针对塔中北斜坡碳酸盐岩内多期应力作用下形成的裂缝,研究了采用叠前P 波方位AVO 反演和叠后相干属性相结合的裂缝分布特征预测方法。结果显示,塔中北斜坡碳酸盐岩内发育单组裂缝和多组裂缝,叠后相干属性预测的裂缝多与断裂控制的裂缝分布一致,这些裂缝多发育在断裂破碎带中,由于断裂附近为两个方向的应力释放区,北东向和北西向裂缝都易发育,易形成多组裂缝;叠前P 波方位AVO 反演预测的裂缝多分布在隆起、背斜顶部,由于隆起、背斜等构造带主要受北东向挤压应力作用,易形成单个方向的裂缝(单组裂缝)。结果表明,叠后预测能够表述裂缝与断裂之间的关系,而叠前预测则能够补充表述断裂之间的裂缝分布,两者结合的预测方法能够更准确地揭示裂缝分布特征,且与塔中北斜坡的地质规律相符合。
A new method for fracture prediction is proposed in this paper, to identify the distribution of carbonate fractures developed under the multi-stage stress action in the North Slope, Tazhong area. Studies show that fractures are developed in a single-azimuth set and a multiple-azimuth set in carbonate rock there. The predicted fractures with the post-stack coherent attribute are mostly distributed around faults, and developed in fault-fracture zones. These fractures are always in a multiple-azimuth set, because they are developed in two main directions by the relief of dipole-stresses. And the fractures predicted by the P-wave azimuth AVO inversion are always developed in the tops of the anticline and the uplift belt. They are always in a single-azimuth set, because they are developed by a persistent and single northeast directional stress relief. Further analysis shows that the prediction results with the post-stack coherent attribute could be used to describe the relation between fractures and faults, while the results of the pre-stack method could be used to describe the fracture distribution between faults. And the integrated prediction results not only more accurately reflect the fracture distributions, but also are consistent with the geological conditions of the North Slope in Tazhong area.
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