Linda M. Bonnell

Bio: Linda M. Bonnell is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Geology & Diagenesis. The author has an hindex of 11, co-authored 12 publications receiving 1081 citations.

Anomalously high porosity and permeability in deeply buried sandstone reservoirs: Origin and predictability

Abstract: Porosity and permeability generally decrease with increasing depth (thermal exposure and effective pressure); however, a significant number of deep (>4 km [approximately 13,000 ft]) sandstone reservoirs worldwide are characterized by anomalously high porosity and permeability. Anomalous porosity and permeability can be defined as being statistically higher than the porosity and permeability values occurring in typical sandstone reservoirs of a given lithology (composition and texture), age, and burial/temperature history. In sandstones containing anomalously high porosities, such porosities exceed the maximum porosity of the typical sandstone subpopulation. Major causes of anomalous porosity and permeability were identified decades ago; however, quantification of the effect of processes responsible for anomalous porosity and permeability and the assessment of the predictability of anomalous porosity and permeability occurrence in subsurface sandstones have rarely been addressed in published literature. The focus of this article is on quantification and predictability of three major causes of anomalously high porosity: (1) grain coats and grain rims, (2) early emplacement of hydrocarbons, and (3) shallow development of fluid overpressure. Grain coats and grain rims retard quartz cementation and concomitant porosity and permeability reduction by inhibiting precipitation of quartz overgrowths on detrital-quartz grains. Currently, prediction of anomalous porosity associated with grain coats and grain rims is dependent on the availability of empirical data sets. In the absence of adequate empirical data, sedimentologic and diagenetic models can be helpful in assessing risk due to reservoir quality. Such models provide a means to evaluate the effect of geologic constraints on coating occurrence and coating completeness required to preserve economically viable porosity and permeability (Begin page 302) in a given play or prospect. These constraints include thermal history and sandstone grain size and composition. The overall effect of hydrocarbon emplacement on reservoir quality is controversial. It appears that at least some cements (quartz and illite) may continue to precipitate following emplacement of hydrocarbons into the reservoir. Our work indicates that integration of basin modeling with reservoir quality modeling can be used to quantify, prior to drilling, the potential impact of hydrocarbon emplacement on porosity and permeability. The best-case scenario for significant reservoir quality preservation due to fluid overpressure development is in rapidly deposited Tertiary or Quaternary sandstones. Our models suggest that significant porosity can be preserved in sandstones that have experienced continuous high fluid overpressures from shallow burial depths. The models also indicate that the potential for porosity preservation is greatest in ductile-grain-rich sandstones because compaction tends to be the dominant control on reservoir quality in such rocks. The case for significant porosity preservation associated with fluid overpressures in pre-Tertiary basins, however, is more problematic because of the complexities in the history of fluid overpressure and the greater significance of quartz cementation as a potential mechanism of porosity loss.

Toward more accurate quartz cement models: The importance of euhedral versus noneuhedral growth rates

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.

The Role of Chemistry in Fracture Pattern Development and Opportunities to Advance Interpretations of Geological Materials

Abstract: This manuscript resulted from discussions at a workshop sponsored by the U.S. Department of Energy (DOE), Office of Science (SC), Office of Basic Energy Sciences (BES), Chemical Sciences, Geosciences, and Biosciences (CSGB) Division that was held in Leesburg, Virginia, in May 2016. We are grateful to James Rustad for his leadership, contributions to discussions at the workshop, and encouragement and support during the preparation of this review. S. E. L. appreciates support in organizing and conducting the workshop and preparing the paper from Grant DE‐FG02‐03ER15430 from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Sandia National Laboratories (SNL) is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE's National Nuclear Security Administration under Contract DENA0003525. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated by Battelle Memorial Institute for the U.S. DOE. Contributions from ORNL, SNL and PNNL are based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. The views expressed in the article do not necessarily represent the views of the U.S. DOE or the U.S. Government. J. L. U. acknowledges funding by the German Science Foundation Project NE 822/34‐1|UR 64/17‐1. We also value discussions with P. Eichhubl, A. Fall, and J. F. W. Gale, contributions to workshop preparation from R. A. Schultz, and discussion and comments from R. Cygan, S.F. Forstner, Q. Wang, and journal reviewers. No data were used in the preparation of this manuscript.

A model for fibrous illite nucleation and growth in sandstones

Abstract: We have developed a model for the formation of fibrous illite in sandstones where kaolinite is a primary reactant and potassium is derived from in-situ K-feldspar grain dissolution or imported into the model reference frame. Illite fiber nucleation and growth are modeled using Arrhenius expressions that consider saturation state in addition to temperature and time. Nucleation occurs on pore walls, and muscovite and detrital illite may be defined as energetically favorable substrates. The model is integrated with other Touchstone™ models to account for the influence of other diagenetic processes on surface area and reactant volumes and to provide input for permeability simulations. We evaluated the illite model performance on two data sets: (1) Jurassic quartzose samples from offshore mid-Norway with maximum temperatures ranging from 108 to 173C (226 to 343F) and (2) Miocene lithic samples from offshore Southeast Asia that have maximum temperatures ranging from 157 to 182C (315 to 360F). The model matches measured abundances of illite, kaolinite, and K-feldspar in both data sets using identical kinetic parameters. Predicted K-Ar ages are consistent with available data given uncertainties associated with detrital contaminants. Although no illite particle-size data are available from the analyzed samples, modeled crystallite thicknesses from the Norway data set are comparable to published measurements of 0.004 to 0.012 m from North Sea samples with similar temperature histories.

The impact of diagenesis on the heterogeneity of sandstone reservoirs: A review of the role of depositional facies and sequence stratigraphy

Abstract: Diagenesis exerts a strong control on the quality and heterogeneity of most clastic reservoirs. Variations in the distribution of diagenetic alterations usually accentuate the variations in depositional porosity and permeability. Linking the types and distribution of diagenetic processes to the depositional facies and sequence-stratigraphic framework of clastic successions provides a powerful tool to predict the distribution of diagenetic alterations controlling quality and heterogeneity. The heterogeneity patterns of sandstone reservoirs, which determine the volumes, flow rates, and recovery of hydrocarbons, are controlled by geometry and internal structures of sand bodies, grain size, sorting, degree of bioturbation, provenance, and by the types, volumes, and distribution of diagenetic alterations. Variations in the pathways of diagenetic evolution are linked to (1) depositional facies, hence pore-water chemistry, depositional porosity and permeability, types and amounts of intrabasinal grains, and extent of bioturbation; (2) detrital sand composition; (3) rate of deposition (controlling residence time of sediments at specific near-surface, geochemical conditions); and (4) burial thermal history of the basin. The amounts and types of intrabasinal grains are also controlled by changes in the relative sea level and, therefore, can be predicted in the context of sequence stratigraphy, particularly in paralic and shallow marine environments. Changes in the relative sea level exert significant control on the types and extent of near-surface shallow burial diagenetic alterations, which in turn influence the pathways of burial diagenetic and reservoir quality evolution of clastic reservoirs. Carbonate cementation is more extensive in transgressive systems tract (TST) sandstones, particularly below parasequence boundaries, transgressive surface , and maximum flooding surface because of the abundance of carbonate bioclasts and organic matter, bioturbation, and prolonged residence time of the sediments at and immediately below the sea floor caused by low sedimentation rates, which also enhance the formation of glaucony. Eogenetic grain-coating berthierine, odinite, and smectite, formed mostly in TST and early highstand systems tract deltaic and estuarine sandstones, are transformed into ferrous chlorite during mesodiagenesis, helping preserve reservoir quality through the inhibition of quartz cementation. The infiltration of grain-coating smectitic clays is more extensive in braided than in meandering fluvial sandstones, forming flow barriers in braided amalgamated reservoirs, and may either help preserve porosity during burial because of quartz overgrowth inhibition or reduce it by enhancing intergranular pressure dissolution. Diagenetic modifications along sequence boundaries are characterized by considerable dissolution and kaolinization of feldspars, micas, and mud intraclasts under wet and warm climates, whereas a semiarid climate may lead to the formation of calcrete dolocrete cemented layers. Turbidite sandstones are typically cemented by carbonate along the contacts with interbedded mudrocks or carbonate mudstones and marls, as well as along layers of concentration of carbonate bioclasts and intraclasts. Commonly, hybrid carbonate turbidite arenites are pervasively cemented. Proximal, massive turbidites normally show only scattered spherical or ovoid carbonate concretions. Improved geologic models based on the connections among diagenesis, depositional facies, and sequence-stratigraphic surfaces and intervals may not only contribute to optimized production through the design of appropriate simulation models for improved or enhanced oil recovery strategies, as well as for CO2 geologic sequestration, but also support more effective hydrocarbon exploration through reservoir quality prediction.

Sandstone diagenesis and reservoir quality prediction: Models, myths, and reality

Abstract: Models and concepts of sandstone diagenesis developed over the past two decades are currently employed with variable success to predict reservoir quality in hydrocarbon exploration. Not all of these are equally supported by quantitative data, observations, and rigorous hypothesis testing. Simple plots of sandstone porosity versus extrinsic parameters such as current subsurface depth or temperature are commonly extrapolated but rarely yield accurate predictions for lithified sandstones. Calibrated numerical models that simulate compaction and quartz cementation, when linked to basin models, have proven successful in predicting sandstone porosity and permeability where sufficient analog information regarding sandstone texture, composition, and quartz surface area is available. Analysis of global, regional, and local data sets indicates the following regarding contemporary diagenetic models used to predict reservoir quality. (1) 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. (2) Vertical effective stress, although a fundamental factor in compaction, cannot be used alone as an accurate predictor of porosity for lithified sandstones. (3) Secondary porosity related to dissolution of framework grains and/or cements is most commonly volumetrically minor (2%). Exceptions are rare and not easily predicted with current models. (4) The hypothesis and widely held belief that hydrocarbon pore fluids suppress porosity loss due to quartz cementation is not supported by detailed data and does not represent a viable predictive model. (5) Heat-flow perturbations associated with allochthonous salt bodies can result in suppressed thermal exposure, thereby slowing the rate of quartz cementation in some subsalt sands.

Kinetics of Water-Rock Interaction

Abstract: Analysis of Rates of Geochemical Reactions.- Transition State Theory and Molecular Orbital Calculations Applied to Rates and Reaction Mechanisms in Geochemical Kinetics.- The Mineral-Water Interface.- Kinetics of Sorption-Desorption.- Kinetics of Mineral Dissolution.- Data Fitting Techniques with Applications to Mineral Dissolution Kinetics.- Nucleation, Growth, and Aggregation of Mineral Phases: Mechanisms and Kinetic Controls.- Microbiological Controls on Geochemical Kinetics 1: Fundamentals and Case Study on Microbial Fe(III) Oxide Reduction.- Microbiological Controls on Geochemical Kinetics 2: Case Study on Microbial Oxidation of Metal Sulfide Minerals and Future Prospects.- Quantitative Approaches to Characterizing Natural Chemical Weathering Rates.- Geochemical Kinetics and Transport.- Isotope Geochemistry as a Tool for Deciphering Kinetics of Water-Rock Interaction.- Kinetics of Global Geochemical Cycles.