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.