A new hydrocarbon exploration play: Upper Cretaceous–Paleocene sand injection complexes in the Austral-Magallanes Basin

Abstract

Recent exploration activity in the Austral-Magallanes Basin revealed the presence of sand injection complexes of Upper Cretaceous–Paleocene age. The discovery of these large-scale sandstone intrusions documents the first onshore example of sand injection complexes as hydrocarbon exploration targets and confirms a more widespread phenomenon than previously known. Integration of regional understanding, three-dimensional seismic reflection data, exploration wells, and whole core have allowed the interpretation of large sand injectites associated with a deep-water depositional system in the Austral-Magallanes Basin. These injectites are characterized seismically by circular to elongate amplitude anomalies with cross-cutting and discordant stratigraphic relationships. Additionally, detailed sedimentological analysis from exploration wells and core confirm the presence of facies consistent with injected sand commonly associated with deep-water depositional systems. The presence of giant sand injection complexes in the Austral-Magallanes Basin records a previously undocumented period of pore-fluid overpressure that led to large-scale hydraulic fracturing of the overburden and subsequent fluidization of sand derived from a deep-water depositional system. The discovery of intrusive traps such as sand injection complexes defines a new play with significant exploration potential; however, additional evaluation is required to understand the nature and degree of primary sandbody geometrical modification and the subsequent impact on reservoir distribution, trap geometry, migration pathways and seals.

A giant sand injection complex: Processes and implications for basin evolution and subsurface fluid flow

“…Subsurface giant injection complexes are always associated with basin-scale aquifers, often deep-water turbidite systems (Huuse and others, 2004;Hurst and others, 2005;Huuse and others, 2005;Serié and Pemberton, 2021;van Oorschot and others, 2021), which represent the source of fluid necessary to form regionally developed hydrofractures and injectite complexes. It is thus reasonable to assume that the presence of a very large aquifer is a pre-requisite for the formation of a giant sand injection complex.…”