Adsorption, Geomechanical, PSS Water Drive & Multi-well Analysis

The adsorption and geomechanical models use formation and rock properties provided in the Properties Editor.

The adsorption model accounts for the adsorped portion of the total gas in place when analyzing unconventional gas reservoirs. In some unconventional gas reservoirs, the amount of adsorbed gas is significant. Failing to account for it can lead to a significant underestimation of the in-place and recoverable gas volumes. For the theory and equations for this model, see Langmuir Isotherm.

The geomechanical model should be used when there is evidence that the reservoir is overpressured. In general, one of the key factors in identifying pressure-dependent permeability behaviour is the inconsistency between the static and dynamic data analyses. As a result of compaction, flowing data is affected by the change in the magnitude of permeability of the formation during the flow period. If the geomechanical model is not active, reserves can be drastically underestimated when compared to a static gas material balance analysis. For the theory and equations for this model, see Geomechanical Reservoir Models.

The pseudo-steady state (PSS) water drive model can be used to analyze data affected by pressure support from an aquifer. For typecurve analysis methods featuring material balance time, boundary-dominated flow is indicated by production data matching on the single depletion stem (unit slope). If the production data deviates from the unit slope upwards, and there is reason to believe water drive is the cause, then it can be modeled using Fetkovich’s water-drive calculations (Dake, 1978), based on two parameters: aquifer size and productivity index (i.e., transfer coefficient). For the theory and equations for this model, see Pseudo-Steady State (PSS) Water-drive Model.

The multi-well pool analysis option accounts for production interference from offset wells. As a result of interference from offset wells, in contrast to aquifer pressure support, boundary-dominated data points deviate below the unit slope depletion stem on the typecurve match. Total reservoir gas-in-place can be estimated with multi-well interference analysis by accounting for the total production of all wells in the pool in the material balance. Multi-well analysis requires you to launch a group of entities for analysis, and select the primary well from the Analysis tab. For the theory and equations for this analysis method, see Single vs. Multiple Well Analysis.