--> --> Characterization of the porous system of Oligo-Miocene, carbonate and siliciclastic sequences in “La Vela” offshore field, Venezuela

AAPG Latin America and Caribbean Region Geoscience Technology Workshop

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Characterization of the porous system of Oligo-Miocene, carbonate and siliciclastic sequences in “La Vela” offshore field, Venezuela

Abstract

The offshore field “La Vela”, in Venezuela, presents siliciclastic and carbonate deposits ranging from medium to condensed, arranged on an igneous metamorphic base. This research seeks to define petrophysical parameters and models, describe petrofacies, analyze rock’s quality and observe the distribution of isoproperties in the field, with the objective to characterize the porous system in deposits of interest of Oligo-Miocene age. An integrated petrophysical evaluation was applied, which focused on the interpretation of well profiles in conjunction with electrical measurements and capillary pressure tests by mercury injection, based on a total of 80 samples analyzed with different tests. All of this while keeping into account the sedimentary units within the seismoestratigraphic sequences. As a result, the obtained parameter "m" allowed to calculate hydrocarbon saturation with a lower degree of uncertainty. This parameter with a value less than two is associated with porosity due to fracture and the presence of authigenic minerals; these indications of secondary porosity were also evidenced from the detailed interpretation of well logs, including thin sections. Microfracturing of particles plays an important role within the field since it interconnects the poral system, which generally includes porosity intraparticle, interparticle, moldic, and micro vugular, although these last two are extremely localized. Capillary pressure tests indicate diversity in petrophysical facies ranging from nano to mega pores. It is then concluded that rock genesis and the diagenetic processes affected pore geometry and architecture. For this reason, the dominant petrofacies together with diagenetic processes, demarcate and impact rock quality. Once the proposal is detailed, its relevance for the present workshop is explained: Globally, in the oil area, more and more challenges arise to determine the best practices and development strategies of our complex deposits. In the last decades Brazil has discovered new fields giving room to the scientific, technological and innovation development of the continent; experts indicate that reservoir characterization using modern multi-disciplinary data analysis as the key to optimizing hydrocarbon production. This qualifies the workflow raised in this research as relevant to identify previously undetected reserves by bringing an important contribution to the challenges of achieving integrated petrophysical, seismoestratigraphic and sedimentological information to facilitate decisions related to the field exploitation.