【作者】 康志勤；

【导师】 赵阳升； 杨栋；

【作者基本信息】 太原理工大学 ， 采矿工程， 2008， 博士

【摘要】 随着国际油价的飙升及在全球能源需求不断增长的今天,石油资源短缺已是制约全球经济发展的重大难题,开发石油及替代品是各国能源开发研究的主要课题,开发油页岩矿藏的时机已经到来。油页岩油气作为一种重要的石油补充和替代能源,以其巨大的储量、丰富的综合利用层次,引起了全世界的关注。我国已探明的油田绝大多数进入老井后期挖潜阶段,未来原油产量难以增加,能源的供需矛盾日益突出。因此,立足国内,寻求油页岩的有效开发与经济利用的途径,对于缓解我国石油供需矛盾,具有重大的现实意义。本文以油页岩原位注热开采新技术为背景,采用宏观与细观实验研究相结合,理论研究与数值模拟相结合的方法,借助于新的实验手段、实验设备及仪器,对油页岩在高温下的热解特征、渗流特性、容重及孔隙率的变化、裂隙和孔隙的发展演化规律等进行了深入细致的研究。利用过热水蒸汽作为热量传输的载体,研究了油页岩在其加热条件下的产油、产气规律。建立了油页岩原位注热开采的热-流-固耦合数学模型,编制相应计算机程序,进行了数值模拟,为进行大规模油页岩原位注热开采提供了理论依据和工程参考。主要研究内容及结果如下:1、油页岩热解失重特征为:从室温到300℃,此阶段的失重主要是由于水分的析出引起,失重约3﹪;300℃～600℃,在这个相对较小的温度区间内,油页岩中的有机质大量热解,生成页岩油和气态产物,失重量很大,失重约占20%;600℃～900℃,此阶段的热失重与方解石、白云石、碳质颗粒的高温崩解相关,失重约3﹪。2、采用比重瓶法,测定了不同温度下抚顺西露天矿油页岩的容重、比重、孔隙率。实验结果表明:从常温到200℃,油页岩的容重、比重、孔隙率变化不大;温度超过200℃后,油页岩的容重随温度升高迅速下降,同时比重、孔隙率则随温度升高而大幅增加。3、利用太原理工大学的MDS-200型三轴渗透实验台测定了干馏后油页岩试件在三维应力状态下的渗透系数,结果表明:干馏后油页岩的渗透系数随体积应力的增加而衰减,随孔隙压力的升高而增大,且满足公式:4、利用太原理工大学和中国工程物理研究院共同研制的μCT225kVFCB型高精度(μm级)CT试验分析系统对边长为7.0mm的正方体油页岩试件内部的热破裂特征进行了无损伤扫描分析。实验表明:当温度低于300℃时,裂隙多发育于原生层理面以及硬质矿物颗粒的周围,破裂面基本都与层理面互相平行,且数量不多,宽度较小。当温度超过300℃,由于受到热分解化学反应的作用,裂隙的数量、长度和宽度有了剧烈的增加,且裂隙面仍具有与层理面平行的特点;同时形成了许多垂直于层理面微裂隙,小裂隙与大裂隙的搭接连通,增大了渗流空间,形成了一个庞大的连通网络结构。从分形理论入手,分析了油页岩的热破裂过程,宏观量化了裂隙的分布状况和复杂程度。研究表明:油页岩内部裂隙的分布具有很强的自相似性规律,符合分形规律。5、对不同温度下φ0.82mm×7mm的油页岩试件进行了CT扫描实验,研究高温下油页岩内部μm级孔隙结构的发展、演化规律。研究表明:从常温到300℃,研究区域内孔隙数量、孔隙占有面积、平均孔径、孔隙率都没有发生大的变化;当温度超过300℃,孔隙数量、孔隙占有面积、平均孔径、孔隙率都在同步急剧增长,500℃时达到最大值,稍后有所回落,因此,将300℃确定为油页岩孔隙结构参数变化的分界点。高于300℃,热解反应促使油页岩内部产生了大量新生孔隙,造成孔径在1.5～3.5μm和大于3.5μm孔隙数量的增加,其次,大量小于1.5μm的孔隙在高温下发生了贯通连接,汇聚成一些较大的孔隙结构,促进了1.5～3.5μm和大于3.5μm孔隙数量的增加,同时也造成了小于1.5μm的孔隙本身数量的相对减少。从总体上看,无论在哪一个温度段,孔径小于1.5μm和1.5～3.5μm的孔隙是油页岩中的主要孔隙结构,两者之和要占到总孔隙数量的90%以上。采用多孔介质三维逾渗理论,计算了不同温度下油页岩三维数字岩芯的逾渗概率。结果表明:当温度到达300℃～400℃时,油页岩存在逾渗阈值,且逾渗阈值处于8﹪～12﹪之间。6、利用太原理工大学自行研制的热解试验台对产自辽宁和内蒙的油页岩进行了热解实验。实验结果表明:两类油页岩经过热水蒸汽加热后,剩余残渣的含油率均保持在0.30%左右,有机成分所剩无几,达到了非常高的油气采收率。同时,在过热水蒸汽的参与下,可使热解气体中H2和CO的产量明显提高。过热水蒸汽的高效驱油机理主要体现在:对流的传热方式、加热降粘作用、高温蒸汽的沸腾剥蚀效应、热膨胀作用、解堵作用和脱气作用。7、在理论分析的基础上,建立了油页岩原位注热开采的热—流—固耦合数学模型,并给出了其数值解法,利用Fortran语言编制的相应计算机程序,对“九点法”布井的一个井组进行了油页岩原位注热开采的数值模拟。模拟结果表明:1)在相同的开采时间内,距离注热井越近,温度越高。系统运行1年时,注热井和采油井之间的大部分油页岩地层的温度都小于400℃,到2.5年时,区域内油页岩地层的温度大部分都达到了500℃。因此,1～2.5年间,为页岩油和热解气体的大量产出期,并确定该模型的运作周期为2.5年。2)流体孔隙压力以注热井为峰值向四周逐渐降低,并随时间延长,压力波及的范围逐渐扩大到采油井以外的区域。注热井、采油井附近区域的压力梯度很大,流速较快;而中间区域的压力梯度较低,流速稳定。同时,顶、底板岩石的渗透性较油页岩弱,最初孔隙压力上升缓慢,明显落后于中部油页岩地层,出现了滞后现象。到1年左右时,两者压差已很小。3)随着地层温度的上升,逐步由压应力演化为拉应力,并随着时间的延长,拉应力作用区域以注热井为中心不断向外扩张。拉应力的提高,使孔隙体积扩大的同时,增加了裂隙的宽度,为高温流体的进一步注入和油气的产出创造了有利条件。4)随着热量的不断注入,注热井和采油井之间的地层出现了明显的膨胀变形,且随时间的延长,鼓起量不断增加。到2.5年时,地表注热井处鼓起量为1.29cm;采油井处鼓起量为0.51cm。更多还原

【Abstract】 Today, with international oil price rises violently and the global energy demand is increasing constantly, petroleum resources shortage already is the great difficult problem of restricting global economic development, develop the petroleum and substitute is the main subject for research of various countries, the opportunity of developing oil shale mineral deposit already come. Oil shale, as a kind of important supplement and substitute petroleum energy, with its enormous reserves and abundant comprehensive use level , have aroused the attention from whole world. The majority verified oil field of our country has already entered the later stage of old well developing, the future output of crude oil of our country is difficult to increase, the imbalance between supply and demand of the energy is conspicuous day by day. So, base on our country, seeking effective and economic utilization route of oil shale, for relieving the imbalance between supply and demand of energy of our country and promoting the development of society have great realistic meanings.This text takes oil shale in-situ steam drive technology as the background, combine macroscopic and detailed view experiment, method of the theoretical research combines with numerical simulation, with the aid of new experiment means, experimental facilities and Instrument, further study the weightless characteristic, permeability characteristic, change of density and porosity, development and evolvement law of fissures and pore of oil shale under different temperatures. Use superheated steam as the carrier of heat transmit, studied the oil and gas producing law of oil shale under its heating condition. Set up the coupled mathematical model of heat, fluid flow and solid deformation for oil shale in-situ steam drive, work out the corresponding computer program, carry on the numerical simulation, it offer theoretical foundation and project reference for carrying on extensive oil shale in-situ steam drive. The following is main research contents and research results:1. The oil shale pyrolysis weightlessness mainly display in 3 temperature sections. From room temperature to 300℃, weightlessness of this stage mainly caused by moisture appear, weightlessness is about 3%. 300℃～600℃, a large amount of organic matter in the oil shale turn into shale oil and pyrolysis gas in this relatively smaller temperature block, weightlessness is about 20%. 600℃～900℃, weightlessness of this stage mainly caused by the breaking out of calcite, dolomite and carbon particle, weightlessness is about 3%.2. Determine the density, proportion and porosity of the Fushun oil shale under different temperature using the specific gravity bottle. The experiment result shows: from normal atmospheric temperature to 200℃, the density, proportion, porosity of the oil shale do not change much, after temperature exceeds 200℃, the density of the oil shale drops rapidly with the rising of temperature, at the same time, proportion and porosity increase by a wide margin with the rising of temperature.3. The permeability coefficient of distilled oil shale under three dimension stress state is measured through the 3D permeable experimental machine (MDS-200) devised by Taiyuan University of Technology. Result of study show the permeability coefficient of distilled oil shale attenuates with the increase of volume stress and increases with the rise of pore pressure, and follows the formula:4. Utilized theμCT225kVFCB micro-CT experimental system (μm grade), which was newly co-designed by Taiyuan University of Technology, and Applied Electronics Institute, Academy of Engineering Physics of China, carried on the no damaged triaxial micro-observation and analysis on thermal cracking of oil shale of square body of 7.0mm to be long under different temperatures. The experiment shows: Under 300℃, it was observed that certain few micro-fissures in the specimen which mainly evolved from the raw original bedding and the border of hard mineral particle, the fissure surfaces were basically all parallel with each other, and there is little quantity, the width is relatively small. After temperature exceeded 300℃, due to the influence of chemical reaction of the oil shale pyrolysis, the quantity, length and width of the fissures had seen a violent increase, all fissure surfaces were still parallel with each other, At the same time, formed a lot of micro-fissures perpendicular to the bedding direction, caused the connection between small fissures and large fissures, so formed a huge connecting network structure, fundamentally improved the influent ability of the oil shale. Start with fractal theory, analyzed the thermal cracking course of the oil shale, quantized distribution state and complexity of the fissures. Studies have suggested: The thermal fissures have strong self-similarity, according with fractal law.5. Carry on CT scan experiment to the oil shale standard ofφ0.82mm×7mm under different temperatures, aim to study the development rule of theμm grade pore structure within the oil shale at high temperature. The study show: From room temperature to 300℃, pore quantity, pore area, average of pore diameter and porosity do not change much in the study area. After temperature exceeded 300℃, the above-mentioned parameters all increase sharply and reach the maximum at 500℃, subsequently fall a little, so, confirm 300℃as the boundary point of the pore structure parameters changes. After 300℃, a large number of new pores emerge within the oil shale because of pyrolysis chemical reaction, cause the increase of quantity of medium-sized pores and large pores, secondly, Because a large number of little pores are joined under the high temperature, promote the increase of quantity of medium-sized pores and large pores, at the same time, cause the little pores quantity to reduce relatively. As a whole, no matter in which temperature section, little pores and medium-sized pores are main pore structure within oil shale, the sum of the two should account for more than 90% of the total pore number. Start from pore medium percolation theory, calculate percolation probability of 3D data oil shale under different temperatures. The result of calculation indicates: As temperature is in 300℃- 400℃, the percolation threshold of oil shale is between 8﹪-12﹪.6. Utilized the high temperature and high pressure superheated steam boiler devised by Taiyuan University of Technology carried on pyrolysis experiment to two kinds of oil shales are separately produced in Liaoning and Neimeng. The experimental result shows:The oiliness rate keep about 0.30% of two kinds of oil shale residue after the superheated steam heated,have achieved very high oil and gas recovery ratio. At the same time, the output of H2 and CO is obviously improved in the pyrolysis gas under the participation of superheated steam. The driving oil mechanism of superheated steam mainly embody: The convection heat way, lower viscosity by heating, boiling and denudation effect of high-temperature steam, function of thermal expansion, solve stop up function and take off gas function.7. On the foundation of analyzing of the theory, set up the coupled mathematical model of heat, fluid flow and solid deformation for oil shale in-situ steam drive, work out the corresponding program using Fortran computer language and carry on the numerical simulation to nine point wells disposal. The numerical simulation result show:1) Within the same exploitation time, temperature is relatively high near the hot injection well. In the system runs for one year, the majority oil shale stratum temperature is low at 400℃between hot injection well and oil adopting well, after running for 2.5 years, temperature has already reached 500℃. So, among 1-2.5 years, the shale oil and gas are produced in a large amount and confirm operation cycle of this model as 2.5 years.2) Fluid pressure regard hot injection well as peak value to reduce gradually all around, and as time lengthens, the range that the pressure involves expands to the area beyond the oil adopting well gradually, the pressure gradient is very large and the velocity of flow is very fast near the area of hot injection well and oil adopting well, and the pressure gradient of middle area is relatively low, the velocity of flow is steady. At the same time, because the permeabilities of roof, baseplate rock are weaker than the oil shale, so the fluid pressure slowly rises, obviously lag behind the oil shale stratum. By about one year, the two press difference already very small. 3) With the rising of the stratum temperature, reach from pressure stress change tensile stress progressively, and the extension with time, the area of tensile stress regard hot injection well as the centre to expand outwards constantly. The improvement of the tensile stress, while making the hole volume expand, have increased the width of the fissure, creating the advantage for the furtherly pouring into of high-temperature fluid.4) With the running into constantly of heat, the stratum has presented obvious inflation between hot injection well and oil adopting well, and is up to the extension of time, the heaving amount is increasing constantly. By 2.5 years, The heaving amount in the earth’s surface of hot injection well is 1.29cm and the oil adopting well is 0.51cm.更多还原