TEM-function

In petroleum engineering, true effective mobility (TEM), also called TEM-function is a criterion to characterize dynamic two-phase flow characteristics of rocks (or dynamic rock quality). TEM is a function of relative permeability, porosity, absolute permeability and fluid viscosity, and can be determined for each fluid phase separately. TEM-function has been derived from Darcy's law for multiphase flow.

$𝑇𝐸𝑀=\frac{k{k}_{𝑟}}{\varphi \mu }$

in which $k$ is the absolute permeability, $k_{𝑟}$ is the relative permeability, φ is the porosity, and μ is the fluid viscosity. Rocks with better fluid dynamics (i.e., experiencing a lower pressure drop in conducting a fluid phase) have higher TEM versus saturation curves. Rocks with lower TEM versus saturation curves resemble low quality systems.

TEM-function in analyzing relative permeability data is analogous with Leverett J-function in analyzing capillary pressure data. Furthermore, TEM-function in two-phase flow systems is an extension of RQI (rock quality index) for single-phase systems.

Also, TEM-function can be used for averaging relative permeability curves (for each fluid phase separately, i.e., water, oil, gas, CO₂).

$\text{Average kr}=\frac{\sum _{i=1}^n{𝑇𝐸𝑀}_i}{\sum _{i=1}^n{\left(\frac{k}{\varphi \mu }\right)}_i}=\frac{\sum _{i=1}^n{\left(\frac{k{k}_{𝑟}}{\varphi \mu }\right)}_i}{\sum _{i=1}^n{\left(\frac{k}{\varphi \mu }\right)}_i}$

See also

• Lak wettability index
• USBM wettability index