Interpretation of Recrystallization Processes of Sedimentary Dolomites as Deduced From Crystal Structural and Geochemical Data With Implications for Reservoir Characterization

Abstract

Most sedimentary dolomites are meta-stable upon formation and either transform into more stable dolomite via recrystallization, or persist as meta-stable phases over deep geological time. How recrystallization alters the crystal structure and chemistry of dolomite remains poorly understood. Limited evidence suggests correlation between various chemical and crystallographic properties; however, the relationship with the underlying geological processes is not known. The overall goal of this research is to better understand how diagenetic environments affect dolomite recrystallization. The specific objective is to characterize the crystallographic and chemical parameters of recrystallized sedimentary dolomites formed in various diagenetic environments, and identify any notable differences. Here, results from Rietveld refinement of high-resolution diffraction data are presented that include crystallographic parameters, such as fractional site occupancies, atomic coordinates, unit cell, and thermal parameters. Based on the recrystallization temperature of sedimentary dolomites, determined using clumped isotopes and fluid inclusions, the effect of temperature on crystallographic parameters are elucidated. In addition, we present correlations between crystallographic characteristics, elemental composition (stoichiometry, minor and trace element content) and isotope geochemistry. A status update is presented on the development of classification criteria to characterize recrystallization as applicable to dolomite-hosted reservoirs worldwide.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018