OGIP Per Measure Calculations

Some important considerations to note:

OGIP Prorating

If an OGIP per measure is selected, the model prorates OGIP per measure to individual layers by layer net pay w/r to total measure net pay.

V_L and P_d Calculations

1. Langmuir Volume (V_L) is calculated from the degree of undersaturation (see also gas saturation in the Isotherm chapter), the Langmuir Pressure (P_L), and the initial gas content (GC_i). For commercial reservoirs, saturation should be a relatively high number (80%+).

   1. In AFA, regardless of the distribution, the maximum allowable value for undersaturation is 100%, otherwise physically impossible values of V_L and P_d can be calculated.

   2. To find V_L, we solve:

2. After calculating Langmuir Volume (V_L) from above, desorption pressure is calculated according to

Water Saturation Conflicts

When running simulations, there is also potential conflict for water saturation and desorption pressure. For any simulation, if P_i > P_d, then the initial water saturation or S_wi = 100% (the cleats are completely filled with water). For additional details refer to Statistical Concepts and Parameter Consistency in Monte-Carlo