An Investigation of Asphaltene Precipitation During Natural Production and the CO₂Injection Process

Abstract

Some of Iranian oil reservoirs suffer from operational problems due to asphaltene precipitation during natural depletion, so widely investigation on asphaltene precipitation is necessary for these reservoirs. In this study, a reservoir that is candidate for CO 2 gas injection process is selected to investigate asphaltene precipitation with and without CO 2 injection. In this case, asphaltene precipitation is monitored at various pressures and reservoir temperature. Then, a series of experiments are carried out to evaluate the amount of precipitated asphaltene by injection different molar concentrations (25%, 50%, and 75%) of CO 2 . The results show that during primary depletion the amount of precipitated asphaltene increases with pressure reduction until bubble point pressure. Below the bubble point the process is reversed (i.e., the amount of precipitated asphaltene at bubble point pressure is maximum). The behavior of asphaltene precipitation versus pressure for different concentrations of CO 2 is similar to primary depletion. Asphaltene precipitation increases with CO 2 concentration at each pressure step. In the modeling part, solid model and Peng-Robinson equation of state are employed which show a good match with experimental results.

Carbon Capture and Storage in Depleted Oil and Gas Reservoirs: The Viewpoint of Wellbore Injectivity

“…Crude oil is a complex mixture containing different hydrocarbons, primarily saturates, aromatics, resins, and asphaltenes (SARA) [56,104,105]. The most polar components are asphaltenes because they contain heteroatoms like oxygen, sulfur, or nitrogen, while saturated and aromatic compounds are nonpolar [55,106].…”

“…Asphaltenes, the heaviest and most polar crude oil fractions, have a molecular weight of 100 to 10,000 g/mol [55,56,81,[104][105][106][107][108][109][110][111]. They are composed mainly of carbon and hydrogen, with condensed aromatic rings surrounded by insoluble aliphatic chains [55,56,81,[104][105][106][107][108][109][110][111].…”

The Simultaneous Effect of Brine Salinity and Dispersed Carbonate Particles on Asphaltene and Emulsion Stability

“…Therefore, during the waterflooding process, they are mostly attracted to the oil/water interface and form a rigid film that prevents the water droplet coalescence. This process can lead to stable emulsion formation, asphaltene instability, and deposition. ,− Moreover, asphaltene particles could adsorb and deposit on the reservoir rock surface and alter the rock wetting state to oil-wet conditions, causing pore plugging and injectivity/productivity decline. ,− …”

N2 and CO2 Huff-n-Puff for Enhanced Tight Oil Recovery: An Experimental Study Using Nuclear Magnetic Resonance

“…CO 2 is considered a suitable gas for HnP injection as a result of its higher solubility and lower minimum miscibility pressure (MMP). , However, it is hard to implement the CO 2 HnP method in oilfields owing to the problems of insufficient CO 2 gas sources, pipeline and wellbore corrosion, and asphaltene precipitation. , N 2 is abundant in the atmosphere and non-corrosive and can also enhance crude oil recovery by dissolving in crude oil, which expands the oil volume, reduces oil viscosity, and improves oil mobility. , It is of great interest to understand and contrast the enhanced oil recovery (EOR) effectiveness of N 2 and CO 2 HnP in tight reservoirs.…”