Thermal Recovery Research Articles

Granular Calcium Carbonate Reinforced the Cement Paste Cured by Elevated Temperatures.

In a heavy oil thermal recovery well, cement paste experiences the cyclic elevated temperature and steam of steam stimulation, the elevated temperature and steam of steam driving, and the high-concentration CO2 (HCC) of in situ combustion conditions in sequence. To understand the effects of different conditions of heavy oil thermal recovery wells on the properties and microstructure of the cement paste, this paper investigated the influence of the cyclic elevated temperature, elevated temperature, and high-concentration CO2 conditions on the compressive strength of the cement paste. Then, low-field nuclear magnetic resonance, scanning electron microscopy, and X-ray diffraction were used to test the pore structure, microstructure, and crystal type of the cement paste cured under different conditions. Experimental results showed that the elevated temperature curing loosened the microstructure of the cement paste and increased its pore size and porosity, resulting in reducing the compressive strength to 21.04 MPa, compared with that of the cement paste at cyclic elevated temperature. For the cement paste cured under high-concentration CO2 conditions, the calcium hydroxide and calcium-silicate-hydrate reacted with CO2 to generate granular vaterite, aragonite, and calcite in the pores and cracks, which repaired the cement paste by reducing the porosity and pore size of the cement paste and increasing its compressive strength. When the carbonation time increased to 28 days, the cement paste was completely carbonized, and the compressive strength of the cement paste increased by approximately 169%, compared with that of the cement paste cured at an elevated temperature.

Current Status and Development Direction of Low-Carbon Exploitation Technology for Heavy Oil

With the strategic goal of “carbon peaking and carbon neutral” in China, new requirements are also put forward for the thermal recovery of heavy oil. In view of the problems of excessive greenhouse gas emission, low steam utilization rate, poor economic efficiency, and limited reservoir application of steam stimulation replacement technology in China, the emerging technologies of medium- and low-temperature thermal fluid, solvent-assisted high-temperature steam injection, solvent-based medium- and low-temperature waterless recovery and in situ electric heating-assisted recovery are discussed in terms of technical principles, technical parameters, experimental/field effects, and technical and economic potential. The technical principles, technical parameters, experimental/field results, and techno-economic potential of low-carbon heavy oil recovery technologies are summarized and future development directions and trends are anticipated. The study’s findings indicate that some of the technologies that have been tested in the field, such as HWVP, EMVAPEX, AH-VAPEX, LASER, and ESEIEH, can be developed by relying on the original well groups for production and can reduce greenhouse gas emissions, such as CO2, by about 80% and improve crude oil recovery by 5% to 10%, while the technologies concerned have outstanding effects on increasing oil production rate and lowering upfront capital investment. Some of the technologies that have been tested significantly increase oil production rate, lower initial capital expenditure, and enable solvent recycling, among other things. Among them, COBEEOR and N-SOLV technologies can also lower the amount of asphaltene in the output crude oil, enhance the API of the recovered crude oil, and provide strong economic advantages. CSP, CHSI, and hot water solvent injection were tested in indoor two-dimensional and three-dimensional experiments to validate their feasibility, while CO2, propane, and butane solvents were initially screened and some of the technologies’ mechanisms were revealed to lay the groundwork for pilot projects. The executive summary of the research findings will serve as a guide for future low-carbon extraction technology research and development in China.

Optimized geothermal energy extraction from hot dry rocks using a horizontal well with different exploitation schemes

In the foreseeable future, the geothermal exploitation from hot dry rocks (HDR) using a horizontal well will bear potential. Thus, in-depth studies should be conducted on the selection of injection-production scheme (IPS) and working fluid, design of reinjection parameters, optimization of wellbore structure and materials, and analysis of geological settings. This paper proposed a fully coupled model to study the above scientific questions. For Model A, the working fluid was injected into the annulus and then flowed out of the thermal insulation pipe (TIP). Its temperature passes through two stages of temperature rise and two stages of temperature decline. But for model B, the working fluid was injected into the TIP and then flowed out of the annulus. Its temperature undergoes five stages, four stages of temperature rise and one stage of temperature decline. The results show that the Model A is the best IPS owing to its high outlet temperature, stable thermal recovery, and low fluid injection volume. In Model A, when the working fluid was supercritical carbon dioxide and the liquid injection volume was 135.73 m3/d, the heat recovery ratio (HRR) was as high as 85.40%, which was 17.85% higher than that of the Model B whose working medium was water, and its liquid injection volume was only 25% of that. Meanwhile, over ten years of continuous production, the outlet temperature decreased by 7.5 °C and 18.38 °C in the latter. The optimal working fluid has a low volume heat capacity and thermal conductivity for any IPS. Sensitivity studies showed that for the area that met the HDR standard, the effect of reinjection temperature on the outlet temperature can be ignored. As for Model A, HRR drops sharply by 6.74–9.32% when TIP goes from completely adiabatic to nonzero thermal conductivity. Meanwhile, the horizontal segment length of the TIP is shorter when Model A obtains the optimal outlet temperature compared with Model B. In addition, the correlation between the outlet temperature and different formations of thermophysical properties was seriously affected by the IPS and exploitation period, which was summarized in detail.

Dimethyl ether-steam assisted gravity drainage: Physical 2D heavy oil simulation

Steam-assisted gravity drainage (SAGD) is a mature heavy oil thermal recovery technology but inherently limited to low recovery efficiency at mid-late stage due to the increasing heat loss in the steam chamber. Here, the dimethyl ether (DME)-assisted SAGD technology and its relevant transport and interfacial properties are specifically investigated through physical 2D heavy oil simulation. A total of four-set physical experiments, with different DME injection ratios, were conducted and compared with the traditional SAGD. The experimental results indicate DME is capable of reducing the heavy oil’s viscosity and interfacial tension at high temperatures. Three stages, rising, lateral expansion, and descending stages, are determined in the SAGD steam chamber’s development; the mid-late SAGD stage is defined when the steam chamber extends to the caprock boundary. With DME additions at the mid-late SAGD stage, higher oil recovery factor and sweep efficiency could be reached and the dew point temperature of steam chamber’s lead decreases by 0.7–1.8 °C. The optimum gas–water ratio is determined to be 3:1, with the fastest oil recovery growth and the highest final cumulative oil-vapor ratio of 0.163. This study provides reliable experimental bases and valuable analyses for the DME-SAGD technology and its application in heavy oil reservoirs.

Uncertainty quantification and optimization method applied to time-continuous geothermal energy extraction

Uncertainties in static and dynamic subsurface parameters are involved in geothermal field modeling. The quantification of such uncertainties is important to guide field-development alternatives and decision-making. This work presents a novel method for estimating thermal recovery and produced-enthalpy rates, combined with uncertainty quantification and optimization. We use time-continuous, multi-objective uncertainty quantification for geothermal recovery by water re-injection. The uncertainty ranges were determined using a database of 135 geothermal fields. Thermal recovery and produced-enthalpy rates are then evaluated as functions of dimensionless uncertainty parameters. Using the proposed method, a set of 25 geothermal fields are analyzed to determine optimal well spacing. This method quantifies time-continuous uncertainty and global sensitivity for geothermal field modeling undergoing re-injection when detailed subsurface data are not available.

Introduce dimethyl ether (DME) as a solvent for steam-assisted gravity drainage (SAGD) co-injection: An effective and environmental application

Conventional heavy oil and bitumen thermal recovery is currently facing increasing energy demands and climate-related challenges. Dimethyl ether (DME) as a renewable and sustainable solvent was recently proposed as a possible solution for a carbon transition to hydrogen economics. However, only limited studies with unclear mass transfer mechanisms have been conducted on DME and its co-injected on steam-assisted gravity drainage (SAGD) optimization. In this study, a numerical model was developed to investigate the DME-based expanding-solvent SAGD (ES-SAGD) process to capture the complex mechanisms involved. The impact of temperature on relative permeability curves and coupled heat/mass transfer were further discussed in detail. The results of DME-based ES-SAGD and conventional SAGD were compared in terms of process performance and energy efficiency as well as carbon intensity. The optimal range of DME concentration was investigated to achieve the highest recovery factor, and with the assistance of DME carbon intensity can be reduced to one quarter to half of that in conventional SAGD. The study confirmed DME is a novel solvent that leads to the viable performance of ES-SAGD to meet carbon emission reduction objectives.

An Algorithm to Optimize Water Injection Temperature for Thermal Recovery of High Pour Point Oil

With the advancement of conventional water displacement technology, cold damage may affect the vicinity of high pour point oil wells to a certain extent. Thus, the optimization of thermal recovery parameters of high pour point oil is of great significance to the oil field. In this study, a comprehensive model of the temperature distribution of the wellbore fluid was constructed, and the function of f(tD) was introduced to participate in the calculation of the thermal resistance of the formation. The temperature distribution along the wellbore was calculated and simulated under different conditions. The results show that the surface water injection temperature of 60.8℃ could ensure the desired water temperature reaching the target layer, and the injection temperature of 60.4°C could meet the needs of efficient development after considering the design of the 750-m insulated tubing. The final thermal recovery parameter optimization system could provide a theoretical reference for the thermal recovery design of the same type of reservoir.

Repetitive High-Power Microwave Pulses Induced Failure on a GaAs HBT LNA

This study aims at studying the damage effect of gallium arsenide (GaAs) heterojunction bipolar transistor (HBT) low noise amplifier (LNA) with repetitive high-power microwave (HPM) pulses. The theoretical function for the thermal accumulation effect is derived, which depends on the pulsewidth, the pulse repetition frequency (PRF), and the input power. A simulation model is established to investigate the thermal accumulation effect of repetitive HPM pulses on the HBT. The electric field, current density, and temperature distributions in the HBT with repetitive HPM pulses are discussed first. The influence of the repetitive HPM pulse parameters on the thermal accumulation effect is studied by theoretical analyses and simulations. Results show that the thermal recovery time increases with the pulsewidth or the input power increases. In addition, it is concluded that the frequency does not affect the thermal recovery time. The simulation results agree with the theoretical results. Finally, the damage effect of repetitive HPM pulses is experimentally verified.

The Coming Tide of Wind Turbine Blades Retirement: Threats and Treatment Measures

Wind energy is a kind of clean energy widely used all over the world. Since the 10th of this century, the world has been facing the environmental problem of a large amount of waste produced by retired wind turbines. The blades are difficult to be recycled because of their high strength, corrosion resistance and special materials. The scrapping of wind turbines brings challenges to the sustainable utilization of wind energy. This paper studies the problems brought by the previous methods of treating waste wind turbine blades, including the impact on the surrounding soil and water environment, the emission of air pollutants and greenhouse gases, and the harm to animals, plants and microorganisms in the environment. This paper also introduces the current feasible recovery processes: the mechanical recovery process is relatively simple and has low energy consumption, but the application of the recovered materials is narrow; Thermal recovery can produce widely used products and its by-products have additional value, but the energy consumption is high; Chemical treatment can obtain high-quality recycled products, but the high cost and slow reaction speed make it difficult to deal with a large number of waste blades. The biological treatment methods which has certain application prospect are expected. At the same time, from the perspective of waste generation, this paper studied the recyclable blade materials that includes thermoplastic resin and biomass composites, which provides a feasible way to completely solve the problem of waste wind power blades in the future.

Experimental and theoretical investigation of the damage evolution of irradiated MoAlB and WAlB MAB phases

The MAB phases are an advanced set of ceramic materials, some of which have been recently found to theoretically possess good shielding capacity against both gamma-rays and neutrons with different energies. The radiation tolerance and thermal recovery processes of WAlB were investigated and compared with MoAlB (both type-222 MAB phases) in this work using a combination of experimentation and DFT calculations for the first time. GIXRD and Raman spectroscopy of damaged and annealed specimens for bulk MoAlB and WAlB revealed that they have similar tolerance to radiation-induced amorphization and display similar recrystallization at high temperatures. Defect behavior was assessed and discussed relating to the type of atomic interactions within the crystal structure, as well as defect kinetics. This study suggests that type-222 MAB phase materials are promising radiation shielding materials which should be considered in future nuclear fusion reactor designs.

Wetting hysteresis as the mechanism of heat pipe post-dryout thermal hysteresis and recovery

Heat pipes and vapor chambers are passive thermal management devices used for efficient heat transport by phase change. Their passive operation is enabled by capillary pumping of the working fluid in a porous wick, which is operationally limited by the maximum pressure head it can provide. This capillary limit marks the maximum heat input at which the capillary pressure generated can overcome the pressure drop in the wick; operating above the capillary limit at steady state leads to dryout. Heat pipes and vapor chambers are increasingly being used in electronics systems where end-user activity dictates the transient power input which can therefore be highly variable and time-dependent. It was recently shown that heat pipes can withstand a power pulse exceeding the capillary limit for brief time intervals. Under such operating conditions, the heat pipe will experience dryout only if the duration of the pulse load is longer than a certain characteristic time interval. The pulse-load-induced dryout may result in an increased thermal resistance when the power is reduced back down to pre-dryout levels, thus exhibiting a hysteresis in heat pipe thermal performance. In this work, we experimentally characterize the recovery from pulsed-load-induced dryout. We further propose that the observed change in steady-state thermal performance before and after dryout results from contact angle hysteresis at the three-phase contact line of the wick-liquid interface. A model is developed based on this proposed mechanism to predict the nature of recovery from dryout-induced thermal hysteresis, as well as to identify that a given heat pipe has a maximum possible hysteresis. The experiments illustrate the trends inferred from the model for the recovery process and confirm the existence of a “maximum hysteresis line,” which identifies the worst-case scenario for thermal hysteresis after heat pipe dryout. Based on these mechanistic learnings, a new testing protocol is proposed for experimentally characterizing this post-dryout maximum hysteresis signature for a heat pipe.

MXene based immobilized microorganism for chemical oxygen demand reduction of oilfield wastewater and heavy oil viscosity reduction to enhance recovery

The high energy consumption drawbacks of thermal recovery of heavy oil are becoming increasingly apparent, contrary to the goal of being green, environmentally friendly and low carbon. In this work, a carrier was designed for the immobilization of Bacillus subtilis using lecithin(PC)-modified magnetized Ti2C3 MXenes (PC-g-Fe3O4/Ti2C3) for heavy oil exploitation, which effectively reduced the chemical oxygen demand (COD) of oilfield wastewater and viscosity of heavy oil. According to orthogonal tests, the ideal temperature for immobilizing Bacillus subtilis was 38 °C, the ideal pH was 7, the desired mineralization was less than 20,000 ppm, the COD removal rate was over 80 %, and the heavy oil's viscosity was reduced by 77.5 %, and the carrier could be recycled and reused. As the results of the displacement experiment showed, the microbial oil drive with the carrier (PC-g-Fe3O4/Ti2C3) could enhance the recovery of heavy oil by 28.39 %, which was due to the reduction of COD and viscosity of the heavy oil in the reinjection water. So, PC-g-Fe3O4/Ti2C3 has excellent potential for use in the oil field because it is very effective, affordable, and ecologically benign.

Gravity Drainage of Bitumen Induced by Solvent Leaching.

Steam-based thermal recovery processes are energy-intensive and pose environmental concerns due to their high greenhouse gas emissions. The application of solvents has shown promise in reducing the environmental impact of these processes. In this work, the solvent chamber theory is used to study the gravity drainage of bitumen. The results reveal that the drainage rate can be scaled using the thermophysical properties of solvents. The drainage rate is shown to be directly related to the density difference between bitumen and solvent and inversely proportional to the mixture viscosity. A universal scaling relation between the Sherwood number, as a measure of the mass transfer, and Rayleigh number, as a measure of the natural convection, in the form of Sh = βRa is presented using the experimental data of various solvents. This linear relationship is consistent with the theoretical studies of buoyancy-driven convection. Moreover, the scaling prefactor β is found to decrease with increasing natural log of the mobility ratio (α), which results in a lower rate of convective mass transfer. Furthermore, a new critical Rayleigh number equation based on the power-law mixing rule (PLMR) is derived, and the results are compared with the available theories in the literature based on the exponential mixing rule (EMR). The findings provide insights into understanding the convective dissolution with large viscosity contrast. Furthermore, the developed scaling relation provides a useful tool to predict the convective mixing of different bitumen/solvent systems. The results find application in the design of the solvent-based bitumen recovery processes.

Molecular Dynamics Investigation of Wettability Alteration of Quartz Surface under Thermal Recovery Processes.

One of the primary methods for bitumen and heavy oil recovery is a steam-assisted gravity drainage (SAGD) process. However, the mechanisms related to wettability alteration under the SAGD process still need to be fully understood. In this study, we used MD simulation to evaluate the wettability alteration under a steam injection process for bitumen and heavy oil recovery. Various oil droplets with different asphaltene contents were considered to determine the effect of an asphaltene content on the adsorption of the oil droplets onto quartz surfaces and wettability alteration. Based on the MD simulation outputs, the higher the asphaltene content, the higher the adsorption energy between the bitumen/heavy oil and quartz surfaces due to coulombic interactions. Additionally, the quartz surfaces became more oil-wet at temperatures well beyond the water boiling temperature; however, they were extremely water-wet at ambient conditions. The results of this work provide in-depth information regarding wettability alteration during in situ thermal processes for bitumen and heavy oil recovery. Furthermore, they provide helpful information for optimizing the in situ thermal processes for successful operations.

Heat transfer enhancement and free convection assessment in a double-tube latent heat storage unit equipped with optimally spaced circular fins: Evaluation of the melting process

To overcome the weak conduction heat transfer of phase change materials (PCM), this investigation aimed to assess the behavior of a double-tube latent heat storage unit with circular fins through the charging process. The influence of free convection in the presence of fins of various arrangements and sizes was comprehensively studied. The geometrical characteristics of the fins, i.e., their size and number, were assessed to optimize their performance. Moreover, a sensitivity assessment was performed on the characteristics of the heat transfer fluid passing through the inner tube, i.e., the Reynolds number and temperature. Charging time diminished by 179% when nine 15 mm fins were added compared with the finless scenario, assuming the same phase change materials volume. Moreover, the system’s thermal recovery rate improved from 20.5 to 32.9 W when nine fins with the heigth of 15 mm were added. The use of more fins improved the thermal behavior of the phase change materials because of the higher total fin area. The melting time and heat storage rate changed by 76% and 71%, respectively, for the system with 19 fins compared with those with four fins. Moreover, the outcomes indicated that a higher heat storage rate can be achieved when the working medium’s faster flow and inlet temperature were used.

Thermal recovery characteristics of rock and soil around medium and deep U-type borehole heat exchanger

Medium and deep U-type borehole heat exchanger (MDUBHE) coupled with ground source heat pumps is a novel technique to extract geothermal energy from deep rock and soil. The thermal recovery characteristics of rock and soil are critical for the sustainable exploitation of deep geothermal energy. However, the thermal recovery characteristics of rock and soil around MDUBHE are unclear. In this study, a coupled heat transfer model considering multilayer properties is established to reveal the thermal recovery characteristics of rock and soil. The root mean square errors (RMSE) of this model are 1.8 °C and 0.3 °C compared with the experimental and CFD simulation data, respectively. The temperature distribution of rock and soil under short-term and long-term operations is investigated. The results show that the thermal recovery rate of deep rock and soil is over 91.2% after one heating-recovery cycle (1 year). The thermal decay rate of rock and soil after 15 years of operation is less than 9.3%. Furthermore, the thermal effect zone of MDUBHE increases faster early and slower later. The thermal effect zones of the descending pipe are 38.2 m, 74.3 m, 109.1 m, and 132.2 m in the 1st, 5th, 10th, and 15th years, respectively. This study could promote the stable utilization of deep geothermal energy with MDUBHE system.

Change Characteristics of Heavy Oil Composition and Rock Properties after Steam Flooding in Heavy Oil Reservoirs

The thermal recovery method of steam flooding is one of the most common development methods for heavy oil reservoirs. However, after multiple rounds of steam injection development, the composition of crude oil and reservoir rock properties have changed greatly, which is unfavorable for the subsequent enhanced oil recovery. It is necessary to study the distribution of the remaining oil after the thermal recovery of heavy oil reservoirs, and clarify the change characteristics of the components of the crude oil under different steam injection conditions. At the same time, the change of porosity and the permeability of the rocks after steam flooding, and its influence on oil recovery, are investigated. In this paper, the composition changes of heavy oil before and after steam flooding are studied through experiments and numerical simulation methods. A numerical model is established to study the retention characteristics of heavy components in heavy oil reservoirs by the CMG software. The effects of different steam injection conditions, and heavy oil with different components on the residual retention of heavy components, are compared and studied. The changes of rock physical properties in heavy oil reservoirs after steam flooding is clarified. The results show that after steam flooding, the heavy components (resin and asphaltenes) of the recovered oil decrease, and the heavy components in the formation increase in varying degrees. With the increase of heavy components in the crude oil, the remaining oil in the formation increases after steam flooding, and the retention of heavy components increases; after steam flooding, the stronger the rock cementation strength, the higher the degree of reserve recovery, and it is difficult to form breakthrough channels; the greater the steam injection intensity, the earlier to see steam breakthrough in the production well, and the lower the degree of reserve recovery. The research reveals the changes of heavy oil components and rock properties after steam flooding, providing support for the subsequent enhanced oil recovery.

Thermal Recovery of the Electrochemically Degraded LiCoO2/Li7La3Zr2O12:Al,Ta Interface in an All-Solid-State Lithium Battery.

All-solid-state lithium batteries are promising candidates for next-generation energy storage systems. Their performance critically depends on the capacity and cycling stability of the cathodic layer. Cells with a garnet Li7La3Zr2O12 (LLZO) electrolyte can show high areal storage capacity. However, they commonly suffer from performance degradation during cycling. For fully inorganic cells based on LiCoO2 (LCO) as cathode active material and LLZO, the electrochemically induced interface amorphization has been identified as an origin of the performance degradation. This study shows that the amorphized interface can be recrystallized by thermal recovery (annealing) with nearly full restoration of the cell performance. The structural and chemical changes at the LCO/LLZO heterointerface associated with degradation and recovery were analyzed in detail and justified by thermodynamic modeling. Based on this comprehensive understanding, this work demonstrates a facile way to recover more than 80% of the initial storage capacity through a thermal recovery (annealing) step. The thermal recovery can be potentially used for cost-efficient recycling of ceramic all-solid-state batteries.

Integrating Physical and Numerical Simulation of Horizontal Well Steam Flooding in a Heavy Oil Reservoir

Abstract LD-N extra-heavy oil reservoir in Bohai Sea is characterized with deep burial and large bottom water. Horizontal-well steam huff “n” puff has been applied, yet due to water coning and serious heat losses, the oil recovery after three cycles turned out to be rather low (1.58%). To find an appropriate follow-up process, this study proposed and analyzed three different flooding schemes: steam flooding, multiple-thermal-fluid flooding, and foam flooding. Scaled 3D physical experiments and corresponding numerical simulation have been conducted to investigate the heating chamber development and fluid production. History match and parametric analyses have been carried out to optimize the well performance and operating conditions. The optimized results include 360 m3/d instantaneous steam injection rate, 1.3–1.4 production-injection ratio, and 13–16 m water avoidance height. In addition, the production well is recommended to be placed above the injection well. These findings provide a useful guidance for the design of thermal recovery schemes and the optimization of production processes for heavy oil reservoirs with bottom water.

Assessment of chronic limb threatening ischemia using thermal imaging

ObjectivesCurrent chronic limb threatening ischemia (CLTI) diagnostics require expensive equipment, using ionizing radiation or contrast agents, or summative surrogate methods lacking in spatial information. Our aim is to develop and improve contactless, non-ionizing and cost-effective diagnostic methods for CLTI assessment with high spatial accuracy by utilizing dynamic thermal imaging and the angiosome concept. ApproachDynamic thermal imaging test protocol was suggested and implemented with a number of computational parameters. Pilot data was measured from 3 healthy young subjects, 4 peripheral artery disease (PAD) patients and 4 CLTI patients. The protocol consists of clinical reference measurements, including ankle- and toe-brachial indices (ABI, TBI), and a modified patient bed for hydrostatic and thermal modulation tests. The data was analyzed using bivariate correlation. ResultsThe thermal recovery time constant was on average higher for the PAD (88%) and CLTI (83%) groups with respect to the healthy young subjects. The contralateral symmetry was high for the healthy young group and low for the CLTI group. The recovery time constants showed high negative correlation to TBI (ρ = -0.73) and ABI (ρ = -0.60). The relation of these clinical parameters to the hydrostatic response and absolute temperatures (|ρ|<0.3) remained unclear. ConclusionThe lack of correlation for absolute temperatures or their contralateral differences with the clinical status, ABI and TBI disputes their use in CLTI diagnostics. Thermal modulation tests tend to augment the signs of thermoregulation deficiencies and accordingly high correlations were found with all reference metrics. The method is promising for establishing the connection between impaired perfusion and thermography. The hydrostatic modulation test requires more research with stricter test conditions.