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.

No abstract

Synthetic plugs are available to understand oilfield properties and the behavior of oil in reservoirs where natural plugs cannot be extracted. Specifically, in cases where it is necessary to reproduce representative mineralogical and petrophysical characteristics from carbonate reservoirs, it is evident that there is a lack of publications focusing on synthetic plug construction. In this work, a methodology to construct synthetic carbonate plugs is proposed using disintegrated carbonate rock with controlled particle size, mixed in different weight fraction, uniaxial compaction with controlled load force velocity, pH, temperature, and bonding materials. Preliminary analysis of consolidation (basic consolidation and consolidation by water immersion test), wettability (contact angle measurements) and petrophysical properties (nitrogen expansion porosimetry measurements and theoretical porosity calculation) are reported in this study to determine which composition of the synthetic samples provides similar properties compared to that expected for natural rocks from carbonate reservoirs. Two compositions are recommended to construct synthetic samples: Composition 1 with a total quantity of 100 g of base material (50% w/w of <20 μm, 50% w/w of 20–74 μm) + 5% w/w of amide wax (relative to 100 g of base material) + 6% w/w (relative to 100 g of base material) of pH 3 hydrochloric acid solution; and Composition 2 with a total quantity of 100 g of base material (50% w/w of 150–300 μm, 50% w/w of 300–600 μm) + 5% w/w (relative to 100 g of base material) of amide wax + 6% w/w (relative to 100 g of base material) of pH 3 hydrochloric acid solution. In addition to the compositions, it is necessary to follow the reported procedure based on the uniaxial compaction with controlled load force (200 kN) and velocity (25 mm/min) and the sample’s drying temperature of 100 °C for 1 h aiming to obtain similar samples. These preliminary results will guide further dedicated petrophysical and wettability analysis to deeply understanding these sample’s properties and enhance the construction of synthetic samples more similar to the natural rocks from carbonate reservoirs.

Purpose Among the many influencing effects that the medium has on the CO2 corrosion of carbon steel, flow is one of the most important because it can determine the formation of corrosion product scales and its stabilisation, thus influencing the attack morphology and corrosion rate. This paper aims to summarise some factors affecting aqueous CO2 corrosion and the laboratory methodologies to evaluate one of the most important, the flow, with an emphasis on less costly rotating cage (RC) laboratory methodology. Design/methodology/approach Regarding the key factors affecting CO2 corrosion, both well-established factors and some not well addressed in current corrosion prediction models are presented. The wall shear stress (WSS) values that can be obtained by laboratory flow simulation methodologies in pipelines and its effects over iron carbonate (FeCO3) scales or inhibition films are discussed. In addition, promising applications of electrochemical techniques coupled to RC methodology under mild or harsh conditions are presented. Findings More studies could be addressed that also consider both the salting-out effects and the presence of oxygen in CO2 corrosion. The RC methodology may be appropriate to simulate a WSS close to that obtained by laboratory flow loops, especially when using only water as the corrosive medium. Originality/value The WSS generated by the RC methodology might not be able to cause destruction of protective FeCO3 scales or inhibition films. However, this may be an issue even when using methodologies that allow high-magnitude hydrodynamic stresses.

No abstract