Schlumberger announced at the 2009 International Petroleum Technology Conference the release of its new MaxCO3 Acid degradable diversion acid system. This new polymer-free, non-damaging acidizing system can be used for both matrix and fracture stimulation in carbonate reservoirs with permeability contrasts or natural fractures.
The MaxCO3 Acid system is designed to be used in oil or gas wells in both open-hole and cased-hole intervals, regardless of deviation. Treatment design, execution and evaluation are optimized using Schlumberger proprietary software applications.
The MaxCO3 Acid treatment was successfully applied to a major operator's well in the Khuff carbonate formation in Qatar's main North field reservoir (in the South Pars complex), the largest gas field in the world. Wells drilled in this thick, heterogenic reservoir are susceptible to large variations in transmissibility (kh). In addition, high permeability contrasts between zones are common -- up to a factor of 100 -- and the hydrostatic column of stimulation fluids in these typical, deep gas wells tend to stimulate the bottom zones at the expense of the upper reservoir layers.
"As part of our continued commitment to understand and improve productivity in carbonate reservoirs, our MaxCO3 Acid system offers breakthrough performance in reservoir stimulation and productivity enabling access to reserves that may otherwise have been left in place," said Lars Mangal, vice president, Stimulation Services, Schlumberger Well Services.
Applications of MaxCO3 Acid yielded a 500% production increase from an acid fracturing treatment in the Bluell formation in North Dakota. Elsewhere around the world, productivity increases in excess of 100% are frequently being achieved, with significant improvements being made to efficiency in operations. Treatment volumes were reduced by up to 50%, resulting in shorter well cleanup times and less flaring. Rig-related and operational times are typically reduced by 30% as a result of no requirement for multiple operations traditionally needed to perforate and stimulate the zones individually.
MaxCO3 Acid treatments can be bullheaded or pumped through coiled tubing, batch-mixed for small volume jobs or mixed on the fly for larger treatments. The treatment works effectively at low treatment rates and continues to stimulate as it degrades.