A reactive transport model for celestite precipitation in shale reservoirs subject to hydraulic fracturing
Abstract
Celestite (SrSO4) precipitation is an unresolved secondary mineral scaling problem in hydraulic fracturing systems, especially in basins where large concentrations of naturally occurring strontium are present, such as the Midland Basin. Here we present a validated and flexible geochemical model capable of predicting celestite formation under such unconventional resource recovery conditions. Simulations were built using the open-source software CrunchFlow based on batch experimental data performed under various synthetic hydraulic fracturing fluid conditions. These data allowed constraint of key kinetic and thermodynamic parameters for celestite precipitation. Effects of ionic strength, saturation index, and the presence of additives are considered in the combined experimental and modeling construction. We find it is necessary to explicitly model persulfate breaker where appropriate due to its ability to drive more celestite formation. A transition state theory rate law was used to model celestite formation rates and to determine the set of parameters (i.e., solubility product, reaction rate constant, and reaction rate order), yielding an accurate representation of 14 different experimental conditions. This validated geochemical model was then coupled with a more complex system where interactions between hydraulic fracturing fluids and shale rocks were investigated subject to diffusive transport. We find that the carbonate content of a given shale and the presence of persulfate breaker in the system both strongly impact the location and extent of celestite formation throughout these different scenarios. The resulting reactive transport model for celestite precipitation produced in this study offers a reliable tool to constrain the chemical compositions of fluid necessary to mitigate celestite scale formation. Importantly, the proposed model can aid further experimental design in the pursuit of celestite and other mineral scale behavior under extreme conditions typical of hydraulic fracturing in shale formations.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H55B0757D