新场气田上沙溪庙组的应力场特征

CHARACTERISTICS OF STRESS FIELD IN UPPER SHAXIMIAO FORMATION,XINCHANG GASFIELD

新场气田位于四川盆地西部坳陷的中部。其构造展布方向 ,形变强度等方面与两侧都有较明显的差别。从整体上看 ,新场气田属弱形变区。印支期至燕山晚期 ,新场气田长期处于NS向反扭和EW向挤压 ,仅中喜马拉雅形变世代的EW向挤压应力场较为明显 ;该构造属于弱形变强度的构造 ,仅发育少数小断裂 ,岩芯上应力场踪迹少 ;其应力场特征是 :最大水平主应力的主体方向为 15 6°左右 ,最大主应力 (σv)与最小主应力 (σh)近于水平 ,最大主应力稍大于岩层的垂直应力 (σH)和岩石的破裂应力。

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.