29 June 2017
Event phone: +44 (0)20 7408 2000
With Professor Andrew Hurst, University of Aberdeen & Professor Mads Huuse, University of Manchester
Sand injectites are the product of subsurface sand remobilization and injection. Large-scale sand injectites were first reported about a Century ago from outcrops in California where they were linked with oil migration through shales. Over the past three decades sand injectites have increasingly become important in the Paleocene to Eocene deepwater sandstone play of the North Sea Basin and injectites are important reservoir units in some of the largest ongoing developments in the UKCS including Mariner, Kraken and Catcher. Sand injection leads to enhanced connectivity across large distances of otherwise low permeabilty mudstones, and targeting of oil accumulations within large-scale sand injectite ‘wings’ has led to rejuvenation of fields such as Gryphon and Harding, although detailed geometries can be complex and difficult to model. Detailed outcrop work has provided vital analogue data that together with increasingly high-definition 3D seismic data are used to inform more optimal development and production scenarios of oil fields hosted in sand injectites.
This workshop aims to present an overview of the characteristics of large-scale sand injection complexes around the world and in California and the North Sea in particular and, to outline their importance to development and production. It should be of interest to anyone involved with exploration, development and production in deepwater clastic sequences including the North Sea Paleogene, but also more frontier areas such as the North and South Atlantic, East Africa, etc.
In most subsurface examples sand injectites co-exist with polygonal fault systems, affecting pelagic and hemipelagic deepwater mudstone sequences, although the presence of polygonal faults is difficult to confirm in most outcrop examples. The best exposures of sand injectites are located in the San Joaquin Basin where detailed examination of individual sandstone intrusions as well as entire injection complexes is possible over hundreds of square kilometres. Outcrop characterization provides useful analogues for subsurface modelling and highlights the significance of dykes which are notoriously difficult to image using subsurface techniques.
Widespread and repeated occurrence of sand injection within the North Sea and San Joaquin basins suggests that triggering and driving mechanisms affected large tracts of the basins more or less simultaneously, although the specific combination of processes has proven difficult to establish and may vary for each basin and injection episode. Impacts of large-scale sand remobilization includes major re-organization of basin plumbing systems, shifting of km3 of sand (reservoir), and insertion of field-size sandstone-prone intervals with geometrically complex geometry that imaging fails to resolve and modelling techniques struggle to represent. The focus of the workshop will be on identification and characterization of sand injectites and on the assessment of their impact on exploration and development.
University of Aberdeen
+44 (0)1224 272 000