利用各向异性模型计算水平地应力

Calculation of Horizontal Stress by an Anisotropic Model

地层中大部分岩石存在各向异性,垂直方向与水平方向纵横波呈现波速差异性.以往应用测井资料计算水平地应力,都是基于各向同性的计算模型,没有考虑地层各向异性的存在,计算结果与实际地层存在着较大差别.为尽量消除这种差异,从阵列声波测井中斯通利波波形数据及纵横波慢度入手,根据频谱加权平均慢度定理反演水平剪切模量C66.利用反演得到的结果及其他弹性模量计算水平、垂直方向弹性模量及泊松比,并根据各向异性模型计算水平地应力.用该模型计算大庆油田深层致密砂岩气5口井水平地应力,对计算结果与实验数据进行了比较,数据显示非常好的一致性,验证了计算结果的可靠性.

P-wave velocity and S-wave velocity are different in vertical and horizontal directions due to rock anisotropy.Usually,horizontal stress is calculated based on an isotropic model using well logging data,but without considering rock anisotropy,the result is quite different from the real condition.In order to eliminate such difference,this paper inverses the horizontal shear modulus of C 66 according to the weighted spectral average slowness theorem based on the Stoneley wave and the slowness of P-wave and S-wave from array acoustic wave data,calculates the elastic modulus and Poisson’s ratio in vertical and horizontal directions,and finally calculates the horizontal stress according to an anisotropic model.The model is used to calculate horizontal stresses in 5 deep tight sandstone gas wells in Daqing oilfield.The results are in good agreement with experimental data.