The significance of systematic combination of various geophysical methods: in view of a failure example in determining well locations

Compared to a single geophysical method, systematic combination of various geophysical methods can make a full use of each method to obtain more accurate detections, which is not emphasized enough in prectice. To discuss the significance of the combined geophysical methods, a failure example in determination of well locations with the geophysical method is investigated. Comparison of determination results among the high-density resistivity method, magnetic resonance sounding (MRS) method, and the combination of these two methods is examined. Feasibility of the combined methods is discussed through analyzing the advantages and disadvantage of each method and calculating the economic cost. The results show that (1) The high-density resistivity method and MRS have different advantages and disadvantages, the high-density resistivity method can provide the information about the overall structure change of strata, but has the strong uncertainty in lithology determinations, and MRS can be used to the lithology determinations which are consistent with borehole data, but does not judge the existence of faults or fractures. (2) The high-density resistivity method, in conjunction with MRS, can give accurate inference of the cross-sectional thickness and lithology changes which are well fit to the borehole data. The combination of the different geophysical methods is an effective way to reveal the lithology changes and location of aquifers, which should attract more attentions. (3) Compared to a single geophysical method, the conjunct methods have lower cost and are feasible in practical applications.