Geochemical Modeling of Celestite (SrSO₄) Precipitation and Reactive Transport in Shales

Abstract

Celestite (SrSO4) precipitation is a prevalent example of secondary sulfate mineral scaling issues in hydraulic fracturing systems, particularly in basins where large concentrations of naturally occurring strontium are present. Here, we present a validated and flexible geochemical model capable of predicting celestite formation under such unconventional environments. Simulations were built using CrunchFlow and guided by experimental data derived from batch reactors. These data allowed the constraint of key kinetic and thermodynamic parameters for celestite precipitation under relevant synthetic hydraulic fracturing fluid conditions. Effects of ionic strength, saturation index, and the presence of additives were considered in the combined experimental and modeling construction. This geochemical model was then expanded into a more complex system where interactions between hydraulic fracturing fluids and shale rocks were allowed to occur subject to diffusive transport. We find that the carbonate content of a given shale and the presence of persulfate breaker in the system strongly impact the location and extent of celestite formation. The results of this study provide a novel multicomponent reactive transport model that may be used to guide future experimental design in the pursuit of celestite and other sulfate mineral scale mitigation under extreme conditions typical of hydraulic fracturing in shale formations.

Influence of sequential stimulation practices on geochemical alteration of shale

“…Calibration of the models with experimental data validates the model and decodes important mechanisms (Deng et al, 2017;Li et al, 2017;Meile and Scheibe, 2019;Ling et al, 2020;Jew et al, 2022). The calibrated models can then serve as tools to explore a wider range of scenarios including unique reaction conditions or extended temporal/spatial scales (Xu et al, 2010;Esteves et al, 2022). The model framework used in this study has been calibrated with experimental observations in our previous work (Li et al, 2020).…”

“…As neutral fracturing fluids are subsequently injected, precipitation of barite, celestite, and iron (hydr)oxides is expected. Mineral precipitation removes ions from the aqueous phase, fills rock porosity and hinders flow (Vankeuren et al, 2017;Xiong et al, 2020;Esteves et al, 2022), leading to the possibility for rapid loss in productivity.…”

“…It remains unclear to what extent batch and coreflood experimental results resemble one another (Esteves et al, 2022;Khan et al, 2022) or how well either of the experimental designs represents a realistic pumping schedule during operation. The objective of the current study is to utilize reactive transport models set up based on prior experimental data as a rapid method of testing these comparisons.…”

Quantification of the Impact of Acidified Brine on Fracture-Matrix Transport in a Naturally Fractured Shale Using in Situ Imaging and Modeling

“…A quantitative and predictive understanding of transport across fracture-matrix interfaces in shale formations is vital to the management and engineering of a range of flow and transport processes. These processes include groundwater protection from infiltrating contaminants, storage security of geologically sequestered CO 2 , − resource recovery following hydraulic fracturing, − and long-term nuclear waste storage security. , …”

Quantification of the impact of acidified brine on fracture-matrix transport in a naturally fractured shale using in situ imaging and modeling

“…A quantitative and predictive understanding of transport across fracturematrix interfaces in shale formations is vital to the management and engineering of a range of flow and transport processes. These processes include groundwater protection from infiltrating contaminants [1], storage security of geologically sequestered CO 2 [2,3,4], resource recovery following hydraulic fracturing [5,6,7], and long-term nuclear waste storage security [8,9].…”