A Fast and Direct Method of Permeability Measurements on Drill Cuttings

Abstract

Summary Permeability is one of the most important petrophysical parameters for reservoir characterization, but also one of the most difficult to obtain. Logs provide a good estimate of porosity and saturations, but the accuracy on permeability derived from nuclear magnetic resonance (NMR) is rather poor. So far, reliable values of permeabilities are obtained only from laboratory measurements on core samples for local measurements and well testing for a larger scale-averaged determination. We present an original method for measuring the permeability of drill cuttings without any specific laboratory conditioning (cleaning, coating, etc.). A volume of approximately 100 cm3 of cuttings is placed in a pressure vessel. The cell is then filled with a viscous oil. The process of oil invasion into the cuttings always traps a certain amount of gas. When a pulse of pressure is applied on the cell, the oil enters into the cuttings thanks to the gas compressibility. The permeability is then derived from the dynamic of the oil invasion by using a simple model. The method was tested by using various crushed-rock samples of known permeability. Excellent reproducibility and good agreement between cores and cuttings permeabilities were found for many decades of permeabilities. This method presents many advantages. The measurements can be performed in a few minutes, leading to the possibility of operating on site during drilling. The limitations of the method are related mainly to the size, the representativity of the drill cuttings, and the absence of the confining stress. In developing this method, our purpose is not to replace core analysis but, rather, to provide additional quick and inexpensive information on reservoir characterization.