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This study investigates the impact of tailings characteristics, particularly fine tailings, on the efficiency and effectiveness of mining engineering backfill operations. Contrary to the common underestimation, fine tailings significantly affect the mechanical properties and failure mechanisms of Cemented Tailings Backfill (CTB). Through a series of experiments examining various particle size distributions and employing advanced Scanning Electron Microscopy (SEM) and Mercury Intrusion Porosimetry (MIP) techniques, this research clarifies the role of fine tailings in modifying the mechanical strength and failure patterns of CTB. Adding 20 % fine tailings optimally enhances both the early and long-term strength of backfill materials. With aging, adding 30 % fine tailings shows a rapid strength increase from 7d to 28d, with the 28d strength slightly lower than that of specimens with 20 % addition, but the specimens demonstrate better ductility after reaching peak strength. As the content of fine tailings increases, crack propagation in the specimens shifts from radial to axial, simplifying the fracture mode from complex to singular. Consequently, the fracture mechanism changes from ductile to brittle, and then reverts to ductile. Moreover, using particle flow simulation and moment tensor analysis to study the failure processes indicates that while increased fine particle content boosts the material's initial strength, it ultimately leads to a simpler crack network and volumetric expansion as the primary failure mode. In terms of energy conversion mechanisms, as the content of fine particles increases, the energy first increases and then decreases. During the elastic stage and the early stage of the plastic stage, the energy is mainly converted into strain energy and PB bonding energy, which affects the elasticity of the sample. In the later stage of the plastic phase, the energy is mainly converted into dissipated energy, leading to the failure of the sample. • Investigates the mechanical behavior and fracture mechanism of CTB with diverse fine particle. • Introduces a Weibull-based particle flow model with diverse fine particle. • Based on the moment tensor theory, the failure mechanism of CTB with diverse fine is verified. [ABSTRACT FROM AUTHOR]

In this paper, a new semi-analytical model considering the non-isothermal effect is proposed to predict heated radius and production performance in a cyclic steam stimulated (CSS) horizontal well. Firstly, an assumption of three heated areas based non-isothermal distribution is introduced. Based on the fluid flow behavior of CSS process in a horizontal well, the spreading of heated area can be classified into three stages. And the heated radius can be derived using the energy conservation equation and area equivalent principle respectively. Then a new semi-analytical model for predicting the production performance by using the equivalent flow resistance method is established. After validation of the new model with numerical simulation and oil field data, the effect of non-isothermal on production performance is analyzed in detail. The results show that a larger injection rate, a bigger error caused by isothermal model when steam injection rate exceeds 200 m3/d. Also, the average water saturation rise has an increase of 1.85% and the average temperature has a drop of 21.12% if the non-isothermal effect is considered. This paper provides an accurate and quick method for estimating the heated radius and production performance in a horizontal well during CSS process. • Temperature distribution in reservoir during steam injection is non-isothermal. • A new semi-analytical model considering non-isothermal effect is proposed. • Non-isothermal effect on cyclic steam stimulation with horizontal well is analyzed. • Non-isothermal effect should not be neglected in a high steam injection rate. • The proposed model predicts the production performance more accurately. [ABSTRACT FROM AUTHOR]

Steam-Assisted gravity drainage (SAGD) technique has been successfully applied to unlock the oilsands resources in Canada. But to accurately estimate the steam chamber expansion and productivity of the entire lifetime of a SAGD well pair is still challenging. In this paper, a new comprehensive model is proposed encompassing the different stages of SAGD. Firstly, for the rising stage, based on the theory of volumetric displacement, an analytical model is developed for the rise speed and oil rate. Thereafter, based on Butler's theory, a 2D numerical approach is modelled for predicting the lateral spreading and confinement stage of steam chamber. Thus, combining the two different mathematical models, the steam chamber shape and recovery performance of a SAGD process can be calculated. The calculation results are also compared against 3D experimental results and field data to confirm the accuracy of this model. Then, a sensitivity analysis is performed to discuss the effects of operation parameters on steam chamber expansion and recovery performance of SAGD process. Results indicate that the calculated results can match the experiment results and field date very well. The calculated peak oil production rate causes a large error and the plateau time of SAGD process obviously is shortened if the preheating stage is neglected. A higher steam chamber pressure results in a narrower inverted triangle interface shape in the rising stage and a more concave-like interface in the sideways expansion stage. In addition, the oil rate increases with steam chamber pressure allowing for varying steam injection rate, whereas the increasing trend of ultimate recovery decreases with the steam chamber pressure increases, which indicates that a proper steam chamber pressure to be chosen can not only achieve a preferable ultimate recovery but also benefit for project economics. • A new comprehensive model encompassing different stages of SAGD was developed. • A 3D physical experiment was conducted for verifying the proposed model. • The preheating period has a little impact on the ultimate recovery. • Steam chamber pressure has a great effect on steam chamber evolution. [ABSTRACT FROM AUTHOR]