Effect of calcium content on the dissolution rate of dolomites in HCl acid

In previous dissolution studies, dolomite has been commonly assumed to have an ideal composition of CaMg(CO3)2. The objectives this work are determine (1) if dolomites composing hydrocarbon reservoir rocks vary in chemical composition, specifically Ca content, and (2) the effect uptake on rate HCl acid. Dolomitic from different sources were analyzed using several techniques, including: X-ray diffraction (XRD), fluorescence (XRF), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), acid solubility. Most Fe/Mn poor nonstoichiometric with 1.02 < nCa <1.13, where is average number atoms per formula unit. To quantify content dolomite, samples similar mineral microstructure, but uptake, reacted 21.5 wt% a rotating disk apparatus (RDA). At 24 °C Ca1.067Mg0.933(CO3)2 dissolved 1.7 times faster than ones Ca1.015Mg0.985(CO3)2. 50 difference rates increased 2.2 times. Further increase temperature decreased 1.5 1.4 at 75 100 °C, respectively. This non-linear dependence explained by shift process surface reaction predominantly diffusion (mass-transfer) limited. Results also indicate that was not constant along sampled intervals same wells. Since reactivity depends calcium spatial variation should be considered when designing well-stimulation operations. present study innovatively determines mineral.