Rocks dissolution

By adding an oil-wetting surfactant to an acid, one can promote the temporary formation of a film on formation surfaces thus reducing the rate of rock dissolution. Acids containing these surfactants are known as chemically retarded acids. 

Making a=(l— r) 1, the equation of Allegre and Minster (1978) for wall-rock dissolution during fractional crystallization is obtained, which is therefore equivalent to the AFC equation (9.4.17) derived by DePaolo (1981). 

Physical and chemical analyses of the samples were made in order to interpret the results of the sorption experiments and to provide basic data for the calculation of mass transfer which occurred in the rock dissolution experiment. Cores, 3.2 cm in diameter, were taken from each of the rock samples and sectioned in tap water for subsequent analyses (Figure 1). 

In catalytic systems morphological changes of the pore structure, brought upon by the reaction and sorption processes, typically result in a reduction of the available pore volume. In some instances the internal pore structure is eventually blocked and becomes completely inaccessible to transport and/or reaction. In the field of noncatalytic fluid-solid reactions and acid rock dissolution, on the other hand, the chemical reaction consumes the solid matrix of the porous medium leading eventually to fragmentation and... 

H2CO3 in recharge water was made from six Rainier Mesa water samples for which reliable pH and HCO3 values were available. In simple silicate rock dissolution, all carbonate species result from reaction of H2CO3 with the rock. Thus, HCO3 + C03 + H2CO3 at any point in the flow path is assumed to be a constant. Calculations of concentrations of these species in the six samples previously mentioned allowed calculation of H2CQ3 initially available for reaction. These data are presented in Table I. The arithmetic mean was used in subsequent calculations. 

One of the key objectives in estimating fresh rock compositions is to determine the chemical inventory present before alteration in a given reference volume of altered rock. This is different from the fresh-rock composition, because water-rock interaction occurs in an open system. The pitfalls arising from open-system behavior can be illustrated in two examples secondary mineral precipitation and rock dissolution. 

In the dissolved load, the preferential dissolution of the different types of lithology or mineral can cause large variations in trace-element abundances in rivers. A classical tracer of rock dissolution is strontium. The isotopic ratio of strontium in river waters is, to a first approximation, explained by mixing between different sources. Rain, evaporite dissolution, and carbonate and silicate weathering are the predominant sources of strontium in rivers (see Chapter 5.12). Examples of the use of Ca/Sr, Na/Sr, and Sr isotopic ratios to quantify the proportion of strontium derived from carbonate weathering in large basins can be found in Negrel et al. (1993)... 

For both cases of CaC03 dissolution, representative values of d are given in Figure 7.12. A comparison of these figures illustrates that C information may aid in deciding whether carbonate rock dissolution occurs mainly under open- or closed-system conditions. 

Rates of dissolution or weathering of rocks and minerals are proportional to their surface areas exposed to a given volume of solution, or rate a AIV). Exposed areas can vary widely, depending on the occurrence ol the rock. In this problem you are asked to compare and contrast the rates of rock dissolution under attack by acid rain and in the pores of a rock. We will assume that the rock, temperature, pressure, and solution chemistry are the same in both cases. 

Waters that recharged the aquifer had undergone water-rock interaction, mixing oxygen values from meteoric waters with those derived from dissolution of 0-enriched minerals in the rock. Dissolution of framework grains, particularly volcanic rock fragments and feldspar, is common in the Zia Formation. 

Kinetics of chemical weathering are important to understand the rates of rock dissolution, sediment formation, and acid neutralization in the environment. In this chapter, there are three principal objectives (1) to describe the theoretical kinetics of chemical weathering for pure minerals, (2) to discuss the relative advantages and disadvantages of various experimental apparatus for measuring those kinetics in soils, and (3) to make comparisons between laboratory and field measurements of weathering rates and solute transport. A case study of laboratory and field measurements at Bear Brook Watershed, east of Orono, Maine, at Lead Mountain, will be used to illustrate the principles discussed in this chapter. 

Zoysa, A.K.N., Loganathan, P. and Medley, M.J. (1998) Phosphate rock dissolution and transformation in the rhizosphere of tea (Camellia sinensis L.) compared with other plant species. European Journal of Soil Science 49, 477-M86. 

Chemical Weathering Chemical weathering is very common in the territories of excessive humidity and is the major rock weathering process on the surface of continents. It is caused by the domination of rock dissolution over secondary minerogenesis on large territory of the continental surface. Its intensity depends on the nature of relic rocks and climate conditions. 

Krumrine, P.H. Falcone, Jr., J. S. Rock Dissolution and Consumption Phenomaia in an Alkaline Recovery System , SPE Reservoir Engineering (1988) (2) 62. 

In other words, the polymer molecules in the blend solution slug would adsorb and coat the water-wet portions of the pore walls, so that the alkaline agent would have only limited sites for the rock dissolution and ion exchange reactions. Hence, the saved useful alkalinity could be used for the reactions with the organic acids in the crude oil in order to mobilize the residual oil. Moreover, as in the first version of PAAF, chasing fresh polymer slug would provide the mobility control and the efficient volumetric sweep. 

Through rock dissolution reactions—the dissolved minerals are then prone to consuming more alkali or precipitating elsewhere and causing reservoir plugging. 

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