Strontianite, 856 table

We then equilibrate the formation fluid, using data from Table 30.1. Since pH measurements from saline solutions are not reliable, we assume that pH in the reservoir is controlled by equilibrium with the most saturated carbonate mineral, which turns out to be witherite (BaCC U) or, for the Amethyst field, strontianite (SrC03). Using the Miller analysis, the procedure for completing the calculation is... 

Fig. 30.1. Volumes of minerals precipitated during a reaction model simulating the mixing at reservoir temperature of seawater into formation fluids from the Miller, Forties, and Amethyst oil fields in the North Sea. The reservoir temperatures and compositions of the formation fluids are given in Table 30.1. The initial extent of the system in each case is 1 kg of solvent water. Not shown for the Amethyst results are small volumes of strontianite, barite, and dolomite that form during mixing.

Strontium is the thirty-eighth element in the Periodic Table and the sixteenth most abundant element in Earth s crust. It was first recognized by Adair Crawford in 1790, who named the substance strontianite, after the Scottish town of Strontian where samples were originally obtained. However, it was Sir Humphrey Davy who actually isolated strontium in elemental form in 1808, using his electrolysis apparatus. 

Strontium is a member of the alkaline earth elements (group 2 of the periodic table) with atomic number 38 and molecular weight 87.62. It possesses four stable isotopes Sr (0.55%), Sr, (9.75%), Sr (6.96%), and Sr (82.74%). In its chemical characteristics it resembles calcium and barium and has properties intermediate between these two elements. The strontium atom easily loses two electrons in the 5s level to form the divalent ion Sr [3]. This ion occurs in many simple compounds such as SrC03 (strontianite) and SrS04 (celestite). However, to biologists, the compounds consisting of strontium and phosphate are of main interest because in chemical respect they are closely related to calcium phosphate compounds found in calcified tissues. 

Strontianite (strontium carbonate) is an important mineral of strontium. Calculate the solubility of strontium carbonate, SrC03, from the solubility product constant (see Table 18.1). 

Siderite, strontianite and magnesite are also calculated to be close to saturation (Table 6). However, these results reflect the fact that the various metal carbonates were simulated as discrete phases, rather than as calcite-dominated solid solutions. The rather high contents of Fe, Mg and Sr found in calcite from fracture fillings supports the hypothesis that the siderite, strontianite and magnesite actually occur in solid solution with calcite (Table 2). 

---