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Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines, but negative effects may occur as the fracturing fluids are absorbed into the coal seam. Gas wettability alteration (GWA) technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change. However, there have been few reported field tests in coal mines using GWA technology. This paper describes a pilot-scale field test in Xinjing coal mine, Yangquan, China. The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate (PMP) was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process. The study focuses on the comparison of two boreholes (Boreholes #9 and #10) and one other borehole (Borehole #8) with and without using GWA approach. A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration. The field test results showed that the average methane drainage rates of Boreholes #9 (39.28 m3/d) and #10 (51.04 m3/d) with GWA treatment exceeded that of Borehole #8 (21.09 m3/d) without GWA treatment, with an increase of 86.3% and 142.1%, respectively. The average methane concentrations of Boreholes #9 (4.05%) and #10 (6.18%) were 64.6% and 151.2% higher than that of Borehole #8 (2.46%), respectively. On the other hand, the dewatering ratio of Boreholes #9 (4.36%) and #10 (3.11%) was almost 19 times and 13 times greater than that of Borehole #8 (0.22%). These field test results were in agreement with the experimental data. The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines. Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.
Lin Jia; Kewen Li; Xiaohong Shi; Lipeng Zhao; Jianshe Linghu. Application of gas wettability alteration to improve methane drainage performance: A case study. International Journal of Mining Science and Technology 2021, 31, 621 -629.
AMA StyleLin Jia, Kewen Li, Xiaohong Shi, Lipeng Zhao, Jianshe Linghu. Application of gas wettability alteration to improve methane drainage performance: A case study. International Journal of Mining Science and Technology. 2021; 31 (4):621-629.
Chicago/Turabian StyleLin Jia; Kewen Li; Xiaohong Shi; Lipeng Zhao; Jianshe Linghu. 2021. "Application of gas wettability alteration to improve methane drainage performance: A case study." International Journal of Mining Science and Technology 31, no. 4: 621-629.
There have been many reports on laboratory experiments measuring TEG (thermoelectric generator) power output at different flow rates of water, different temperatures, and other different conditions, but there have been few field tests utilizing geothermal wells. To this end, we designed a geothermal-TEG apparatus that has a six-layer modularized design to allow expanded power production by increasing the number of layers. After demonstrating the TEG's performance in the laboratory, we tested the apparatus in the field at a well located in the Bottle Rock geothermal field in The Geysers, CA, USA. The whole six-layer TEG device could generate about 500 W electricity with a temperature difference of about 152 °C between the hot and cold fluid manifolds, while each individual TEG chip could generate about 3.9 W. The steam pressure at the inlet of the TEG apparatus was about 122 psi, close to the wellhead pressure of 125 psi. After optimizing the field infrastructure, the TEG device could generate electricity without any leak at the wellhead pressure of 125 psi and the temperature over 176 °C (349 °F). The field test of the six-layer TEG device at Bottle Rock geothermal power plant was considered successful, and plans have begun to design and build a TEG device that could produce power up to 20 kW.
Kewen Li; Geoffrey Garrison; Yuhao Zhu; Michael Moore; Changwei Liu; Jay Hepper; Larry Bandt; Roland Horne; Susan Petty. Thermoelectric power generator: Field test at Bottle Rock geothermal power plant. Journal of Power Sources 2020, 485, 229266 .
AMA StyleKewen Li, Geoffrey Garrison, Yuhao Zhu, Michael Moore, Changwei Liu, Jay Hepper, Larry Bandt, Roland Horne, Susan Petty. Thermoelectric power generator: Field test at Bottle Rock geothermal power plant. Journal of Power Sources. 2020; 485 ():229266.
Chicago/Turabian StyleKewen Li; Geoffrey Garrison; Yuhao Zhu; Michael Moore; Changwei Liu; Jay Hepper; Larry Bandt; Roland Horne; Susan Petty. 2020. "Thermoelectric power generator: Field test at Bottle Rock geothermal power plant." Journal of Power Sources 485, no. : 229266.
Technology using thermoelectric generators (TEG) has many advantages such as compactness, quietness, and reliability because there are no moving parts. One of the great challenges for TEG to be used for power generation is large-scale utilization. It is difficult to manufacture a TEGS system even at the scale of a few kilowatts (kW). To this end, we have designed and built a five-layer TEG apparatus with 90 individual power-producing TEG modules that can be installed with modularized units. Such a system with a layered structure could be expanded in power, something similar to solar Photovoltaics (PV). In this study, laboratory experiments were conducted using the built TEG apparatus to measure the power output and efficiency at different flow rates of water, different temperature, and different temperature differences between hot and cold sides. The effects of these parameters on voltage, power output, and efficiency were investigated and analyzed. The five-layer TEG device could generate about 45.7 W electricity with a temperature difference of 72.2°C between the cold and hot sides. The power of each module was about 0.51 W at this temperature difference. The experimental data can be applied to the design of commercial TEG systems. The expandable TEG system with layered structure provides a possible solution to scaling up TEG power generation to a commercial size.
Kewen Li; Geoffrey Garrison; Michael Moore; Yuhao Zhu; Changwei Liu; Roland Horne; Susan Petty. An expandable thermoelectric power generator and the experimental studies on power output. International Journal of Heat and Mass Transfer 2020, 160, 120205 .
AMA StyleKewen Li, Geoffrey Garrison, Michael Moore, Yuhao Zhu, Changwei Liu, Roland Horne, Susan Petty. An expandable thermoelectric power generator and the experimental studies on power output. International Journal of Heat and Mass Transfer. 2020; 160 ():120205.
Chicago/Turabian StyleKewen Li; Geoffrey Garrison; Michael Moore; Yuhao Zhu; Changwei Liu; Roland Horne; Susan Petty. 2020. "An expandable thermoelectric power generator and the experimental studies on power output." International Journal of Heat and Mass Transfer 160, no. : 120205.
Despite having many promising advantages for environment and sustainability, renewable energy is not yet cost-competitive with crude oil in all locations due to issues with low capacity factor, grid instability, and intermittency. In particular, hybrids of geothermal and solar power systems (e.g. photovoltaic and concentrated solar power) have been shown to be mutually beneficial and a promising combination of renewable energy sources. Worldwide, there are many areas with both high geothermal heat flux and surface radiation, which makes integration of geothermal and solar energies possible. The geothermal industry targets geothermal resources with high temperatures, because the efficiency of power generation from thermal energy is directly proportional to the resource temperature. Unfortunately, most of the geothermal resources have low to moderate temperatures of about 150 °C or less. Alternatively, solar could be used to increase the temperature of geothermal fluids, significantly improving the efficiency of geothermal power generation. Geothermal fluids can serve as storage systems for solar energy, which may solve many problems of solar systems such as weather dependence and instability. On the other hand, the inclusion of photovoltaic (PV) panels in a geothermal power plant may be able to cope with the peak power demand during day time, which is helpful to extend the lifespan of geothermal fields. In this review, we briefly discuss the fundamentals of solar and geothermal power systems. Secondly, we review important progress in the literature towards stand-alone solar or geothermal power systems. Thirdly, we highlight the configurations, mechanisms, and unique features of hybrid solar-geothermal power plants, while also developing a methodology to evaluate their efficacy. Finally, we assess and classify the predominant hybrid solar-geothermal power systems by summarizing and analyzing the stand-alone efficiency, hybrid efficiency, and the percentage of incremental efficiency from the literature. It can be concluded that combining geothermal and solar systems will increase the efficiency and power generation of both energy systems, representing an exciting opportunity for both scientific and practical exploration.
Kewen Li; Changwei Liu; Shanshan Jiang; Youguang Chen. Review on hybrid geothermal and solar power systems. Journal of Cleaner Production 2019, 250, 119481 .
AMA StyleKewen Li, Changwei Liu, Shanshan Jiang, Youguang Chen. Review on hybrid geothermal and solar power systems. Journal of Cleaner Production. 2019; 250 ():119481.
Chicago/Turabian StyleKewen Li; Changwei Liu; Shanshan Jiang; Youguang Chen. 2019. "Review on hybrid geothermal and solar power systems." Journal of Cleaner Production 250, no. : 119481.
Development of geothermal resources on abandoned oil reservoirs is considered environmentally friendly. This method could reduce the rate of energy consumption from oil fields. In this study, the feasibility of geothermal energy recovery based on a deep borehole heat exchanger modified from abandoned oil reservoirs using in situ combustion technology is investigated. This system could produce a large amount of heat compensated by in situ combustion in oil reservoir without directly contacting the formation fluid and affecting the oil production. A coupling strategy between the heat exchange system and the oil reservoir was developed to help avoid the high computational cost while ensuring computational accuracy. Several computational scenarios were performed, and results were obtained and analyzed. The computational results showed that an optimal water injection velocity of 0.06 m/s provides a highest outlet temperature of (165.8 °C) and the greatest power output of (164.6 kW) for a single well in all the performed scenarios. Based on the findings of this study, a geothermal energy production system associated with in situ combustion is proposed, specifically for economic reasons, because it can rapidly shorten the payback period of the upfront costs. Modeling was also performed, and based on the modeling data, the proposed technology has a very short payback period of about 4.5 years and a final cumulative net cash flow of about $4.94 million. In conclusion, the present study demonstrates that utilizing geothermal resources or thermal energy in oilfields by adopting in situ combustion technology for enhanced oil recovery is of great significance and has great economic benefits.
Yuhao Zhu; Kewen Li; Changwei Liu; Mahlalela Bhekumuzi Mgijimi. Geothermal Power Production from Abandoned Oil Reservoirs Using In Situ Combustion Technology. Energies 2019, 12, 4476 .
AMA StyleYuhao Zhu, Kewen Li, Changwei Liu, Mahlalela Bhekumuzi Mgijimi. Geothermal Power Production from Abandoned Oil Reservoirs Using In Situ Combustion Technology. Energies. 2019; 12 (23):4476.
Chicago/Turabian StyleYuhao Zhu; Kewen Li; Changwei Liu; Mahlalela Bhekumuzi Mgijimi. 2019. "Geothermal Power Production from Abandoned Oil Reservoirs Using In Situ Combustion Technology." Energies 12, no. 23: 4476.
Hydraulic fracturing is a widely applied technique used to improve productivity in the oil and gas industry. Spherical proppants are commonly used in hydraulic fracturing, and massive studies have been conducted on proppants of this shape. Rod-shaped proppant has raised considerable interest in recent years, but few researches have been reported on the quantitative evaluation of the new shape proppant. In this paper, based on Hertz theory of elastic contacts, mathematical models were derived to calculate fracture conductivity, reduction in fracture aperture, proppant embedment, and deformation of rod-shaped proppants. The models for calculating the porosity of the fracture with proppants in loose and close packing modes were also established in this study. The results showed that, compared with spherical proppants, rod-shaped ones are theoretically more promising for hydraulic fracturing, especially under low elastic moduli and high closure pressures. From these derived models, rod-shaped proppant of big size might provide better fracture conductivity. It is concluded that the analytical models with correction coefficients could match the rod-shaped proppant embedment and fracture conductivity at different closure pressures. They are of great significance in selecting proppants and helpful to achieve high oil or gas production from hydraulic fracturing with proppants.
Lin Jia; Kewen Li; Jianbin Zhou; Zhiming Yan; Fusang Wan; Mohammed Kaita. A mathematical model for calculating rod-shaped proppant conductivity under the combined effect of compaction and embedment. Journal of Petroleum Science and Engineering 2019, 180, 11 -21.
AMA StyleLin Jia, Kewen Li, Jianbin Zhou, Zhiming Yan, Fusang Wan, Mohammed Kaita. A mathematical model for calculating rod-shaped proppant conductivity under the combined effect of compaction and embedment. Journal of Petroleum Science and Engineering. 2019; 180 ():11-21.
Chicago/Turabian StyleLin Jia; Kewen Li; Jianbin Zhou; Zhiming Yan; Fusang Wan; Mohammed Kaita. 2019. "A mathematical model for calculating rod-shaped proppant conductivity under the combined effect of compaction and embedment." Journal of Petroleum Science and Engineering 180, no. : 11-21.
Both capillary pressure and resistivity in porous rocks is a function of the wetting phase saturation. Mathematically, there should be a relationship between the two parameters because of this common feature. However, few studies have been made regarding this issue. Capillary pressure may be neglected in high permeability reservoirs but not in low permeability reservoirs. It is more difficult to measure capillary pressure than resistivity in many cases. It would be useful to infer capillary pressure from resistivity well logging data if a reliable relationship between capillary pressure and resistivity can be found. To confirm the previous study of a power law correlation between capillary pressure and resistivity index and develop a mathematical model with a greater amount of rock samples, a series of experiments for simultaneously measuring gas–water capillary pressure and resistivity data in 16 core samples from two wells in an oil reservoir were conducted. The permeability of the core samples ranged from 9 to 974 md. The gas–water capillary pressure data were measured with confining pressures using a semi-porous plate technique. We developed a specific experimental apparatus to measure gas–water capillary pressure and resistivity simultaneously. The results demonstrated that the previous power law model correlating capillary pressure and resistivity works well in many cases studied. A more general relationship between the exponent of the power law model and the rock permeability was developed.
Kewen Li; Binchi Hou; Huiyuan Bian; Hongliang Liu; Chengrong Wang; Ronghua Xie. Verification of model for calculating capillary pressure from resistivity using experimental data. Fuel 2019, 252, 281 -294.
AMA StyleKewen Li, Binchi Hou, Huiyuan Bian, Hongliang Liu, Chengrong Wang, Ronghua Xie. Verification of model for calculating capillary pressure from resistivity using experimental data. Fuel. 2019; 252 ():281-294.
Chicago/Turabian StyleKewen Li; Binchi Hou; Huiyuan Bian; Hongliang Liu; Chengrong Wang; Ronghua Xie. 2019. "Verification of model for calculating capillary pressure from resistivity using experimental data." Fuel 252, no. : 281-294.
Kewen Li. A Special Issue on Geothermal Energy and Its Application. Mathematical Geosciences 2019, 51, 267 -269.
AMA StyleKewen Li. A Special Issue on Geothermal Energy and Its Application. Mathematical Geosciences. 2019; 51 (3):267-269.
Chicago/Turabian StyleKewen Li. 2019. "A Special Issue on Geothermal Energy and Its Application." Mathematical Geosciences 51, no. 3: 267-269.
Heat pump systems and radiant floor heating systems are extensively employed to adjust indoor temperatures. Both types of system can reduce energy consumption and increase the coefficient of performance, with some limitations, to further improve energy conservation and environmental protection. For this reason, the development of an environmentally friendly and energy-saving system that is suitable for future energy demands is necessary. A new space heating system coupled with an underground energy storage system, without the use of heat pumps, is proposed herein. To validate the practicality and feasibility of the methodology established in this study, many simulations were performed, and sensitivity analyses of possible influencing factors were conducted. The modeling results proved that human indoor space heating demands can be satisfied with almost zero carbon emissions using the system proposed in this study.
Guoxiang Zhao; Kewen Li; Changwei Liu; Lin Jia; Bheki Mahlalela Mahlalela. Modeling of a Space Heating System Coupled with Underground Energy Storage. Mathematical Geosciences 2018, 51, 373 -400.
AMA StyleGuoxiang Zhao, Kewen Li, Changwei Liu, Lin Jia, Bheki Mahlalela Mahlalela. Modeling of a Space Heating System Coupled with Underground Energy Storage. Mathematical Geosciences. 2018; 51 (3):373-400.
Chicago/Turabian StyleGuoxiang Zhao; Kewen Li; Changwei Liu; Lin Jia; Bheki Mahlalela Mahlalela. 2018. "Modeling of a Space Heating System Coupled with Underground Energy Storage." Mathematical Geosciences 51, no. 3: 373-400.
The addition of nanoparticles into water based fluids (nanofluid) with or without other chemicals to Enhance Oil Recovery (EOR) has recently received intensive interest. Many papers have been published in this area and several EOR mechanisms have been proposed. The main EOR mechanisms include wettability alteration, reduction in InterFacial surface Tension (IFT), increase in the viscosity of aqueous solution, decrease in oil viscosity, and log-jamming. Some of these mechanisms may be associated with the change in disjoining pressure because of the addition of the nanoparticles. The experimental data and results reported by different researchers, however, are not all consistent and some even conflict with others. Many papers published in recent years have been reviewed and the associated experimental data have been analyzed in this paper in order to clarify the mechanisms of EOR by nanofluids. Wettability alteration may be one of the most accepted mechanisms for nanofluid EOR while reduction in IFT and other mechanisms have not been fully proven. The main reason for the inconsistency among the experimental data might be lack of control experiments in which the effect of nanoparticles on oil recovery would be singled out.
Kewen Li; Dan Wang; Shanshan Jiang. Review on enhanced oil recovery by nanofluids. Oil & Gas Science and Technology 2018, 73, 37 .
AMA StyleKewen Li, Dan Wang, Shanshan Jiang. Review on enhanced oil recovery by nanofluids. Oil & Gas Science and Technology. 2018; 73 ():37.
Chicago/Turabian StyleKewen Li; Dan Wang; Shanshan Jiang. 2018. "Review on enhanced oil recovery by nanofluids." Oil & Gas Science and Technology 73, no. : 37.
Polymer flooding, as one of the Enhanced Oil Recovery (EOR) methods, has been adopted in many oilfields in China and some other countries. Over 50% oil remains undeveloped in many oil reservoirs after polymer flooding. It has been a great challenge to find approaches to further enhancing oil recovery when polymer flooding is over. In this study, a new method was proposed to increase oil production using gas flooding with wettability alteration to gas wetness when polymer flooding has been completed. The rock wettability was altered from liquid- to gas-wetness during gas flooding. An artificial oil reservoir was constructed and many numerical simulations have been conducted to test the effect of wettability alteration on the oil recovery in reservoirs developed by water flooding and followed by polymer flooding. Production data from different scenarios, water flooding, polymer flooding after water flooding, gas flooding with and without wettability alteration after polymer flooding, were calculated using numerical simulation. The results demonstrate that the wettability alteration to gas wetness after polymer flooding can significantly enhance oil recovery and reduce water cut effectively. Also studied were the combined effects of wettability alteration and reservoir permeability on oil recovery.
Kewen Li; Changhui Cheng; Changwei Liu; Lin Jia. Enhanced oil recovery after polymer flooding by wettability alteration to gas wetness using numerical simulation. Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 2018, 73, 33 .
AMA StyleKewen Li, Changhui Cheng, Changwei Liu, Lin Jia. Enhanced oil recovery after polymer flooding by wettability alteration to gas wetness using numerical simulation. Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles. 2018; 73 ():33.
Chicago/Turabian StyleKewen Li; Changhui Cheng; Changwei Liu; Lin Jia. 2018. "Enhanced oil recovery after polymer flooding by wettability alteration to gas wetness using numerical simulation." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 73, no. : 33.
Water coning is a major problem in oil reservoirs with bottom water. It reduces the oil production and overall oil recovery. Excessive water production causes corrosion problems in production facilities and increases the cost of water disposal. This may cause the early shutdown of oil wells. In this study, an experimental apparatus has been designed and developed to physically model an oil reservoir with bottom water. The reservoir model was transparent and the change in water coning could be visualized. Many water-flooding tests were conducted at different pressures and oil viscosities ranging from 22 to 260 mPa s. The effects of production pressures and oil viscosity on oil production were investigated. The results indicated that for a medium oil viscosity of 74 mPa s, the optimal production pressure was about 0.054 bar. For minimum and maximum oil viscosity (22 mPa s and 260 mPa s), the smaller the production pressure, the larger the water breakthrough time and oil recovery. Five types of flooding characteristic curves were used to characterize the water-cut variation, and their applicability were compared and analyzed. The water drive curves were fitted using the water-cut models and the oil “reserves” (originally placed in the reservoir model) were predicted using the mathematical models with the experimental data. The results indicated that the Maksimov model of water-drive characteristic curve is more suitable to match the water production performance. Most interestingly, when applying the most suitable model Maksimov water-drive characteristic curve to predict oil reserves, the cases with optimal production pressures have a greater accuracy.
Changwei Liu; Kewen Li; XiaoMing Tian; Guoxiang Zhao; Youguang Chen; B.M. Mahlalela. Experimental studies on production performance of oil reservoirs with bottom water. Journal of Petroleum Science and Engineering 2018, 172, 527 -537.
AMA StyleChangwei Liu, Kewen Li, XiaoMing Tian, Guoxiang Zhao, Youguang Chen, B.M. Mahlalela. Experimental studies on production performance of oil reservoirs with bottom water. Journal of Petroleum Science and Engineering. 2018; 172 ():527-537.
Chicago/Turabian StyleChangwei Liu; Kewen Li; XiaoMing Tian; Guoxiang Zhao; Youguang Chen; B.M. Mahlalela. 2018. "Experimental studies on production performance of oil reservoirs with bottom water." Journal of Petroleum Science and Engineering 172, no. : 527-537.
Much attention has been paid to the application of low temperature thermal resources, especially for power generation in recent years. Most of the current commercialized thermal (including geothermal) power-generation technologies convert thermal energy to electric energy indirectly, that is, making mechanical work before producing electricity. Technology using a thermoelectric generator (TEG), however, can directly transform thermal energy into electricity through the Seebeck effect. TEG technology has many advantages such as compactness, quietness, and reliability because there are no moving parts. One of the biggest disadvantages of TEGs is the low efficiency from thermal to electric energy. For this reason, we redesigned and modified our previous 1 KW (at a temperature difference of around 120 °C) TEG system. The output power of the system was improved significantly, about 34.6% greater; the instantaneous efficiency of the TEG system could reach about 6.5%. Laboratory experiments have been conducted to measure the output power at different conditions: different connection modes between TEG modules, different mechanical structures, and different temperature differences between hot and cold sides. The TEG apparatus has been tested and the data have been presented. This kind of TEG power system can be applied in many thermal and geothermal sites with low temperature resources, including oil fields where fossil and geothermal energies are coproduced.
Jinlong Chen; Kewen Li; Changwei Liu; Mao Li; Youchang Lv; Lin Jia; Shanshan Jiang. Enhanced Efficiency of Thermoelectric Generator by Optimizing Mechanical and Electrical Structures. Energies 2017, 10, 1329 .
AMA StyleJinlong Chen, Kewen Li, Changwei Liu, Mao Li, Youchang Lv, Lin Jia, Shanshan Jiang. Enhanced Efficiency of Thermoelectric Generator by Optimizing Mechanical and Electrical Structures. Energies. 2017; 10 (9):1329.
Chicago/Turabian StyleJinlong Chen; Kewen Li; Changwei Liu; Mao Li; Youchang Lv; Lin Jia; Shanshan Jiang. 2017. "Enhanced Efficiency of Thermoelectric Generator by Optimizing Mechanical and Electrical Structures." Energies 10, no. 9: 1329.
Minghui Zhou; Wenjie Sun; Kewen Li. Experimental research of nano catalyst assisted oxidization upgrading of super heavy oil. SCIENTIA SINICA Technologica 2017, 47, 197 -203.
AMA StyleMinghui Zhou, Wenjie Sun, Kewen Li. Experimental research of nano catalyst assisted oxidization upgrading of super heavy oil. SCIENTIA SINICA Technologica. 2017; 47 (2):197-203.
Chicago/Turabian StyleMinghui Zhou; Wenjie Sun; Kewen Li. 2017. "Experimental research of nano catalyst assisted oxidization upgrading of super heavy oil." SCIENTIA SINICA Technologica 47, no. 2: 197-203.
Changwei Liu; Kewen Li; Dong Ma; Youguang Chen. More general relationship between capillary pressure and resistivity data in gas-water system. Journal of Petroleum Science and Engineering 2016, 146, 505 -514.
AMA StyleChangwei Liu, Kewen Li, Dong Ma, Youguang Chen. More general relationship between capillary pressure and resistivity data in gas-water system. Journal of Petroleum Science and Engineering. 2016; 146 ():505-514.
Chicago/Turabian StyleChangwei Liu; Kewen Li; Dong Ma; Youguang Chen. 2016. "More general relationship between capillary pressure and resistivity data in gas-water system." Journal of Petroleum Science and Engineering 146, no. : 505-514.
Static formation temperature (SFT) is required to determine the thermophysical properties and production parameters in geothermal and oil reservoirs. However, it is not easy to determine SFT by both experimental and physical methods. In this paper, a mathematical approach to predicting SFT, based on a new model describing the relationship between bottom hole temperature (BHT) and shut-in time, has been proposed. The unknown coefficients of the model were derived from the least squares fit by the particle swarm optimization (PSO) algorithm. Additionally, the ability to predict SFT using a few BHT data points (such as the first three, four, or five points of a data set) was evaluated. The accuracy of the proposed method to predict SFT was confirmed by a deviation percentage less than ±4% and a high regression coefficient R2 (>0.98). The proposed method could be used as a practical tool to predict SFT in both geothermal and oil wells.
Changwei Liu; Kewen Li; Youguang Chen; Lin Jia; Dong Ma. Static Formation Temperature Prediction Based on Bottom Hole Temperature. Energies 2016, 9, 646 .
AMA StyleChangwei Liu, Kewen Li, Youguang Chen, Lin Jia, Dong Ma. Static Formation Temperature Prediction Based on Bottom Hole Temperature. Energies. 2016; 9 (8):646.
Chicago/Turabian StyleChangwei Liu; Kewen Li; Youguang Chen; Lin Jia; Dong Ma. 2016. "Static Formation Temperature Prediction Based on Bottom Hole Temperature." Energies 9, no. 8: 646.
One of the key issues to a successful EGS (Enhanced or engineered Geothermal System) is the creation of a great density of fractures. The detection and characterization of the created fractures is crucial in evaluating the geothermal energy resources in such EGS projects as well as in reservoirs for CO2 sequestration and storage. Methods to evaluate the fractures after stimulations are few, and limited in application. To this end, an approach to detecting and evaluating the fractures using resistivity data measured at different frequencies was developed in this study. The effects of fractures on resistivity measurements at different frequencies have been investigated as a function of water saturation in rocks with different porosity, permeability and lithology. Different rocks (Berea sandstone, and greywacke from The Geysers geothermal reservoir) were used in this study. The permeability of the samples ranged from 0.5 to over 1000 md for the matrix. The frequency ranged from 100 to 100,000 Hz. It was found that the effect of frequency on resistivity is different in rocks with and without fractures, especially in the range of low water saturation. The validity of the Archie equation depends on the existence of fractures, the frequency, and the range of water saturation. The relationship between resistivity and water saturation did not follow the Archie equation at low water saturation in some rocks with fractures. Models for characterizing different types of rocks with specific fracture patterns have been established using the resistivity data measured at different frequencies and different water saturations.
Kewen Li; Baozhi Pan; Roland Horne. Evaluating fractures in rocks from geothermal reservoirs using resistivity at different frequencies. Energy 2015, 93, 1230 -1238.
AMA StyleKewen Li, Baozhi Pan, Roland Horne. Evaluating fractures in rocks from geothermal reservoirs using resistivity at different frequencies. Energy. 2015; 93 ():1230-1238.
Chicago/Turabian StyleKewen Li; Baozhi Pan; Roland Horne. 2015. "Evaluating fractures in rocks from geothermal reservoirs using resistivity at different frequencies." Energy 93, no. : 1230-1238.
Spontaneous imbibition happens in many natural and chemical engineering processes in which the mean advancing front usually follows Lucas-Washburn’s law. However it has been found that the scaling law does not apply in many cases. There have been few criteria to determine under what conditions the Washburn law works. The effect of gravity on spontaneous imbibition in porous media was investigated both theoretically and experimentally. The mathematical model derived analytically was used to calculate the imbibition rates in porous media with different permeabilities. The results demonstrated that the effect of gravity on spontaneous imbibition was governed by the hydraulic conductivity of the porous media (permeability of the imbibition systems). The criteria for applying the Lucas-Washburn law have been proposed. The effect of gravity becomes more apparent with the increase in permeability or with the decrease in CGR number (the ratio of capillary pressure to gravity forces) and may be ignored when the CGR number is less than a specific value ≅ 3.0. The effect of gravity on imbibition in porous media can be modeled theoretically. It may not be necessary to conduct spontaneous imbibition experiments horizontally in order to exclude the effect of gravity, as has been done previously.
Kewen Li; Danfeng Zhang; Huiyuan Bian; Chao Meng; Yanan Yang. Criteria for Applying the Lucas-Washburn Law. Scientific Reports 2015, 5, 14085 .
AMA StyleKewen Li, Danfeng Zhang, Huiyuan Bian, Chao Meng, Yanan Yang. Criteria for Applying the Lucas-Washburn Law. Scientific Reports. 2015; 5 (1):14085.
Chicago/Turabian StyleKewen Li; Danfeng Zhang; Huiyuan Bian; Chao Meng; Yanan Yang. 2015. "Criteria for Applying the Lucas-Washburn Law." Scientific Reports 5, no. 1: 14085.
Gas wells may suffer a significant decline in gas production or may even be destroyed as a result of the influx of water into production zones. The situation may even be worse in horizontal wells. Closing off the water-producing zone may not be appropriate and the disposal of produced water is, in many cases, expensive. A substantial decline in gas production is usually associated with an increase in water production or water cut. Water shut-off/reducing water production is helpful in maintaining gas production at high values. In this study, the feasibility of reducing the water production in modelled gas reservoirs by changing the wettability of the gas zone from preferential water- to gas-wetness using a fluorine carbon surfactant has been investigated experimentally. The basic mechanism used is that the entry capillary pressure has to be overcome prior to water entering the gas zone after the wettability has been altered to gas-wetness. Naturally, water can imbibe into gas zones spontaneously because the rock in gas zones is, most probably, water wet. After wettability alteration from water- to gas-wetness, water cannot enter gas zones if the differential pressure is less than the entry capillary pressure, and so the water flux will be significantly reduced even if the differential pressure is greater than the entry capillary pressure. An artificially made, consolidated two-layer core model was used to conduct the study. The two layers had different permeabilities, and the top layer was served as the gas zone and the bottom layer as the bottom aquifer. The gas production was measured at different initial water saturations with and without wettability alteration from preferential water- to gas-wetness in the gas zone. The experimental results showed that the water breakthrough time could be postponed and that the amount of water entering the gas zone could be reduced significantly by altering the wettability of the gas zone to gas-wetness. The advantages of this approach in reducing water cut were: (1) the permeability of the gas zone was almost unaffected by the chemical treatment for wettability alteration; and (2) the chemical treatment for wettability alteration had great longevity.
Kewen Li; Long Ge; Haoping Zhang. Water shut-off by wettability alteration to gas-wetness in modelled gas reservoirs. Petroleum Geoscience 2015, 21, 211 -216.
AMA StyleKewen Li, Long Ge, Haoping Zhang. Water shut-off by wettability alteration to gas-wetness in modelled gas reservoirs. Petroleum Geoscience. 2015; 21 (2-3):211-216.
Chicago/Turabian StyleKewen Li; Long Ge; Haoping Zhang. 2015. "Water shut-off by wettability alteration to gas-wetness in modelled gas reservoirs." Petroleum Geoscience 21, no. 2-3: 211-216.
Kewen Li; Huiyuan Bian; Changwei Liu; Danfeng Zhang; Yanan Yang. Comparison of geothermal with solar and wind power generation systems. Renewable and Sustainable Energy Reviews 2015, 42, 1464 -1474.
AMA StyleKewen Li, Huiyuan Bian, Changwei Liu, Danfeng Zhang, Yanan Yang. Comparison of geothermal with solar and wind power generation systems. Renewable and Sustainable Energy Reviews. 2015; 42 ():1464-1474.
Chicago/Turabian StyleKewen Li; Huiyuan Bian; Changwei Liu; Danfeng Zhang; Yanan Yang. 2015. "Comparison of geothermal with solar and wind power generation systems." Renewable and Sustainable Energy Reviews 42, no. : 1464-1474.