成像测井缝洞解释评价研究进展

Advances in fracture and vug interpretation using microresistivity imaging logs

综合露头刻度井、数值模拟和物理模拟的实验结果对微电阻率扫描成像测井缝洞解释评价的研究进展进行了总结和探讨,分别包括岩芯归位、缝洞刻度率、岩芯和成像裂缝参数的差异性,以及裂缝宽度和地层孔隙度的计算。岩芯归位确定了缝洞体在地层中的深度和方位。电成像测井对过井眼未充填缝和孔洞发育段的刻度率为100%,而单个孔洞在岩芯和电成像测井中通常无法一一对应。单条裂缝的倾角或井周长度在岩芯和成像测井中具有较高的相关性,而裂缝宽度的相关性一般。数模和物模的结果表明电成像测井裂缝宽度的计算受多种因素影响,当裂缝的视宽度大于0.1 mm时,电成像测井计算的裂缝宽度和裂缝视宽度基本一致,当小于0.1 mm时,电成像测井计算的宽度值误差较大。目前电成像测井通过孔隙度谱法和图像分割法计算地层的孔隙度,但都受限于除孔洞的其他低阻地质体的影响,因此需要加强岩芯刻度的功能。

In combination with outcrop calibration well,numerical and physical simulation,advances in fracture and vug interpretation using microresistivity imaging logs have been analysed and discussed,which include core-shifting,calibration rate,correlation of fracture parameter between cores and imaging logs,and fracture aperture and formation porosity calculation,respectively.Unfilled fractures cutting through drilling wells and pore or vug intervals have a 100%calibration rate,while a single pore or vug generally lost one to one correspondence.Dip angle or circumferential length of a single fracture show good correlation between cores and imaging logs,yet have a moderate relation for fracture apertures.Numerical and physical simulations both indicate that fracture apertures derived from imaging log are controlled by several factors.Apparent apertures more than 0.1 mm,are basically equal to the calculated apertures;on the contrary,the value error increases.Present methods for formation porosity based on imaging logs include porosity spectrum and image segmentation,yet both are restrained by other conductive geological objects except open pores and vugs.Thus,cores should be further used to calibrate borehole images.