ICE 2022


The Boicobo structure lies northwest of the Margarita(MGR)/Huacaya(HCY) gas-condensate field, in the southern sub-Andean zone of Bolivia. The structure, interpreted as a three-way dip, fault-dependent closure, is the northwestern continuation of the MGR/HCY duplex system. A major thrust fault separates Boicobo from the backlimb of the Huacaya structure. The BCS-X1ST exploration well, drilled in 2020, targeted this structure and encountered a gas condensate accumulation in the naturally-fractured sandstones of the well-known Devonian Huamampampa Fm. The major thrust fault that separates the Boicobo and Margarita/Huacaya structures has been interpreted in 3D seismic data. While the drill-stem test conducted at BCS-X1ST did not show clear indications of nearby faults during the main build-up phase, the measured fluid properties are notably distinct when compared to adjacent accumulations. Furthermore, there is ~100 m difference between the gas–water contacts of the Huacaya field and the Boicobo discovery. This has spurred a multi-disciplinary effort, based on post-drill analyses, to better understand the geological and geochemical characteristics of the gas condensate accumulation in the Huamampampa reservoir found at the BCS-X1ST location, principally aimed at pinpointing its relationships with neighboring structures and petroleum accumulations. This contribution will summarize some of the outcomes of this multi-disciplinary study, including: 1.Structural interpretation and modelling, geological mapping and integration with published and newly-acquired thermochronological data, which indicate that the thrust fault separating Boicobo and Huacaya was developed in the last 3 Ma. 2.A fault juxtaposition analysis performed for the fault plane which is interpreted to separate the Boicobo and Huacaya structures. shows a favorable fault seal juxtaposition of the Huamampampa sandstones (hanging wall) against the Los Monos seal (footwall), with only three relatively small areas with juxtaposition of reservoir intervals. 3.A geochemical assessment of reservoir compartmentalization using oil and gas separator samples from the Huacaya-2ST and BCS-X1ST wells. Oils were investigated using bulk fraction characterization, whole oil high-resolution gas chromatography and gas chromatography–mass spectrometry. Gases were analyzed by gas chromatography and gas chromatography–isotope ratio mass spectrometry. Data were processed and integrated to characterize their similarities.