Carbon Formation dolomite

The waste contained about 3.5% dissolved solids, 1.7% chlorides, 0.4% sodium hydroxide, and tens to hundreds of ppm of chlorinated hydrocarbons and chlordane its pH was generally greater than 13 (Brower et al., 1989). At the time of drilling, analysis of formation samples indicated that the injection zone was composed of nearly pure dolomite [CaMg(CC>3)2]. The carbonate formation was thought to be safe for accepting an alkaline waste water because carbonates are considered stable at high pH. 

Therefore the formation of magnetite in that way could hardly be of essential importance in the metamorphism of iron-formations, and martitiza-tion is still less hkely. However, in deposits of other genetic types, for instance skam deposits, oxidation of iron silicates to magnetite at the contact with large masses of carbonate rocks (dolomite, magnesite) can be considered an ore-forming process. The last conclusion is still feasible because the carbon dioxide released in the dissociation of carbonates probably had an undisturbed CO O2 ratio. 

Miocene the closure has moved to the south because of structural tilting. Wood Boles (1991) consider that large-scale tectonic processes can trigger major carbonate cementation within years or even months, and it is possible that the Angel Formation dolomite cements formed on the same short timescale. 

Porosity. The fraction of total (bulk) volume occupied by the voids is defined as the porosity of the porous medium. A porous medium can be classified according to the type of porosity involved. In sandstone and unconsolidated sand, the voids are between sand grains, and this type of porosity is known as intergranular. Carbonate rocks are more complex and may contain more than one type of porosity. The small voids between the crystals of calcite or dolomite constitute intercrystalline porosity (47). Often carbonate rocks are naturally fractured. The void volume formed by fractures constitutes the fracture porosity. Carbonate rocks sometimes contain vugs, and these carbonate rocks constitute the vugular porosity. Still some carbonate formations may contain very large channels and cavities, which constitute the cavernous porosity. 

Some fracturing fluids may include nitrogen and carbon dioxide to help foaming. Oil-based fluids find use in hydrocarbon-bearing formations susceptible to water damage, but they are expensive and difficult to use. Acid-based fluids use hydrochloric acid to dissolve the mineral matrix of carbonate formations (limestone and dolomite) and thus improve porosity the reaction produces inert calcium chloride salt and carbon dioxide gas. 

Fracture acidizing treatments have been generally confined to carbonate formations, including vugular and naturally fractured chalks, limestones, and dolomites. Acid fracturing treatments of carbonates are conducted to serve one or both of two purposes ... 

Soak periods are sometimes necessary in scale removal treatments and in very slowly reacting carbonate formations, such as low-temperature dolomites. 

Al and Fe may also contribute to the hardness of water but their ionic concentrations in natural waters are generally negligible. Surface waters contain very small amounts ofdissolved impurity. However, rain water percolates into soil, it dissolves CO2 (released by bacterial action on organic matter) and attacks basic materials like limestone formations, dolomite, etc., and dissolves the insoluble carbonates present ... 

The amount of hardness present in natural surface and groundwaters depends to a large extent on the action of dissolved carbon dioxide in rainwater on the watershed s geological formations (such as limestone, dolomite, gypsum, or magnesite). The dissolved hardness levels remain relatively low because of the sparingly soluble nature of the salts formed. Typically, MU water sources initially contain anywhere from 5... 

Sedimentary rocks that are most likely to meet the first three criteria are unfractured shale, clay, siltstone, anhydrite, gypsum, and salt formations. Massive limestones and dolomites (i.e., carbonates with no continuous fracturing and solution channels) can also serve as confining layers. Then-suitability must be determined on a case by case basis. The fourth criterion has no relationship to lithology. 

Marble. The word marble is used as the common name for two types of monomineral rocks one derived from limestone and therefore composed of calcium carbonate, the other derived from dolomite and composed of calcium magnesium carbonate. Extremely high pressures and heat during past geological times modified the structure of both limestone and dolomite, compacting them into a characteristic crystal structure. Most marble is white however, minor and trace amounts of metallic impurities cause the formation of stains in a variety of colors, hues, and patterns, or of colored marble. 

Effect of Rock Permeability. The effect of rock permeability has been investigated by comparison of mobility measurements made with Baker dolomite and Berea sandstone. Mobility measurements carried out with Rock Creek sandstone (from the Big Injun formation in Roane County, W.Va) is also reported. Rock Creek sandstone has a permeability of 14.8 md. A direct comparison was made with Berea sandstone and Baker dolomite measured with 0.1% AEGS. As mentioned in an earlier section, the permeability of Baker dolomite (a quarried carbonate rock of rather uniform texture with microscopic vugs distributed throughout) was 6.09 md, and of Berea sandstone was 305 md. The single phase permeabilities were measured with 1% brine solution. 

Dolomite is one of the most abundant sedimentary carbonate minerals but its mode of formation and its surface properties are less well known than for most other carbonate minerals. As we have mentioned, the nucleation of dolomites and its structural ordering is extremely hindered. There is a general trend for the "ideality" of dolomite to increase with the age of dolomite over geological time (Morse and Mackenzie, 1990). Most dolomites that are currently forming in surfacial sediments and that have been synthesized in the laboratory are calcium-rich and far from perfectly ordered. Such dolomites are commonly referred to as "protodolomites . Morse and Mackenzie (1990) have reviewed extensively the geochemistry (including the surface chemistry of dolomites and Mg-calcites. 

Bodies of Water and the Chemical Sediments ,— The chemistry of the deposition of salts from sea-water has already been made the subject of special research, and van t Hoff s results in this field are already familiar. The deposition of calcium carbonate awaits a similar thorough study. Allied questions are the formation of dolomite, the deposition of various salts from inclosed bodies of water, the deposition of phosphate rocks, the precipitation of colloidal suspensions of clay and other substances, and the origin of the great deposits of sedimentary iron ore. 

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