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Investigate key structural factors in mudstones affecting CO2 migration, identify flow control types, and define textural connectivity for leakage. Study mudstone textures, modeling steps, and expected flow properties. Analyze leakage elements and conclude on factors influencing mudstone sealing efficiency.
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Mudstone CO2 sealing efficiency K. Kurtev, A. Aplin and S. Abrakasa University of Newcastle
High TOC due to asphaltenes Tmax is low – no HC formation
Modelling studies Goals 1. To identify the key structural control factors in mudstones important for CO2migration; 2. To recognize and formulate the basic typesof 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 CO2 leakage;
CO2 Leaking Systems Leakage is a multiscale Flow Process in Clay-Rich Sediments Intermediate scale: log interval or ~ 1 m scale Sample 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 A Facies C Facies B FaciesD Basic facies defined at Wales outcrops Each faciess is characterised by a specific internal architecture (i.e. internal geometry) indicated as its texture. 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;
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 Aplin1998); • 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
Expected result Flow Modelling results (equivalent permeability) Texture Modelling ~ 1 m scale NZ1 Intermediate texture NZ2 (Stochastic Simulation)
Model ZZ1 Parameters , σeff = 7 MPa Porisity % Picture Clay % Kh [nD] Kv [nD]
Upscaled Kh and Kv for twomodels at different Effectife Stress ( 7, 15 , 23 , 45 MPa) NZ1 NZ2
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;
