Methodology for Constructing Synthetic Carbonate Rocks with Controlled Properties: Overcoming Challenges to Mimic Heterogeneous Carbonate Reservoir Rocks

Abstract Characterizing oilfields involves testing rock plugs. However, carbonate reservoirs like the Brazilian pre-salt basins pose challenges due to their high heterogeneity and deepwater location, making plug extraction costly and risky. To address and contribute to this issue, a new methodology is proposed for constructing synthetic carbonate rocks with controlled physical and chemical properties, which involves utilizing materials of carbonate nature and a novel 3D printing approach to mimic the natural properties, including heterogeneous porosity of vuggy and fracture types. The chemical/mineralogical approach involved the utilization of carefully selected pure minerals as the base material. The methodology uses cement with a high content of carbonate material (>70%w/w) as bonding material, and to enhance the plugs consolidation; the solubility and precipitation of carbonates were regulated by controlling temperature and pH. Regarding the physical pore space approach, the samples were enriched with naturally soluble materials of controlled morphology using the innovative 3D printing solution during the forming process. Subsequently, these materials were removed via a solvent solution, creating controlled void spaces/pores within the synthetic rock matrix, exhibiting a range of predetermined sizes and morphologies. The research findings highlight the critical role of pure minerals with controlled particle size and morphology in achieving a controlled synthetic rock matrix. By employing a combination of pure minerals, limestone cement with a high carbonate content in a controlled ratio, it becomes possible to mimic the mineral heterogeneity observed natural reservoirs. The particle size distribution of the base materials directly influences the microporosities, enabling their regulation. The proposed novel methodology, based on a 3D printing solution, offers a viable alternative for controlling the morphology of naturally soluble materials. This control extends to macro and meso porosities, such as vuggies and fractures. Consequently, the synthetic plugs combine micro, meso, and macro porosities, accurately mimicking the highly heterogeneous pore network found in natural rocks from reservoirs. This methodology enables the reproduction of controlled chemical and physical properties similar to rocks from carbonate reservoirs. Furthermore, the resultant synthetic plugs exhibit significant consolidation in both dry and wet conditions, allowing their utilization in laboratory tests conducted under various environmental settings. This work was motivated by the need for solutions when obtaining reservoir samples for research is impractical, as well as the scarcity of publications addressing the construction of representative heterogeneous carbonate plugs. The outcomes of this research provide valuable assistance to the scientific community in creating controlled and reproducible synthetic carbonate rocks, in addition to the 3D printing approach, offering valuable insights into the regulation of pore space networks in an accessible and cost-effective way.