Wellbores drilled to extract oil and gas can be significantly reinforced with a small amount of modified graphene nanoribbons added to a polymer and microwaved, according to Rice University researchers.
The Rice labs of chemist James Tour and civil and environmental engineer Rouzbeh Shahsavari combined the nanoribbons with an oil-based thermoset polymer intended to make wells more stable and cut production costs. When cured in place with low-power microwaves emanating from the drill assembly, the composite would plug the microscopic fractures that allow drilling fluid to seep through and destabilize the walls.
Results of their study appeared in the American Chemical Society journal ACS Applied Materials and Interfaces.
The researchers said that in the past, drillers have tried to plug fractures with mica, calcium carbonate, gilsonite and asphalt to little avail because the particles are too large and the method is not efficient enough to stabilize the wellbore.
In lab tests, a polymer-nanoribbon mixture was placed on a sandstone block, similar to the rock that is encountered in many wells. The team found that rapidly heating the graphene nanoribbons to more than 200 ˚C with a 30-watt microwave was enough to cause crosslinking in the polymer that had infiltrated the sandstone, Tour said. The microwave energy needed is just a fraction of that typically used by a kitchen appliance, he said.
This is a far more practical and cost-effective way to increase the stability of a well over a long period.—James Tour
In the lab, the nanoribbons were functionalized with polypropylene oxide to aid their dispersal in the polymer.
Mechanical tests on composite-reinforced sandstone showed the process increased its average strength from 5.8 to 13.3 megapascals, a 130% boost in this measurement of internal pressure, Shahsavari said. Similarly, the toughness of the composite increased by a factor of six.
Mechanical testing at smaller scales via nanoindentation exhibited even more local enhancement, mainly due to the strong interaction between nanoribbons and the polymer. This, combined with the filling effect of the nanoribbon-polymer into the pore spaces of the sandstone, led to the observed enhancements.—Rouzbeh Shahsavari
Lead authors of the paper are postdoctoral researcher Nam Dong Kim and graduate student Andrew Metzger, both of Rice. Co-authors are postdoctoral researchers Vahid Hejazi and Seoung-Ki Lee, graduate students Yilun Li and Ruquan Ye, alumni Jason Mann and Anton Kovalchuk and research scientist Carter Kittrell, all of Rice. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering. Shahsavari is an assistant professor of civil and environmental engineering and of materials science and nanoengineering.
MI-SWACO, a Schlumberger company, partially supported the research.
Nam Dong Kim, Andrew Metzger, Vahid Hejazi, Yilun Li, Anton Kovalchuk, Seoung-Ki Lee, Ruquan Ye, Jason A. Mann, Carter Kittrell, Rouzbeh Shahsavari, and James M. Tour (2016) “Microwave Heating of Functionalized Graphene Nanoribbons in Thermoset Polymers for Wellbore Reinforcement” ACS Applied Materials & Interfaces doi: 10.1021/acsami.6b01756