Everyone with a water faucet knows the nuisance of limescale, the chalky deposits of minerals that tend to build up inside of water heaters, pipes and pots. If left untreated, limescale can obstruct the flow of water through pipes and cause serious damage to various components of water lines and water heating systems.
Similarly, mineral scaling inside of oil wells poses significant obstacles to efficiently extracting energy resources. Naturally-occurring minerals inside of oil wells can collect on the surface of rocks, equipment or pipes, forming a coating similar to limescale. The build up of mineral scale inside of oil wells can drastically hinder the flow of oil out of the well and compromise the effectiveness of oil production equipment.
A researcher at the UH Cullen College of Engineering is currently collaborating with researchers from multiple universities and national labs on a major Department of Energy (DOE) project to tackle one of the biggest challenges in the energy industry—controlling mineral scaling to improve oil production efficiency.
Yandi Hu, assistant professor of civil and environmental engineering, was awarded a three-year, $204,000 research project to study the growth of barium sulfate, a scale-forming mineral commonly found inside of oil wells and reservoirs. Hu serves as a co-principal investigator (PI) on the project, which is led by PI Andrew Stack of Oak Ridge National Laboratory. Hu’s research group goal is to reveal the fundamentals of barium sulfate scale formation to better control mineral scaling in oil production processes and sites.
“We’re looking at the nucleation and growth—the initial stages—to understand how barium sulfate starts to form on the rocks’ surfaces,” she said.
Barium sulfate scaling occurs inside of an oil well when the mineral precipitates. In severe cases, the scaling can form solid mineral deposits on the surface of production equipment and inside of production piping, rendering the equipment ineffective and sometimes plugging the piping completely.
Even in milder cases, the precipitation of barium sulfate causes massive headaches for oil producers. In the hydraulic fracturing process, wherein liquid is injected at high pressure into shale, a thin layer of oil-rich rock, scaling can restrict or block the flow of oil through the rock’s tight pores and cracks.
Although scale removal is common for oil well operation, current methods are costly and limited in effectiveness. Producers can add polymers, for instance, to inhibit the production of barium sulfate, but the method is expensive and difficult to control, sometimes even leading to a permanent decrease in oil production in a reservoir.
Hu will conduct laboratory experiments on synthetic organic coatings on rock surfaces to understand the fundamental growth mechanisms of barium sulfate mineral scale formations in oil and gas reservoirs at the molecular level. Her experiments will take into account various conditions, such as the presence of impurity ions like Strontium and Radium, as well as the presence of inhibitors and other organic materials inside of the well that could impact scale formation.
“Once we have such fundamental understanding, we can better predict and control what’s happening in the subsurface environment,” she said. “With this data we can give some useful suggestions about the selection of the operation conditions and how industry can design the appropriate inhibitors. We are providing the basis for further applications.”