A high-resolution fault assessment workflow for unconventional reservoirs exploration: A case study on the onshore Sergipe-Alagoas Basin, Brazil. (January 2022)

• Record Type: Journal Article
• Authors: Rocha, Natacha M.; Coelho, Ana C.M.Q.; Menezes, Paulo T.L.
• Is Part Of: Journal of South American earth sciences. Volume 113(2022)
• Publication Date: 2022-01
• Subjects: Unconventional exploration in South America -- Seismic resolution -- Interpretation workflow -- Natural fracture system mapping -- Coqueiro Seco Formation -- Sergipe-Alagoas Basin; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2021.103641
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: Apart from Vaca Muerta's case history in Argentina, the unconventional exploration in South America is still underdeveloped, and one of the causes is the scarcity of geological studies. The present paper enlightens the embryonic unconventional exploration in the Sergipe-Alagoas Basin by introducing a seismic interpretation workflow to map thin shale layers and the natural fracture system, a challenge in unconventional reservoir explorations. Fracture and faults are critical elements in exploring ultra-low permeability shale oil/gas reservoirs. Identifying and locating these structures influence modeling fluid flow, hydraulics, and simulation models to improve horizontal well-drilling plans. The workflow comprises four main steps: data pre-conditioning, well-to-seismic tie, seismic spectral blueing (for frequency enhancement), and, finally, spectral decomposition and advanced fault attributes. The proposed workflow was applied to a seismic dataset from the onshore Brejo Grande oilfield focusing on the source rocks of the Coqueiro Seco Formation, the main unconventional reservoir candidate in the basin. That approach allowed mapping the lateral continuity, truncation, faults, and fractures in these thin shale layers previously below seismic resolution. The mapped structures belong to the complex natural fracture system with faults distributed to all trend directions. These faults are distributed along two zones with distinct fault densities with a possible sweet spot outline. Highlights: We present an interpretation workflow implemented to unconventional reservoirs. The workflow combines seismic-resolution enhancing techniques and fault attributes. As a result, thin-shale layers and fault zones were identified at Coqueiro Seco Fm.