Researchers at the University of Houston and Petroleum University in Chengdu have developed a new nanofluid for use in EOR, with some heady results.
With new drilling slowing down dramatically, more will have to be made of old wells. Beyond secondary recovery using water flooding, however, enhanced oil recovery (EOR) techniques tend to take over, and making such procedures cheaper will be vital to ensuring output in the next few years. Some academic efforts have recently borne fruit.
Researchers at the University of Houston (UH) have recently published a paper describing “a nanotechnology-based solution” which could increase tertiary oil recovery by 15%, and reduce the amount of additional fluid pumped downhole. Best of all for beleaguered shale producers, its investors say it can be deployed “at low cost.”
The researchers’ paper, published in June in the Proceedings of the National Academy of Sciences, argues that graphene-based Janus amphiphilic nanosheets can match and outperform conventional chemical and other nanotechnology solutions.
So-called Janus particles possess two or more physical properties, allowing different types of chemistry to occur on the same particle: in the case of these nanosheets, that means both hydrophobic and hydrophilic qualities. In a press statement, co-author and UH graduate student Dan Luo explained that when fluid meets with the brine/oil mixture in the reservoir, the nanosheets in the fluid spontaneously go to the interface, reducing interfacial tension and aiding oil flow towards the production well.
Because of its Janus and amphiphilic qualities, in certain conditions the nanosheet-based fluid also forms a strong elastic and recoverable film at the oil and water interface, instead of forming an emulsion.
M D Anderson Chair professor of physics Zhifeng Ren, the paper’s lead author, explained the current understanding of the process via email, commenting: “Our speculation is that the amphiphilic nature makes the surfactant able to only stay at the interface of water and oil when both are present at the same time, even though it can uniformly distribute in either water or oil.”
In tests, it has been fairly effective. Ren highlighted that existing nanofluids used for tertiary recovery shift less than 5% of the remaining oil in place when used at a 0.01% concentration. At the same concentration, experiments with the group’s nanosheet show recoveries of 15% – comparable to existing chemical methods and three times more efficient than rival nanofluids.
That improvement in efficiency permits the same (or greater) amount of oil recovery with one third the amount of fluid – a major saving on fluid purchasing, logistics and pumping volume, though the team has not calculated any direct cost comparisons.
From an environmental standpoint, as the authors note, it also reduces the concentrations of polymers, surfactants and other fluids used downhole. Indeed, the authors note: “We anticipate that this work will bring simple nanofluid flooding at low concentration to the stage of oilfield practice, which could result in oil being recovered in a more environmentally friendly and cost-effective manner.” Beyond the initial tests, Ren confirmed that higher concentrations of the fluid could raise recovery rates even higher, “but higher concentrations would mean higher cost owing to more usage of the surfactant.”
The research is a joint effort between Luo and fellow UH graduate student Yuan Liu, principal investigator at the Texas Center for Superconductivity at UH, and Zhifeng Ren, as well as researchers Feng Wang and Feng Cao, and UH professor of Chemical and Biomolecular Engineering Richard C Willson. Other authors, from China’s Southwest Petroleum University in Chengdu, include Jingyi Zhu, Xiaogang Li and Zhaozhong Yang.
According to Ren, the team is now working on a commercial product. The hope is that they can “scale up the surfactant and foster collaboration with oil companies.”
If it can be made commercially, it is likely to pique the interest of producers across the globe, especially Chinese producers in basins such as Daqing, where water flooding has been used for decades to shore up output, but which have recently offered diminishing returns. Indeed, in 2014 Daqing was put at the centre of a push to develop new polymers, surfactants and other EOR avenues. It may now be time to extend those efforts to include nanotechnology.
Ren’s scope remains larger still than China: he concludes bombastically that “our hope is to apply it to all the wells worldwide.”