VARIABILIDAD PETROFÍSICA, GEOMECÁNICA Y GEOQUÍMICA DE DELTAS VOLCANICLÁSTICOS DE LA FORMACIÓN POZO D-129 EN LA SIERRA SILVA, CUENCA DEL GOLFO SAN JORGE

ALLARD JOSÉ; FOIX NICOLAS; BUETI SEBASTIAN; OLAZÁBAL SABRINA XIMENA

Mendoza

Congreso; 10 Congreso de Exploración y Desarrollo de Hidrocarburos; 2018

Instituto Argentino del Petróleo y del Gas

 ABSTRACT:Petrophysical,Geomechanical and Geochemical Variability of Volcaniclastic Delta Deposits fromPozo D-129 Formation at the Sierra Silva Outcrops, Golfo San Jorge Basin The Pozo D-129Formation is linked to the sedimentary filling of a big lake during the basalChubut Group (Barremian?-Aptian) in the Golfo San Jorge Basin. This unitincludes the main source rock of the basin as well as reservoirs rocksassociated with litoral lobes (deltas) and deep lobes (deep fans). The outcropsof these units are few and restricted to the San Bernardo Fold Belt. New observationsover the Cerro Kepi anticline expose deltaic front and channel/bar complexlithofacies associations. The stratigraphic study accomplished there include insitu air-permeability (Kair), Schmidt Hammer rebound index (R) and XRay portable fluorescence measurements. Petrophysical and geomechanical parametersstatistics are: I) Kair (n: 97), Mean: 24.9 mD (Std: 48.7), Q1: 3.4mD, Q3: 26 mD, and II) R (n: 101), Mean: 47.4 (Std: 8.1), Q1: 43, Q3: 52.Vertical and lateral trends define an increase of hardness and a decrease of permeabilitywhen tuffaceous proportion increase. Geochemical results show thatconcentration of K is similar in tuffaceous sandstones and siltstones, while Fehas values in 75% interquartile bigger for sandstones. The Ca has an interquartilerange bigger for sandstones than for tuffaceous siltstones. At the same time,the Q3 in Fe is higher in sandstones. The distribution of Fe and Ca is associatedto alteration and cementation favored by coarse-granulometries permeabilities. Thequantitative results shows the limited applicability of classic subsurfaceelectrofacies models under volcaniclastic stressed paleoenvironments.Traditional surface sedimentary-logs combined with last-generation equipment allowthe calibration and evaluation of an excellent outcrop analogue of deltaic reservoirsfrom the top of Pozo D-129 Formation.