How to trace oil in the land and what technologies are being used,

with the help of latest technologies like satellite and global positioning systems, scientists and engineers they explores different parts of the lands where they examine and study rock samples of the land to find some signs ofpresence of oil , if signs are good then they drill a hole to drop pipes and tools into the well , but even after getting good signs of oil , they can not give guarantee unless oil is found ,they built a complete setup with all the requiredtools to suck oil from the earth,
smell sensors that are specially created to trace the oil in the land by its smell, 3-D , 4-D seismic is another way to find the reserves of oil , they do survey analyse geological features on the surface , they also study and examinegravity and magnetic conditions , another method is a thumper truck, by it they throw vibrations through the ground and measured them when come back ,

what is seismic technology and how it works