Initial screening of new generation chemicals using sandpack flooding tests for recovery improvement of gravity driven steam applications

Abstract

Reservoirs containing very heavy oil or extremely heterogeneous/fractured geology are not convenient for steam flooding and even cyclic steam injection. But, steam can be used to heat the reservoir and accelerate the recovery by gravity drainage. Two well-known applications of this method are steam assisted gravity drainage (SAGD) and thermally assisted gas oil gravity drainage. Although the latter is not commercially applied, the former is a proven technology with remarkable production in Canada and Venezuela. An alternative is to use chemicals as suggested a few decades ago to alter the interfacial forces and improve microscopic displacement. This paper presents experimental results on testing – the new generation – chemicals for their capability in recovery improvement.Sandpack experiments were conducted to evaluate the incremental in oil recovery by chemical additives compared to sole steam injection. Steam and chemicals were heated and introduced to the system from separate channels at the entrance of the vertically situated sandpack (4 inch length, 2 inch in diameter). The chemicals used include thermally stable surface agents, such as anionic surfactants (AAS J1111, O352, LTS-18), non-ionic surfactants (Tween80/85, Span80/85, Novelfroth190, Triton X-100), a biodiesel (FAME), ionic liquid (BMMIM BF4), high pH solution (NaBO2), solvent (heptane, DME), and nanoparticles (SiO2). The oil selected was 27,000 cP crude.Incremental recoveries were monitored and related to the thermal stability and commercial prices of the chemicals. A comparative analysis was provided as to their contribution to the reduction of the cost (lower SOR) and chemicals were classified based on their recovery improvement performance and thermal stability using thermogravimetric analysis (TGA). Through this experimental schematic, the highest increase in oil recovery was achieved by heptane which was also cheap in comparison to the other tested chemicals. Asphaltene precipitation was quantified by conducting SARA analysis of samples taken from the sandpack flooding experiments. The nanoparticle was placed initially into the core holder and had the second-best performances in the steam-to-oil ratio (SOR). Biodiesel also improved oil recovery, but the effects need to be further investigated. The non-ionic surfactants showed great thermal stability and Span80, Tween80, as well as Novelfroth190, lowered the SOR by improving oil recovery. On the other hand, the injection of LTS-18 as anionic surfactant showed an increment of ultimate oil recovery by around 3%. As a wettability modifier, the ionic liquid proved to be profitable in rising oil recovery from the sandpack experiment in a tertiary and an initial injection attempt; however, the ionic liquid is the most cost-effective chemical of the tested candidates.