Место издания: СПб. , Год издания: 2020

Russian lateral logging is widely used in Russia to evaluate formations resistivity, but the behaviour of these logs in complex enviroments is still unclear. In sedimentary sections, some formations are interbedding of two rocks with different resistivity, as a result a quasiperiodic layered structure arises. In this case we need to understand how to divide layered sequence into separate layers, and in which cases we can consider it as one anisotropic layer. To answer this question, we performed 2D numerical simulation of the lateral logs, which are sensitive to the vertical resistivity. Models contain a ~5m periodic sequence composed of interlayers. 2D inversion of the simulated logs results in anisotropic parameters close to the values calculated analytically for the periodic structure, even if a large interlay period causes significant logs oscillations. We also simulated lateral logs in a 3D model, which includes a thinly-layered formation crossed by a highly deviated well filled with a low-resistivity mud. Permeable layers contain invaded zones. Logs inversion results to obtaining average geometric mean of the equivalent anisotropic layer horizontal and vertical resistivities. This value corresponds to the dependences known for the gradient probe signal lying in the bedding plane of a homogeneous anisotropic medium.