Permeability is how the porosity is interconnected. Follow these instructions to set the print quality of the pdf. Fractured reservoirs carbonate sidewall core 1 inch carbonate reservoirs. Existing models for dolomitization emphasize that penecontemporaneous dolomitization can occur in both subtidal and supratidal environments if the necessary chemical and physical factors favorable for the development of magnesiumrich hypersaline waters exist. Pdf converter is a online webbased document to pdf converter software. Two different dolomitization models are proposed for the two sites.
Dolomitization is a geological process by which the carbonate mineral dolomite is formed when magnesium ions replace calcium ions in another carbonate mineral, calcite. Relative timing of dolomitization and silica cementation. A white or lightcolored mineral, essentially camg 2, used in fertilizer, as a furnace refractory, and as a construction and ceramic material. The impact of dolomitization on reservoir quality evolution. With the development of intergranular pores in the dolomitization process, a lot of dissolved poresvugs and fractures were formed by denudation in the later periods because of the influence of thermal fluids including the associated fluids of volcanic activities and the expelled hydrocarbon fluids of the source rocks. Dolomites and dolomitization models carbonate sedimentology. Sedimentology, dolomitization and diagenetic fluid evolution of the middle devonian sulphur point formation, northwestern alberta by jeffley scott lonnee a thesis submitted to the coilege of graduate studies and research through the department of earth sciences.
The patterns of dolomitization are easily recognizable in this cross section of the yoyo reef and the adjacent bank edge. Holocene shallowwater hypersaline environments that have the potential to produce dolomite without deposition of more soluble. The geochemical process in supratidal sabkha areas where magnesium mg ions from the evaporation of seawater replace calcium ca ions in calcite, forming the mineral dolomite. Linking process, dimension, texture and geochemistry in dolomite. Sedimentology, dolomitization and diagenetic fluid. The study results show that the forming environment of dolomite in the nanpu sag is a freshwater lake environment, and the dolomite is. Dolomitization of the hope gate formation north jamaica by seawater. These carbonate minerals react quickly with natural waters that either dissolve the carbonates, or precipitate new carbonates to bring the water into equilibrium with the host carbonate sediments and rocks. Insights to controls on dolomitization by means of. In this context, a diagenesis study was performed on upper cretaceous reservoir of an onshore oil fie. Carbonate diagenesis and porosity, volume 46 1st edition. Dolomitization in a mixing zone of nearseawater composition, late pleistocene, northeastern yucatan peninsula. Sedimentology, dolomitization and diagenetic fluid evolution of the. Dolomitization definition of dolomitization by merriamwebster.
Dolomitization of devonian carbonate platforrns and reefs in western canada has been studied by many researchers. Michigan dolomite camg co 32 volume decrease leads to new porosity. It is common for this mineral alteration into dolomite to take place due to evaporation of water in the sabkha area. Dolomitisation article about dolomitisation by the free. Dolomitization and the causes of dolomitization dolomite. Dolomitization definition of dolomitization by merriam. The kesrouane formation, which is characterized by pervasive dolomitization. Distinguished lecture and main part of presentation at tulsa. The rock of gibraltar comprises two tectonically separated limbs of an isolated klippe of liassic gibraltar limestone formation. Some of the mineral deposits are contaminated with heavy metals lead, cadmium, etc. The volume of dolomite is less than that of calcite, so the replacement of calcite by dolomite in a rock increases the pore space in the rock by % and forms an important reservoir rock. In its broadest sense, diagenesis encompasses those natural changes which occur in sediments or sedimentary rocks between the time of initial deposition and the time if ever when the changes created by elevated temperature, or pressure, or by other conditions can be considered to have crossed the threshold into the realm of metamorphism. Dolomitization was followed by 5 million years of subaerial exposure.
The benicassim area maestrat basin, eastern spain constitutes an excellent field analogue for faultcontrolled stratabound hydrothermal dolomitization. Controls on dolomitization of the upper ordovician trenton limestone of southcentral kentucky collin j. Under print quality paper pdf, set the desired quality to an option of your choice. Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. Dolomitization, process by which limestone is altered into dolomite. The second type, shallow burial dolomitization, is the most significant genetic type of dolomite reservoir in this area. Pdf dolomitization process and its implications for. Insights into the dolomitization process and porosity. The formation of pore space in this system is similar to dolomitization, where the created porosity ranges from % to 25% merino and canals, 2011.
Camgco 3 2 which is called overdolomitization halley and schmoker, 1983. These questions are drawn from individual lectures. Reefs karst dissolution dolomitization fracture systems healed fractures vs open fractures fracture controlled production example carbonate porosity types. In this lesson, youll learn about the process of dolomitization, including how its formed, its origins, and much more.
In the powerpoint preferences dialog box, click general. However on occasion if the recrystallization is coarser it can lead to improved permeability. Epigenic dolomitization is caused by the action of subterranean waters enriched with magnesium, as they pass through strata of dolomite, ultrabasic igneous rock, and so forth. Patches of dolomite occur in cores of reefal limestone from the shallow subsurface on the northeastern coast of the yucatan peninsula.
The avon park formation middle eocene in central florida, u. Dolomitization model for upper cambrian and lower ordovician. Cline, university of nevada, las vegas, 4505 maryland. The focus is on limestones and dolostones and the sediments from which they are derived. Relative timing of dolomitization and silica cementation in. Dolomitization in carbonate reservoirs affects the distribution of petrophysical.
Porosity is the presence of interconnected pore spaces. Dolomitization was preceded by freshwater diagenesis, including precipitation of sparry calcite cement, stabilization of mgcalcitic skeletal fragments, and. Subsurface dolomitization and porosity occlusion within early. Partially dolomitized carbonate rocks of the middle east and north america host large hydrocarbon reserves. Dolomitization definition of dolomitization by medical. Dolomitization article about dolomitization by the free. The relationships between dolomitization and porosity and permeability were studied focusing on three 305. Abstract dolomitization, as part of diagenesis of carbonate rocks, may or may not significantly enhance reservoir quality of the altered sediments. Reservoir properties geol493k porosity and permeability porosity. Wiley online library is migrating to a new platform powered by atypon, the leading provider of scholarly publishing platforms. Adapted from oral presentation at aapg annual convention and.
In this model, ascending flow of freshwater mixes with evaporated seawater, leading to extensive dolomitization. Introduction to diagenesis deposited sediments are characterized by loosely packed, uncemented fabrics, high porosities, and high interstitial water content. Diagenetic controls on porosity and permeability in upper miocene. Convert and create pdf from various types of files like word doc, excel xls, powerpoint ppt. Dolomitization involves recrystallization on a large scale. Subsurface dolomitization and porosity occlusion within. The origin of some of these dolomites has been attributed to a hydrothermal mechanism. Carbonate diagenesis is a subject of enormous complexity because of the basic chemical reactivity of carbonate minerals. Fluid oxygen isotopic composition versus formation temperature for calcite and dolomite phases of different origin.
A third dolomitization model considered here is that of baker and kastner 1981, based on the experimental finding that sulfate ions inhibit or retard dolomitization. Subsurface dolomitization and porosity occlusion within early to middle ordovician strata of the illinois basin, usa welcome to the ideals repository javascript is disabled for your browser. As sedimentation continues in subsiding basins, older sediments are progressively buried by younger sediments to depths that may reach tens of kilometers. Toro wvu 342016 geology 493 4 shale wet mud compacted sediment water expelled cemented shale shale microphotograph shale permeability ability of fluids to flow through porous. Carbonate rock ppt free download as powerpoint presentation. Keywords dolomitization, isotopes, lebanon, saddle dolomite. This paper was selected for presentation by an iptc programme committee. Save powerpoint presentations as pdf files office support. Dolomite crystal structure, stoichiometry and ordering. Relative timing of dolomitization and silica cementation in the cambrian potosi and eminence dolomites in the illinois basin, usa welcome to the ideals repository javascript is disabled for your browser. Models of dolomitization, modern and ancient examples. A complete substitution of dolomite for the calcite rarely occurs with these secondary limestone changes.
Jan 30, 2017 introduction to diagenesis deposited sediments are characterized by loosely packed, uncemented fabrics, high porosities, and high interstitial water content. Dolomitization definition of dolomitization by the free. Origins and geochemistry of oolitic dolomite of the. It has ken suggested that dolomitization occuned during exposure to a variety of diagenetic environments, each with different physical and chetnical characteristics. Reassessment of mixingzone dolomite geochemical society. Dolomitization process and its implications for porosity development in dolostones. Apr 11, 2012 this paper utilizes multimethods, such as core observation, slice identification, isotope analysis, trace element analysis, fluid inclusion technique and so on, to study the causes of the dolomite in the nanpu sag and the origins of the dolomite reservoir. Dolomitization and limestone diagenesis geoscienceworld. Times new roman default design microsoft powerpoint slide slide 1 future tasks for 1005 3o6 outline slide 4 slide 5 slide 6 slide 7 slide 8 slide 9 slide 10 slide 11 slide 12 slide slide 14 slide 15 slide 16 slide 17 slide 18 slide 19 slide 20 slide 21 slide 22 slide 23 slide 24 slide 25 slide 26 slide 27 summary and conclusions slide 29. Effects of seepagereflux diagenesis on porosity modification.
Fundamental approaches to dolomitization and carbonate diagenesis in. The purpose of this research is to systematically evaluate the effects and distribution of refluxing systems in carbonate reservoir rocks, as a means for predicting porosity distribution. The new model is constrained by data from upper miocene strata of southeast spain, where dolomite yields fluidinclusion tmice data that range from. Four cycle types are recognized on the basis of vertically repeated. Dolomitization definition, the conversion of limestone into dolomite. A number of modern sedimentary dolomites are not in accord with this model in that they are forming from brines with large sulfate concentrations, 2 to 70 times that of seawater.
It is a common phenomenon that pores are occluded by dolomite cements e. Questions on the exams may draw their content from across lecture material and not focus on any one specific area as the questions do here. Sedimentology, dolomitization and diagenetic fluid evolution. The approach is general and universal and draws heavily on fundamental discoveries, arresting interpretations, and keystone syntheses that have been developed over the last five decades. Carbonate reservoirs porosity strongly controlled by postdepositional processes high initial porosity rapid cementation dissolution creates secondary porosity usually due to acidic water outline carbonate porosity primary vs. Dolomitization definition is the process of converting into dolomite. Pdf the accurate prediction of the geometry of subsurface dolomite. A case study from the lower triassic feixianguan formation, jiannan area, eastern sichuan basin, china. Sample questions answers given at the bottom of the page note. Critical geologic characteristics and viable models jean s.
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