The Research About Average Relaxation Time Calculation Based On Surface MRS Method And Application

Surface magnetic resonance sounding (MRS) is the only method that allows directdetermination of water, under the effect of excitation electromagnetic fields, hydrogennuclei is excited.MRS signal through inversion can obtain thickness, depth, water contentso on of underground aquifers. The results through MRS inversion method have someadvantages with uniqueness, quantitative and high efficiency of measurement so on.Hydrogeological parameter is the important criterion that reflecting hydrogeologicalproperties of aquifer or permeable layer. Such as permeability coefficient, waterconductivity, porosity and water inflow and so on. Existing research shows that MRSmethod can provide the permeability coefficient of aquifer in the range of allowable error.But the effect is not ideal in the actual application because the estimates and pumping testof calculated value have large deviation. And the existing research has little knowledge forthe because of causing this deviation, these problems often appear in actual production.The paper introduces inversion methods of MRS contain initial amplitude inversionand QT inversion. The inversion result can obtain accurate and stable average distributionof relaxation time and content. According to the characteristics of MRS signal, uses QTinversion to extract distribution of the relaxation time for the multiple index characteristicsof MRS signal. The paper research uses distribution of the relaxation time to describe thedistribution of geology, that is, the average relaxation time has directly relationship with theparameters of hydrogeological. Including the calculation method of porosity, averagerelaxation time has relationship with free water and bound water, the calculation method ofpermeability and the influence factors about permeability, and the calculation method aboutpermeability coefficient, conductivity coefficient and water inflow.Through studying the influence about empirical coefficient (CP) value of empirical formula for the calculation of permeability coefficient. So the paper selects the data of MRSin Mongolia region, based on the data of MRS, drilling lithology and pumping test data inthe region. The paper put forward a method about using the average relaxation time tocalculate the value of (Cp). The value is used to calculate the permeability coefficient andtransmission coefficient. Then, comparing the permeability coefficient of calculation withthe drilling results of measuring point, further tests the accuracy of the calculation of Cp.Finally, the paper has made the designs and tests of hydrogeological parameterscalculation software, including the software design of QT inversion results to calculatehydrogeological parameters, the software design of permeability coefficient calculation, thesoftware design of conductivity coefficient calculation and water inflow calculation.Through selecting these MRS data and the result of measurement in a region of InnerMongolia, QT inversion results are obtained by inversion interpretation of the nuclearmagnetic resonance data. Using the average relaxation time form QT inversion to calculatehydrogeological parameters through selecting these MRS data and the result of calculationcompare with the adjacent point of drilling. The result verifies effectiveness about softwareapplication.