Characterization of carbonate facies and study of their relationship with dissolution and wettability in CO2 injection

Abstract

Hydrocarbon reserves can be found in porous reservoir rocks, which may be of siliciclastic or carbonate origin. Each type of rock presents its own characteristics, which directly impact the recovery of oil and gas. To better understand the heterogeneity of carbonate rocks, their geological processes and behavior of fluid flow, this work aims to characterize carbonate facies and simulate its behavior with the injection of carbonated water, evaluating the dissolution of the minerals and the superficial interactions, giving indications about the wettability of these facies. The characterization of the facies involved the observation of macro and micro images of the carbonate frameworks, identification of petrophysical characteristics and attribution to the reservoir rock. From this characterization, six facies models, three calcitic and three dolomitic, with different properties were chosen to be used in the simulation with a Surface Complexation Model (SCM) to identify the dissolution behavior of minerals and Total Bond Product (TBP) during the injection of carbonated water. This paper purpose is to analyze different carbonate facies and understand the relationship of these facies to the change in wettability due to CO2 injection. The facies were identified in four groups, travertine, biogenic, chemical, and reworked, that differ in their geological processes, identifying how the precipitation of minerals influences the geological structure. The mineral dissolution presented higher dissolution for the calcite mineral compared to dolomite, presenting significant differences between the facies and between the concentration of CO2 for both minerals. For the dissolution of kaolinite, which presented higher values when present in the dolomitic facies, significant differences were identified between the rocks, calcitic and dolomitic, between facies, between the concentrations of CO2 and the correlations between factors. The calculation of TBP, a factor that assesses oil-mineral adhesion and may interfere with rock wettability, indicated a decrease in the value as the porosity of the facies increases, however, the statistical analysis indicated that there is no significant difference between the carbon dioxide concentrations in the alteration of TBP. The results made it possible to achieve the proposed objectives, as well as to make room for subsequent discussions.