Sediments cementation

Undoubtedly, the site named as locality no. 3 is the richest of all the Villany faunas. Kormos called this locality Villany-Kalkberg-Nord (Picture 6). The site is situated on the northern wall of the eastern end of the ridge quarry. A cleft, on the average 1 m wide and lying in a direction east to west, cuts through the Lower Malm Oxfordian limestone, and is filled with red sediment cemented by secondary calcite formation. 

Carbonate cements are often among the dominant components of diagenesis and hence are of decisive importance in determining the reservoir quality of sandstone sequences. Despite this, the timing, the geochemical conditions of precipitation and dissolution, as well as the source and fate of these cements are not fully understood. In continental and near-shore sediments, cements commonly precipitate as calcretes and dolocretes in the vadose and phreatic zones, and attain a variety of mineral-ogical, textural and distribution patterns as well as elemental and isotopic compositions. These cements form lenses and layers of densely cemented... 

Stratigraphic traps are formed by depositional and sedimentary factors. In such traps the depositional process and the follow-on cementing process, which changes the sediment bed into a rock, create porosity and permeability alterations in geometric forms that provide traps. 

The Cenozoic portions of the Gulf Coast sedimentary basins are immature therefore, little cementing of the sediments has taken place. Poisson s ratio varies with depth for such sedimentary columns, reflecting the variation of properties through the column. At great depth (i.e., approaching 20,000 ft), Poisson s ratio approaches that of incompressible, plastic materials (i.e., 0.5) [35]. 

Granulated fly ash [6] can substitute for Portland cement to an extent of 40% to 60%. Fly ash is used in granulated form and has a moisture content around 10% to 20%. The formulation can be used for cementing oil and gas wells within a temperature range of 20° to 250° C. The solution has reduced water absorption and increased sedimentation stability. A formulation [1388] is shown in Table 18-2. Hydrosil (Aerosil) is used to increase the adhesion of the produced cement rock to the casing string. It also reduces the density and water absorption. 

N. A. Okishev, A. G. Ivanov, and I. V. Karpenko. Plugging solution for oil and gas wells with increased sedimentation stability—containing Portland cement, nitrile trimethyl phosphonic acid, polyoxyethylene, water-soluble cationic polyelectrolyte and water. Patent RU 2039207-C,1995. 

Using a newly developed, transversely heated graphite atomizer and D2-back-ground correction (for details see Sections 2.2 and 4.3), Cd, Pb and Cr were determined in cement and river sediment samples. Of the various calibration approaches applied the best results, also in comparison with wet chemical procedures, were achieved with calibration curves constructed by means of different BCR CRMs with different analyte concentrations and usually n = to individual intakes (Nowka and Muller 1997). 

Chung GS, Swart PK (1990) The concentrahon of ttranium in freshwater vadose and phreatic cements in a Holocene ooid clay a method of identifying ancient water tables. J Sediment Petrol 60 735-746 Cliff RA, Spotl C (2001) U-Pb dahng of speleothems from the Spannagel Cave, Austria. XI EUG... 

Surface sealing. Surface sealing applies cement, quicklime, or other grouting materials to the surface or mixed with bottom sediments to create a seal. 

Diagenesis is the set of processes by which sediments evolve after they are deposited and begin to be buried. Diagenesis includes physical effects such as compaction and the deformation of grains in the sediment (or sedimentary rock), as well as chemical reactions such as the dissolution of grains and the precipitation of minerals to form cements in the sediment s pore space. The chemical aspects of diagenesis are of special interest here. 

The physical characteristics of sewer deposits can be described in terms of individual particle and bulk properties. The hydraulic and structural conditions in the sewer, together with the nature of the inputs, will control the type of material that deposits at a given location. Crabtree (1989) has proposed a sewer sediment taxonomy that is relevant mainly in terms of physical properties but also to chemical and biological processes (Table 3.5). The taxonomy is based on four primary classes with a fifth class B comprising agglutinated or cemented class A material. 

The region is substantially covered by regolith sediments, which conceal prospective bedrock sequences. The regolith sediments include windblown sand, alluvial gravels, and caliche horizons. Commonly, the vertical profile of the regolith sediments consists of surface lag or loosely windblown sand underlain by weakly cemented sands and dense caliche-cemented sediments with gypsum. 

Carbonate sediments deposited in shallow marine environments are often exposed to the influence of meteoric waters during their diagenetic history. Meteoric diagenesis lowers 8 0- and 8 C-values, because meteoric waters have lower 8 0-values than sea water. For example. Hays and Grossman (1991) demonstrated that oxygen isotope compositions of carbonate cements depend on the magnitude of depletion of respective meteoric waters. 5 C-values are lowered because soil bicarbonate is C-depleted relative to ocean water bicarbonate. 

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