干热岩裂隙渗流—传热试验及储层模拟评价研究

发布时间：2018-01-01 12:15

  本文关键词：干热岩裂隙渗流—传热试验及储层模拟评价研究　出处：《吉林大学》2016年博士论文　论文类型：学位论文

  更多相关文章： 干热岩 增强型地热系统 渗流传热 数值模拟 室内试验 储层模拟

【摘要】：自工业革命以来,能源科学的不断发展成为推动社会进步的强大动力,人类也因此享受到前所未有的便捷与舒适生活。然而伴随着近一个世纪以来的人口膨胀及经济发展,以常规化石燃料为主的能源结构所带来的环境负面效应逐渐凸显。为应对环境问题,改善能源结构,世界各国纷纷将目光投向潜力巨大且清洁无污染的干热岩地热资源。干热岩(Hot Dry Rock, HDR)是指埋藏于深部地下的低孔、低渗的高温岩体,储存在其中的能量需要通过人工改造形成增强型地热系统(Enhanced Geothermal System, EGS)才能得以开采。干热岩资源的开发是一个复杂的系统工程,需要包括岩石力学、水文地质、地球物理、工程热物理、钻探等在内的多学科相互配合。热能开采是干热岩开发中一个重要的课题,其本质是换热工质(水或超临界CO2)在高温裂隙岩体中的流动换热过程。从科学问题的角度归纳来说,主要涉及以下两个方面：一是裂隙岩体的渗流问题；二是流体掠过岩石裂隙表面的对流换热问题。干热岩储层的模拟及场地的水热产出能力预测与开采方案的优化设计是干热岩开发中的另一个重要问题,合理预测场地的产热能力对于EGS工程的规划、设计、施工均有重要的意义。想要准确的对场地的热产出能力进行评价,需要对储层的地质情况有充分的认识,这需要先进的地球物理手段对储层进行探测,同时借助数值模型的手段,建立合理的储层模型,从而获得合理的预测值。针对上述关键问题,本文首先对岩石单裂隙渗流及传热问题开展室内试验研究,结合松辽盆地莺深井区地球物理资料,分析研究区储层天然裂隙发育情况及地应力状态,并针对松辽盆地裂隙型火山岩储层建立多重介质模型,分析了场地的产热特征,开展了裂隙属性对产热能力的敏感性研究。针对松辽盆地致密砂岩储层,基于现场水力压裂试验,借助拟三维水力压裂程序,拟合地表压力曲线,获得裂缝的几何形态与导流能力分布特征,并建立包含裂缝信息的三维水热耦合模型,对场地的产热能力、能源效率、环境效应等做出评价。裂隙渗流方面,首先开展了岩心巴西劈裂,粗糙裂隙面三维激光扫描,及扫描电镜等基础性试验研究,后重点研究了砂岩、花岗岩平直裂隙渗流性质、花岗岩-支撑剂系统的渗流性质,以及应力历史与应力过程对裂隙渗流性质的影响等。(1)花岗岩与砂岩平直裂隙渗流试验结果表明,各级围压下的流量与渗透压力基本呈现线性正相关关系,在低围压条件下,裂隙的水力开度随渗透压力的增大而增大；当围压水平较高时,裂隙的水力开度不随渗透压力改变。(2)裂隙-支撑剂系统的渗流试验结果表明,支撑剂对于改善裂隙的渗流能力具有显著的效果。当围压水平较高时,支撑剂在应力与渗流作用下发生破碎,产生的碎屑堆积堵塞渗流通道,导致裂隙渗流能力下降。同时支撑剂在裂隙面的不均匀分布使得裂隙面局部受到张力作用,导致裂隙面岩体产生新的裂纹。(3)加、卸载围压下的裂隙渗流试验结果表明,对于平直裂隙而言,循环荷载对其总体渗透能力影响不大。但在每一级加载后卸载的过程中,裂隙渗流能力的恢复存在滞后现象。对于粗糙裂隙来说,加载与卸载阶段,裂隙的渗流能力存在量级与规律性上的差异,经历过加载过程的粗糙裂隙往往难以恢复初始的渗流水平。裂隙渗流传热研究方面,开展了岩石单裂隙渗流传热特性试验研究。试验以蒸馏水为换热工质,采用预制平直裂隙与粗糙裂隙的花岗岩与砂岩岩样,在不同的温度与水流条件下,研究了岩石裂隙的流动换热特性。同一温度水平下,对流换热系数的量值与流量基本成线性正相关关系。裂隙面粗糙度的存在一定程度上增大了对流换热过程的强度,但岩性的区别对于对流换热过程无明显影响。裂隙面不同位置处换热强度存在差异,粗糙度对换热过程的影响较为显著。根据试验结果,拟合了Nu与Re和Pr的幂指数关系式,其基本形式为Nu=CR en Rrm。拟合结果显示,与流体掠过光滑平板的经验特征数方程相比,C值基本相同,而n值范围较经验值偏大,这说明岩石裂隙渗流传热过程与光滑平板模型相比存在差异,主要考虑为粗糙度和裂隙面材料性质的影响。讨论了松辽盆地北部地区徐家围子干热岩靶区的天然裂隙发育特征及地应力状态。对该地区天然裂隙的定量研究表明,裂缝的水力开度在0.01-1.40 mm之间,裂隙发育密度在1.57-5.18/m之间,裂缝视孔隙率在0.002-0.138%之间。对地应力场方向的研究表明,现今地应力场的最大水平主应力方向为近东西向。地应力大小的研究主要依据现场水力压裂测试,密度测井,震源机制解释等手段,确定出的垂向应力,最小水平主应力分别为96.5MPa和82MPa。确定出最大水平地应力的下限值为96.5MPa。针对松辽盆地莺深井区裂隙型火山岩地热储层,建立了基于多重介质模型思想的数值模型,主要分析热能开采中储层的温度、压力、流体密度等的演化规律,以及裂缝参数对于产热特征的影响。研究表明,在系统运行的初期,注入井附近裂隙单元的温度低于基质的温度,但这种差异随着与注入井距离的增大及注采循环的不断进行而趋于消失。储层温度的降低导致流体密度、粘度的增大,引起注入井井底压力的升高。裂隙属性对储层产热特征的影响研究表明,裂隙渗透率增大会加快生产井温度的降低,加快热突破(Thermal breakthrough)的发生。但另一方面会降低注入井井底压力,减小系统的流动阻抗。裂隙间隔的增大会减小注入井与生产井之间渗流路径的复杂程度,减小热交换面积,加速热突破过程,但裂隙间隔对注入井井底压力的影响不明显。松辽盆地致密砂岩地热储层地热能开采分析评价研究中,从干热岩供暖的实际问题出发,基于松辽盆地达深井区实际地质资料及现场水力压裂试验,建立了拟三维水力压裂数值模型,通过拟合模型计算的井口压力曲线与现场监测曲线,校正了模型的准确性。进而获得了现场压裂所得水力裂缝的几何尺寸及导流能力空间分布特征。后基于压裂所得的裂缝信息,建立了预测热储产热能力的三维数值模型,分析了场地最大生产流速,温度、压力时空分布和产热功率等。研究结果表明,热储合理的生产流速为8 kg/s,系统运行三十年的过程中,储层流动阻抗保持在经济标准的9.78-12.32倍。在系统的运行过程中,生产井温度由初始的112.69℃降低至第三十年的89.01℃,对应的产热功率由初始的1.96 MW降低至第三十年的1.17 MW。热突破发生在系统运行的第七年,此时生产井温度降幅接近10%。人工热储30年内的累积产能为1.36×1015J,三十年内可节约用煤5.04×107kg,减少二氧化碳排放1.18×108kg,二氧化硫排放7.75×105kg。
[Abstract]:Since the industrial revolution, the development of energy science has become a powerful driving force to promote social progress, therefore the human enjoy the hitherto unknown convenience and comfort of life. However, with nearly a century of population expansion and the development of economy, the negative environmental effect of energy structure with conventional fossil fuel based brought to cope with the increasingly prominent. The environmental problems, improve the energy structure, the world will have eyes dry and clean the huge potential of rock geothermal resources. (Hot Dry Rock, hot dry rock HDR) refers to the low hole buried deep underground rock mass, high temperature and low permeability, in which the energy storage needs through artificial modification enhanced geothermal formation the system (Enhanced Geothermal System, EGS) in order to exploit the resource of hot dry rock is a complex system engineering, including rock mechanics, hydrogeology, geophysics Science and engineering thermal physics, multidisciplinary drilling, cooperate with each other. Energy exploitation is an important topic in the development of hot dry rock, its essence is the heat transfer medium (water or supercritical CO2) at high temperature in fractured rock flow and heat transfer process. From the perspective of inductive scientific problems, mainly involving the following two one is the seepage problem of fractured rock mass; two is the convection heat transfer across the rock fracture surface. The optimization design of hot dry rock reservoir simulation and ground water heat output capacity prediction and mining plan is the hot dry rock in the development of another important problem, reasonable prediction of heat production capacity site for the EGS project planning, design, construction has important significance to accurately. On the site of the heat output ability evaluation, the geological conditions of the reservoir need to have sufficient knowledge, which requires advanced geophysical methods for reservoir Detect at the same time with the numerical model, a reservoir model is reasonable, so as to obtain a reasonable forecast value. According to the above key issues, this paper carried out experimental study on indoor single rock fracture seepage and heat transfer problems, combined with the deep zone of Songliao Basin's geophysical data analysis, reservoir natural fracture and the stress state, and the establishment of multi medium model in Songliao Basin fractured volcano rock reservoir, analyzed the heat production of the site, the sensitivity of crack attributes on the heat production capacity. The tight sandstone reservoir in Songliao Basin, the hydraulic fracturing tests based on the three-dimensional hydraulic fracturing process, fitting the surface pressure curve. The distribution geometry and conductivity characteristics of cracks, and a three-dimensional water heat coupling model contains the crack information, to heat production capacity space, energy efficiency Rate of environmental effect was evaluated. The fracture seepage, firstly carried out the core of Brazil splitting, 3D rough fracture laser scanning, basic test and scanning electron microscope, after focusing on the properties of sandstone, granite straight fracture seepage, seepage properties of granite - supporting agent system, and stress history and stress the influence of process on seepage properties. (1) of granite and sandstone straight fracture seepage test results show that the flow rate and osmotic pressure at different confining pressures linearly correlated, under low confining pressure, the increase of hydraulic crack opening with the osmotic pressure increases when the confining pressure level; when high crack hydraulic aperture with osmotic pressure change. (2) fracture seepage test results supporting agent system show that the seepage ability of proppant to improve the crack has a significant effect when the confining pressure is higher, Support agent in the role of stress and seepage is broken, the debris flow channel blockage, resulting in a decline in the seepage ability. At the same time supporting agent in the fractured surfaces of the uneven distribution of the fracture surface by local tension, leading to new cracks of rock surface. (3), seepage test results of unloading confining pressure the results indicate that for the straight fracture, the cyclic load on the overall permeability little effect. But in the process of unloading each level after loading, the seepage ability recovery lags behind. For rough fracture, loading and unloading stage, differences in magnitude and regularity on the seepage capacity of fissure seepage the level of experienced rough fracture loading process is often difficult to recover. The initial research for flow and heat transfer in fissures, carried out experimental study on heat transfer characteristics of single fracture rock test with distilled water. As the heat transfer medium, the granite and sandstone samples with prefabricated straight fracture crack, temperature and flow in different conditions, the research of rock fracture flow and heat transfer characteristics. Under the same temperature level, the convective heat transfer coefficient values of a linear positive correlation with the surface roughness of fissure flow. There is a certain extent increase the intensity of convective heat transfer, but the difference of lithology on the heat transfer process has no obvious effect. Fracture surfaces at different positions of heat transfer intensity differences, the roughness effect on the heat transfer process is significant. According to the test results, the exponential relationship between Nu and Re and Pr were fitted. The basic form of Nu=CR en Rrm. fitting results show that compared with the past experience of the characteristics of flat smooth fluid equations, the C value is basically the same, but the n value range is the experience value is too large, the rock seepage heat transfer through Cheng Yuguang The sliding plate model compared with the differences, mainly consider the effect of crack surface roughness and material properties were discussed. The development characteristics and stress state of natural fracture in the North Songliao Basin Xujiaweizi dry rock target area. The quantitative research on the natural fractures in the area showed that the crack hydraulic aperture in 0.01-1.40 between mm, fracture the density between 1.57-5.18/m, fracture porosity in 0.002-0.138%. Research on the stress field direction shows that the maximum horizontal in-situ stress field and the principal stress direction is nearly east-west. Study on the basis of field test of hydraulic fracturing, the stress size density logging, focal mechanism explanation and other means to determine the vertical stress, minimum the horizontal principal stress are respectively 96.5MPa and 82MPa. determine the limit of maximum horizontal stress value is 96.5MPa. in Songliao Basin deep fractured zone warbler volcano rock heat Reservoir numerical model is established based on the idea of multi medium model, the main thermal analysis of mining reservoir temperature, pressure, evolution of fluid density, and fracture parameters influence the thermogenic characteristics. The results show that in the early stage of system operation, the injection wells near the fracture unit temperature is lower than the temperature of a substrate. But the difference with the increase of injection and injection well distance mining cycle continuously and tends to disappear. To reduce the temperature of the reservoir causes the fluid density, viscosity increases, increase the injection well bottom hole pressure. Fracture property indicates that the reservoir characteristics of heat production of fracture permeability increases will reduce the temperature and speed up the production wells the accelerated thermal breakthrough (Thermal breakthrough) occurred. But on the other hand will reduce the injection well bottom pressure, flow resistance decrease system. The increase will reduce the fracture interval and injection wells The complexity of the production well between the seepage path, reduce the heat exchange area, accelerate the heat breakthrough process, but the influence of crack spacing on injection well bottom pressure is not obvious. Mining analysis and evaluation research of tight sandstone geothermal geothermal reservoir in Songliao Basin, starting from the actual problem of heating hot dry rock, Songliao Basin of deep well hydraulic fracturing zone test the actual geological data and field based on a quasi three-dimensional numerical model of hydraulic fracturing, by fitting the model to calculate the wellhead pressure curve and field monitoring curve correction, the accuracy of the model. The spatial distribution characteristics of geometric dimensions of fracturing and hydraulic fracture conductivity and the fracture information. After fracturing is established based on the a three-dimensional numerical model for predicting the thermal storage heat production capacity, analysis of the maximum production rate, temperature field, pressure distribution and heat power. The research results The reservoir reasonable production rate was 8 kg/s, the process of system operation in thirty years, the reservoir flow impedance is maintained at 9.78-12.32 times of economic standard. In the process of running the system, the temperature of production well is reduced from the initial temperature of 112.69 to thirtieth years of 89.01 DEG C, corresponding to the production of thermal power from the initial 1.96 MW reduced to thirtieth years in 1.17 MW. thermal break occurred in the system for seventh years, the cumulative capacity of production wells temperature decline of nearly 10%. artificial reservoir in 30 years is 1.36 * 1015J, thirty years can save coal 5.04 * 107kg, to reduce carbon dioxide emissions of sulfur dioxide emissions of 1.18 * 108kg, 7.75 * 105kg.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P314
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本文编号：1364454