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Long, Bernard François1, Francis Moore1, Mathieu Jacques Duchesne1 
(1) National Research Scientific Institute, Quebec City, QC

ABSTRACT: Porosity CAT-Scan Signature Changes Related to Variations of Sedimentation Rate: Theoretical and Physical Modeling Versus Field Deposits

Porosity study is a key factor for potential reservoirs determination. Since the late 1980s CAT-scan is used to image and quantify pore space in rocks. However, this technology has never been applied to measure the effect of variations of sedimentation rate on porosity changes during consolidation. In this project, distinct and characteristic CAT-scan signatures of multi-layered deposits obtained from theoretical and physical models are transposed to field data to enhance the comprehension of the effect of sedimentation rate variations on porosity and permeability. First, a theoretical finite element model adapted from Gibson’s model was developed to simulate the porosity evolution in a multi-layered deposit. Gibson’s model is employed for self weight consolidation analysis and uses a non-constant permeability which is function of the porosity. Second, the theoretical model was validated with a series of synthetic sedimentary columns containing various grain size layers representing different sedimentation rates. The 4-D porosity evolution of the synthetic sedimentary columns was measured by CAT-scan analysis. Physical models included a single layer for calibration, a fine-grained and sand couplet as well as a succession of fine-grained and sand layers. The effects of a fine-grained layer on the consolidation state of underlying sand-prone layers were also documented. The very-high-resolution of the CAT-scan (0.1 mm) allowed to obtain detailed profiles of the porosity evolution in function of sedimentation rate variations and time. Finally, CAT-scan signatures derived from the theoretical model were compared with field data coming from consolidated deltaic deposits and modern deep-sea deposits.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.