3D Petrophysical Interpretation of Horizontal Wells

Abstract

Conventional interpretation of well logging data is done based on coaxial - cylinder model, which was initially developed and proved its reliability in vertical wells. But utilization of this model in horizontal wells may cause false interpretation results. The reason for it is the fact that properties change in vertical direction affect measurements in different way, due to their depth of investigation (DOI). In other words, tool measurements are influenced by formations at the distance with different properties. All this above adds the complexity into petrophysical interpretation - true formation properties evaluation (lithology, porosity, permeability etc.). Consequently, for correct well logging data interpretation in horizontal wells for wireline and logging-while-drilling (LWD) data, the new approach must be implemented, which should be based not only on tool measurements, but also on well trajectory and dip of rock layers; which means it must be in done in three-dimensional space. This work explains the methodology of logging-while-drilling data interpretation in three-dimensional space. The results of several wells interpretation are compared with standard approach (coaxial – cylinder model) and with 3D. The difference in formation properties and net-to-gross (NTG) are shown for both methods with the recommendation of 3D approach.