Rock-Drilling Fluid Interaction Studies on the Diffusion Cell

摘要

This paper presents a new set of rock-drilling fluid interaction tests carried out in the diffusion cell using saline solutions and mineral oil on a Brazilian offshore shale. The diffusion cell was designed to apply hydraulic and chemical gradients through shale samples in order to evaluate shale- fluid interaction. The proposed test allows the determination of rock permeability, the coefficient of reflectivity (membrane efficiency) and the ionic diffusion coefficient. These parameters are essential to carry out proper wellbore stability analysis when taking shale-drilling fluid interaction into account. Shale characterization, testing methodology and test results are described. The results showed an average permeability of 46 nD and membrane efficiency less than 2 % for the tested shale.