潜山花岗岩裂缝性储层阵列声波测井数值模拟研究

A numerical simulation study on array acoustic logging of fractured granite reservoirs in buried hills

南海琼东南盆地潜山储层储集空间类型复杂多样,裂缝多发育,导致储层具有较强的非均质性,该地区多见花岗岩沉积,因此有效评价花岗岩储层中裂缝的发育情况至关重要。利用COMSOL Multiphysics有限元模拟软件,采用有限元方法,对使用阵列声波测井探测不同宽度、不同倾角及不同长度的花岗岩储层进行模拟,总结出不同发育状态裂缝的阵列声波测井响应特征。研究发现:裂缝性地层横波受裂缝宽度变化影响不明显,横波衰减程度与裂缝倾角变化呈反比,与裂缝长度变化呈正比;斯通利波对裂缝宽度、裂缝倾角、裂缝长度等变化均有明显响应,斯通利波衰减程度与裂缝宽度及裂缝倾角均呈正比;在裂缝长度小于0.1 m时,斯通利波衰减程度与裂缝长度呈正比,裂缝长度大于0.1 m之后,斯通利波对裂缝长度变化无明显响应。本文研究结果为采用阵列声波测井方法判断花岗岩储层中裂缝的发育状态提供了依据。

The buried-hill reservoirs in the Qiongdongnan Basin of the South China Sea exhibit intricate reservoir spaces and numerous fractures,leading to their pronounced heterogeneity.Since granite sediments spread across the study area,it is critical to effectively evaluate the development of fractures in granite reservoirs.Based on the COMSOL Multiphysics software and the finite element method,this study simulated the use of array acoustic logging to detect granite reservoirs with different widths,dip angles,and lengths,summarizing the response characteristics of fractures in different development states.The results are as follows:(1)Shear waves in fractured formations are subjected to non-significant influence of fracture widths,and their attenuation is inversely proportional to fracture dip angles and directly proportional to fracture lengths;(2)Stoneley waves manifest significant response to the changes in fracture widths,dip angles,and lengths,and their attenuation is proportional to both fracture widths and dip angles;(3)The attenuation of Stoneley waves is directly proportional to fracture lengths below 0.1 m but shows subtle response to fracture lengths above 0.1 m.The results of this study provide a basis for determining the development state of fractures in granite reservoirs using the array acoustic log method.