摘要
利用正交阵列偶极声波测井可以提取地层各向异性,但有效区分各向异性的成因类型,特别是区分应力诱导成因还是裂缝等固有成因是个难题。在应力引起的各向异性中,由于应力的集中效应,快弯曲波方位角度在高、低频段的差值接近90°,而在裂缝、页理等固有的各向异性中,快弯曲波方位角度在高、低频段的差值接近0°。基于快、慢弯曲波声源信号一致的特征,构建了新的特征函数,实现了全频段快弯曲波方位角度的计算,同时在反演过程中引入全频段快弯曲波慢度始终小于慢弯曲波的约束条件,极大提高了反演计算的正确率。该方法不仅使正交阵列偶极声波测井能够提取各向异性,还能进一步区分各向异性类型,有效扩展正交阵列偶极声波测井在非常规储层勘探中的应用领域和深度。
Cross-dipole acoustic well-logging technology has been applied to determine formation anisotropy,but it is very difficult to identify effectively the types of anisotropy.The stress-induced anisotropy can result in a large difference between azimuths of fast flexural wave between far-field and near borehole.The difference is theoretically equal to 90 degrees.However,the difference caused by the intrinsic anisotropy,such as shales,layering and fractures,is theoretically close to 0 degree.This paper presented a new object function based on the fact that the source waves inverted by fast and slow flexural waves are the same source.And the fact that slowness of fast flexural wave must be equal or greater than the slowness of slow flexural wave in the frequency domain as a limitation was introduced to the inversion procedure,which improved the correct rate.The difference between azimuths of fast flexural waves between far-field and near borehole can be used to identify the types of anisotropy.The method can not only determine anisotropy,but also identify the stress-induced anisotropy and intrinsic anisotropy.The method can be used in processing the field data.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2015年第4期457-468,共12页
Acta Petrolei Sinica
基金
国家重大科技专项"复杂储层油气测井解释理论方法与处理技术"(2011ZX05020-008)资助