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为深入研究褐煤原位注热开采过程物性特征的衍变,应用高温高压实验平台,研究7 MPa三轴等压条件下,Φ50 mm×100 mm褐煤以3℃/min升温速率由室温升高到400℃过程中及恒温恒载5 h的变形特征规律。并应用显微CT、压汞、液氮吸附解吸方法综合分析褐煤不同孔径范围的孔裂隙衍化规律。研究发现:热力耦合作用下,褐煤变形过程可以划分为缓慢膨胀阶段(室温~170℃)、剧烈压缩阶段(170℃~289℃)及缓慢压缩阶段(289℃~400℃),褐煤脆性–韧性转变临界温度为180℃。恒温恒载5 h过程中,褐煤轴向线应变终值随温度的升高先增大后减小,最大值为2.5%(200℃),最小值为1.3%(100℃)。褐煤最大径向累积压缩应变约为19%(400℃),最大体积累积压缩应变约为41%(400℃)。热力耦合作用下,褐煤变形对其结构衍化有重要影响。随着温度的升高,褐煤总孔隙率表现为先增大后减小,孔裂隙率极大值为21.46%(200℃),最小孔裂隙率为7.61%(23℃);主要孔裂隙的孔径逐渐增大。褐煤孔裂隙率衍化具有较好的分形特征,随着温度的升高,孔裂隙率的分形维数表现为先减小后增大、分形初值则先增大后减小。
In order to further study the physical property evolution of lignite in situ injection process, the high temperature and high pressure experimental platform was used to study the effect of 3 MPa pressure on lignite with Φ50 mm × 100 mm lignite at room temperature 400 ℃ during the process of constant temperature and constant load 5h deformation characteristics. And the microscopic CT, mercury intrusion, liquid nitrogen adsorption and desorption method were used to comprehensively analyze the fissure evolvement rule of lignite in different pore size range. The results show that the deformation process of lignite can be divided into two stages: slow expansion stage (room temperature ~ 170 ℃), severe compression stage (170 ℃ ~ 289 ℃) and slow compression stage (289 ℃ ~ 400 ℃) Change the critical temperature of 180 ℃. In the process of constant temperature and constant load for 5 h, the final value of axial strain of lignite first increases and then decreases with the increase of temperature, the maximum value is 2.5% (200 ℃) and the minimum value is 1.3% (100 ℃). The maximum radial cumulative compressive strain of lignite is about 19% (400 ℃) and the maximum cumulative compressive strain is about 41% (400 ℃). Due to the thermal coupling, the deformation of lignite has an important influence on its structure evolution. With the increase of temperature, the total porosity of lignite first increased and then decreased, the maximal pore fracture rate was 21.46% (200 ℃) and the smallest pore fracture rate was 7.61% (23 ℃). The main pore fissures Aperture gradually increased. Fractal rate of lignite pores has good fractal characteristics. With the increase of temperature, the fractal dimension of pore fracture rate decreases first and then increases, and fractal initial value first increases and then decreases.