Salinity and pH effects on water-oil-calcite interfaces by using molecular dynamics

Area of Science:

• Petroleum Engineering
• Surface Chemistry
• Computational Chemistry

Background:

• Smart water injection is an economical and eco-friendly method for altering oil-rock wettability.
• Traditional methods for wettability alteration are often costly and environmentally impactful.

Purpose of the Study:

• To investigate the effect of various salts on calcite wettability using molecular dynamics.
• To explore the influence of salinity and pH on the interaction between calcite and crude oil models.

Main Methods:

• Molecular dynamics simulations were employed to study the (104) calcite surface.
• The study examined the impact of different salt types (NaCl, Na2SO4, CaCl2, CaSO4, MgCl2, MgSO4) on wettability.
• Simulations were conducted as a function of salinity and pH.

Main Results:

• The electrical double layer significantly influences crude oil detachment from the calcite surface.
• Divalent ion salts (CaCl2, CaSO4, MgCl2, MgSO4) do not form an electrical double layer on calcite.
• Monovalent ion salts (NaCl, Na2SO4) successfully form an electrical double layer.
• Calcite's affinity for non-polar crude oil is independent of salinity.
• Calcite's affinity for polar crude oil is sensitive to salinity and pH.

Conclusions:

• The formation of an electrical double layer by specific salts is key to smart water injection mechanisms.
• Salinity and pH are critical parameters for optimizing the interaction between polar crude oil and calcite.
• Findings offer insights for enhancing oil recovery processes through tailored smart water injection strategies.