剪切滑移裂缝对井眼声波传播的影响

Study on the Propagation of Borehole Acoustic Wave by Shear-slip Fracture

裂缝对储层含油气性和产能有直接的影响,裂缝的测井识别与评价是致密砂岩储层油气勘探开发的关键。在研究过程中发现,如果将天然裂缝视为光滑裂缝,理想平板模型所计算的结果会与实际结果有误差。通过分析,造成这种误差的原因,一方面与裂缝结构的粗糙性有关,另一方面与裂缝结构有关。非常规储层通过压裂形成的裂缝结构有拉张型裂缝结构和剪切滑移裂缝结构,通常将粗糙裂缝视为拉张型裂缝结构,在剪切滑移作用下,裂缝的结构会产生变化。斯通利波反射系数对裂缝宽度反应灵敏,常用来识别裂缝,对井孔模型进行数值模拟,研究粗糙裂缝对斯通利波的影响。采用迂曲度对裂缝表面的粗糙程度进行描述,在研究过程中发现粗糙裂缝的剪切滑移会对斯通利波的衰减造成一定的影响,通过拟合得到斯通利波的衰减系数与滑移距离、迂曲度的计算公式。

Fractures have a direct impact on the oil-gas bearing capacity and productivity of reservoirs. Logging identification and evaluation of fractures is the key to oil and gas exploration and development of tight sandstone reservoirs. During the research,it is found that if the natural cracks are regarded as smooth cracks,the calculated results of the ideal plate model will have errors with the actual results. Through analysis,the causes of this error are related to the roughness of the crack structure on the one hand and the crack structure on the other hand. Fracture structures formed by fracturing in unconventional reservoirs include tensile fracture structure and shear slip fracture structure. Generally,rough fractures are regarded as tensile fracture structure,and the fracture structure will change under the action of shear slip. The reflection coefficient of stoneley wave is sensitive to fracture width,which is often used to identify fractures. Numerical simulation of borehole model is carried out to study the influence of rough fractures on stoneley wave. Curvature is used to describe the roughness of crack surface. During the research,it is found that the shear slip of rough crack will have certain influence on the attenuation of stoneley wave. Through fitting,the calculation formulas of attenuation coefficient,slip distance and tortuosity of stoneley wave are obtained.