用正交偶极阵列声波测井研究地层地应力场

Researching earth stress field using cross-dipole acoustic logging technology

提出了一种利用正交偶极子声波测井资料计算地层主应力的新方法。该方法利用了当地层地应力不均衡时,横波发生双折射形成快横波和慢横波的物理特征,在应力不均衡井段建立快、慢横波应力-速度方程。通过岩心实验确定了快、慢横波应力-速度方程的耦合系数,从而计算地层最大、最小水平主应力数值,并从理论上证明了快横波传播方向与最大水平主应力方向一致。应用该方法,对大港油田碳酸盐岩地层进行了地应力评价,并用成像测井对评价结果进行验证,结果证明该方法有效。

A novel method of calculating earth stress field by using cross-dipole acoustic logging technology was proposed. The physical characteristics, that shear wave propagating in the formation is double refraction and split into fast shear wave and slow shear wave when earth stress is non-equilibrium, were used in this method. The stress-velocity equations of fast and slow shear waves were set up for the well section of non-equilibrium earth stress. The coupling coefficients of the stress-velocity equations were obtained from the core analysis, and the maximum and minimum horizontal major stresses were calculated. It is proved that fast shear wave propagates along the direction of the maximum major ground stress in theory. The earth stress of carbonate formation in Dagang Oilfieht of Tianjin was evaluated by this method, and the evaluation results were checked by imaging logging, which shows that the method is effective.