Yongchuan deep mountain shale gas block is located in Huayingshan fold belt, which is a low anticline group with broom like spreading to the south. The structural folds are strong and the faults are developed. The target layer of Longmaxi Formation has the characteristics of great difference in burial depth, high ground pressure and ground temperature and large difference in horizontal stress, while the crossing layer has strong abrasiveness, easy instability of well wall and poor drillability. The lack of early geological knowledge leads to low drilling time, long construction period and frequent complex situations, and the fracturing effect of multiple wells is not ideal. In order to solve the main problems faced by Yongchuan work area, researches on the geomechanical parameters, such as drillability, hardness, abrasiveness laboratory experiments, drillability profile establishment, formation three pressure prediction, 3D in-situ stress finite element, simulation and fracture propagation simulation under different horizontal stress difference modes, and horizontal well geological engineering double sweet spot prediction, have been conducted respectively. The results show that the formation drillability level is high, the safe drilling fluid density window is narrow, the difference of in-situ stress direction is large, and the formation of hydraulic fracturing network is affected by high stress difference. Based on the research results of geomechanics, the engineering technology has been adjusted. The drilling speed and fracturing production increase effect are obvious, which has reference significance for the development of deep shale gas in South Sichuan.