Summary A solvent-based thermal recovery process has the advantages of low capital expenditure, less energy consumption, and less greenhouse gas emission. Dimethyl ether (DME), as a renewable solvent, has been considered as a novel additive in the thermal bitumen recovery process. Being soluble in both water and oil phases, DME has the potential to enhance mass transfer and improve oil production. In this work, a phase behavior model of the DME-bitumen-water system is first developed considering DME partitioning between oil and water. A field-scale numerical simulation model with fine gridblocks is developed to investigate the heat and mass transfer mechanisms between DME and bitumen in the interface of a DME vapor chamber. The numerical model is validated with physical experiment results. The close agreement between measured and simulated production profiles indicates that the mechanisms are adequately captured. Meanwhile, various simulation scenarios are performed to evaluate the production performance and the energy efficiency, which is defined as the energy/oil ratio. It is found that the oil production rate in DME injection is 15% higher than that in butane injection at the early stage of production. The solvent penetration depth in DME injection is larger than that in butane injection. This is attributed to the enhanced mass transfer between DME and bitumen caused by the high diffusion of DME in the water phase and preferential partitioning of DME into the oil phase. Furthermore, energy consumption in the warm DME injection process is 48% less than that in warm butane injection and 75% less than that in steam-assisted gravity drainage (SAGD). This is because DME injection can be operated at a lower-temperature condition, leading to less energy transferred to heat reservoir rock/fluids and less heat loss to over/underburden. Therefore, DME is proved to be a technically promising and environmentally friendly solvent to enhance bitumen recovery. The DME-based thermal recovery technique exhibits superior advantages in unlocking poor-quality reservoirs, especially in high water saturation reservoirs and thin reservoirs.

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Air sampler is an important measuring instrument for environmental monitoring. With the rapid development of environmental protection industry, the direct reading air sampler has been widely used and this is also related to the improved develop rate of new products. As it only aims at the situation that the standard meter is soap film flowmeter and the measured meter is rotor air sampler, the JJG 956-2013 metrological verification regulation for air sampler is not applicable to the direct reading air sampler. Meanwhile, the corresponding standard meters are also developing rapidly and more results showed that the laminar differential pressure mass flowmeter has more advantages than the soap film flowmeter in the regulation. It can not only improve calibration efficiency, but also realize automatic calibration or remote calibration. In this paper, the method of calibrating direct reading air sampler by laminar flow differential pressure mass flowmeter is studied. The mathematical model of flow rate and relative indication error used in the calibration condition is proposed, and the uncertainty of indication error is also analyzed in detail. In addition, the evaluation example is given accordingly, which fills the blank in the regulation.

With the atmospheric air as the working fluid, the premature unchoking phenomena were investigated with 18 sets of critical flow Venturi nozzles under 8 types of upstream flow conditions. Unlike the available research, there were no clear relationship between the upstream flow condition and the flow rate fluctuation and flow rate recovery for the premature unchoking phenomena. However, the diverse and unsteady characteristics of the premature unchoking phenomena were shown. With the comparison of upstream flow conditions, the new disturbance might be resulted from the "improper" upstream flow condition, which might influence the intensity and the position of the shock in the diffuser section of CFVN, and finally resulted in the diverse and unsteady characteristics of premature unchoking phenomena.

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