In situ stress has been proven to be of great significance for hydrocarbon exploration and development, especially for deep hydrocarbon reservoirs, unconventional hydrocarbon reservoirs, and reservoirs with particularly complex geological structures, which have become a frontier topic in the world and a major topic in the petroleum industry. The clear distribution of the in-situ stress field can provide an important basis for well displacement, the design of fracturing transformation and production increase and the development plan of the oilfield.This book introduces a set of methods for predicting the comprehensive distribution of in situ stress in deep fault block reservoirs and expounds in detail the geological and geomechanical modeling methods, the main controlling factors of rock mechanical parameters and the distribution of the in-situ stress field, as well as the application of relevant research in the prediction of natural fractures in reservoirs, hydraulic fracturing prediction and engineering parameter design.This book not only summarizes the latest research results on the theoretical understanding and analysis methods of in situ stress in the world but also carries out detailed applied research in full combination with the actual situation of the oilfield. It can be used as an important text for higher education students and professionals in academia, research, and industry.