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1 Geocosm LLC, 3311 San Mateo Drive, Austin, Texas 78738; roblander{at}geocosm.net
2 Consultant, 3025 East 6th Ave., Durango, Colorado 81301
3 Geocosm LLC, 3311 San Mateo Drive, Austin, Texas 78738
Rob Lander develops diagenetic models for Geocosm LLC. He obtained his Ph.D. in geology from the University of Illinois in 1991, was a research geologist at Exxon Production Research from 1991 to 1993, and worked for Rogaland Research and Geologica AS from 1993 to 2000. He is also a research fellow at the Bureau of Economic Geology.
Dick Larese is a sandstone petrologist based in Durango, Colorado, where he specializes in laboratory diagenesis experiments and petrographic characterization. He received his Ph.D. in geology from West Virginia University in 1974 under the supervision of diagenesis legend Milton Heald and was a research scientist for Amoco Production Company from 1974 to 1999. He was an AAPG Distinguished Lecturer in 1997–1998.
Linda Bonnell develops diagenetic models and conducts reservoir quality prediction studies for Geocosm LLC. She received her Ph.D. in geology from the University of Illinois in 1990 and subsequently was a research scientist at Washington University, Rice University, Rogaland Research, and Geologica AS. She is also a research fellow at the Bureau of Economic Geology. Linda was an AAPG Distinguished Lecturer in 2003–2004.
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.
This article has been cited by other articles:
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  J. E. Olson, S. E. Laubach, and R. H. Lander Natural fracture characterization in tight gas sandstones: Integrating mechanics and diagenesis AAPG Bulletin, November 1, 2009; 93(11): 1535 - 1549. [Abstract] [Full Text] [PDF]
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 S.E. Laubach and K. Diaz-Tushman Laurentian palaeostress trajectories and ephemeral fracture permeability, Cambrian Eriboll Formation sandstones west of the Moine Thrust Zone, NW Scotland Journal of the Geological Society, March 1, 2009; 166(2): 349 - 362. [Abstract] [Full Text] [PDF]
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