Modelo geológico para la FM. Bajo Barreal (cretácico): integración y optiMización entre datos de superFicie y suBsuelo. cuenca del golFo san jorge, provincia de santa cruz, argentina

FERREIRA, L.; SANTANGELO, A.; GEORGIEFF, S.M.

Mar del Plata

Congreso; VIII Congreso de Exploración y Desarrollo de Hidrocarburos; 2011

Instituto Argentino del Petróleo y del Gas

La paginación del trabajo es: 327-352, el archivo pdf excede el límite permitido para la carga y por eso sólo se incluyen las páginas del principio y final. The outcrops from Bajo Barreal Formation (Cretacic) located around the Sin Nombre lagoon can be correlated in the subsurface with hydrocarbon reservoirs belonging to Cerro Guadal Norte oil field, in the Basin of San Jorge’s Gulf (Chubut and Santa Cruz provinces, Argentina) assuming this as one of the main productive formations in the basin these days. The outcrops allow to quantitative reconstruct the fluvial deposits and compare them with the well information from Cerro Guadal Norte oil field (YPF S.A.) using different methods of subsurface data capturing. A stratigraphic log was measured in the outcrops and 15 fluvial sandstone bodies were recorded. The correlation between outcrops and a near oil well is proposed by using seismic sections. The distance from the outcrops to the wells is about 600 mts. The layers dip towards east with angles between 45° and 15°, the deposits were described by means of lateral short profiles, the thickness of the sand bodies varies from 1,5 to 3 mts. and also show apparent thicknesses from ten to hundred mts. The paleocurrent measurements indicate that the outcrops are perpendicular to oblique concerning the flow direction. The seismic slices permitted the correlation between surface and subsurface. This way, analog stratigraphic sections were defined and different studies on electric profiles, well images and cutting took place. The images allowed to define synthetic stratigraphic profiles, calculate thickness, identify sedimentary structures, estimate paleocurrent directions and also associate them with resistivity-sp profiles. Once the subsurface analog stratigraphic section was defined, seismic slices were displayed considering the amplitude as a seismic attribute in order to use it to define fluvial geoforms (Santangelo et al., 2009). From the information obtained from the outcrops and the geoforms identified on the seismic horizons, it was possible to obtain the thickness and sinuosity of the fluvial sand bodies, which exposed values from 150 to 250 mts. for the thicknesses and 1.15 to 1.35 for the sinuosity. The obtained information was compared with the equations proposed by Bridge and Tye (2000) (width) and the sin function (sinuosity). For the first case, the thicknesses were overestimated on a 25% whereas the sinuosity values were underestimated on 0.2-0.3. By comparing the surface deposits with the images, it was possible to make a facies analysis and define the presence of fluvial bars and channels. Petrology, diagenesis and petrophysical (porosity measurement and estimation of permeability) of hydrocarbon bearing sands allowed to know the characteristics of the sand bodies carrying Hc and plan the right way of development. The integration of data from different sources (surface and subsurface) enable to optimize the proposal of a quantitative sedimentary model for Bajo Barreal Formation, being this a fundamental backup on the characterization of the reservoirs in the actual development fields.