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.

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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 O 2 , so the safety risk of explosion caused by the mixture of O 2 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 component in heavy oil. Besides, catalyst MnO 2 promotes the reaction by decreasing the activation energy of the reaction. In this paper, several static oxidative decomposition experiments are conducted to study the change characteristics of pressure, gas composition, oil composition, and oil viscosity after the reactions with different temperatures, pressures, and water saturations. In addition, four dynamic displacement experiments are conducted to compare the displacement effect of different displacement methods, including N 2 -injection displacement, air-injection displacement, steam flooding, and airinjection-assisted steam flooding. Experimental results show that air-injection can effectively improve the development effect of steam flooding in heavy oil reservoirs. Upgrading and viscosity reduction for heavy oil by the combination of the LTO reaction and the aquathermolysis reaction can slow down steam channeling and increase production rate, thereby enhancing the ultimate recovery of steam flooding.

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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.