基于各向异性梯度的裂缝密度反演

摘要

Fracture density is an important parameter for reservoir evaluation. This paper proposed a new method for calculating fracture density by using the anisotropic gradient.Firstly fractured medium is equivalent to the anisotropic HTI medium with the equivalent theory,then the AVO attributes of fractured medium were obtained so as to calculate the anisotropic gradient of fractured medium;finally the fracture density of fractured medium was got based on the relationship between the anisotropic gradient and fracture density.In the actual processing we can obtain the anisotropic gradient from the seismic data and then get the fracture density.The numerical examples suggest that we can get the accurate fracture density of the fractured medium by the method in the present study.The inversion results are consistent with the initial model,verifying the correctness of the method.In addition,we can also get the fracture density from the seismic data with noise,suggesting the stability of the method.%裂缝密度是评价裂缝性储层的重要参数。本文提出一种利用各向异性梯度计算裂缝密度的新方法，即运用裂缝介质等效理论将高陡倾角裂缝介质等效为横向各向同性介质，得到裂缝介质 AVO 响应特征，从而得到裂缝介质的各向异性梯度，之后由该梯度与裂缝密度的关系得到裂缝介质的裂缝密度。实际处理中可以根据地震数据直接求取裂缝介质的各向异性梯度，最后求取裂缝介质的裂缝密度。模型试算表明，该方法能得到裂缝介质准确的裂缝密度。反演结果与初始模型基本一致验证了该方法的正确性；另外地震记录添加一定的信噪比后也能反演得到准确的裂缝密度，证明了该方法的稳定性。