半航空瞬变电磁法在古河道结构探测中的应用

Application of semi-airborne TEM to structure exploration in the old channels

嘉陵江河曲发育,古河道分布广泛,复杂的地形、地貌环境限制了其研究精度.半航空瞬变电磁法具有效率高、成本低、适应性强的特点,具有广阔的应用前景.为查明古河道地层结构特征,本文以南充市石梁乡境内的嘉陵江古河道为例,首次将无人机半航空瞬变电磁法应用于古河道结构的探测.首先,通过对该区域的无人机半航空瞬变电磁探测数据进行预处理和反演解释,获得了研究区古河道"低-高"模式的二元电性结构以及三维空间结构模型,从而可推断出古河道地层结构主要有W型、U型两种形态,河道中间松散堆积层厚度平均为20 m,两端变薄,平均为5 m.其次,基于现场地质地貌调查和钻探资料,结合等值反磁通瞬变电磁法、综合测井等地球物理方法所获得的探测结果对无人机半航空瞬变电磁数据推断的古河道地层结构特征进行综合标定与验证,结果表明半航空瞬变电磁法应用于古河道结构的探测是可行的,并且半航空瞬变电磁法获得的物性参数与地质特征结合,可快速、准确获得古河道地层结构,对研究其沉积环境和演化具有重要的支撑作用.

The curvature of the Jialing River is developed and the ancient channel is widely distributed,complex topography and geomorphic environment limit its research accuracy.Because of its high efficiency,low cost and adaptability to complex geological and topographic conditions,the semi-airborne TEM has a broad application prospect.In order to find out the stratigraphic structure characteristics of the ancient river course,this paper takes the ancient river course of Jialing River in Shiliang Township,Nanchong City as an example,and for the first time,UAV semi-airborne TEM is applied to the detection of the ancient river course structure.First of all,by preprocessing and inversion interpretation of UVA semi-airborne transient electromagnetic detection data in this area,the binary electrical structure and three-dimensional spatial structure model of the"low-high"model of the ancient channel in the study area are obtained,thus it can be inferred that the stratigraphic structure of the ancient channel mainly has two forms,W type and U type.The average thickness of the loose accumulation layer in the middle of the channel is 20 m,and the two ends are thinner with an average thickness of 5 m.Secondly,based on the field geological and geomorphic survey and drilling data,combined with the detection results obtained by opposing coils TEM,integrated logging method,the paper comprehensively standardized and verified the stratigraphic structure characteristics of the ancient channel inferred from the UVA semi-aerial transient electromagnetic data.The results show that the application of semi-airborne TEM to the detection of ancient river channel structure is feasible,and the physical parameters obtained by semi-airborne TEM combined with geological characteristics can quickly and accurately obtain the stratigraphic structure of ancient river channel,which plays an important supporting role in the study of its sedimentary environment and evolution.