深井砂岩微观孔隙渗流特性及扩腔注浆堵水机理研究

In China, one of the water seepage in the deep rock of coal mine kilometer deep well is difficult to be blocked by grouting, which is from the deep sedimentary sandstone microscopic pore surface water seepage. As a result of the few experimental and theoretical research of micro-pore structure of coal sandstone and its permeability mechanism currently, which lead to the arbitrariness of the grouting parameters and the randomness of the grouting effect, it seriously affected the wellbore acceptance and long-term stability of the shaft. In this paper, the deep water permeable sandstone is taken as the research object, microscopic scanning of pore structure and chemical slurry was carried out by SEM and CT test, based on the three - dimensional finite element method and the discrete element numerical simulation analysis technique, micro - fine quantitative model of three - dimensional pore structure is constructed, the method of quantitative evaluation of porosity structure of sandstone was established based on permeability. Through the use of triaxial stress permeation test system and large-scale nuclear magnetic resonance instrument, which reveal the seepage, diffusion, expansion mechanism of the chemical slurry in the micro-pore. The grouting mechanics model of the cavity is established, and the grouting technology and parameters for effectively blocking the microscopic pore water seepage of the deep well sandstone are explored. The research results provide important theoretical basis and application value for the solution of microscopic pore grouting and water shutoff in deep well.

我国煤矿千米深井井筒深部围岩难以注浆封堵的渗水之一，是来自深部沉积砂岩微观孔隙的面渗水。由于目前对煤矿砂岩微观孔隙结构及其渗透机理的试验与理论研究很少，导致其注浆参数的随意性和注浆效果的随机性，这严重影响了井筒验收移交和井壁长期稳定性。本课题以深井渗水砂岩为研究对象，通过扫描电镜和CT扫描试验对孔隙结构及化学浆液进行微观研究，结合三维有限元、离散元数值模拟分析技术，构建三维孔隙结构的微观精细定量模型，建立以渗透率为基础的定量评价砂岩孔隙结构的方法。通过采用三轴应力渗透试验系统及大型核磁共振仪，分析揭示化学浆液在微观孔隙中渗流、扩散、扩腔机制，建立扩腔注浆力学模型，探求有效封堵深井砂岩微观孔隙渗水的注浆参数。研究成果为深井围岩微观孔隙注浆堵水难题的解决提供重要的理论基础与应用价值。

深井围岩难以注浆封堵的渗水之一，是来自深部砂岩微观孔隙的面渗水，传统的裂隙水防治方法用于孔隙水的防治效果并不理想，孔隙灌浆法可以直接堵塞砂岩孔隙中的水，虽然目前难度大，但成本低、效果好。而深井砂岩孔隙注浆堵水技术难题主要集中在可注性及减渗率两个方面，可注性大小主要取决于砂岩的孔隙结构，因此，深入研究深井砂岩孔隙结构及其渗透机理，对提高注浆效果具有十分重要的意义。 .本项目以深井井筒孔隙注浆堵水难的鲁西南煤田的深井砂岩为例，基于铸体薄片观察、扫描电镜分析、粒度分析、物性分析及压汞试验等大量实验资料，结合室内渗流实验、数值模拟分析等手段，深入研究了深井砂岩微观孔隙结构特征、影响因素、分类和定量评价、多因素耦合渗流实验和孔隙结构三维建模及其渗流数值模拟5方面内容。结果表明：①鲁西南煤田侏罗系砂岩原始粒间孔普遍发育，以缩颈状喉道为主、喉道较粗，二叠系砂岩原始粒间孔数量少且分布离散，以片状弯片状喉道为主、喉道细小。②成岩作用是造成砂岩孔隙结构差别的主要因素，它控制了砂岩孔隙结构发育的垂向分带性：沉积作用是造成孔隙结构差别的次要因素,它控制了砂岩孔隙结构发育的平面分区性。③根据渗透率、孔隙度、平均孔喉半径、成岩综合系数和分选系数5个代表性评价指标，采用以渗透率为基础、多指标综合定量评价方法，将其孔隙结构划分为两大类（I、II）四亚类（I1、I2、II1、II2），I1类是中孔中喉型孔隙，适于悬浮液分离型浆液注浆，I2类是中小孔细喉型孔隙、II1类是中小孔细喉型-小孔微喉型孔隙，适于化学浆液注浆、II2类是微孔微喉型孔隙，难以注浆。④深井条件下的围压、水压和温度对不同孔隙结构深井砂岩渗流的影响不同，多因素耦合作用控制了深井砂岩渗流过程。本项目研究成果可为煤矿深井围岩的微观孔隙分类注浆堵水设计与施工提供重要理论基础，同时，也对类似地下工程深部围岩的微观孔隙注浆堵水研究具有重要应用价值。