随钻电阻率成像测井仪定量评价地层界面探究

随钻电阻率成像测井仪不仅可以通过井壁电成像直观显示微小的地质体特征，还具有识别地层界面的能力。为了探索随钻电阻率成像测井仪在界面处的测井响应特征，利用三维有限元方法，研究了其具有方位性时的地层界面测井响应规律，并根据模拟结果建立了地层界面参数定量计算模型。结果表明，该仪器在水平井中不同方位钮扣电极的电阻率测量差值和仪器与地层界面的距离呈较好的幂指数关系；该仪器在斜井中与地层界面的夹角和不同方位钮扣电极电阻率曲线犄角间的最大距离呈幂指数关系，且基本不受地层界面上下地层电阻率对比度的影响。建立的地层界面参数解释模型表明:仪器与地层界面的距离小于1.00 m，可以识别出地层界面；仪器与地层界面夹角小于20°时，可定量计算出二者夹角。研究结果为随钻电阻率成像测井的地质工程应用提供了理论依据。 

Probe into Quantitative Stratigraphic Interface Evaluation Using a Resistivity Imaging LWD Tool

Resistivity imaging LWD tool can not only visually display the characteristics of micro geological bodies through borehole wall electric imaging, but also can identify the formation interface. In order to explore the logging response mechanism of the tool at the interface, this paper studies the logging response law of the azimuthal resistivity imaging LWD tool at formation interface by using the three-dimensional finite element method. In doing so, it established a quantitative calculation model of formation interface parameters according to the simulation results. The results showed that the resistivity measurement difference of different azimuthal button electrodes of the tool exhibited a good power exponent relationship with the distance from tool to the formation interface in horizontal wells. The angle between the tool and formation interface and the maximum distance between resistivity curve spikes of different azimuthal button electrodes was power exponentially in deviated wells, which is not affected by resistivity contrast of the upper and lower strata at the formation interface. The model for the formation interface parameters interpretation indicated that the tool can be recognized within 1.00 m to the horizontal interface, and the angle can be calculated quantitatively when the angle between the tool and formation interface is less than 20 degrees. The research results can provide a theoretical basis for the application of a resistivity imaging LWD tool in geological engineering.