Evaluation of experimental methods to determine wettability
Abstract
Two methods to evaluate the wettability of carbonates have been investigated: Aqueous cationic surfactant
solutions contact angles on oil-wet calcite crystals, and imbibition time of surfactant drops into oil-wet outcrop
chalk slices, both immersed in n-decane during measurements. The procedure to measure contact angles offered
good repeatability, and the results were according to theory. However, the effectiveness of the surfactants was
ordered differently depending on which pure carboxylic acid was used to create oil-wet crystals, and it would
perhaps be desirable to use crude oil instead. The repeatability in the imbibition experiments was poor, and
water and/ or brine often imbibed faster than surfactants, this was attributed to weakly oil-wet chalk slices.
Ignoring water and brine, the effectiveness of the surfactants were ordered like in Amott-tests reported by
Standnes and Austad (2000). Overall in both experiments, C12TAB and C14TAB were the most effective
wettability modifiers. In the imbibition experiments, oil expulsion from the chalk slices was also observed.
Description
Master's thesis in Petroleum engineering