The use of MDEA-based solvents has allowed the processing scheme of the sour natural gases treated at the Lacq plant to be modified, leading to substantial savings in operating costs. Compared to the well known SNPA-DEA process, the new MDEA-based solvents meet the same performance requirements as regards H2S and CO2 removal, but are far more economic in terms of energy consumption. MDEA is used to selectively remove H2S from the gas, while activated MDEA is used when total acid gas removal is necessary. The adequate activator has been selected from among a series of products, according to the actual plant specificity. Optimization of the process has included the selection of the proper contacting device: for this mass transfer enhanced by chemical first order reaction, structured packings have proven to be more efficient than trays.