微波加热对致密砂岩孔隙水的影响

Effect of microwave heating on pore water in tight sandstone

为研究微波辐射下致密砂岩孔隙水的时空分布特征,评价工程中微波注热对含水储层的除水效果,对预处理后的饱水红砂岩样品进行微波加热,采用核磁共振测试样品的含水率。通过拟合分析,得到样品T2图谱与含水量之间的对应关系。基于poly函数的曲面拟合,确定微波的干燥时间和传播距离与岩石样品含水率的关系。研究结果表明:基于样品预处理方法获得的实验结果符合微波在自由空间传播的特点;与微波的传播距离相比,岩石含水率对干燥时间的敏感性更强;一定能量密度的微波干燥存在一个时间阈值,超过阈值的微波加热无法继续去除岩石中剩余的水分;采用功率为6 kW的微波加热100 s后可以基本去除长度为10 cm的样品内70%以上的水分;微波的干燥时间和传播距离与岩石样品含水率的关系揭示了微波作用下孔隙水的迁移规律以及微波对含水砂岩的干燥效果,可为利用微波注热技术消除储层水锁损害提供指导。

In order to study the spatial and temporal distribution characteristics of pore water in tight sandstone under microwave radiation,and to evaluate the drying effect of microwave heating on water bearing reservoir,microwave heating of the pre-treated saturated red sandstone samples was conducted,and the water content based on the nuclear magnetic resonance test was investigated.The relationship between T2 spectrum and water content of the sample was obtained by fitting analysis.Through fitting analysis,the function relationship among drying time,propagation distance and water content were determined.The results show that the temperature obtained by the pretreatment method accords with the characteristics of microwave propagation in free space.Compared with propagation distance,the water content is more sensitive to microwave drying time.There is a time threshold for microwave drying,beyond which microwave heating cannot continue to force out the remaining water in the rock.Microwave heating at 6 kW for 100 s can basically remove water within 10 cm of tight sandstone.The function relationship among drying time,propagation distance and water content reveals the migration pattern of pore water during microwave stimulation,and the drying effect of microwave on water-bearing sandstone can be investigated,which provides guidance for eliminating water lock in reservoir by microwave heat injection.