Multi-Scale Characterization of Analogues Outcrops Integrating Reservoir Properties and Geologic Processes

Abstract

Studies using analogues outcrops has been developed in the last few years. This kind of studies helps to solve important questions that in subsurface are not totally possible to understand. In Sergipe-Alagoas Basin, Northeast of Brazil, the carbonatic and hybrid potential reservoirs intervals from Riachuelo Formation provides great outcrops for studies of carbonate analogs in comparison to all Atlantic basins of east margin of Brazil. Deposits from shallow carbonate environments from Carapeba quarry were completely characterized using a multi-scale reservoirs characterization approach with different tools. Rappel practice was applied to detail lithology description of 19 vertical log profiles complemented with gamma ray logging of the detailed intervals. Five were correlated in a stratigraphic sections and 130 thin sections were described using microfacies methodology to characterize microscale heterogeneities of pore system. Laser scanner and GPR were done in strategic positions, aiming understand the depositional architecture and internal geometry of sets. According to their compositional and textural character¬istics, 12 different microfacies were recognized and grouped in 6 main facies, dolostone, grainstone, hybrid, dolomitized packstone, dolomitized wackstone and shale, which were used in 3D geological model. Petrophysical data base from 49 samples associated to petrography data were analyzed in order to introduce permeability and porosity data of each facies in 3D model. The highest values of porosity are in the hybrid lithologies, followed by dolomitized packstones. Dolostones were less porous samples. Hybrid samples, with porosities values between 12.23 to 18.197%, the permeability ranges from 0.0383 to 1,63mD, while in dolostone samples, porosity is between 6.528 to 14.101%, the permeability varies from 0.0029 to 1.77 mD. Diagenetic features identified are micritization, dolomitization and dissolution. The facies characterized in Carapeba quarry correspond to usual carbonate complexities founded in this important type of reservoir, which good porosity values are identified, but bad connectivity between pores is evidenced by low permeability. However, in higher depths and with a different burial history, these rocks can be different when fractured or dissolved. Next steps will consider the extension of 3D outcrop modeling to regional context, at oil field scale, considering stratigraphic correlation at the distribution of different lithologies.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015