Geochemical Characterization of Oil Spills Samples and Oil Samples from Wells Adjacent Areas in Order to Determine the Origin by Oil-Oil Correlation, Two Case Studies, Monagas, Venezuela

The geochemical characterization is a specialty widely used in the oil industry, with multiple applications that help to understand the petroleum system in the area. Below are two study cases, in which geochemical characterization was applied to determine the source of oil spills, in the area North of Monagas in Venezuela. The samples were analyzed by general and special geochemical techniques, to determine the origin and maturity of these, as well as any possible oil-oil correlation, to determine the source of the spill.

For the evaluation and characterization of the samples collected, the following analytical methods were carried out: SARA, gas chromatographic on saturates fraction (GC), and gas chromatographic- mass spectrometry (GC-MS) of saturates and aromatic fraction.

The first Case is about geochemical characteristics of an oil sample A-1 from a spill in area C and a oil sample B-1 from well B located in the area C. The results showed clear differences between the samples, indicating a negative oil-oil correlation between oil samples A and B, which indicates that the oil sample A does not come from wells in the area, although samples are associated with a carbonate rock deposited under anoxic conditions and a marine origin, the differences were found in the maturity and biodegradation.

The second Case is about geochemical characteristics of oil seepage samples E-1, E-2, E-3, E-4, E-5, E-6, detected in the field D and an oil sample F-1, from well F, located in the field D, in order to conduct an evaluation to determine if these oil samples correspond to oil seepages or oil spills caused by abandoned wells in the area. The results suggest that the oil seepage samples and the well oil sample are positively correlated, indicating that the abandoned well is leaking oil, in addition, the characterization determined that the samples are associated with a carbonate rock deposited under anoxic conditions, a marine origin and maturity is between early and oil window. Besides the lack of paraffins and isoprenoids and the presence of the compound 25-Norhopane established that the samples show a high degree of alteration (grade 8) due to the effect of biodegradation and / or oxidation of the compounds.
 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California