Performance of Polyamidoamine-Enhanced Inhibitor in Mitigating Silicate Scale from Alkaline Surfactant Polymer (ASP) Flooding

Abstract

Alkaline surfactant polymer (ASP) flooding is an effective chemical enhanced oil recovery technique to recover more hydrocarbon from maturing oilfields. However, the alkaline slug with high pH would dissolve quartz mineral in the sandstone formation which will result in silicate scaling issue. Silicate scales would precipitate in the formation near the production wellbore region, and further deposit inside production equipment and facilities. Consequently, the productivity of a well will be impeded. Scaling issues can be treated using chemical scale inhibitor (SI) through the application of squeeze treatment, continuous injection, or both. Many commercial SI available are not intended to mitigate silicate scale and these chemicals possess low biodegradability. Hence, more environment-friendly or "green" SI are being developed and tested for their effectiveness on scale inhibition. This paper aims to evaluate the performance of developed green silicate SI in mitigating silicate scale formation. The developed green silicate SI are composed of pteroyl-L-glutamic acid (PteGlu) that has enhanced with polyamidoamine dendrimers, either PAMAM-1.0 or PAMAM-2.0. Several experiments are conducted to assess the SI compatibility with synthetic brines, SI thermal stability, as well as SI effectiveness in treating silicate scale formation in static and dynamic conditions. Static adsorption test is also performed to determine the potential of developed green silicate SI for squeeze treatment. Results revealed that all tested SI are compatible with different synthetic brines. Among all, PAMAM-2.0-PteGlu SI yielded the best laboratory results at its optimum ratio of 1:333. It has the highest thermal stability as it experienced 34% weight loss at temperature 95°C. This SI also achieved 73.1% effectiveness in static scale inhibition test. From dynamic tube blocking experiment, it also managed to delay silicate scale precipitation by 48 times longer than the base case. Besides that, the adsorption capacity of PteGlu SI on crushed sandstone is also improved by approximately 60% with the addition of PAMAM-2.0. The green silicate SI developed in this paper could be utilized as environment-friendly alternatives in silicate scale control.