|英文题名||Numerical and experimental study of atomized droplets mixing and lifting oil|
|关键词||雾化液滴 多相掺混 气举携带 数值模拟|
我国稠油资源丰富，目前已探明的储量约占石油总量的20%,成为石油资源的主要构成，稠油开采具有重要的能源战略意义。但是，由于稠油黏度高、密度大，常规的开采方法在稠油的开发中遇到了诸多问题，限制了稠油资源的正常开采。目前，稠油开采主要采用掺稀降黏的方法，但是已有的掺稀方案开采效果并不理想，主要原因在于入井前天然气与稀油通过管线简单混合，气油混合液在环型井筒内易产生分离，导致气油混合液达到井底后，不能与稠油均匀掺混，形成气窜，气举效率大幅降低。本文研究中，为提高稠油掺稀降黏开采的效率，基于液相雾化和掺混理论，以及液滴的破碎与聚并机理的研究，提出了稀油雾化掺混的方法，即把稀油通过喷嘴喷入井筒内，使之形成雾状小液滴，并利用井筒内的高压环境维持液滴到达底部，均匀的与底层稠油掺混，最大程度上降低稠油的黏度，提高开采的效率。 本文针对雾化液滴掺混稠油的过程和方案开展系统的理论和应用研究，通过室内实验和数值模拟的方法，给出雾化掺混的效率和规律，优化结构设计。 研究中，首先基于液相雾化理论，提出了利用气体辅助式雾化混配器将稀油雾化成油滴的方法，并通过井筒内驱动压降和重力的作用使得稀油液滴在底部与稠油均匀的掺混，以较为充分地降低气-稀油-稠油混合液的黏度。然后，基于上述方法，优化设计给出了气体辅助式雾化混配器，以及配套的雾化掺稀降黏模拟装置。实验测试中，配比不同的液量（0.36~1.08m³/h，气液比为10:1）对垂直管道内雾化液滴的破碎和聚并，以及迁移运动的规律进行观察和测量，得出：①雾化液滴向下迁移运动过程中出现聚并的现象，并在管壁形成具有较大动量的稀油液膜，在一定程度上影响雾化掺混的效率；②垂直管道底部气-液-液混合均匀，且稠油举升现象明显，有效提高了稠油开采的效率，验证了雾化掺混的可行性；③测量并计算举升液中底部被净携带的液体，定量给出了雾化掺混携带底部液体的规律，其明显优化单相气体的举升效果。 另一方面，通过数值模拟的方法，采用雾化喷嘴离散相模型，重点研究了二次破碎雾化后液滴在管道内的迁移速度、浓度和粒径等参数的变化规律，同时给出了井筒底部气-液-液多相掺混的情况。研究结果表明，雾化液滴在管内分布均匀，且压力越大，平均直径越小，即雾化效果越好,同时，液滴迁移速度降低导致的聚并现象易在壁面附近形成液膜，掺稀携带效率随着入口液量的增大逐渐增加。对于超长管道，在超高压（大于12MPa）情况下，相对于低压（小于0.6MPa）条件，垂直管道内雾化液滴的速度明显增加，且破碎现象大于聚并现象，液滴充盈整个管路，液相雾化效果增强，可有效提高底部稠油掺稀携带的效率。 通过上述研究，充分验证了采用提出的雾化掺混进行稠油开采的可行性，并给出了雾化掺混技术的标准和理论依据，有效促进了稠油开采技术的发展。
Heavy oil resources are rich in our country, and proven reserves of oil has accounted for about 20% of the total, which is the main part of oil sources. It is strategicly significant that heavy oil is exploited. The common methods for extraction of crude oil are facing many problems due to high viscosity and density of heavy oil. Recently, blending light oil with heavy oil has become the main method for oilfields, but exploitation efficiency is not very ideal, the light oil and gas counter just by simple pipelines before pushed into the well; annulus volume is so big that the separation status exisits that oil and gas are prone to sepatate and form a state of oil under gas; worsely, at the same time , the gas that is injected into the annulus pipe also fails to be mixed with crude oil uniformly, which easily results in that the gas escapes out of well and contributes to that the production of crude oil volume is less than the amount of that of injected light oil. This means gas-lift efficiency becomes low. To improve the efficiency of heavy oil blended with light oil, based on the theory of liquid phase atomization and mixing coupled with droplet breakup and coalescence mechanicsm research, this paper puts forward that thin oil atomization method, namely the thin oil through the nozzle spray into the wellbore, to form fog droplets, and use within the wellbore pressure to maintain the droplets reached the bottom, heavy oil mixed evenly with the bottom, aimed to reduce the viscosity of heavy oil and improve the efficiency of exploitation. In this paper, the system of theoretical and applied study of atomized droplet mixing heavy oil mainly through laboratory shrinkage scale experiment and numerical simulation of two aspects, gives laws to optimize the design of the structure. Firstly, based on the theory of liquid phase atomization, this study paper proposes a novel method to use air-blast atomizer to produce atomized light oil drops, the pressure drop and the effect of gravity makes these light oil droplets fully mixed with crude oil at the bottom, which can achieve the purpose of reducing viscosity. Based on this method, this article designs a set of deivce about indoor light oil atomization and blending it with crude oil for reducing the viscosity, plus a set of supporting device. In the experimental tests, it is observed and gauged that atomized droplets move and change in the pipe through different fluid volume (0.36~1.08m³/h and the gas and liquid ratio is 10:1), which finds that: ① droplets coalescence forms the thin wall-films with larger momentum adhering to pipe walls, affecting the efficiency of spray mixing; ② the phenomenon of liquid-gas or liquid-gas-liquid blending and lifting exisits at the next moment, which verifies the feasibility of spray mixing.；③ the carried liquid from the bottom is measured and calculated, obviously, which is better than single-phase gas lifting effect by summarizing the law of carried liquid which is blended with gas or another liquid. On the other hand, by the way of numerical simulation, this paper uses the atomizer model to focus on the simulatation of the changes of physical parameters of droplet secondary atomization in the indoor laboratory pipe and long pipe (droplet velocity, droplet concentration, droplet diameter, etc.), as well as to simulate the situation of crude oil blended with wall-films or gas at the bottom of the main pipe. The experimental and numerical simulation results show that the more uniformly atomization droplets distribute in pipes and the greater the pressure inlet is, the better the effect of atomization is (the average diameter is smaller), droplet velocity is reduced at the same time, which brings about the phenomenon that gathering droplets close to the pipe wall are prone to form wall-films，which also leads to the improved efficiency of carried liquid. Similarly, under the condition of ultra pressure(12MPa), compared with low pressure(less than 0.6MPa), droplet velocity increases quickly during the vertical pipe, the breakup effect is over the coalescence effect, which makes droplets filled the entire pipe and presents a good atomization, effectively improving the efficiency. Through the above research results, the feasibility and practicability are verified that the atomization and blending method could be applied to the crude oil expolitation. A standard of atomization and theoretical basis is also given, which effectively promotes the development of the heavy oil extraction technology.
|徐文凯. 雾化液滴掺混稠油的数值和实验研究[D]. 北京. 中国科学院大学,2018.|