Three sources of soil with different petroleum contamination ages were studied in an oil field in the province of Santander, Colombia. All the studied soils showed rapid infiltration and high permeability, characteristics of sandy soils. Nonetheless, water retention capacity and porosity were affected by the hydrophobic character of the hydrocarbons. The carbon-nitrogen-phosphorus ratio, temperature and pH evaluated in the contaminated soils, showed optimum values, adequate for bioremediation processes. The best results, in terms of hydrocarbon elimination (42.6%), were obtained when the soils were treated separately, mixed with clean soil, lacking not only the addition of the selected and enlarged mixed microbial pool, but also the pre-treatment with the bio-surfactant, which was composed by bacteria of the genus Serratia. The soil mixture composed of 50% of the soil with the oldest contamination, and an equal 25% proportion of both the medium and shortest contamination age soils, showed a total petroleum hydrocarbon (TPH) elimination percentage of 28,6%. This soil underwent one week of pretreatment process, and a mixed microbial pool addition at the beginning and half way through a three-week biodegradation treatment period. An independent remediation treatment, without addition of both pre-treatment and microbial pool was conceived for the initial treatment design. However, considering that biodegrading soil solely as a mixture of contaminated soils avoids the transfer of contaminants to the clean soil, and that the best treatment using this technique reached a 3,0% content of total hydrocarbons (value recommended by the Louisiana 29B regulation), this treatment was recommended combined with the optimum treatment conditions obtained.