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The in situ conversion process (ICP) is a retorting method pyrolyzing the kerogen in shale into oil and gas products, which shows great potential to promote the recovery of oil shale resources. In this work, a thermo-hydro-chemical-coupled model for the in situ conversion process is established, considering the temperature dependence of key properties and the transverse isotropy caused by the layered characteristics of oil shale. Based on the proposed model, a series of simulations is conducted to evaluate the production performance of the in situ conversion process of oil shale reservoirs. The results indicate that energy efficiency reaches a maximum of 2.7 around the fifth year of the heating process, indicating the feasibility of in situ conversion technology. Furthermore, the sensitivity analysis shows that the heating temperature should be higher than 300 °C to avoid the energy output being less than the energy input, and the oil/gas ratio decreases with increasing heating temperature. Moreover, thermal conductivity is positively with production while heat capacity is negatively correlated, and the energy efficiency decreases with increasing thermal conductivity and matrix heat capacity. Finally, the heating period should be no longer than 4 years to maximize the heating efficiency. [ABSTRACT FROM AUTHOR]

Due to its sedimentary characteristics and natural fractures, oil shale shows anisotropy in heat transfer characteristics. Moreover, the anisotropic thermal conductivity will change with the temperature. This change in the anisotropic thermal conductivity coefficient affects the temperature field distribution and heating efficiency during the in situ electric heating pyrolysis of oil shale. Therefore, it is very important to study the evolution of the anisotropy thermal conductivity coefficient of oil shale with temperature. In this study, the variation of weight loss and the specific heat of an oil shale with temperature is investigated using a differential scanning calorimeter. The variation of the anisotropic pore and fracture structure of the oil shale with temperature is studied through CT scanning technology. The variation of the anisotropic thermal conductivity with temperature is studied through the hot disk method. Finally, the relationship between the change in the anisotropic heat conductivity of the oil shale and the evolution of the anisotropic pore and fracture structure is discussed. The results show that the mass loss of oil shale mainly occurs after 400 °C. The thermal conductivity of both perpendicular and parallel to bedding directions decreases linearly with the increase of temperature. The research results of this study can serve as an important reference in the study of the in situ pyrolysis of oil shale. [ABSTRACT FROM AUTHOR]

Cyclic steam stimulation (CSS) is a typical enhanced oil recovery method for heavy oil reservoirs. In this paper, a new model for the productivity of a CSS well in multilayer heavy oil reservoirs is proposed. First, for the steam volume of each formation layer, it is proposed that the total steam injection volume will be split by the formation factor (Kh) for the commingled steam injection mode. Then, based on the equivalent flow resistance principle, the productivity model can be derived. In this model, the heavy oil reservoir is composed of a cold zone, a hot water zone, and a steam zone. Next, using the energy conservation law, the equivalent heating radius can be calculated with the consideration of the steam overlay. Simultaneously, a correlation between the threshold pressure gradient (TPG) and oil mobility is also applied for the productivity formula in the cold zone and the hot water zone. Afterward, this model is validated by comparing the simulation results with the results of an actual CNOOC CSS well. A good agreement is observed, and the relative error of the cumulative oil production is about 2.20%. The sensitivity analysis results indicate that the effect of the bottom hole pressure is the most significant, followed by the TPG, and the effect of the steam overlay is relatively slight. The formation factor can affect the splitting of the steam volume in each layer; thus, the oil production rate will be impacted. The proposed mathematical model in this paper provides an effective method for the prediction of preliminary productivity of a CSS well in a multilayer heavy oil reservoir. [ABSTRACT FROM AUTHOR]