基于实例研究的磁共振探测估算含水层导水系数准确性提升方法

Improvement the accuracy for application the magnetic resonance sounding to the estimation of transmissivity:a case study

磁共振探测(MRS)是目前唯一直接找水的地球物理方法,常被用于估算含水层导水系数.与传统的通过抽水试验获取导水系数值相比,该方法具有低成本及非侵入等优点,但其估算误差较大,准确性有待提升.本文以蒙古国伊和塔拉盆地的MRS为具体实例,通过比较常用计算公式不同参数取值下MRS估算的导水系数与抽水试验计算值的差异,定量探讨了MRS推断含水层深度的准确性、计算公式中关键参数的取值等主要因素对估算结果的影响,并以此为基础在多个环节对原有方法进行了改进.结果显示:(1)MRS推断含水层深度的平均误差为4.85 m,存在随深度增加误差增大的现象.(2)C_P的正确取值是控制误差在合理范围的关键,C_P取最优值,估算的平均误差为15.53%,且其在取值范围内取最大值或最小值,误差均小于原有方法的常用取值.(3)计算公式中关键参数a、b的取值,Seevers公式(a=1、b=2)的估算效果优于Kenyon公式(a=4、b=2).通过比较发现,改进后的方法较原有方法能明显提升估算结果的准确性,具有很好的适用性.

Magnetic Resonance Sounding（MRS） is currently the only geophysical method directly to water,was often used to the estimation of Transmissivity.Appling the MRS estimate the transmissivity was low cost and non-invasive than pumping test method,but which have large errors.Take the MRS in Yihetala basin as a case,discussed the aquifer location accuracy and the key parameters of formula brought the errors on estimate the transmissivity.Based on the forementioned results,analysis of the causes of possible errors,and then present the improving method at the measuring point layout,signal acquisition,data interpretation,transmissivity coefficient estimates.The results showed that：（1）The average error for MRS infer aquifer depth was 4.85 m,have the phenomenon for error increases with the depth.（2） CPtake optimal value,the estimation error with an average of 15.53%.CPtake maximum and minimum within the range,the estimation errors are less than thecommon parameter settings.（3） Using the Seevers＇s formula（a=1,b=2） estimation the transmissivity,the errors are less than the Kenyon＇s formula（a=4,b=2）.Through the comparison,the improved method can improve the accuracy of the estimation result and has the better applicability.