Neutral wet proppant plays a pivotal role in maximizing the flow back of fracturing fluids and the recovery of produced hydrocarbons. An accurate and repeatable contact angle measurements are extremely challenging because of proppant spherical shape and small size. This paper presents a methodology of direct contact angle measurements in spherical particles examined with high strength coated ceramic proppant.
20/40 and 25 HSP non coated proppants were used for the study. Coating material was applied to the proppant sample to obtain non-wetting characteristics. KRUSS Drop shape Analyzer was utilized to measure the contact angle using a modified pendent drop method. Step by step procedure is detailed and possible sources of errors were identified, and recommendations were introduced accordingly.
HSP coated proppant showed contact angle measurements of 117-120° and 84-114° with deionized water and hydrocarbon samples, respectively. Ideally, a neutrally wetted surface would have a contact angle of 90°. This indicates that the proppant is neutral to slightly oil-wet. Wetting characteristics are dependent of hydrocarbon type. For instance, Condensate 2 have a contact angle of 102.3° indicating neutral wetting characteristics, whereas Condensate 3 shows contact angle of 84.5° indicating slightly oil-wet character. Geometry of hydrocarbon droplets modified the adhesion tension of oil, nevertheless had insignificant effect with water drops. For example, tripling the droplet size of Condensate 2 and Diesel resulted in increment in contact angle values of 12° and 15°, respectively.