Impact of Rock Aging Time on the Initial Wettability of Minerals and Analogue Rocks Using Pre-Salt Fluids Under Reservoir Conditions

Abstract

Wettability is an important property in reservoir characterization. For the heterogeneous carbonate reservoirs in the Brazilian Pre-Salt, parameters that represent wettability are needed to obtain improved reservoir models. In this work, we applied contact angle measurements to analyze rock-fluid interactions between synthetic brine, crude oil from a Pre-Salt field and rocks and minerals with similar characteristics to the Pre-Salt formations. We studied the effects of aging time on different solid substrates. We found that, even though unaged quartz showed greater interaction with the high basic number oil than carbonates, it re mained water-wet for different aging times. On the other hand, calcite and coquinas had increasing contact angles with aging times and were strongly oil-wet after 30 days aging. This evidences that the interactions between acid compounds in the oil and basic sites in the substrate are strong enough to disrupt the water film after aging for 30 days. Therefore, under the Pre-Salt conditions studied in this work, these carbonate rocks and minerals should be considered as preferentially oil-wet.