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The influence of P content on Curie temperature, magnetic properties and microstructures of Fe81.5Si3B10+xP3.5−xC0.2Cu0.8Nb1 (x = 0, 1, 2, and 3 at.%) alloys subjected to magnetic field annealing has been studied. Here, the decrease in P content can improve Curie temperature of alloys from about 575 to 584 K, which increases the operating temperature of magnetic device. Via optimal field annealing technique, the amorphous alloy with x = 3 exhibits good soft magnetic properties, including saturation magnetic flux density of 1.53 T, high effective permeability above 12,000, low coercivity below 3 A/m, and low core loss around 0.18 W/kg. The hysteresis loops show that tuning down the content of P relative to B can increase the saturation magnetic flux density of alloy system. Besides, the investigation about the microstructures of alloys annealed at optimal conditions indicates that longitudinal magnetic field annealing can improve the stability of amorphous phase, thereby ensuring the amorphous structure annealed at a higher annealing temperature compared with the general annealing for alloys.

Phosphorus (P) is a cheap and effective element that inhibits grain growth and improves soft magnetic properties in Fe-based nanocrystalline alloys. However, most alloys usually require high P content, leading to problems such as volatilization and oxidation during production process. In this paper, we study and report new findings regarding the effect of P microalloying on the magnetic properties, microstructure and magnetic domain structure of Fe77.8Si10B9−xCu0.6Nb2.6Px (x = 0 and 1) nanocrystalline alloys. The substitution of B by 1 at% P has little influence on the crystallization behavior, saturation magnetic flux density (Bs) and permeability (μ) of the alloy, while effectively reduces the coercivity (Hc) in a wide annealing temperature range. The reduced Hc can be attributed to the low magnetocrystalline anisotropy and wide magnetic domains caused by uniform and fine α-Fe(Si) grains. The mechanism of structural evolution induced by 1 at% P is also been discussed. The P microalloyed nanocrystalline alloy with high Bs of 1.43 T, high μ up to 27,000 at 1 kHz, and low Hc of 1.4 A/m is suitable for magnetic shielding piece of wireless charging.

Horizontal well based thermal recovery processes have been widely applied to recover the heavy oil resources all over the world. But, the flow behavior of hot fluids along a horizontal wellbore is still unclear. In this paper, a scaled cylindrical wellbore model is designed to experimentally simulate the steam injection process using horizontal well. Based on this model, a set of experiments are firstly performed to analyze the steam injection profile along horizontal wellbore. And the effects of different sensitive parameters on stream conformance are discussed. Results indicate that different steam injection operation can yield a different heating performance. During steam injection process, the wellbore segments closed to the steam outflow point can have a better heating performance. In comparison, a high steam injection rate is more beneficial on the uniform steam conformance along horizontal wellbore. The two-ends steam injection strategy can produce a more uniform steam injection profile than the single heel/toe end injection method. The addition of non-condensable gas (NCG) can also improve the steam conformance along horizontal wellbore. Moreover, from the experimental observation, it is also observed that the permeability heterogeneity along the horizontal wellbore is a significantly important parameter on the steam injection profile. The well completion method tremendously impacts the steam conformance along horizontal wellbore. For field operation, in order to obtain a more uniform steam conformance, it should be avoided to place the horizontal well in a high heterogeneous area, and slotted liner will be the preferred method for a horizontal well based thermal recovery process.

The development of Fe-based nanocrystalline alloys with high saturation magnetization (Bs), excellent magnetic softness and good manufacturability is highly desirable. Here, the effect of substituting 1 at% P for B and Si on the thermal stability, microstructure and magnetic properties of Fe76Cu0.8Nb2.2B9Si12 alloy has been studied in detail. It was found that replacing B with P effectively reduces the coercivity (Hc) of the alloy without deteriorating the Bs and permeability (μ). However, replacing Si with P has little effect on the Hc and Bs, yet significantly reduces the μ. The variation in the magnetic properties can be well understood from the evolution of the microstructure and magnetic anisotropy induced by P microalloying. The Fe76Cu0.8Nb2.2B8Si12P1 alloy with a good processing window, a high Bs of 1.41 T, a great μ of 29,000 at 1 kHz and a low Hc of 0.6 A/m is suitable for high-power electronic devices.

Metalloid elements significantly affect the microstructure and magnetic properties of Fe-based nanocrystalline alloys. However, adding multiple metalloids would complicate the impact of each metalloid on magnetic properties. Here, we have found that Fe81.3SixByP17-x-yNb1Cu0.7 nanocrystalline alloys exhibit high saturation magnetic flux density (Bs) of 1.73–1.79 T and low coercivity (Hc) of 4–6 A/m. It was found that Si, B and P elements have strong synergistic effects on the thermal stability, magnetic properties, microstructure and crystallization kinetics of the alloys. Keeping the P content and Si/B ratio at a moderate level is the key to obtaining an ultrafine nanocrystalline structure with high Bs and good soft magnetic properties. The underlying mechanism by which the addition of multiple metalloids affects the microstructure and magnetic properties has been revealed.

The effect of Si/B ratio on the magnetic properties, microstructure, magnetic domain structure, and crystallization kinetics of Fe77Si10+xB9-xNb2Cu1Al1 (x=0, 1, 2 at%) nanocrystalline alloys has been investigated. The slight increase in Si/B ratio has minimal effect on the saturation magnetization of the alloys, but effectively increases the permeability and decreases the coercivity in a wide annealing temperature range. Substituting 2% Si for B significantly increases the activation energy of α-Fe(Si) growth and Fe3B precipitation, leading to the formation of uniform, fine and stable α-Fe(Si) grains. This structure is beneficial to reduce the magnetocrystalline anisotropy and magnetoelastic anisotropy of the alloy, and form wide and smooth-moving magnetic domains, thus significantly improving the soft magnetic properties.

Using the methods of physical simulation and numerical simulation, the feasibility of polymer-enhanced foam injection after polymer flooding is studied. First, an experiment-based screening criteria for polymer-enhanced foams is presented, and the influence of polymer concentration on foam mobility is investigated. Thereafter, the parallel experiments of polymer-enhanced foam injection and conventional foam injection after polymer flooding are performed. A Lorentz–Monte-Carlo method is then proposed to establish the heterogeneous geological models with different interlayer and plane heterogeneity. Thus, the sensitivity of reservoir heterogeneities on oil recovery of enhanced foam injection is analyzed numerically, and the implementation plan is optimized.

With the increasing demand of energy, technical research of how to enhance oil recovery of steam flooding for heavy oil reservoirs has attracted widespread attention at present. Air-injection is an effective technology that has been used to improve the development effect of steam flooding in heavy oil reservoirs. The low-temperature oxidation (LTO) reaction and the high-temperature combustion reaction are the main mechanisms of air-injection technology. The high-temperature combustion reaction can decompose the heavy component in heavy oil, but it requires a higher-temperature condition, which the steam flooding process cannot offer. In addition, the LTO reaction between air and heavy oil consumes the O2, so the safety risk of explosion caused by the mixture of O2 and hydrocarbon gas can be eliminated. Nevertheless, oil viscosity will increase. During the steam flooding process, an aquathermolysis reaction occurs between heavy oil and high-temperature water, which decreases the content of the heavy compon...

As a new improved oil-recovery technique, multi-thermal fluid injection technology through a horizontal well has been widely used in the development process of heavy oil reservoirs. The flow and heat transfer characteristic of multi-thermal fluid in horizontal wellbore is significantly important for the productivity evaluation and parameters design of the horizontal well. Considering the specific physical properties of multi-thermal fluid, fluid absorption in perforation holes and pressure drop characteristics along the horizontal wellbore, this paper developed the flow and heat transfer model of multi-thermal fluid in perforated horizontal wellbore. In order to evaluate the heating effect of the multi-thermal fluid, a concept of effective heating length of a horizontal well is proposed. Then, a sensitivity analysis process is performed to study the influence of reservoir/fluid parameters and operating parameters on the flowing process of multi-thermal fluid in horizontal wellbore. Simultaneously, using the method of orthogonal numerical test, differential analysis and variance analysis are also conducted. Results show that the flowing process of multi-thermal fluid in horizontal wellbore includes a single-phase flowing process and a gas–liquid two-phase flowing process. The influence of oil viscosity on the flow and heat transfer characteristics of multi-thermal fluid in horizontal wellbore is most significant. Thereafter, the solution of our semi-analytical model is compared against the test results of an actual horizontal well from an oilfield in China. It is shown that the model results are in good agreement with the real test results. This model could be used to calculate and predict the flow and heat transfer characteristics of multi-thermal fluid (or saturated steam) in a perforated horizontal wellbore.

Through the sufficient analysis of heat transfer mechanisms between multi-thermal fluid and formation, the flow and heat transfer models of multi-thermal fluid in three different horizontal wellbores (single-string wellbore, concentric dual-string wellbore, and parallel dual-string wellbore) were developed here. It sufficiently considered the influences of wellbore temperature and pressure on the physical properties of multi-thermal fluid. Then, using the node analysis method, these models were solved, and thus, a parametric sensitivity analysis process was carried out. Thereafter, the models were validated from the test data of a dual-string horizontal well in Junggar basin.

Steam channeling is one of the main barriers for EOR after steam flooding. In order to enhance the oil recovery in steam flooded reservoirs, steam channel volumes should be precisely known. In this paper, a set of methods has been established in order to study steam channeling quantitatively by using dynamic data. Firstly, steam channeling wells are identified through curves of watercut and temperature. Then, considering the hysteresis phenomenon, channeling relations are identified with the correlation coefficients between injection wells and production wells under different conditions. Lastly, an analytic model, in which steam condensation, pressure and temperature are considered, is established to calculate the steam channel volumes. A production well named L31615 in some block in Henan Oilfield in China is systematically analyzed by using the method established. The whole block is further analyzed, and the distribution map of steam channels and the steam channel volumes are obtained. The results show that steam channeling does not only occur inside a well group, but also sometimes occurs between wells in different well groups. The calculation of the steam channel volumes provides a theoretical basis for bringing a remedial action like plugging into operation.

As a temperature-sensitive non-Newtonian fluid, the seepage of heavy crude oil in porous media shows the non-linear characteristics. The flowing behavior of three heavy oils through porous media is experimentally investigated, and the influence of temperature and pressure-drop on this flowing process is also described. Thereafter, based on the flowing behavior of heavy crude oil, the new models of productivity of the thermal producers (including vertical well and horizontal well) are proposed. In these models, both the threshold pressure gradient (TPG) and thermal effect are taken into account. The flowing experiments of heavy oil in porous media indicate that the pressure gradient and temperature have the significant influence on the flowing process because of the existence of threshold temperature and TPG. Heavy crude oil begins to flow only when the pressure gradient is in excess of TPG, and there dose not actually exist TPG above the threshold temperature. The viscosity-temperature curves demonstrate that the viscosity of heavy crude oil has an obvious feature of two straight-lines on semilog coordinate. On account of the damage of overlapping phenomena of asphaltenes in crude oil, when temperature is higher than the critical temperature, the reducing trend of TPG (with the increase of temperature) will be lessened. Furthermore, on the basis of flowing process of heavy crude oil, the concepts of threshold temperature and certain production temperature of thermal wells are introduced. That heavy oil with a higher viscosity would have a higher threshold temperature, as well as the certain production temperature. The application of horizontal wells tremendously increases the oil recovery rate in comparison with the vertical wells. This investigation could be used as a tool to study the flowing process of heavy oil and productivity calculation of thermal wells in heavy oil reservoirs.

Recently, the studies on the effects of high magnetic fields on solidification processes have been paid much attention both from the fundamental and applied points of view. With the aid of the enhanced Lorentz force and magnetization effect caused by the remarkably increased magnetic field intensity, several interesting phenomena, such as the control of fluid flow and particle migration in a melt, crystal orientation, and phase alignment, have been obtained. Moreover, the magnetic force induced by the interaction of magnetization and high magnetic field gradient has been evidenced to show significant effects on the microstructure evolution of alloys. In this paper, the recent development of the control of the solidification process by high magnetic fields is reviewed from the view point of uniform magnetic fields and magnetic field gradients.

Controlling the phenomenon of steam channeling is a major challenge in enhancing oil recovery of heavy oil reservoirs developed by steam injection, and the profile control with gel is an effective method to solve this problem. The use of conventional gel in water flooding reservoirs also has poor heat stability, so this paper proposes a new high-temperature gel (HTG) plugging agent on the basis of a laboratory experimental investigation. The HTG is prepared with nonionic filler and unsaturated amide monomer (AM) by graft polymerization and crosslinking, and the optimal gel formula, which has strong gelling strength and controllable gelation time, is obtained by the optimization of the concentration of main agent, AM/FT ratio, crosslinker, and initiator. To test the adaptability of the new HTG to heavy oil reservoirs and the performance of plugging steam channeling path and enhancing oil recovery, performance evaluation experiments and three-dimensional steam flooding and gel profile control experiments are conducted. The performance evaluation experiments indicate that the HTG has strong salt resistance and heat stability and still maintains strong gelling strength after 72 hrs at 200 °C. The singular sand-pack flooding experiments suggest that the HTG has good injectability, which can ensure the on-site construction safety. Moreover, the HTG has a high plugging pressure and washing out resistance to the high-temperature steam after gel forming and keeps the plugging ratio above 99.8% when the following steam injected volume reaches 10 PV after gel breakthrough. The three-dimensional steam flooding and gel profile control experiments results show that the HTG has good plugging performance in the steam channeling path and effectively controls its expanding. This forces the following steam, which is the steam injected after the gelling of HTG in the model, to flow through the steam unswept area, which improves the steam injection profile. During the gel profile control period, the cumulative oil production increases by 294.4 ml and the oil recovery is enhanced by 8.4%. Thus, this new HTG has a good effect in improving the steam injection profile and enhancing oil recovery and can be used to control the steam channeling in heavy oil reservoirs.

In the development process of oilfields, dynamic data, which is easy to obtain, reflects the connectivity between injection wells and production wells commendably. A set of method has been established in this paper for studying on steam breakthrough channels quantitatively by using dynamic data. Firstly, steam breakthrough wells were identified through curves of watercut and temperature. Then, breakthrough relations were identified with the correlation coefficient method. Lastly, an analytic model, in which pressure and temperature were considered, was established to calculate the breakthrough channel volume. A production well named L31815 in LZ27 block in Henan oilfield in China was systematically analyzed by using the method established. The whole block was further analyzed, and the distribution map of steam breakthrough channels and the breakthrough channel volume were obtained. The results show that the steam breakthrough level around L31513 is serious, while the steam breakthrough level around L31917 is mild. Therefore, steam breakthrough does not only occur limitedly inside a well group, but also sometimes occurs between wells in different well groups. It is proved that the results are credible. The calculation of the breakthrough channel volume provides a theoretical basis for bringing the measures like plugging into operation.

There is abundant super heavy oil resource in the world, however, due to the very high viscosity and density, conventional steam stimulation process will result in high steam injection pressure and small heating area, leading to very bad development effect. To improve the development effect of steam injection in super heavy oil reservoirs, a compound stimulation enhanced thermal recovery technology is proposed. Steam injection is conducted through horizontal well assisted by carbon dioxide and oil-soluble composite dissolver, so this kind of technology is called HDCS for short. HDCS technology synthetically utilizes the physical and chemical characteristics of dissolver, carbon dioxide and steam, so that viscosity reduction, mixing and mass transfer, increasing energy and assisting cleanup of the three components are combined. In this paper, three-dimensional thermal recovery physical simulation experiment apparatus is used to conduct the comparison experiments between steam stimulation and HDCS stimulation, to analyze the development advantage and mechanisms of HDCS stimulation. Experimental results indicate that HDCS stimulation realizes the rolling replacement of viscosity reduction effect of dissolver, carbon dioxide and steam, keeping the oil in steam front with a low-viscosity, and enlarging the viscosity reduction range of super heavy oil by steam injection. Besides, the dissolver injection beforehand decreases the subsequent steam injection pressure, and the dissolution and release of carbon dioxide in super heavy oil can complement the reservoir energy. Compared with the condition after conventional steam stimulation, after HDCS stimulation the steam has larger swept volume and heating range, and the content of heavy component and viscosity of crude oil decreases by larger amplitude. The properties of super heavy oil are improved better than conventional steam stimulation. HDCS stimulation significantly improves the development effect of steam in super heavy oil reservoirs.

Controlling the steam channeling is a major challenge for increasing production in heavy oil reservoirs developed by steam injection. The conventional gel used in water flooding reservoirs always has poor heat resistance, so this paper proposed a novel high-temperature gel (HTG) blocking agent on the basis of a laboratory experimental study. The HTG consists of nonionic filler and unsaturated amide monomer with graft polymerization and crosslinking. The optimal gel system has a high gelling strength and controllable gelation time, which is achieved through incomplete orthogonal design method. Then the stability and plugging performance are studied through singular and parallel sand-pack experiments. The results indicate that the HTG has strong salt resistance and dilution resistance. In addition, the HTG can still maintain high strength at 200°C for 72hr. The singular sand-pack experiments suggest that the HTG has good injectability that ensures the on-site construction safety. Moreover, the HTG has a high breakthrough pressure gradient after gelling and could keep the plugging ratio above 99.8% after gel breakthrough when the subsequent injected volume reaches 10PV. The results obtained in parallel sand-pack experiments show that the HTG can effectively plugging the steam channeling after injecting into the high permeability sand-pack from the production end, and force the subsequent steam to enter the low permeability sand-pack. That raises the producing degree of the low permeability sand-pack. Finally, the difference between high and low permeability sand-pack liquid production is reduced by 99.098%, indicating that the producing profile is tremendously improved, and the oil recovery is enhanced by 41.34%. As a result, the novel HTG blocking agent can be used to control the steam channeling in heavy oil reservoir.