Assessment of Imperfect Heater Contact due to in-situ Pyrolysis of Oil Shale
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油页岩是非常规石油资源之一，世界储量约.2万亿桶。油页岩是一种富含干酪根的精细沉积岩，可以通过称为热解的加热过程转化为原油。在油页岩的原位热解过程中，在井筒中安装了电阻式电加热器，称为井加热系统。加热元件本身实际上并没有接触到井筒，从而造成加热器接触不良。在本项目中，将量化加热器接触的不完善性，并对电加热器和井筒之间的气隙对油页岩原位热解的影响进行评估。其中，将识别加热器井系统中空气间隙的厚度，并通过模拟分析完美加热器和不完美加热器接触之间的传热性能。在本次模拟中，绿河组油页岩将被加热至3200℃及以上的转化温度。
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通过解释从模拟中获得的温度曲线，将比较完美和不完美加热器接触的油页岩转化量。目标油页岩层深度在281米至540米之间，起始温度为250摄氏度。同时，将确定影响加热过程及其重量和灵敏度的参数。根据本项目的结果，气隙确实会影响油页岩的原位热解性能。据观察，气隙越厚，油页岩转化越少。此外，本研究还确定了加热炉的输入温度和加热时间是影响原位热解油页岩转化距离的最主要因素。油页岩质量和气隙初始温度对本研究的影响可以忽略不计。
Abstract
- Oil shale, known as one of the unconventional oil sources, has world reserve of an equivalent to 3.2 trillion barrelsof crude oil. Oil shale is a kerogen rich fine sedimentary rock which can be converted into crude oil via a heating process called as pyrolysis. In in-situ pyrolysis of oil shale, a resistive electric heater is installed in a wellbore and it is known as heater-well system. The heating element itself does not actually touches the wellbore which creates imperfect heater contact. In this project, the imperfectness of heater contact will be quantified and an assessment on the effect of air gap on in-situ pyrolysis of oil shale in between the electric heater and wellbore will be done. In that, the thickness of air gap in the heater-well system will be identified and the heat transmission performance between a perfect heater and an imperfect heater contact will be analyzed through simulation. In this simulation, Green River Formation oil shale will be heated up to conversion temperature of 3200C and above.
- The amount of oil shale converted will be compared for both perfect and imperfect heater contact by interpreting the temperature profile obtained from the simulation. The targeted oil shale layer will be in between 281 meters to 540 meters in depth with the starting temperature of 250C. At the same time, parameters that affects the heating process and its weight as well as sensitivity will be identified. Based on the result of this project, the air gap does affect the performance of in-situ pyrolysis of oil shale. It is observed that the thicker the air gap the lesser the oil shale converted. Furthermore, the present study also identifies that the input temperature of heater and the duration of heating are the most influential factors on distance of oil shale converted due to in-situ pyrolysis. The quality of oil shale and the initial temperature of air gap which have also been investigated has negligible effect on this study.
