大斜度井各向异性地层双感应测井响应特征研究

Response Characteristics of Dual Induction Logging in Anisotropic Formation and High Deviated Wells

电性各向异性广泛存在于砂泥岩薄互层、裂缝地层及泥页岩储层等非常规油气藏,受井斜及各向异性影响,电测井仪器响应复杂,极大地增加了储层测井评价难度。为明确大斜度井/水平井中双感应测井响应特征,基于赫兹位函数,给出了各向异性地层双感应测井解析解,研究了井斜角度、电阻率对比度及各向异性系数等对双感应测井的影响,并初步探索了双感应测井对各向异性的识别能力。模拟结果表明,井斜角小于30°,双感应测井主要反映地层水平电导率,无各向异性识别能力;随着井斜角度的增大,双感应测井响应由水平电阻率向垂直电阻率过渡,地层界面处出现犄角;深感应测井响应对各向异性的敏感性大于中感应测井响应,且井斜角度及各向异性系数越大,双感应测井各向异性识别能力愈强。

Electrical anisotropy is commonly developed in unconventional reservoirs such as laminated sand/shale formation,fractured and shale reservoirs.Effected by borehole inclination and formation anisotropy,the responses of electric logging tools become much more complex,which significantly increases the difficulty of accurate evaluation of reservoir.To identify the response characteristics of dual induction tool in high angle and horizontal wells,the analytical solution of dual induction logging is derived on the basis of Hertz potential function.Then,the effects of deviation angle,the resistivity contrast,anisotropy coefficient,are investigated.Numerical simulation results show that dual induction tool can accurately measure the horizontal resistivity as the dipping is lower than 30 degree.With the increase of inclination,the measured resistivity of dual induction tool is varied from horizontal resistivity to vertical resistivity.Meanwhile,large horn could be observed at the formation boundary.Deep induction response is more sensitive to anisotropy compared with medium induction,and the bigger dipping angle and anisotropy coefficient are,the stronger the ability to identify anisotropy will be.