Hydro-geomechanical modelling of seal behaviour in overpressured basins using discontinuous deformation analysis

Abstract A coupled hydro-geomechanical modelling environment, developed to evaluate the coupled responses of fluid flow in deforming discontinuous media, is described. A staggered computational framework is presented, where the two simulations tools, HYDRO and DDA, communicate via the mapping of an equivalent porosity (and related permeabilities) from the rock system to the fluid phase and an inverse mapping of the pressure field. Several algorithmic and modelling issues are discussed, in particular the computational procedure to map the current geometry of the discontinuous rock blocks assembly into an equivalent porosity (and permeability) field. A generic, geometrically simple, overpressured reservoir/seal system is analysed for illustration. Further examples investigate discontinuous, fractured configurations in flexure causing a degree of spatial variability in the induced stresses. Model predictions show that the combination of hydraulic and mechanical loads causes a dilational opening of some pre-existing fractures and closure of others, with strong localisation of the modified flow pattern along wider fracture openings.

[1]  Richard E. Goodman,et al.  Generalization of two‐dimensional discontinuous deformation analysis for forward modelling , 1989 .

[2]  Michael Andrew Christie,et al.  Upscaling for reservoir simulation , 1996 .

[3]  G. Couples.  A Hydro-Geomechanical View of Seal Formation and Failure in Overpressured Basins , 1999 .

[4]  G. Garven,et al.  Theoretical analysis of the role of groundwater flow in the genesis of stratabound ore deposits; 1, Mathematical and numerical model , 1984 .

[5]  G. I. Barenblatt,et al.  Basic concepts in the theory of seepage of homogeneous liquids in fissured rocks [strata] , 1960 .

[6]  Elias C. Aifantis,et al.  On the problem of diffusion in solids , 1980 .

[7]  Roland W. Lewis,et al.  A novel finite element double porosity model for multiphase flow through deformable fractured porous media , 1997 .

[8]  Mohamed Rouainia,et al.  Hydro-DDA modelling of fractured mudrock seals , 2001 .

[9]  M. F. Lough,et al.  Efficient Finite-Difference Model for Flow in a Reservoir With Multiple Length-Scale Fractures , 2000 .

[10]  Geology, geometry and effective flow , 1995, Petroleum Geoscience.

[11]  Derek Elsworth,et al.  FLOW-DEFORMATION RESPONSE OF DUAL-POROSITY MEDIA , 1992 .

[12]  G. Couples,et al.  Geomechanical simulations of top seal integrity , 2002 .

[13]  D. V. Griffiths,et al.  Programming the finite element method , 1982 .

[14]  Bernard P. Boudreau,et al.  Diagenetic Models and Their Implementation: Modelling Transport and Reactions in Aquatic Sediments , 1996 .

[15]  C. A. Kossack,et al.  Realistic Numerical Models for Fractured Reservoirs , 2000 .

[16]  E. N. Bromhead,et al.  Computer methods and advances in geomechanics: G. Beer, J.R. Booker and J.P. Carter (eds) Balkema, Rotterdam, 1991, £122, (3 volumes) ISBN (Set) 90-6191-189-3 , 1993 .