Three-dimensional seismic interpretation plays a key role in robust hydrocarbon exploration and production of subsurface reservoirs. With the dramatic growing size of 3D seismic surveys, however, manually interpreting a seismic volume turns to be even more challenging. In recent years, artificial intelligence and machine learning techniques have been successfully applied in various disciplines, which greatly promotes its applications in the seismic domain for mimicking an experienced interpreter's intelligence and assisting seismic interpretation in various tasks, including facies analysis and structure detection (e.g., faults and salt domes). In this study, we first apply two most popular neural network frameworks, the multi-layer perceptron (MLP) network and the convolutional neural network (CNN), to the problem of seismic salt-body delineation and compare their performance. Then, we investigate two factors that contribute to the better performance of the CNN framework in understanding seismic signals and identifying the important seismic structures. Specifically, on one hand, the CNN is capable of automatically generating a suite of features from the original seismic images, which reduces the dependency on interpreters for computing and tuning seismic attributes. On the other hand and more importantly, the CNN classification is patch based, in which local seismic reflection patterns are taken into account for defining and learning the features of the target structures. In this way, the random/coherent seismic noise and processing artifacts of distinct patterns can be effectively identified and excluded.