− | The rate of [[Hydrocarbon migration|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 [[clay]]s, like [[shale]]s, 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 [[Hydrocarbon migration|migration]] for [[oil]] or [[natural gas|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 [[clay]]s, like [[shale]]s, 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. |