Construction of synthetic carbonate plugs: A review and some recent developments

Plugs are cylindrical rocks with known dimensions that are extracted typically from reservoir formations with representative mineralogical compounds, petrophysical properties and oilfield fluids. They are used in the laboratory to understand the behaviour of oil in reservoirs. One of their applications is to study the screening of chemicals, such as surfactants and polymers, for enhanced oil recovery research before being applied in the reservoir. Many of Brazil's pre-salt basins are located in ultra-deep waters, and the high heterogeneities of its offshore carbonate reservoirs make the extraction of representative rock samples difficult, risky and expensive. The literature reports the construction of synthetic plug samples that reproduce rocks as an alternative and viable solution for this issue. However, there is a lack of publications that focus on the construction of representative carbonate plugs that considers both the mineralogical composition and petrophysics properties, such as porosity and permeability. In this work, the construction of synthetic plugs is studied, using a combination of published methodologies to achieve an alternative construction of synthetic carbonate plugs for laboratory scale studies. Using a procedure based on the use of pulverized rock matrices with known particle sizes, uniaxial compaction, and probable CaCO3 solubility control by changing temperature and pH, it was possible to obtain synthetic carbonate plugs with a similar mineralogy to the natural carbonate reservoir. However, further studies are necessary to obtain more controlled petrophysical properties of such samples.