--> Hydrocarbon Versus Microquartz Inhibition of Quartz Cementation in North Sea Sandstones: Empirical and Experimental Evidence, by Linda M. Bonnell, Richard E. Larese, and Robert H. Lander; #90052 (2006)
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Hydrocarbon Versus Microquartz Inhibition of Previous HitQuartzNext Hit Cementation in North Sea Sandstones: Empirical and Experimental Evidence

Linda M. Bonnell1, Richard E. Larese2, and Robert H. Lander1
1 Geocosm LLC, Austin, TX
2 Clastic Petrology Consultant, Durango, CO

The occurrence of high porosity zones in the Brae Formation sandstone, Miller Field, UK North Sea has been attributed to the inhibition of Previous HitquartzNext Hit cementation by early hydrocarbon charge (Marchand, et al., 2000, 2001, 2002). Alternatively, Aase & Walderhaug (2005) suggest that Previous HitquartzNext Hit cementation in this field has been inhibited by the presence of microcrystalline Previous HitquartzNext Hit coatings on Previous HitquartzNext Hit grains. Our group independently examined data from 4 Miller Field wells that transect the hydrocarbon and water legs. Like Aase & Walderhaug, we found a strong correlation between the occurrence of microcrystalline Previous HitquartzNext Hit coatings and low Previous HitquartzNext Hit cement abundances.

The inhibition of Previous HitquartzNext Hit cementation by microcrystalline Previous HitquartzNext Hit coatings has been described by Aase et al. (1996) in Ula Formation sandstones. However, other workers interpret these coatings to be incipient overgrowths that ceased to grow due to hydrocarbon incursion. To evaluate these contrasting interpretations, we used a hydrothermal reactor to induce Previous HitquartzNext Hit cementation in Miller Field and Ula Field samples. The samples had both microcrystalline Previous HitquartzNext Hit coatings and naked Previous HitquartzNext Hit surfaces at grain contact scars. While large Previous HitquartzNext Hit overgrowths formed on naked contact scars, surfaces covered by microcrystalline Previous HitquartzNext Hit showed only minor growth indicating that these coatings can inhibit the formation of normal Previous HitquartzNext Hit overgrowths.

To further test whether microcrystalline Previous HitquartzNext Hit in Miller Field samples could account for observed porosity preservation, we modeled Previous HitquartzNext Hit cement in all samples using the Touchstone diagenesis model. Previous HitQuartzNext Hit cementation kinetics were calibrated to water leg samples and used to predict Previous HitquartzNext Hit cement in hydrocarbon leg samples. If cementation was retarded by hydrocarbons, the model should overpredict Previous HitquartzNext Hit cement in hydrocarbon leg samples. We found, however, that models that account for grain coatings accurately predict Previous HitquartzTop cement in both water and hydrocarbon leg samples.