【作者】 李强；

【导师】 孙友宏；

【作者基本信息】 吉林大学 ， 地质工程， 2012， 博士

【摘要】 能源与人类社会相生相伴。追溯人类社会历史，能源应用的进步和更替始终贯穿于人类社会发展的每个阶段。随着工业化在全球各个角落逐渐深入，能源消费增加也成为客观必然，能源安全问题也成为影响未来人类社会发展最重要的因素。化石能源是不可再生能源，总会有枯竭的一天，寻找和开发可替代能源成为当务之急。中国是现今世界上最大的发展中国家。随着我国经济进入快速增长阶段，对能源的需求不断增大，能源的供求差距也越来越大。到2011年，我国超过55%的石油依赖外国进口，所有的战略石油储备仅够使用4个月，对国家能源安全构成严重威胁。只有不断加快我国非常规油气资源的勘探开发利用，才能降低我国未来油气资源对外的依赖程度，满足国家建设的需要。油页岩是一种灰分超过40%的可燃有机沉积岩，低温干馏可获得页岩油，含油率在3.5%～18%之间，有机质含量较高。油页岩资源储量巨大，全世界油页岩资源所能提取的页岩油量大约为4110亿t，相当于目前世界已探明的原油和凝析油剩余可采储量的3倍。我国油页岩资源也很丰富，可提炼页岩油约476亿t，相当于传统石油资源量1.5倍，居世界第4位。而已查明资源27亿t，仅占页岩油资源的5.67%，勘探潜力巨大。所以只要突破油页岩开采的技术瓶颈，通过使用新技术将成本控制在合理的范围，油页岩资源开采将前途无量。从经济上分析，油页岩地表干馏生产页岩油的成本约为1500元/t左右（40美元/桶），过去看来较高的油页岩生产成本在今天变得很经济。所以大规模开发油页岩已成为很紧迫的任务。油页岩的开发和应用有近200年历史。相对油页岩来说，天然石油质优且加工工艺简单，利用的成本相对较低，一直被广泛使用。随着上世纪70年代能源危机的出现，油页岩的开发才又繁荣起来。目前开采油页岩的方式有两种，燃烧发电和干馏炼油，两种方式都只适合于埋藏较浅的矿床。无论是燃烧发电或干馏炼油，都有污染大，效率低，适应地层有限，维护成本高等缺点。为了规避这些缺点，油页岩原位加热干馏技术被开发出来，虽然原位开采优势明显，但也存在许多技术问题，所以至今仍然没有被大规模推广，本文以油页岩的基础物理性质入手，研究油页岩的热解特性，孔裂隙发展规律，油页岩热渗透性，油页岩内部热传递规律；通过搭建油页岩热解试验台，得出油页岩热解产油产气规律，并分别验证热物性规律和孔裂隙特性；建立了油页岩原位开采热-固耦合模型，按照实验测得的参数设置模型边界，用有限元仿真分析再一次研究油页岩加热过程中热量迁徙规律。油页岩热解是指油页岩在不与外界空气接触的条件下加热至其裂解温度而发生的一系列物理反应及化学反应的过程，热解过程可以看作油页岩的失重过程。对油页岩热解失重的深入分析，就是以油页岩裂解过程中不同阶段脱水或油气等析出为对象，是研究油页岩热破裂、孔隙结构演化、容重、渗流特性等变化的基础，具有非常重要意义。油页岩的热裂解是有规律可循的，大致可分为四个阶段：油页岩干燥脱水阶段；干酪根软化，长链分子断裂重组阶段；干酪根的充分受热分解的阶段；油页岩中的方解石等矿物质受热分解阶段。油页岩原位渗透性能在热解过程中呈现先降低再升高的过程。并可以划分为三个阶段，第一阶段为室温～250℃，油页岩渗透性迅速升高，水分以蒸汽的形式析出促进了液体渗透；第二阶段为250℃～450℃，渗透性急剧降低，此段是干酪根软化过程，干酪根软化后堵塞了空隙和裂隙，降低了渗透油页岩性能，第三阶段为450℃～520℃，渗透率开始缓慢增大，此阶段干酪根大量裂解，油页岩中产生了大量孔隙和裂隙，促进了液体渗透。油页岩的热传导系数，比热容随着预处理温度升高呈现出逐级下降趋势，而热扩散系数却是先上升，再下降，又上升的过程。这些热物理参数的变化受岩样含水率、孔隙率、裂隙大小、化学物质的析出等因素影响。油页岩热解产油、产气是宏观的过程，但是热解过程本身是微观的过程，其中涉及到许多细微的化学物理变化，如干酪根分解、相变，油气渗流，孔隙、裂隙变化等。要想深入研究热解过程中内部物质性状变化情况，就需要使用精密放大仪器观察热解过程中全温度段油页岩形貌特征及内部物质的变化。电镜扫描能很好的承担这一角色。随着温度增高，油页岩中孔隙也会增加，且单个孔隙的面积也会增大，而孔隙的增加和增大的过程主要是由于干酪根等物质物理化学变化的过程。350℃前,干酪根未热解,孔隙变化缓慢,350℃后,干酪根热解生成油气,并沿渗流通道析出,造成了孔隙爆发性增长；加热油页岩过程中,裂隙的长度、宽度、数量都在分阶段增加,这不仅与热应力有关系,也明显受油页岩加热裂解后一系列化学物理变化影响。油页岩加热裂解的过程是能量在内部传递,造成油页岩化学、物理变化的过程,由于变化过程复杂,造成了能量传递的过程也很复杂。油页岩加热过程中的热传导遵循傅里叶提出的导热的基本定律,即对油页岩各种性质的研究都是为油页岩原位开采服务的,本章将利用自行研制的油页岩准原位热解实验台,对产自吉林省桦甸的油页岩进行了不同温度、不同颗粒性状条件下热解产油、产气规律的实验室研究,分析热量作用机理,评价了油气的产出效果,并对生产的油气等进行了色谱分析,分析了油页岩裂解气的成分与温度的关系。并总结出油页岩热解关系式：建立了油页岩热固藕合模型,分析了油页岩加热过程中温度变化和能量迁徙规律。认为模拟加热功率越大,达到稳态传热的时间越短。到达稳态的时间和稳态温度与加热井和冷冻井的距离有直接关系,冻结井距离越远,到达稳态的时间越长,稳态温度也越高。在设计原位干馏产油系统时要全面考虑加热功率,井孔布置等因素。更多还原

【Abstract】 Energy is closely linked to the human society. Tracing back to the history, thereplacement of energy applications always runs through each development stage ofthe human society. With gradual deepening of industrialization across the globe, theincrease of energy consumption becomes a necessity, and energy security has beenone of the most important factors affecting future development of human society.Fossil fuels are not renewable energy, and will be exhausted one day. Finding anddeveloping alternative energy sources have become atop priority. China is the largestdeveloping country in the world today, as China’s economy has entered a stage ofrapid growth, demands for energy is increasing rapidly, the energy supply-demandgap is also growing. By2011, more than55percent of the oil depends on foreignimports in China, the strategic petroleum reserve can only use for four months, andpose a serious threat to national energy security. In order to reduce China’sdependence on external oil and gas, and to meet the needs of national construction,exploration and development on unconventional oil and gas resources must beaccelerating.The oil shale is combustible organic sedimentary rock, which contains morethan40%ash. Oil can be obtained by pyrolysis; oil content can reach between3.5to18%, and organic content is high. Its reserves are huge; the shale oil extracted fromoil shale resources through the world is about411billion tons, equivalent to threetimes of the remaining recoverable reserves of world’s proven crude oil andcondensate. China’s oil shale resources can extract about47.6billiontons ofshale oil,equivalent to1.5times ofconventionaloil resources, which are ranking the4th in theworld. But only2.7billion tons resources are identified, accounting for only5.67%of the shale oil resources, exploration potential is huge. So, as long as webreakthrough the technology bottleneck in oil shale mining, and control the cost in a reasonable range through using new technologies, the oil shale resource extractionwill be promising. From the economic analysis, the costsof surface carbonization oilshale are about1500Yuan/tons (30U.S dollars/barrel), which seemed higher in thepast, but become very economical now. Large-scale development of oil shale hasbecome a very urgent task.Development and application of oil shale have nearly200years of history.Comparing oil shale, natural oil has been widely used, because of high quality,simple processing technology, and relatively low cost. With the1970’s energy crisis,oil shale exploration flourishes again. Now, two ways are used to operate oil shale,burned to generate electricity or dry distillation refinery, two ways are only suitablefor lowly buried deposits. But whether it is burned to generate electricity or drydistillation refinery, there are disadvantages-pollution, low efficiency; limitedadaptation to stratigraphic and high maintenance cost. In order to prevent theseshortcomings, in situ dry distillation heating technology of oil shale has beendeveloped; although in situ mining has obvious advantages, there are many technicalproblems as well. So it is still no large-scale promotion. The article starts with thebasic physical properties of oil shale, researching pyrolysis characteristics of oilshale, development of cracks and pores, thermal permeability of oil shale, theinternal heat transfer law. By building oil shale pyrolysis test stand, laws of gas oroil-producing in oil shale pyrolysis are obtained, and then the thermal properties andcharacteristics of cracks development are verified. Besides, establishingthermosetting coupling model of oil shale in situ heating, the model boundary withmeasured parameters in test experimentally are set.And by using finite element, heatmigration patterns of heating oil shale are studied once again.Oil shale pyrolysis is defined that, the process of series physical reactions andchemical reactions occurred in pyrolysis temperature without contacting to outsideair. Pyrolysis process can be seen as a weight loss of oil shale. In-Depth study ofweight loss in pyrolysis actually analyzes the dehydration and oil precipitation in oilshale pyrolysis process at different stages, which is the basis of researching oil shalethermal cracking, pore structure changing, bulk density, and seepage characteristics, and has very important significance. Pyrolysis of oil shale is a pattern, which can bedivided into four phases: oil shale desiccation stage; the kerogen softening stage;kerogen pyrolysis stage and thermal decomposition stage of other minerals in oilshale.In situ permeabilityof oil shale in the pyrolysis process revealed a decrease firstand then an increase. And it can be divided into three phases: the first phase at roomtemperature～250℃, oil shale permeability rises rapidly, water precipitation inthe form of steam promote liquid penetration; the second phase of250℃～450℃, the permeability drastically reduced. This section is the softening process ofkerogen, softening kerogen block the cracks, penetration properties reduced. thethird phase of450℃～520℃, the penetration rate begins a slow increase,kerogen in this stage almost pyrolysis, a large number of pores and cracks in the oilshale promotes the penetration of liquid.Oil shale thermal conductivity, specific heat capacity show the step-down trendas the pretreatment temperature rises, while the thermal diffusivity is indeed firstincreased and then decreased. Thermo physical parameters are affected by themoisture content of rock sample, the factors of porosity, fracture size, theprecipitation of chemical substances.Producing oil and gas in oil shale pyrolysis is a macroscopic process, while thepyrolysis process itself is a microscopic process, which involves many subtlechemical and physical changes, such as kerogen decomposition, phase transition, oiland gas seepage, pores, cracks change and so on. To make in-depth study of theinternal material traits in pyrolysis process, you need to observe morphologycharacteristics and internal material changes in oil shale pyrolysis by precision zoominstruments on full temperature range. The scanning electron microscope can takethis role.As the temperature increases, the pores in oil shale increase, as well as thewhole area ofa single. While the process ofpores increased is mainly due to physicaland chemical changes in substances, such as kerogen. Before350℃, the kerogencheese do not pyrolysis, the porosity changes slowly. After350℃, the kerogen pyrolysis produces oil and gas, and precipitates along the seepage channel, resultingin explosive growth of pores. In the process of heating, cracks length, width andnumber increase, not only connected with thermal stress, but also significantlyaffected by series of chemical physical changes.In the pyrolysis process, heating energy transferred in the internal oil shale,resulting in chemical and physical changes. Due to the complexity of changingprocess, energytransfer process is caused quite complex. The heat transfer process inthe oil shale follows the Fourier thermal conductivity basic laws.Study of oil shale nature can lay a solid foundation for oil shale in situ mining,by using the oil shale quasi-situ pyrolysis bench developed by Jilin University. I havedone some pyrolysis laboratory studies on Hua Dian oil shale at different heatingrates and different particle characteristics. According to the laboratory researches,heat mechanism of action is analyzed, output effects of oil and gas are evaluated,chromatographic analysis of production and gas composition analysis on differenttemperature have been made, and the oil shale pyrolysis equation is summed up:In situ heating thermosetting coupling model ofoil shale has been established toanalysis temperature changes and energy migration patterns. Conclusions have beenobtained that, the greater heating power is, the quicker steady state heat transfer willbe reached. Steady state temperature and reaching time are directly related to thedistance between heat wells and frozen wall. If freeze wall is farther away, thereaching time to steady state is longer, and the steady state temperature is higher.When we design in situ dry distillation oil-producing system, heating power andlayout borehole must be taken into full account.更多还原