Many authors have proposed that significant volumes of porosity are created by deep-burial dissolution in carbonate reservoirs. We argue, however, that this model is unsupported by empirical data and violates important chemical constraints on mass transport. Because of the ubiquitous presence and rapid kinetics of dissolution of carbonate minerals, the mesogenetic pore waters in sedimentary basins can be expected to be always saturated and buffered by carbonates, providing little opportunity for the preservation of significantly undersaturated water chemistry during upward flow, even if the initial generation of such undersaturated pore water could occur. A review of the literature where this model has been advanced reveals a consistent lack of quantitative treatment. In consequence, the presumption of mesogenetic dissolution producing a net increase in secondary porosity should not be used in the prediction of carbonate reservoir quality.
Research Article| September 01, 1989 Comment and Reply on "Sandstone porosity as a function of thermal maturity" S. N. Ehrenberg; S. N. Ehrenberg 1Statoil, P.O. Box 300, N-4001 Stavanger, Norway Search for other works by this author on: GSW Google Scholar James W. Schmoker; James W. Schmoker 2U.S Geological Survey, Box 25046, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Donald L. Gautier Donald L. Gautier 2U.S Geological Survey, Box 25046, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Author and Article Information S. N. Ehrenberg 1Statoil, P.O. Box 300, N-4001 Stavanger, Norway James W. Schmoker 2U.S Geological Survey, Box 25046, Federal Center, Denver, Colorado 80225 Donald L. Gautier 2U.S Geological Survey, Box 25046, Federal Center, Denver, Colorado 80225 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1989) 17 (9): 866–868. https://doi.org/10.1130/0091-7613(1989)017<0866:CAROSP>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation S. N. Ehrenberg, James W. Schmoker, Donald L. Gautier; Comment and Reply on "Sandstone porosity as a function of thermal maturity". Geology 1989;; 17 (9): 866–868. doi: https://doi.org/10.1130/0091-7613(1989)017<0866:CAROSP>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract No abstract available First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Eight samples of brachiopod shell material have been analyzed for their strontium isotope composition in order to more accurately date Lower to Upper Permian siliceous biogenic strata of Spitsbergen (Kapp Starostin Formation) and the southern Barents Sea (Røye Formation). The results are interpreted as showing a mid‐Artinskian age for the basal Vøringen Member of the Kapp Starostin Formation and a range of late Artinskian to Roadian for the overlying part of this unit. The upper part of the Røye Formation yields ages in the range Roadian to Wuchiapingian. These results are consistent with available biostratigraphic data and confirm the potential of strontium isotope stratigraphy for developing a more accurate chronology of the widespread spiculite deposits that characterize the northern margin of Pangea in late‐Early Permian to Late Permian time and which constitute a potential target for petroleum exploration.
A publicly available data set has been examined for relationships between average values of porosity, permeability, depth, temperature, pressure, thickness, age, and play type for 11,833 sandstone reservoirs, mostly of Miocene age and younger, from the United States offshore Gulf of Mexico (GOM). Porosity shows wide scatter as a function of burial depth, but the median (P50) porosity trend decreases smoothly with depth. The GOM trend has much higher porosity for the given depth than the P50 trend of sandstone reservoirs worldwide, reflecting rapid sedimentation rates and young ages of GOM reservoirs, most of which have spent relatively little time at temperatures more than 80C, where quartz cementation becomes active. Multivariate regression analysis shows that porosity is best predicted by temperature (r2 = 0.40), with the fit improved slightly by adding age and then depth (r2 = 0.44). Arithmetic average permeability (represented by its logarithm) shows a correlation of maximum and P50 trends with porosity. GOM P50 permeability lies 0.2–0.4 log units below the P50 trend for sandstone reservoirs worldwide, probably reflecting very fine grain size of most GOM sands. Water saturation can be used to calculate the effective (petroleum-filled) porosity of each reservoir, which shows strong correlation with permeability. Grouping the reservoirs by chronozone reveals regular trends of decreasing average porosity and permeability with increasing age, reflecting increasing average depth and temperature with age. Porosity and permeability functions representing depositional sand quality show only subtle differences between different age groupings and play types. The results presented here can be useful for specifying realistic distributions of parameters for both exploration risk evaluation and reservoir modeling.
We review published studies characterizing the Thamama‐B reservoir zone in the upper Kharaib Formation (late Barremian) in Abu Dhabi oilfields and at outcrops in Oman. Available data for oxygen and carbon isotope compositions, fluid inclusion measurements, cement abundance and formation water composition are interpreted in terms of a paragenetic model for the Thamama‐B in field F in Abu Dhabi where the interval is deeply buried. The present synthesis provides a useful basis for understanding and predicting reservoir quality in static models and undrilled prospects, as well as for planning promising directions for further research. The goals of this study were to summarize the geologic setting and petrology of the Thamama‐B reservoir and its surrounding dense zones, and to examine how sedimentology, stratigraphy and diagenesis have interacted to control porosity and permeability. Results that may have useful applications for similar microporous limestone reservoirs in general include: the depositional environments and stratigraphy of the subject strata; a model for how porosity variations result mainly from calcite cementation sourced from stylolites, with little dependence on lithofacies other than the localization of chemical compaction by depositional clay linked to sequence stratigraphy; the use of solidity (rock thickness with porosity removed) as a check on porosity creation by burial dissolution; observations linking high‐permeability streaks with storm lag beds and fractures; the concept of strata being gradually buried through a relatively static salinity‐stratified water column; integration of conventional and clumped stable‐isotope data with petrologic observations to constrain the timing of porosity evolution.
ABSTRACT Sandstone cores from two wells in Statfjord Nord Field have been studied to evaluate a local correlation problem. In well 33/9-14, cores have been taken in sandstones of both the Upper Jurassic Draupne Formation and the Middle Jurassic Brent Group. In well 33/9-13, a 67 m cored interval was originally identified as Brent but was subsequently suggested to be Draupne Formation. It has not been possible to confirm the correlation of this interval by biostratigraphic study or conventional heavy mineral analyses. In order to determine the feasibility of identifying the sandstones in well 13 on the basis of their bulk chemical composition, bulk chemical data from the known stratigraphic intervals in well 14 were examined using the statistical technique of discriminant analysis. Consistent c mpositional differences were found between the Upper Jurassic and Middle Jurassic sandstones, and the sandstones from the disputed interval in well 13 were found to match the Middle Jurassic compositions. The most significant compositional difference is higher phosphorous content in the Upper Jurassic sandstones. This difference is consistent with the observation of glauconite pellets (a feature commonly associated with phosphorous mineralization) throughout the Upper Jurassic interval in well 14 and the complete absence of glauconite in both the Brent in well 14 and the disputed interval in well 13. The approach used in this study--including both the use of bulk chemical analyses as a correlation parameter and the use of discriminant analysis for differentiating between stratigraphic un ts--has potential application to correlation problems in a wide variety of rock types.
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