Scale is caused by the build-up of metal compounds that are not soluble in water. Claw-like organic molecular structures called chelates can tightly “grip” the metal ions, allowing scale to be prevented or removed. Chelates are already widely used in cleaning applications, such as laundry and personal care, and are now set to expand their applications into the oil and gas industry.
“In some projects, water injection is required to increase the amount of oil that is produced,” says Auribel Dos Santos, Well Production and Stimulation Engineer in AkzoNobel Specialty Chemicals’ Chelates business. “These injectors, located near the oil production well, force water into the ground, effectively ‘pushing’ more oil to the well and back up to the surface.”
Enhanced Oil Recovery (EOR) is a term used by the oil and gas industry which refers to a variety of practices designed to maximize an oil field's output. Injecting water, steam, gas, or chemicals increases the pressure in an oil field and reduces the viscosity of oil so that it flows easily and directly toward the surface.
But, due to constant exposure to water and ground elements, scale builds up in the injection systems. As scale builds up, more pressure is required to push the water through the system. “This is a real problem,” Auribel says. “With increasing pressure, less and less water can be injected without fracturing the rock and damaging the production wells, increasing operating costs and reducing efficiency of oil extraction.”
Traditionally, oil companies have used hydrochloric acid to remove the scale. However, this is a hazardous chemical which must be removed from the well before injection can resume, causing additional costs and lost time. Two companies approached AkzoNobel Specialty Chemicals with a challenge: find a way to remove the scale build-up in a safer, faster, and more efficient way.
These two companies, Colombia’s state-owned oil company, Ecopetrol, and US-based Occidental Petroleum Co, also known as Oxy, jointly operate the La Cira-Infantas Field located 250 km north of Bogotá, the capital of Colombia.
AkzoNobel’s proposed solution was to use our StimWell chelates. Based on natural and sustainable raw materials, these effectively clean the injection systems and can be left downhole once spent as they are non-toxic and readily biodegradable.
“Acids can damage the clay in reservoirs, causing it to weaken, break off, and cause more clogging in the formation. StimWell doesn’t cause any such damage,” Auribel explains. “Without the need for expensive and time-consuming flow-back to remove acids, operations can resume immediately after cleaning is complete.”
Tests by Ecopetrol and Oxy have confirmed that StimWell chelates provide a safe and effective way to remove scale build-up in water injection systems. The first pilot using StimWell resulted in a 52% increase in the “injectivity index”, a measure of the efficiency of the injection system, while two additional field tests showed increases up to 100%. “Now that we have strong proof of concept, Oxy is preparing to use StimWell to clean more wells,” Auribel says.
“This technology offers performance and environmental benefits to a wide range of industrial applications that involve the use of water, especially important in sensitive areas,” Auribel explains. “Furthermore, the global spread of our manufacturing facilities ensures that it can be delivered easily to any part of the world.”