Journal ArticleDOI
Toward more accurate quartz cement models: The importance of euhedral versus noneuhedral growth rates
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TLDR
In this paper, the euhedral effect of grain size on the growth rate of quartz overgrowths was investigated and it was shown that small-scale discontinuities dramatically reduce initial rates of quartz growth.Abstract:
Existing quartz cement models assume that the rate of growth per unit surface area is independent of grain size. Application of one such model to four geologically diverse data sets reveals a systematic error with grain size such that values in finer grained sandstones are overpredicted. Our laboratory synthesis of quartz overgrowths indicates that this grain-size effect results from the more rapid development of euhedral crystal forms on smaller grains. Experiments show that the rate of growth along the quartz c axis drops by a factor of about 20 after euhedral faces develop. Our numerical simulations of quartz growth in two dimensions indicate that this euhedral effect should be significant in sandstones despite the complexity that arises from the interaction of multiple growing crystals and small pore sizes. Simulations also suggest that this phenomenon is responsible for the common observation that quartz overgrowths are less extensively developed on chert and polycrystalline grains compared to monocrystalline grains. This euhedral effect may also explain the common observation that quartz growth rates are significantly faster on fracture surfaces compared to detrital grain surfaces. Most sand grains have well-developed dust rims that reflect minor adhesions of nonquartz materials or damage from surface abrasions or impacts. Our numerical and laboratory experiments indicate that such small-scale discontinuities dramatically reduce initial rates of quartz growth because they break overgrowths into separate smaller crystal domains that are bounded by euhedral faces. The paucity of nucleation discontinuities on fracture surfaces should lead to substantially faster rates of growth compared to grain surfaces.read more
Citations
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Journal ArticleDOI
Sandstone diagenesis and reservoir quality prediction: Models, myths, and reality
Thomas R. Taylor,M. R. Giles,Lori Hathon,Timothy N. Diggs,Neil R. Braunsdorf,Gino V. Birbiglia,Mark G. Kittridge,C. I. Macaulay,Irene Espejo +8 more
TL;DR: In this article, the effectiveness of grain coatings on quartz grains (e.g., chlorite, microquartz) as an inhibitor of quartz cementation is supported by abundant empirical data and recent experimental results.
Journal ArticleDOI
Natural fracture characterization in tight gas sandstones: Integrating mechanics and diagenesis
TL;DR: In this paper, Poroelastic stress calculations combined with fracture mechanics criteria show that it is possible to sustain opening-mode fracture growth with sublithostatic pore pressure without associated or preemptive shear failure.
Journal ArticleDOI
Microfractures: A review
TL;DR: In geologic settings, microfractures commonly form as Mode I (opening) fractures where the minimum principal stress exceeds the elastic tensile strength creating a narrow opening displacement; in isotropic rocks such fractures mark the plane perpendicular to the least compressive principal stress during fracture growth as discussed by the authors.
Journal ArticleDOI
Sandstone reservoir quality prediction: The state of the art
TL;DR: A new generation of reservoir quality models that have successfully predicted porosity and permeability in diverse siliclastic reservoirs under many different burial conditions is presented in this article. But the authors do not consider the impact of early diagenetic control on reservoir quality.
Journal ArticleDOI
Insights into rates of fracture growth and sealing from a model for quartz cementation in fractured sandstones
R. H. Lander,Stephen E. Laubach +1 more
TL;DR: In this paper, a model was proposed to account for crystal growth patterns and internal textures in quartz cement in sandstone fractures, including massive sealing deposits, thin rinds or veneers that line open fracture surfaces, and bridge structures that span otherwise open fractures.
References
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Journal ArticleDOI
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