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Abstract:Quantification of Quartz Cement and Pressure Solution Volumes, East Brae Field, Offshore UK

GRAU, ANNE, Colorado School of Mines, Department of Geology and Geological Engineering, Golden, CO

While quartz cements have been studied in a wide variety of geological settings, there is little agreement regarding the source of the cement or the open vs. closed nature of the chemical system. Historically, quantitative studies have been few. The purpose of this study is to quantify quartz cement volumes and the volume of sandstone lost to pressure solution, and to relate the distribution of these components to reservoir fluid flow. Cement volumes will be measured using image analysis of cathodoluminescent images obtained from a scanning electron microscope. Pressure solution studies will focus on stylolites as well as grain-to-grain compaction indices. A profilometer will be used to measure topography and quantify minimum volumes of silica lost to pressure solution along stylolite surfaces. The use of this instrument, normally used to measure surface roughness, will develop an experimental technique previously not applied to sandstone diagenesis. This study will be performed in a Jurassic sandstone reservoir, located offshore UK, in a field chosen for excellent core control, a large petrophysical database, and a documented variability in stylolite, quartz vein, and quartz overgrowth abundance. The project will provide research benefits in the form of a quantitative case study comparing quartz cement and pressure solution volumes. Integration of these results with wire-line log signatures can then be applied to field wide porosity modeling, quantification of reservoir pore volume, and overall reservoir characterization. In addition, this project bears significant implications for sandstone diagenesis research. Given the historical significance of the water volume problem and silica budget issues, any effort to constrain and quantify quartz cement and pressure solution volumes should improve the understanding of a long-standing problem in sandstone petrology and petroleum geology.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid