Determination of the Overburden Permeability of North Sea Chalk

Excerpt

Absolute permeability is a key reservoir parameter and is particularly vital for reservoir management during the reservoir life cycle. The basic law of fluid flow in porous media is Darcy’s Law. The Darcy equation demonstrates that the velocity of a fluid in a porous medium is inversely proportional to the fluid viscosity and proportional to the pressure gradient (Ahmed and McKinney 2005): where Q is the volumetric flow rate, K is the absolute permeability, A is the cross-sectional area of flow, and \(\frac{{{\text{d}}P}}{{{\text{d}}L}}\) and µ are the pressure gradient and fluid viscosity, respectively. Typically, absolute permeability measurements are performed nitrogen gas flow tests because 100% fluid saturation is easily obtained, a steady state is rapidly achieved, and gas does not react with the minerals in the rock (Ahmed and McKinney 2005). Klinkenberg observed deviations in permeability values measured using gases to mimic fluid flow compared to those achieved when using liquids. Gas permeability depends on parameters such as the temperature, pressure and molecular size of the gas; therefore, measured gas permeability values require correction (Klinkenberg 1941). …