A Different Approach to Evaluate Dynamic Compatibility in Rock-scCO2-Brine Systems

Unofficial AI-generated summary based on the public title and abstract. Not an official translation.

🔬研究者:Offers a reproducible experimental protocol for evaluating fluid-rock interactions under CO2 injection, useful for CCS feasibility studies.

🏢実務担当者:Provides a practical test method to assess reservoir compatibility before full-scale injection, reducing operational risks.

🏛政策担当者:The established criteria can inform regulatory guidelines for CCS project approval and monitoring requirements.

One of the most important tests that should be performed when saline aquifers are considered as a storage site for CO2 captured from different industrial processes is the dynamic compatibility tests in rock-scCO2-brine systems. From these tests it is possible to evaluate (a) in-situ reactions including mineral dissolution, precipitation, and fine migration; (b) changes in the main flow properties such as injectivity, permeability, wettability, and relative permeability. In this study we propose a method that combines an injectivity test during a cycling scCO2-brine injection to access potential incompatibilities with a coreflood test where scCO2 and brine is injected to measure dissolution rate and precipitation to assess the potential of scaling. The tests were performed on two rocks from saline aquifers. Rock samples were submitted to initial measurement of porosity, permeability, and grain density. Synthetic brine was prepared according to reservoir water composition. One component scCO2 was used. The experiment was performed in two steps. In the first step samples were loaded into a triaxial coreholder, saturated with brine and the effective permeability to brine was measured at stable low capillary number. In the second step, scCO2 was displaced using a step-rate scheme and the pressure drop was recorded. The effluent was collected and analyzed for pH, suspended solids, ions, and anions. The system was shut in for 5 days to ensure the gas-brine diffusion and acidification. Finally, a batch of fresh brine was injected and the effluent collected and analyzed. This is repeated one time and at the end of the test, porosity and permeability were measured. Effluent water samples were collected during the brine injection and will continue until there are at least three effluent water samples. A final permeability to brine is measured at three flow rates, keeping the pore pressure constant. Results indicate strong fluid-rock interaction in the analyzed systems. Significant changes in the permeability and porosity were observed. From the effluent mineral dissolution rates were calculated using calcite as proxy. The potential of scaling was determined through a saturation index (SI) based on content of calcium, bicarbonate, and pH. Compatibility criteria were established based on thresholds. A rock-fluid system is compatible when (a) the change in permeability is < 10%; (b) low dissolution (low content of metals and ions); (c) low content of fines (< 0.1 mg per porous volume); and (d) SI < 0 with stable pressure. The two-step test performed on two samples of different lithology is highly recommended to accurately measure the compatibility in scCO2-brine systems. The method constitutes a novel approach to measure dynamic compatibility as part of the regulation's requirements for CCS and CCUS projects.

• semanticscholar https://doi.org/10.4043/36911-msfirst seen 2026-05-06 00:16:42