Simulation of Gas Transport in TightShale Gas Reservoirs by a Multicomponent Model Based on PEBI Grid

الملخص EN

The ultra-low permeability and nanosize pores of tight/shale gas reservoir would lead to non-Darcy flow including slip flow, transition flow, and free molecular flow, which cannot be described by traditional Darcy’s law.

The organic content often adsorbs some gas content, while the adsorbed amount for different gas species is different.

Based on these facts, we develop a new compositional model based on unstructured PEBI (perpendicular bisection) grid, which is able to characterize non-Darcy flow including slip flow, transition flow, and free molecular flow and the multicomponent adsorption in tight/shale gas reservoirs.

With the proposed model, we study the effect of non-Darcy flow, length of the hydraulic fracture, and initial gas composition on gas production.

The results show both non-Darcy flow and fracture length have significant influence on gas production.

Ignoring non-Darcy flow would underestimate 67% cumulative gas production in lower permeable gas reservoirs.

Gas production increases with fracture length.

In lower permeable reservoirs, gas production increases almost linearly with the hydraulic fracture length.

However, in higher permeable reservoirs, the increment of the former gradually decreases with the increase in the latter.

The results also show that the presence of CO2 in the formation would lower down gas production.