Use of Sacrificial Agents to Reduce Carboxymethylated Ethoxylated Surfactant Loss during Chemical Flooding.

摘要

Surfactant losses of carboxymethylated ethoxylated surfactants (CME) were measured in static and coreflood experiments. The effect of several types of sacrificial agents on CME adsorption were also measured. In static tests, lignosulfonate and sodium carbonate/bicarbonate were effective sacrificial agents at low salinity or low temperature conditions. Under these conditions, surfactant loss was mainly a result of adsorption on the rock surface. However, these agents were less effective at higher salinities and temperatures where surfactant phase separation becomes an important mechanism for surfactant loss. Similar results were observed in oil recovery experiments using Berea sandstone cores and dodecane. However, under conditions which favored low surfactant retention, the surfactant was ineffective in mobilizing oil. Under conditions which produced at least some oil from the core, surfactant losses were excessively high. The most successful oil recovery conditions were observed using a CME in solution with pH adjusted to the pK(sub a) of the carboxylate group (pH = 4.6 for a CME surfactant with an average of 6.5 ethoxylate groups per molecule). This may help balance the surfactant affinity for both oil and brine. 16 refs., 12 figs., 11 tabs.