Impacts of Smart Waters on Calcite–Crude Oil Interactions Quantified by “Soft Tip” Atomic Force Microscopy (AFM) and Surface Complexation Modeling (SCM)

Abstract

The interactions of calcite surface with crude oil are influenced by the ionic chemistry of the injection water in "smart water" flooding; however, the molecular evidence of their influences is missing in the current studies. To address this issue, we measured the calcite−oil interactions in four kinds of smart waters by driving a droplet of crude oil ("soft tip") toward and away from the calcite surface using atomic force microscopy (AFM). The force behaviors showed that the calcite−oil interactions were repulsive in smart waters containing low concentrations of Ca 2+ ions, such as seawater (SW) and seawater with one-fourth of Ca 2+ concentration (SWCa), which have produced extremely weak adhesions and works of adhesion in these two brines. In contrast, the force curves showed "jump-in" behavior in seawater with four times increased SO 4 2− concentration (SWSO) or Mg 2+ concentration decreased to one-fourth (SWMg) compared to SW, which has produced extremely large adhesions and works of adhesion. The underlying reasons for calcite−oil interactions in response to different smart waters were investigated by the method of surface complexation modeling (SCM), which combined a charge-distribution multisite ion complexation (CD-MUSIC) model and a basic Stern model (BSM) to describe the complex electrochemical reactions of calcite, smart water, and crude oil. The adhesion energies were calculated based on the surface complexations, which showed good agreements with the AFM force results. The SCM results suggested that the weak calcite−oil interactions in SW and SWCa solutions can be attributed to the mitigation of cation (Ca 2+ ) bridging interactions owing to a deficiency in surface Ca 2+ ions. The strong calcite−oil interactions in SWSO and SWMg solutions are caused by a dramatic increase of cation (Ca 2+ ) bridging interactions due to an excess of surface Ca 2+ ions. Overall, the attractions of calcite surface with crude oil follow the order SWCa < SW ≪ SWMg < SWSO, which infers that the oil molecules may be easily displaced from the calcite surface with smart waters containing low concentrations of Ca 2+ and SO 4 2− ions but high concentrations of Mg 2+ ions.

Ionic Interactions at the Crude Oil–Brine–Rock Interfaces Using Different Surface Complexation Models and DLVO Theory: Application to Carbonate Wettability

“…More details on the relevant equations in the TLM model can be found in the literature. 34 , 78 , 85 The DLM presented in this work had been shown in our previous publications with all of the relevant reactions and equations. 11 , 19 , 27 …”

“…This interaction also formed the oil–brine interface. The electrostatic interaction at the rock–brine interface was assembled using a pure and smooth calcite surface by assuming >CaOH and >CO 3 H as the primary hydration sites. ,,,, For the oil–brine interface, −COOH and −NH were assumed as the hydration sites, representing the carboxylic and amine groups, respectively, of a crude oil molecule. ,,,, The charge distribution (Table ), which indicated the placement of ions on different planes, was modeled similar to the approach by Ding and co-workers , and Heberling et al, , for the calcite–brine interface, and Takeya et al for the oil–brine interface. Δ Z i value for each plane in the TLM was used to represent the transfer and sharing of net charge from one plane to the next based on the understanding of ionic placement in the calcite–brine and oil–brine planes.…”

“…In this work, since the ionic strengths of the brines used were in the range of seawater (∼1.1 M), it was justifiable to use a constant capacitance for the calculations. More details on the relevant equations in the TLM model can be found in the literature. ,, The DLM presented in this work had been shown in our previous publications with all of the relevant reactions and equations. ,, …”

Pore-Scale Investigation of the Ion-Tuned Water Effect on the Surface Properties of Limestone Reservoirs

“…Academia and the industry experts have been using spontaneous imbibition, core flooding, atomic force microscopy, zeta potentiometry, and sessile drop contact angle measurements to study the effect of the ion-tuned water flooding. − These studies can be grouped into two categories: macroscale and micro- to nanoscale. The former studies analyze the relationship between the injected and the produced fluids while the latter focus on nanoscale surface properties, though there have been several issues with upscaling the nanoscale surface properties …”

Surface Complexation Modelling of Wettability Alteration during Carbonated Water Flooding

“…SCM has proved useful in understanding the mechanisms in wettability alterations for low salinity water [20][21][22][23], smart water [24], and carbonated water in calcite in more recent studies [25,26]. SCM has successfully been used to capture the trend for some laboratory measurements such as flotation test, zeta potential (ζ-potential), and recently contact angle measurements [21,27,28].…”