油页岩原位开采地下冷冻墙温度场的理论及实验研究

发布时间：2018-06-28 22:26

本文选题：油页岩原位开采 + 冷冻墙　；参考：《吉林大学》2015年博士论文

【摘要】：对于中国而言，目前所生产的原油远不能满足本国的需求，2014年中国进口原油3.08亿吨，是历年来最高的，同比去年增长9.4%，也是涨幅最高的一年。实际上从1993年开始，中国已经成为石油净进口国，而且对国外资源的依赖程度越来越高。为了缓解这种现状，我国高度重视对非常规油气资源的勘探开发和利用。我国的油页岩资源储量丰富，作为常规能源的代替能源，潜力非常巨大。在目前政府对环保要求越来越苛刻的大背景下，对于油页岩的勘探和开发采取地下原位开采的方式成为必然选择。而地下冷冻墙技术是油页岩地下原位开采过程中的一个关键技术，其作用主要有两点，一是防止开采区以外的地下水流入到开采区内，这样就可以保证开采区内的油页岩可以被正常加热从而热解产生油和气，二是防止开采区内部的油页岩被热解后生成的油气产物泄露到开采区外面，这样既可以减少油和气的损失，又能防止开采区外部被污染。由于油页岩矿区的开采范围一般都很大，考虑到在加热区与冻结区之间还存在缓冲区，故所需要的地下冷冻墙的直径相应的会更大。再加之油页岩埋藏深度一般较深，那么要形成一个满足地下原位开采条件的地下冷冻墙就会是一个非常庞大的工程，其冻结时间一般要2年甚至更久，能量消耗大，工程费用高。因此，，如何优化冻结过程中的各个影响冻结壁形成的冻结参数，合理的加快地下冷冻墙冻结壁的交圈速度，从而缩短工期，尽可能的降低成本，节约经费是冷冻墙工程必须要研究和解决的问题。本文通过理论和实验研究的方法来寻求解决此问题的办法。介绍了影响地层温度场分布的土体的热物理性质，并以此为基础，运用能量守恒定律推导得出了地下冷冻墙温度场的导热微分方程。然后分别研究了埋管换热器内壁为恒温条件和恒热流密度条件两种情况下的地下冷冻墙温度场的数学描述和其数值解法，其中恒温条件下可以视为稳态温度场导热问题，而恒热流密度条件下则视为非稳态温度场导热问题。最后将此数学描述的基础理论应用到地下冷冻墙的实际工程中，在简单论述了地层冻结过程之后，分别计算了埋管换热器的换热能力及其冻结时间，给出了冻结壁的平均冻结温度，并最终得出了地下冷冻墙温度场的数学模型和其单值条件。利用ANSYS软件分别对载冷液的流量、冻结孔的间距、冻结孔的孔径以及冻结方式对冻结壁交圈时间和温度场分布的影响规律进行了模拟分析。并模拟分析了各参数的最优耦合。得出以下结论：在保持冻结孔间距、孔径和冻结方式不变的情况下，增加载冷液的流量可以减少冻结壁的交圈时间，但是当其流量增加到一定程度后，继续增加流量对冻结壁交圈时间的影响并不明显；在保持载冷液流量、冻结孔孔径和冻结方式不变的情况下，增加冻结孔的间距会增大冻结壁的交圈时间，而且间距越大，其交圈时间的增加量就会越大；在保持载冷液流量、冻结孔间距和冻结方式不变的情况下，增加冻结孔的孔径会减少冻结壁的交圈时间，而且此时间-孔径的曲线几乎是线性的；在保持载冷液流量、冻结孔间距及孔径不变的情况下，采用局部冻结的方式进行冻结会减少冻结壁的交圈时间；得到最优组合实验为：载冷液流量为20m3/h，冻结孔间距为1m，冻结孔孔径为90mm。根据实验的需要建立了油页岩原位开采地下冷冻墙温度场的实验平台，并在实验平台上进行了相应的实验，最终得到的结论与模拟计算所得到的结论基本一致。但是，实验所需的冻结壁交圈时间总体上比模拟计算所需的时间更短。经过理论分析、模拟计算和实验研究，得出如下结论：在保持其他各参数不变的情况下，冻结壁的交圈时间随着载冷液流量的增大而减小，但随着流量的增大，其交圈时间的减小幅度会越来越小；在保持其他各参数不变的情况下，冻结壁的交圈时间随着冻结孔间距的增大而增大，而且随着冻结孔间距的增大，其交圈时间的增大幅度会越来越大；在保持其他各参数不变的情况下，冻结壁的交圈时间随着冻结孔孔径的增大而增大，且二者几乎是线性的变化关系；另外，局部冻结的冻结方式会减少冻结壁的交圈时间，而且更节能，更环保；而最优组合实验为：载冷液流量为20m3/h，冻结孔间距为1m，冻结孔孔径为90mm。
[Abstract]:As far as China is concerned, the crude oil produced now is far from its own demand. In 2014, China imported 3.08 billion tons of crude oil, the highest in the past year, up 9.4% last year, and the highest increase in the year. Since 1993, China has become a net importer of oil, and the degree of dependence on foreign resources is becoming higher and higher. In order to alleviate this situation, China attaches great importance to the exploration, exploitation and utilization of unconventional oil and gas resources. The reserves of oil shale in China are abundant. As a substitute for energy from conventional energy, the potential is very great.
Under the current government's increasingly demanding environment for environmental protection, it is an inevitable choice for the exploration and development of oil shale by underground mining in situ, and the underground freezing wall technology is a key technology in the process of in situ exploitation of oil shale. The main effect is two points, one is to prevent underground water outside the mining area. In the mining area, it can ensure that the oil shale in the mining area can be heated by normal heating to produce oil and gas, and the two is to prevent the oil and gas products produced from the oil shale after the pyrolysis of the mining area to the outside of the mining area, which can reduce the loss of oil and gas and prevent the pollution from the outside of the mining area.
As the mining area of oil shale is generally large, considering that there is a buffer zone between the heating area and the freezing zone, the diameter of the underground frozen wall will be larger. In addition, the depth of the buried depth of the oil shale is generally deep. The freezing time is usually 2 years or even longer, the energy consumption is large and the cost of the engineering is high. Therefore, how to optimize the freezing parameters which affect the freezing wall formed during the freezing process and speed up the speed of the freezing wall of the frozen wall, thus shorten the short working period, reduce the cost as much as possible, and save the funds for the frozen wall workers We must study and solve problems in the process. This paper seeks to solve this problem through theoretical and experimental research methods.
This paper introduces the thermal physical properties of the soil which affects the distribution of the temperature field of the formation. On the basis of this, the differential equation of heat conduction in the temperature field of the underground freezing wall is derived by using the law of conservation of energy. Then the number of temperature fields of the underground freezing wall under the two conditions of the inner wall of the tube heat exchanger and the constant heat flow density condition are respectively studied. The study description and its numerical solution, in which the constant temperature condition can be regarded as the heat conduction problem of the steady temperature field, and the constant heat flow density is considered as the heat conduction problem of the unsteady temperature field. Finally, the basic theory of this mathematical description is applied to the practical engineering of the underground freezing wall. The average freezing temperature of the freezing wall is given, and the mathematical model of the temperature field of the underground freezing wall and its single value condition are finally obtained.
ANSYS software is used to simulate the influence of the flow of the cooling fluid, the spacing of the freezing hole, the pore size of the frozen hole and the freezing way on the distribution of the time and the temperature field of the freezing wall. The optimal coupling of the parameters is simulated and analyzed. The following conclusions are drawn: holding the distance of the freezing hole, the pore size and the freezing method remain unchanged. In the case of increasing the flow of the cooling liquid, the turning time of the frozen wall can be reduced, but when the flow rate is increased to a certain extent, the effect of the continuous increase of the flow rate on the turning time of the frozen wall is not obvious. The increase of the freezing hole spacing will increase the freezing wall in the condition of keeping the flow of the frozen wall, the pore diameter of the freezing hole and the freezing method unchanged. The greater the interval time and the larger the spacing, the greater the increase in the time of the interlocking. In the case of keeping the flow of the coolant, the spacing of the freezing hole and the freezing method invariable, the increase of the pore diameter of the freezing hole will reduce the time of the interlocking of the frozen wall, and the curve of the time aperture is almost linear; the volume of the cooling fluid and the spacing of the freezing hole are maintained. When the aperture is constant, the freezing wall will be reduced by freezing in the way of local freezing. The optimum combination experiment is that the flow rate of the carrier cooling liquid is 20m3/h, the spacing of the frozen hole is 1m, the pore size of the frozen hole is 90mm.
According to the needs of the experiment, the experimental platform for the temperature field of the underground frozen wall in situ for oil shale is established, and the experimental results are carried out on the experimental platform. The final conclusion is basically the same as that obtained from the simulation calculation. However, the time required for the freezing wall in the experiment is shorter than the time required by the simulated calculation.
Through theoretical analysis, simulation calculation and experimental study, the following conclusion is drawn: in the case of keeping the other parameters constant, the turning time of the frozen wall decreases with the increase of the flow rate of the carrier cooling liquid, but with the increase of the flow rate, the decrease of the time of the turning circle will become smaller and smaller, and the freezing is frozen under the condition of keeping the other parameters constant. The turning time of the wall increases with the increase of the spacing of the frozen hole, and with the increase of the spacing of the frozen hole, the increasing amplitude of the turning time will become larger and larger. In the case of keeping the other parameters constant, the time of the intersection of the frozen wall increases with the increase of the pore size of the frozen hole, and the two are almost linear change relations. In addition, The freezing method of local freezing will reduce the turning time of the frozen wall, and more energy saving and more environmental protection. The optimal combination experiment is that the flow rate of the carrier cooling liquid is 20m3/h, the spacing of the frozen hole is 1m, the pore size of the frozen hole is 90mm.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TD83

【参考文献】