Application of magnetic amplitude inversion in the identification of igneous rocks in superimposed basins: a case study in Qikou depression

The identification of igneous rock in sedimentary basins serves as the basis for the exploration of igneous oil and gas reservoirs. The implementation of magnetic exploration in the identification and delineation of igneous rock can often achieve good results. However, when igneous rock and deep magnetic layers are under the influence of remanence, the reduction to the pole of magnetic anomaly and conventional magnetic inversion methods, which require clear magnetization directions, is limited, and special magnetic anomaly processing and inversion methods are necessary. We present a case study on igneous rock imaging through a strategy involving the joint use of a preferential filtering method and amplitude inversion affected by remanence in the Qikou depression in China. We first extract the weak anomalies of igneous rock from the observed total-field anomaly via preferential filtering and calculate their amplitude data. We then perform amplitude inversion to determine the underground three-dimensional magnetism distribution and propose a reasonable interpretation by combining seismic and other data. This work demonstrates the feasibility and effectiveness of the above strategy in delineating the igneous rock buried deep in sedimentary basins.