A Fast and Direct Method of Permeability Measurements on Drill Cuttings

摘要

Permeability is one of the most important petrophysical parameter for reservoir characterization but the most difficult to obtain. Logs provide a good estimate of porosity and saturations, but the accuracy on permeability derived from NMR is rather poor. So far, reliable values of permeabilities are only obtained 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 about 100 cc 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 enter 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 samples of crushed rock samples of known permeability. An excellent reproducibility and a 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 mainly related to the size and the representativity of the drill cuttings. In developing this method, our purpose is not to replace core analysis, but rather to provide an additional cheap and quick information on reservoir characterization.