
Yu. M. Kulikov ◽  
M. A. Sargsyan ◽  
D. I. Yusupov ◽  
...  
Keyword(s):  
Low Temperature ◽  
Flow Rate ◽  
Gas Flow ◽  
Arc Discharge ◽  
Plasma Jet ◽  
Plasma Generator ◽  
Low Temperature Plasma ◽  
Temperature Plasma ◽  
High Enthalpy ◽  
High Resource

Low-temperature plasma is used in metallurgy for steel alloying by nitrogen, deoxidization of magnetic alloys, obtaining of steels with particularly low carbon content, metal cleaning of nonmetallic inclusions, desulfurization and other refining processes. The wide application of those technologies is restrained by absence of reliable generators of low-temperature plasma (GLP) with sufficient resource of continuous operation. As a result of studies, a universal generator of high-enthalpy plasma jet of various working gases was created. The generator has expanding channel of the output electrode with an efficiency of ~60 % for argon working gas and ~80% for nitrogen and air. It was shown that the developed generator of low-temperature plasma ensures formation of a weakly diverging (2α = 12°) plasma jet with a diameter D = 5–12 mm, an enthalpy of 5–50 kJ/g and a mass average temperature of 5–10 kK, at a full electric power of the arc discharge of 5–50 kW and a plasma-forming gas flow rate of 1–3 g/s. Results of the study of propane additions to the plasma-forming gas effect on the state of cathodes with inserts made of pure tungsten, lanthanum tungsten, and hafnium presented. It was shown that a small propane addition (1%) to the plasma-forming gas, results in reducing effect of the insert material. Study of the GLP operation at arc current 100A with addition to the working gas nitrogen maximum possible volume of propane, which don’t disturb stability of arc showed that for the developed plasma generator at the nitrogen flow rate ~0,45 g/s, the propane flow rate was ~0,33 g/s (not more than ~73 % of the plasma-forming gas). The created high-resource GLP with changeable electrodes enables to obtain at the exit a high-enthalpy plasma flow of various gases (argon, nitrogen, air) and can be a prototype of more powerful plasmotrons of various technological application, in particular for plasma metallurgy.

Oil and Gas Drilling Optimization Technologies Applied Successfully to Unconventional Geothermal Well Drilling

2021 ◽  
Author(s):  
Junichi Sugiura ◽  
Ramon Lopez ◽  
Francisco Borjas ◽  
Steve Jones ◽  
John McLennan ◽  
...  
Keyword(s):  
Geothermal Energy ◽  
Oil And Gas ◽  
Optimization Techniques ◽  
Geothermal System ◽  
Well Drilling ◽  
Geothermal Well ◽  
Gas Drilling ◽  
Drilling Tools ◽  
Drilling Optimization ◽  
Oil And Gas Drilling

Abstract Geothermal energy is used in more than 20 countries worldwide and is a clean, reliable, and relatively available energy source. Nevertheless, to make geothermal energy available anywhere in the world, technical and economic challenges need to be addressed. Drilling especially is a technical challenge and comprises a significant part of the geothermal development cost. An enhanced geothermal system (EGS) is a commercially viable thermal reservoir where two wells are interconnected by some form of hydraulic stimulation. In a commercial setting, fluid is injected into this hot rock and passes between wells through a network of natural and induced fractures to transport heat to the surface system for electricity generation. To construct EGS wells, vertical and directional drilling is necessary with purpose-built drilling and steering equipment. This is an application where oil-and-gas drilling tools and techniques can be applied. A recent well, 16A(78)-32, drilled as part of the US Department of Energy's (DOE's) Utah Frontier Observatory for Research in Geothermal Energy (FORGE) program, highlights some of the technical challenges, which include drilling an accurate vertical section, a curve section, and a 5300-ft 65° tangent section in a hard granitic formation at temperatures up to 450°F (232°C). Extensive downhole temperature simulations were performed to select fit-for-purpose drilling equipment such as purely mechanical vertical drilling tools, instrumented steerable downhole motors, measurement-while-drilling (MWD) tools, and embedded high-frequency drilling dynamics recorders. Downhole and surface drilling dynamics data were used to fine- tune bit design and motor power section selection and continuously improve the durability of equipment, drilling efficiency, and footage drilled. Drilling optimization techniques used in oil and gas settings were successfully applied to this well, including analysis of data from drilling dynamics sensors embedded in the steerable motors and vertical drilling tools, surface surveillance of mechanical specific energy (MSE), and adopting a drilling parameter roadmap to improve drilling efficiency to minimize drilling dysfunctions and equipment damages. Through drilling optimization practices, the instrumented steerable motors with proper bit selections were able to drill more than 40 ft/hr on average, doubling the rate of penetration (ROP), footage, and run length experienced in previous granite wells. This paper presents a case study in which cutting-edge oil-and-gas drilling technologies were successfully applied to reduce the geothermal well drilling time by approximately half.

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