煤岩气藏压裂液损害评价及加入纳米粒子改性

发布时间：2018-12-17 05:43

【摘要】：煤层气作为一种优质清洁能源,其资源量巨大,经济有效的开发利用具有改善煤矿安全、弥补常规能源的不足和保护环境等三方面的意义。煤层气主要以吸附态赋存于煤层中,且煤层气的产出经历解吸—扩散—渗流三个过程。由于致密煤岩的特殊性质,使其压裂技术有其自身特点,关键在于控制煤粉的产出和压裂液对于煤岩的损害。同时,煤岩气藏是一个气—液—固三相共存的系统,压裂液与煤岩相互作用,不仅引起煤岩渗透率降低,而且导致其表面性质改变从而影响煤岩吸附/解吸及扩散能力。论文以宁武盆地南部太原组9号煤层为研究对象,基于对该区煤岩矿物组分、物性特征、孔隙结构特征及表面特性的分析,研究了压裂液作用对煤岩渗透率、吸附/解吸及扩散的影响,综合分析压裂液对煤岩的损害程度及其损害机理,并采用纳米技术优化煤岩气藏压裂液。描述了9号煤岩矿物组成及孔隙结构。通过采用X射线衍射、扫描电镜(SEM)、 CT扫描、氮气吸附等实验手段对煤岩矿物组成及孔径分布、裂隙空间分布进行综合表征。研究表明,该区煤岩中无机矿物以石英为主,黏土矿物主要为高岭石；煤岩基质孔隙以纳米级孔隙为主,孔径分布峰值出现在4nm处；煤岩孔隙结构复杂,微裂隙较为发育,但空间连通性较差。明确了压裂液作用前后煤岩的表面性质。煤岩红外光谱观察表明,压裂液浸泡改变煤岩分子间和分子内的作用力类型和大小,对煤岩-OH、—COOH基团影响较大,促使其在游离态与缔合态之间转化。煤岩与模拟地层水及压裂液之间的润湿接触角实验表明,不同压裂液与煤岩之间的润湿接触角均较模拟地层水与煤岩之间的接触角小,压裂液对煤岩的润湿性好,易于吸附在煤岩表面。综合评价了压裂液对煤岩吸附/解吸—扩散—渗流能力的损害。开展了不同压裂液作用前后煤岩的渗透率、吸附/解吸及扩散能力的变化实验,研究表明,压裂液对煤岩渗透率的损害最显著；在压裂液作用煤岩的吸附实验中,由于气—液—固三相之间存在竞争吸附,故压裂液作用使煤岩的吸附量下降；而在解吸—扩散实验中,由于压裂液引起的煤岩基质膨胀、孔喉堵塞等一系列问题,使解吸—扩散能力出现不同程度的降低。其中,各项损害中损害程度最弱的均为清洁压裂液。提出纳米粒子改性压裂液控制煤粉产出的新思路。利用SEM表征了实验采用纳米粒子粒径大致在10～100nm范围内；开展了加入纳米粒子前后清洁压裂液的性能评价及对煤粉的控制能力实验,结果表明,加入纳米粒子后压裂液的黏弹性、携砂性、滤失性等均有所改善,且加入Si02纳米粒子压裂液的效果显著；纳米粒子通过吸附作用能够有效的控制煤粉产出,使产出煤粉减少达50%以上。对煤岩气藏压裂液损害进行综合评价能够更准确的预测压裂施工效果,同时采用纳米粒子控制煤粉产出,可改善压裂施工效果,促进煤层气高效开发。
[Abstract]:As a kind of high-quality clean energy, the coal-bed gas has great resource, effective and effective utilization of coal-bed gas, and has the significance of improving the coal mine safety, making up for the shortage of the conventional energy and protecting the environment. The coal-bed gas is mainly adsorbed on the coal bed, and the output of the coal-bed gas is subjected to the three processes of desorption, diffusion and seepage. Because of the special properties of the compact coal rock, the fracturing technology has its own characteristics, the key point is to control the output of the pulverized coal and the damage of the fracturing fluid to the coal rock. At the same time, the coal-rock gas reservoir is a system of three-phase and three-phase co-existence of a gas-bearing liquid, and the interaction between the fracturing fluid and the coal-rock not only causes the permeability of the coal rock to be reduced, but also causes the surface property of the fracturing fluid to change so as to influence the adsorption/ desorption and diffusion capacity of the coal rock. Based on the analysis of the mineral composition, physical property, pore structure and surface characteristics of the coal rock in the southern part of the Ningwu basin, the paper studies the effect of fracturing fluid on the permeability, adsorption/ desorption and diffusion of the coal rock. In response, the damage degree and the damage mechanism of the fracturing fluid to the coal rock are comprehensively analyzed, and the nano technology is adopted to optimize the fracturing of the coal rock gas reservoir. The mineral composition and pore of No. 9 coal rock are described. The composition of the coal and the distribution of pore size and the distribution of the fracture space were studied by means of X-ray diffraction, scanning electron microscope (SEM), CT scanning, and nitrogen adsorption. The study shows that the inorganic minerals in the coal rock are mainly quartz, and the clay minerals are mainly kaolinite; the pore of the coal-rock matrix is dominated by the nano-scale pores, and the peak of the pore size distribution is at 4nm; the pore structure of the coal-rock is complex, the micro-cracks are more developed, but the space communication Poor performance. It is clear that the coal and rock before and after the fracturing fluid The observation of the infrared spectrum of the coal rock shows that the type and size of the acting force between the coal-rock molecules and the molecules of the fracturing fluid are changed, and the effect of the coal-rock-OH and HCOOH groups is large, so that it is in free state and association. The contact angle between the coal and the simulated formation water and the fracturing fluid shows that the contact angle between the different fracturing fluid and the coal rock is small, the contact angle between the formation water and the coal rock is small, the wettability of the fracturing fluid to the coal rock is good, On the surface of the coal rock, the diffusion of the fracturing fluid on the adsorption/ desorption of the coal rock is comprehensively evaluated. The effect of fracturing fluid on the permeability, adsorption/ desorption and diffusion capacity of the coal rock before and after different fracturing fluid has been carried out. The study shows that the damage of the fracturing fluid to the permeability of the coal rock is the most significant; in the adsorption experiment of the coal rock with the fracturing fluid, the gas-gas-liquid is solid three-phase. In the experiment of desorption and diffusion, a series of problems such as the expansion of the matrix of the coal rock caused by the fracturing fluid, the blockage of the pore and the throat, etc. To a lesser extent, where the degree of damage in each of the lesions is the weakest. It is a clean fracturing fluid. It is proposed that the nano-particle modified fracturing fluid control The new idea of the production of pulverized coal is characterized by SEM. The particle size of the nano-particles is about 10-100 nm. The performance of the clean fracturing fluid before and after the addition of the nano-particles and the control ability of the pulverized coal are carried out. The results show that after the nano-particles are added, the fracturing fluid is fractured. The viscoelasticity, the sand-carrying property and the filter loss of the liquid are improved, and the effect of adding the Si02 nano-particle fracturing fluid is remarkable; and the nano-particles can effectively control the pulverized coal output by the adsorption action, so that the produced coal The reduction of the powder by over 50%. The comprehensive evaluation of the damage of the coal-rock gas reservoir fracturing fluid can more accurately predict the fracturing construction effect, and meanwhile, the nano-particles can be used for controlling the pulverized coal output, so that the fracturing construction effect can be improved.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE357.12

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