Isothermal Titration Calorimetry Study of Brine–Oil–Rock Interactions

Abstract

Isothermal titration calorimetry (ITC) is a technique that allows us to accurately determine the thermodynamic parameters that characterize a binding interaction between two molecular systems. However, this technique has not had a wide application in petroleum science. This study is an attempt to determine the adhesion of different fluids onto a rock surface through ITC experiments. Two artificial brines with different ionic composition were titrated into chalk powder, and then crude oil was added to those systems in order to mimic the processes that take place in an oil reservoir. In addition, the wettability alteration process associated with smart water flooding was investigated from a thermodynamic point of view. The results from the ITC experiments suggest that the interaction between smart water and chalk + brine + oil systems is both exothermic and endothermic. The exothermic heat response indicates chemisorption of sulfate (SO4 2–) onto the mineral lattice, whereas the endothermic response proved the substitution of carboxylate complexes from the chalk surface by magnesium (Mg2+). The ITC results also show that the performance of diluted seawater seems to be higher than smart water with increased sulfate concentration. This is due to dynamic processes like brine dilution resulting in an increased osmotic pressure.

Impact of Compositional Differences in Chalk and Water Content on Advanced Water Flooding: A Microcalorimetrical Assessment

“…Crude Oil. A similar portion of crude oil as specified in Cobos et al 22 was used in the microcalorimetry experiments. A Tiamo 2.4, Metrohm autotitrator unit was used to measure the acid number (AN) and basic number (BN).…”

“…Material obtained by Dankalk A/S from a quarry in Aggersund, Denmark. 22 The formation is a Maastrichtian coccolith zone which exhibits a totally bioturbated ichnofabric. 24 Stevns Klint chalk.…”

“…This synthetic CaCO 3 has purity of 99%. A similar procedure described by Cobos et al 22 was used to prepare Dan chalk and Stevns Klint chalk materials. The chalk material was grounded with a ceramic ball mill and sieved to mesh between 50 and 100 μm.…”

“…The TAM IV instrument is equipped with a thermostat with an accuracy of ±0.1 °C and precision of ±100 nW. 22 In the ITC experiments, 100 mg of different chalk samples was placed in a stainless steel cell. Then, 150 μL of VB was added to the chalk particles.…”

“…Three outcrop rocks (pure biogenic calcite) were investigated: Dan chalk, Stevns Klint chalk, Austin chalk, and synthetic chalk. As in a previous publication, 22 isothermal titration calorimetry (ITC) was used to get the direct interaction enthalpy values (ΔH) for the complex rock−brine and oil−brine systems. Those enthalpy values also took into consideration the mixing of fluids that occur when an advanced fluid (diluted seawater or smart water) is injected into a reservoir that already contains a highly saline brine (connate water).…”