Abstract:

The directional distribution and deformation intensity of structures in Xinchang gasfield,located in the center of western sag in Sichuan basin, have been found to be largely different from those on both sides. As a whole,Xinchang gasfield is in the weak deformation area, it might have been reversely twisted in NS direction and compressed in WE direction during Indosinian to later Yanshan movements,and only the EW direction compressional stress field that occurred during the middle Himalayan deformation stage is relatively evident.The structure is of weak deformation type with only a few little faults,and rarely with stress fields traces in cores.The characteristics of stress field are as follows: the main direction of largest horizontal stress is about 150°,the largest and smallest principal stresses (σ_v and σ_n) are both nearly horizontal,and the largest principal stress is slightly larger than the vertical stress (σ_H) of rock strata and fracturing stress of rock.

Key words: stress field, upper Shaximiao Fm, structural deformation, traces in core