Numerical Modeling of CO₂ and Brine Leakage through Open Fracture in a Fault Zone: Open Channel Flow or Darcy Flow

Abstract

Understanding fluids migration and leakage risk along the fault zone is necessary to guarantee the safety of CO 2 geological storage. The validity of Darcy's law gets challenged in dealing with the flow in open fractures since the occurring of turbulence flow. In this study, we develop a 2D model with usage of T2Well, an integrated wellbore-reservoir simulator, to investigate the leakage problem along open fractures which are embedded in a fault zone from the deep injection reservoir to shallow aquifers. The results record a positive feedback of gas expansion and pressure response in fracture, which causes a quick downward propagation of highly gas saturated zone from the top of fracture and an easy gas breakthrough in the shallower aquifers. The decreasing of aperture size of fracture significantly enhances the leakage rates in fracture, but with less influences as aperture increases. In comparison, the Equivalent Porous Media models show a good approximation with the momentum model of large apertures but poor for the small one. Nevertheless, the differences are small in terms of final CO 2 distribution among various aquifers, suggesting that Darcy's law may be still "effective" in solving flow problem along fractures in a constant injection system at a large time scale.

Evaluation of the performance of the oceanic hydrate accumulation at site NGHP-02-09 in the Krishna-Godavari Basin during a production test and during single and multi-well production scenarios

“…Based on earlier studies that confirmed the validity of the approach (Moridis and Reagan, 2007a,b;Liu et al, 2017), we approximated wellbore flow by Darcian flow through a pseudo-porous medium describing the interior of the well. This pseudo-medium had φ = 1, a very high k = 5x10 -9 m 2 (= 5,000 Darcies), a capillary pressure P c = 0, a relative permeability that was a linear function of the phase saturations in the wellbore, and a low (but nonzero) irreducible gas saturation S irG = 0.005 to allow for the emergence of a free gas phase in the well.…”