Time-Dependent CO₂-Brine-Rock Interaction Effect on Sand Onset Prediction: A Case Study of Dolomite-Rich Sandstone in Air Benakat Formation, South Sumatra, Indonesia

CO₂ injection into geological formation for carbon capture, utilization, and storage (CCUS) including enhanced oil or gas recovery provides a solution to reduce CO₂ emissions and bring on potential economic benefits. However, field operation possesses potential challenges both for injection and production wells. Operational constraints commonly considered are weighted around the injection well and related to well and formation integrity (e.g., limiting the risk of injection-induced fracturing). On the other hand, complexities of CO₂-brine-rock interaction affect sand production phenomena in production wells. This study investigates CO₂-brine-rock interaction to reflect CO₂ injection impact toward reservoir fluid and rocks. This study involves extensive experimental works, namely, time-lapse dry mass measurements, brine compositions and pH analysis, X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), petrographic thin section analysis, porosity measurements, and elastic wave velocity measurements. CO₂-brine-rock batch experiment was designed and utilized to observe mineral dissolution, pore structure alteration, as well as rock physics alteration caused by CO₂-brine-rock interactions. An outcrop sample of dolomite-rich sandstone in Air Benakat formation, South Sumatra, Indonesia, was used as a case study. This study shows that dolomite dissolution was observed and led to ∼6.6% porosity improvement as well as rock strength reduction (as shown by ∼4.3% of P wave and ∼6.2% of S wave reduction, respectively). The results of experimental works were then used to construct sand onset prediction model that considers rock strength alteration caused by CO₂-brine-rock interactions. The sand onset prediction model demonstrates an acceleration of sand onset occurrence due to CO₂-brine-rock interactions which can assist the operator to design a better sand management strategy in producer wells.