Implications of Conceptual and Numerical Modeling of Diagenetic Processes for Reservoir Characterization

Nader, Fadi H.¹; De Boever, Eva ¹; Kohler, Eric ¹; Guichet, Xavier ¹; Daniel, Jean-marc ¹; Lerat, Olivier ¹; Doligez, Brigitte ¹
(1)IFP Energies nouvelles, Rueil-Malmaison, France.

Classical diagenesis studies make use of a wide range of methods and analytical techniques in order to suggest conceptual models that explain specific, relatively time-framed, diagenetic processes and their impacts on reservoirs. Currently used techniques combine petrographical analyses (conventional, CL, fluoresence, and SEM techniques), geochemical measurements (major/trace elements, micro-probe, stable oxygen and carbon isotopes, Sr-isotopes) and fluid inclusion analyses, providing independent arguments to support the proposed model. Still, conceptual models are qualitative and do not yield "real" data for direct use by reservoir engineers for rock-typing and geomodeling. This contribution provides new insights into numerical modeling of some diagenetic processes such as dolomitization, dissolution and anhydrite cementation. The key to successfully predict the impact of such processes on reservoir properties (and achieve a more meaningful rock-typing and reservoir modeling) consists of proposing new means to adequately quantify diagenetic phases (at different scales) and new numerical workflows that honor the conceptual models and the quantified volumes of such diagenetic phases, and express their impacts on porosity and permeability evolution.

This contribution provides new cutting edge technologies and approaches that are currently being developed, all aiming at providing the necessary tools for quantifying and modeling diagenetic processes at varying scales. Coupling µ-CT 3D image analyses, reactive geochemical and pore network modeling, is proposed for the quantification, simulation and prediction of changes in porosity and permeability between different diagenetic phases for a reservoir rock, at the scale of plugs and thin-sections. XRD techniques coupled with Rietveld has been used in order to investigate more properly the stoichiometry of dolomites and to reach a reliable mean for mineralogical quantification, at the scale of well logs. Petrographic analyses coupled with image analyses are also used for quantifying the various diagenetic phases from subsurface wells and to produce diagenesis maps - at the prospect scale - that are invaluable for development of oil and gas fields. Numerical modeling of dolomitization follows two approaches: geostatistical analysis and geochemical reactive transport modeling, both attempting to express conceptual models in more quantitative and predictive terms, thereby bridging the reservoir and basin scales.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.