− | The rate of migration for oil or gas can be estimated using Darcy's law, the principal formula for calculating [[permeability]]. Darcy's law generally holds for rocks with tube-shaped pore systems; however, it is only an approximation for flow in rocks with high percentages of clays, like shales, due to the platey grain shape of the clays. The [[Wikipedia:Kozeny–Carman equation |Kozeny–Carman correction]] estimates the permeability of rocks with high percentages of clays. | + | The rate of migration for oil or gas can be estimated using [[Fluid flow fundamentals|Darcy's law]], the principal formula for calculating [[permeability]]. Darcy's law generally holds for rocks with tube-shaped pore systems; however, it is only an approximation for flow in rocks with high percentages of clays, like shales, due to the platey grain shape of the clays. The [[Wikipedia:Kozeny–Carman equation |Kozeny–Carman correction]] estimates the permeability of rocks with high percentages of clays. |