Impact of Asphaltene Precipitation and Deposition on Wettability and Permeability

Abstract

Asphaltene precipitation and deposition have been a formation damage problem for decades, with the most devastating effects being wettability alteration and permeability impairment. To this effect, a critical look into the laboratory studies and models developed to quantify/predict permeability and wettability alterations are reviewed, stating their assumptions and limitations. For wettability alterations, the mechanism is predominantly surface adsorption, which is controlled by the asphaltene contacting minerals as they control the surface chemistry, charge, and electrochemical interactions. The most promising wettability alteration evaluation techniques are nuclear magnetic resonance, ζ potential, and the use of high-resolution microscopy. The integration of such techniques, which is still missing, would reinforce the understanding of asphaltene interaction with rock minerals (especially clays), which holds the key to developing a strategy for modeling wettability alteration. With regard to permeability impairment, surface deposition, pore plugging, and fine migration have been identified as the dominant mechanisms with several models reporting the simultaneous existence of multiple mechanisms. Existing experimental findings showed that asphaltene deposition is non-uniform due to mineral distribution which further complicates the modeling process. It also remains a challenge to separate changes due to adsorption (wettability changes) from those due to pore size reduction (permeability impairment).

Effect of Sulfate-Based Scales on Calcite Mineral Surface Chemistry: Insights from Zeta-Potential Experiments and Their Implications on Wettability

“…Most largely confirmed in the literature, the wettability alteration of rocks is attributed to the adsorption of the most polar crude oil component (asphaltene). 31 Asphaltene is said to be the heaviest and most polar crude oil component, soluble in aromatic fluids and insoluble in alkanes. 35 Because of the electrochemical interactions, asphaltene coats the pore surface and alters its wettability.…”

“…Due to the significant impact it has on the production capacity, reservoir wettability is a crucial concept in reservoir engineering and has been the focus of numerous studies over the years . Changes in the pore system (for instance, adsorption), which may be brought on by fluid–fluid interactions, rock–fluid interactions, rock mineralogy, and brine chemistry, have been substantially responsible for wettability alteration. , These could cause the rock’s wettability to change completely or partially.…”

Effect of Native Reservoir State and Oilfield Operations on Clay Mineral Surface Chemistry

“…The most polar compounds in crude oil are asphaltene and resins [ 5 ]. Asphaltenes are defined as a solubility class that is soluble in aromatics and insoluble in alkanes, and they have been reported to be responsible for the change in the reservoir rock wettability [ 5 ].…”

“…The most polar compounds in crude oil are asphaltene and resins [ 5 ]. Asphaltenes are defined as a solubility class that is soluble in aromatics and insoluble in alkanes, and they have been reported to be responsible for the change in the reservoir rock wettability [ 5 ]. However, for asphaltenes to interact with surfaces, adsorption-prone surface conditions must exist, as asphaltenes have been reported to be predominantly negatively charged [ 6 ].…”

Feature Ranking and Modeling of Mineral Effects on Reservoir Rock Surface Chemistry Using Smart Algorithms

“…Wettability alteration is said to be caused by asphaltene which is defined as a solubility class soluble in aromatics and insoluble in alkanes. 26 Wettability alterations due to asphaltene is been attributed to the adsorption of asphaltene molecules on the mineral surface via electrostatic interactions and hydrogen bonding. So, to mitigate asphaltene adsorption to the surface, conditions that promote its adsorption must be controlled.…”