Modelling studies Goals 1. To identify the key structural control factors in mudstones important for CO 2 migration; 2. To recognize and formulate the basic types of heterogenity of those key flow control factors ( main mudstone texture types resulted from the different regimes of sedimentation & consolidation); 3. To define method(s) for parametrization of the the basic types of textural / structural connectivity responsible for CO 2 leakage;
CO 2 Leaking Systems Leakage is a multiscale Flow Process in Clay-Rich Sediments Sample scale Intermediate scale: log interval or ~ 1 m scale Seismic scale Leaking Elements: - Pore network; - Grain Sizes; - Microfractures; Leaking Elements: -Thin beds connectivity; - Fracture Connectivity; Leaking Elements: - Fault (zone) permeability; - Seal integrity;
Facies B Facies C Facies A Facies D Defined are: Four dominant texture types: A - high clay content mud flow; B - debris flow deposits; C - thin bedded sequence; D – thin, more laterally continuous and persistent debris flow deposits; Basic facies defined at Wales outcrops Each faciess is characterised by a specific internal architecture (i.e. internal geometry) indicated as its texture.
Modelling steps: - Define Clay content from image: a) by linear projection of the gray colour scale to clay content range ; b) by recognition of the lighter colours as degree of coarse silt content and then calculation of the clay% based on an established correlation; - Porosity calculation based on Clay% and user-defined Effective Stress (Yang and Aplin 1998); -Vertical and Horizontal permeability calculated from porosity based on correlations obtained by Yang and Aplin (1998); We Always should mind the artefacts imposed from the image quality. Needed is a calibration vs. real experiments
NZ1 NZ2 Expected result Intermediate texture Flow Modelling results (equivalent permeability) Texture Modelling ~ 1 m scale (Stochastic Simulation)
NZ1 NZ2 Upscaled Kh and Kv for twomodels at different Effectife Stress ( 7, 15, 23, 45 MPa)
Conclusions - Permeable thin bed connectivity is an important factor for the mudstone sealing efficiency; -Upscaled flow properties highly depends on mudstone texture – defined heterogenity; - Previous experience on HC leakage could be used as a basis for evaluation of the mudstone CO2 sealing efficiency;