Impact of Asphaltenes on Contact-Angle Variations and Surface Topography and Composition

Summary The asphaltene precipitation affects the rock/fluid interaction in a live-oil reservoir, which has a significant effect on oil recovery and flow in the production network. In this work, we examine the changes in interfacial properties (such as contact angle between the live-oil, brine, and quartz system) as well as surface topography and compositions caused by asphaltene precipitations that are related to pressure-depletion processes. The experimental method is based on the pendant-drop-shape method using a high-resolution camera for quantitative image analysis and a high-resolution digital-pressure transducer in a high-pressure high-temperature fluid cell. The contact angle with quartz was measured in the presence of deionized water as the surrounding medium at isothermal condition. The experiments were conducted in a pressure-depletion fashion, where pressure is decreased in steps capturing the asphaltene onset pressure (AOP). At each pressure stage, sufficient time was given to stabilize the contact angle. The transient experimental contact-angle data for a system containing a live oil, brine, and quartz is presented. In particular, we Show that the time of stabilization and contact angle decreases at sequential pressure steps, except near the vicinity of AOP where they have a sharp jump signifying the effect of asphaltene precipitation Use the solubility-parameter approach for asphaltene modeling to predict asphaltene precipitation from live oil at pressures between the saturation point and AOP Relate the amount of precipitation with change in interfacial properties, such as interfacial tension (IFT) and contact angle Use image-analysis techniques such as scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) to analyze the topography and composition of the quartz surface after asphaltene deposition to supplement our observation Despite that asphaltene effects on wettability alteration have been proposed, this is the first experimental evidence that pressure-depletion-driven asphaltene precipitation alters the contact angle at realistic reservoir conditions (high-pressure high-temperature live oils). These data can be used as a basis to establish the benchmark data, model calibration for managing and preventing remediation asphaltene problems, and to design the proper facility and operating conditions for efficient recovery and operational processes.