Jonny Rutqvist¹, Chin-Fu Tsang¹

(1) Lawrence Berkeley National Laboratory, Berkeley, CA

ABSTRACT: Modeling of Multi-phase Fluid Flow, Heat Transfer and Rock Deformations during CO2 Injection in Deep Aquifers

The performance assessment of a CO2 injection site requires analysis of a number of simultaneously interacting processes, including multi-phase flow, heat transfer and mechanical deformation. Rock deformations and rock stresses are important because injection of CO2 in the subsurface will, in general, produce an increase in pore pressure, which in turn, will change the stress field in the rock mass. A change in the stress field can have two effects. First, if sufficiently large, they could cause failure, which can give rise to a leakage paths through fractured rock. Secondly, the induced stresses will act upon pre-existing faults and fractures, and causing opening or slip displacements with accompanying permeability changes. In this study, two computer codes-TOUGH II and FLAC-3D-are coupled together and jointly executed for a coupled analysis of multi-phase flow, heat transport and rock deformations during CO2 injection into deep saline aquifers. The TOUGH II code is designed for geohydrological analysis with multi-phase, multi-component fluid flow and heat transport, while the FLAC-3D code is designed for rock- and soil-mechanics with thermomechanical and hydromechanical interactions. Both codes are well established and widely used in their respective fields. In this paper, the two codes are coupled through external functions and sequentially executed. The external functions are used to calculate changes in effective stress, thermal strain, bulk density, porosity and permeability. The capability of a joint TOUGH-FLAC execution is demonstrated with two examples of CO2 injection into saline aquifers.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado