Calcite saturation

KEYWORDS precipitation rate, calciting, saturation ratio, boiling temperatures, Mindanao Geothermal Production field... 

Notably, well MD1D has high calcite saturation values and yet produces for longer than the calculated utilization periods than AP01D and SP4D using the direct deposition method (Fig. 4). This can be attributed to the lower equilibrium constant of calcite at higher temperatures. Thus, despite the inherently lower calcium... 

The precipitation rate (Eq. 1) indicates comparable values for utilization period at calcite saturation ratio below 1.72 since the results are closer to the observed... 

The calcite saturation ratio is more responsive with regards to detecting the onset of calcite deposition through the sudden shift of the saturation ratio from consistently > 1 to < 1. 

Figure 3 shows a schematic diagram of the C02-E0R site, together with the calculated calcite saturation index for each produced water sample as a function of time and for each well. This figure also shows that there is a clear difference between those wells on the fracture trend and those off-trend. For most of the on-trend wells, the calcite saturation drops shortly after the onset of C02 injection, becoming negative. This is contrasted by the off-trend well behavior, for which the SI remains nearly constant, and positive through most of the period represented. The rapid decrease seen in a few wells... 

Fig-3. Schematic representation of the Penn West Cardium C02 EOR project together with the time evolution of the calcite saturation index. The horizontal line in each SI figure represents an SI of 0. The maximum SI on each figure is 0.8 and the minimum is -0.4, with the exception of well 08-11 with a maximum SI of 0.4 and a minimum of-1.6. 

Figure 7.15 A simple ocean-atmosphere-continent system. Pressure of C02 enhances Ca release from the continental crust (which is assumed to be made of CaSi03) and controls the depth of calcite saturation. Calcite precipitation is therefore controlled by the hypsometric curve, equation (7.4.8), and Pco2-...

Depth in meters of the (a) aragonite and (b) calcite saturation horizons (fi = 1) in the global ooeans. Source-. After Feeley, R. A., et al. (2004). Science 305(5682), 362-366. (See oompanion website for oolor version.)... 

Geothermal reservoir waters are close to calcite saturation. Degassing of such water, which occurs in response to boiling, leads to a sharp rise in the pH of the water. This in turn causes the activity of the carbonate ion (CO3-) to increase much, leading to oversaturation (Arnorsson 1989) ... 

The observed formation of calcite scales in geothermal wells is consistent with calcite saturation calculations (see Fig. 14). The intensity of calcite deposition is largely determined by two factors, the temperature of the water and its salt content (Arnorsson 1978a). In relation to temperature, calcite scale formation is most troublesome around 200 C and it decreases at both higher and lower T. The cause is the temperature variation in the solubility of C02. It is at a... 

Fig. 2. Logarithmic activity diagram depicting equilibrium phase relations among aluminosilicates and sea water in an idealized nine-component model of tire ocean system at the noted temperatures, one atmosphere total pressure, and unit activity of H20. The shaded area represents (lie composition range of sea water at the specified temperature, and the dot-dash lines indicate the composition of sea water saturated with quartz, amotphous silica, and sepiolite, respectively. The scale to the left of the diagram refers to calcite saturation foi different fugacities of CO2. The dashed contours designate the composition (in % illite) of a mixed-layer illitcmontmorillonitc solid solution phase in equilibrium with sea water (from Helgesun, H, C. and Mackenzie, F T.. 1970. Silicate-sea water equilibria in the ocean system Deep Sea Res.).

Table 1.12. Variation of carbonic acid components and calcite saturation in seawater under different conditions.

Other kinetic arguments have some bearing on the composition of meteoric cements. Some results of the experiments of various investigators are shown in Figure 7.20. The figure illustrates data for calcite precipitation rates on calcite seeds at 25°C and a PC02 of 10"2 5 atm (a reasonable meteoric realm value), as a function of calcite saturation state expressed as log (0-1). The supersaturations... 

Figure 7.20. Trends in calcite precipitation rates on calcite seeds in different aqueous solutions at 25°C and a Pc02 °f 10 2-5 atm. as a function of calcite saturation state. Solution compositions are indicated on the diagram. (Data from Reddy et al., 1981 Mucci and Morse, 1983 Walter 1986.)...

Fig. 33 Calcite saturation index of complete and incomplete water analyses (calculated with PHREEQC after data by Merkel 1992)...

Fig. 71 Calcite saturation index and amount of calcite precipitated per year for a discharge of 0.5 L/s in a 400m long karst channel with a flow velocity of 0.25 m/s assuming turbulent mixing (P(C02) = 0.03 Vol%).

To display the secondary Y-axis for the calcite saturation index besides the primary Y-axis with the concentrations for Ca and C, Chart options / Show secondary y-axis must be chosen by click on the right mouse button in the graph. The result of the modeling can be seen in Fig. 72. The figure depicts a convergence to the calcite equilibrium. However, the saturation index shows that... 

Fig. 74 Dissolution of calcite, precipitation of gypsum and iron hydroxides and the development of the calcite saturation index for the AMD water shown in Fig. 73...

The Geochemical Ocean Section Program (GEOSECS) has produced data from which it is possible to profile the saturation state of seawater with respect to calcite and aragonite in the Atlantic and Pacific oceans. Representative north-south calcite saturation profiles for the Western Atlantic and Central Pacific oceans are presented in Figures 5 and 6 (based on 39). It was observed that the saturation state of seawater with respect to calcite at the CCD was close to constant ( 2 = 0.70 I" 0,05) except in the southern extremes (39). Broecker and Takahashi (31) have recently found that the carbonate ion concentration is close to constant at the FL, when appropriate corrections are made for pressure. The saturation state of seawater at the FL, calculated by the method presented in this paper, is 0.80 0.05. Berger (40) has presented profiles for Rq, FL, CCD and CSL (calcite saturation level) in the eastern and western Atlantic ocean (see... 

Figure 5. Distribution of calcite saturation states in the Western Atlantic Ocean...

Figure 7. The depth distribution of the Ro and calcite saturation levels, the foraminiferal lysocline and the calcium carbonate compensation depth in the Western and Eastern Atlantic Ocean (after Ref. 40)...

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