In April, downhole chemical technology provider Flotek Industries acquired water-based, drilling fluid-additive technology from ARC Drilling Fluids. Flotek hopes to use the technology, which it markets as Microsolutions, in areas where using oil-based drilling fluids have traditionally been the only option. Drilling fluids that use water as a base are far cheaper than oil-based fluids, making them more desirable, but oil is less reactive with many rock formations.
The technology is described as a “complex nanofluid” made up of a mixture of solvents and surfactants that reverse the reactivity of water. When combined, the substances form a nano-emulsion that is added to a water-based drilling fluid in concentrations as low as 0.2% to 0.5%. The fluid is being sold through Flotek’s chemical division, CESI Chemical. After being used in North America for nearly a decade by ARC and its clients, CESI is now taking the technology abroad to oil companies in the Middle East and elsewhere.
When water-based drilling fluids react with the clay inside the shale, the clay swells, weakening the fabric of the wellbore, which can lead to mechanical failures downhole. In some cases, clay represents as much as 60% of the weight of shale rock. Clay swelling is a serious problem that has negatively skewed the economics of emerging shale plays, including the Niobrara shale in Colorado, the Cline shale in west Texas, and the Tuscaloosa Marine shale in Louisiana.
“When the drill bit exposes new clay, that clay is super dry,” said Michael Bryan, an account executive at CESI. “It wants to, by capillary action, pull water out of the drilling fluid. That is why so many people use oil-based systems—because it suppresses this problem.”
When clay in a well begins to swell and expand, the wellbore begins to “pinch” the drillstring, Bryan explained. The problem can worsen when larger chunks of the wellbore begin to break off, exposing more virgin clay to water and increasing the potential for large voids in the wellbore to form. And, because clay is so dense, Bryan said bulk surfactants are not easily absorbed into the near-wellbore area. However, nanoparticles are so small that they can flow into the dense clay, carrying with them clay-stabilizing chemicals. “The nanofluid is a delivery mechanism, delivering our solvent,” he said.
The solvent is called d-Limonene, which is extruded from orange oil. Flotek says it not only provides a stronger wellbore, but also helps aid production by reducing the viscosity of the oil in shale, and is combined with a surfactant that helps reduce interfacial tensions of the oil and water in place.
