【作者】 彭辉；

【导师】 杨兆彪；

【作者基本信息】 中国矿业大学 ， 地质工程（专业学位）， 2019， 硕士

【摘要】 在总结滇东黔西研究区中-高煤阶煤储层地质背景的基础上,分别通过高压压汞实验、低温液氮吸附实验、低温CO2吸附实验分析了中-高煤阶煤样不同孔径阶段孔隙结构特征,采用分形数学方法,构建了全孔径阶段孔隙结构模型;通过加压饱和过程和驱替过程中的核磁共振实验,研究了煤样流体分布特征和流体流动性特征。研究结果显示:中-高煤阶煤样全尺度孔隙结构特征区别明显:煤样孔比表面积与孔体积均随煤阶升高而增大,全孔径阶段孔隙分布曲线呈现三峰分布,中煤阶为“高-高-高”或“高-低-高”模式,高煤阶样品以“高-低-低”分布为主,左峰对应超微孔最为发育,尤以高煤阶样品超微孔发育程度最高,高煤阶样品中孔大孔发育程度略低于低阶煤。通过基于高压饱和的核磁共振实验,表明中阶煤样品流动性较好,高煤阶样品在加压饱和实验中含水饱和度变化幅度小,核磁共振驰豫谱右峰较低,表明其渗流孔空间极小;结合液氮吸附实验数据求取表面驰豫率ρ2,提出了孔径转换和可饱和孔径值计算方法,结果显示高煤阶样品在常压或低压阶段已大部分饱和水,饱和水压力增加对增加孔隙含水量作用有限。核磁驱替实验煤样品残余水饱和度随驱替压力增大逐渐减小,在2 MPa驱替压力处出现拐点,之后趋于稳定。中煤阶样品水流动性较好,残余水饱和度低;高煤阶样品水流动性差,残余水较多;建立了驱替过程可动孔径值计算方法,结果显示中煤阶样品可动孔径值变化较大,表明较大孔径范围的孔隙内水被逐渐驱出,高煤阶样品可动孔径值变化幅度小,最终为平均18.08 nm,表明发育程度较高的微孔中流体难以驱出,导致其整体水流动性差。更多还原

【Abstract】 On the basis of summarizing the geological background of medium-high rank coal reservoirs in the study area of eastern Yunnan and western Guizhou,the pore structure characteristics of medium-high rank coal samples of different pore size scales were analyzed by high pressure mercury injection experiment,low temperature liquid nitrogen adsorption experiment and low temperature CO2 adsorption experiment,and the pore structure model of full pore size scale was constructed by fractal mathematics method.Nuclear Magnetic Resonance(NMR)experiments were carried out to study the fluid distribution and fluidity characteristics of medium-high rank coal samples.The results show that there are obvious differences in full scale pore structure characteristics between medium and high rank coal samples: the specific surface area and pore volume of coal samples increase with the increase of coal rank,and the pore distribution curve of the full pore size scale presents a three-peak distribution.The medium rank coal is a "high-high-high" or "high-low-high" model.The high rank coal samples are mainly "high-low-low" distribution,and the left peak corresponds to the most developed supermicro pore,especially the high rank coal.High rank coal samples have the highest degree of micropore development,while high rank coal samples have slightly lower degree of medium pore and macropore development than medium rank coal.The results of NMR experiments based on high pressure saturation show that the fluidity of low-rank coal samples is good,the water saturation of high-rank coal samples varies little during pressure saturation experiments,and the right peak of NMR relaxation spectrum is low,which indicates that the space of seepage pore is very small.Based on the experimental data of liquid nitrogen adsorption,the surface relaxation rate ρ2 was calculated,and the methods of pore size conversion and saturation pore size calculation were proposed.The results show that most of the high rank coal samples have saturated water in the stage of atmospheric pressure or low pressure,and the increase of saturated water pressure has limited effect on increasing pore water content.The residual water saturation of coal samples decreases gradually with the increase of displacement pressure,and the inflection point appears at the displacement pressure of 2 MPa,then tends to be stable.The fluidity of medium rank sample water is good,and the residual water saturation is low;the fluidity of high rank sample water is poor,have more residual water.A method for calculating movable pore size in displacement process is established.The results show that the movable pore size of medium rank coal samples varies greatly,indicating that the water in the pore with larger pore size is gradually driven out,while the movable pore size of high rank coal samples varies slightly,eventually reaching an average of 18.08 nm,indicating that the water in the higher developed micropore is difficult to drive out,resulting in poorl water mobility.更多还原