Since 2000 the Sand Injection Research Group (SIRG), University Aberdeen has developed expertise in the geology and geophysics of sand injectites, and specifically the sandstone intrusion reservoir facies. SIRG is recognised as the global leader in sand injectite research and through close collaboration with sponsors has helped to facilitate wealth creation by defining new hydrocarbon plays that introduced “intrusive traps” and supporting planning and drilling of field developments in excess of 6 billion barrels of reserves.
Our research focuses on the identification, characterization, modelling and prediction of sand injection complexes at all scales and in all types of sedimentary and tectonic settings. Specific to these goals are broadly understanding how sand injectites influence the prospectivity of petroleum systems and specifically evaluating the reservoir potential of sandstone intrusions.
Integral to these high-level goals is establishing and constraining the fundamental processes by which sand becomes fluidised and injected in the (very) shallow crust. To support this SIRG has established the largest global database of giant sand injection complexes using outcrop and subsurface data. Outcrops allow the processes of sand fluidisation to be related to pore-fluid pressure and rock mechanics and, subsurface, most importantly 3D seismic and well data provide basin context for the temporal and spatial development of giant injection complexes.
Who are we?
The Sand Injection Research Group (SIRG), previously Injected Sands Group has operated since 2000 from the University of Aberdeen with collaborators across the UK and around the globe. We currently co-host with the University of Manchester.
Our research focuses on the identification, characterization, modelling and prediction of sand injection complexes at all scales and in all types of sedimentary and tectonic settings. We seek to understand how sand injectites influence the prospectivity of petroleum systems and specifically the reservoir potential of sandstone intrusions.
Why is it important?
From a scientific perspective sand injectites remain somewhat enigmatic – rocks that geologists largely have ignored or treated as exceptions to the geological norm. Our experience shows that sand injection is remarkably pervasive in the geological record and frequently a repeated event as basins evolve over 10,000’s to 100 Ma’s.
Sand injectites have economic significance. In the context of exploration for hydrocarbons sand injectites are primarily important because they offer a new trapping style (intrusive traps) that is generally untested in most petroleum systems. Even when the presence of sandstone intrusions is recorded fortuitously (not drilled deliberately), many interpretations fail to recognize, or fail to consider their reserve potential. Because entirely-injected sandstone reservoirs are known to contain >100 million barrels STOOIP, and depositional sandstone that is significantly modified by sandstone intrusions may reservoir >1 billion barrels STOOIP, they contain major reserves in many basins, even when not identified as being sand injectites. Because sandstone intrusions are not bedding-parallel features interpretation of seismic data, well-to-well correlation and, in general, reserve estimation, are problematic.
- Professor Andrew Hurst
Chair of Production Geoscience, University of Aberdeen
- Professor Andrew Morton
Co-founder of Heavy Mineral Research
- Professor Jeff Wilson
Honorary Fellow of The James Hutton Institute
- Dr Quan Gan
Lecturer, University of Aberdeen
- Dr. Brian Burnham
- Dr. Gustavo Zvirtes
- Dr. Matt Brettle
- Robert Waltham
- Daniel Holden
- Wiktor Luzinski
University of Aberdeen
Past Research Students
- University of Aberdeen
- Sarah Jane Flaws
- Lional Fernandes
- Douglas Watson
- Genny Keilar
- Johnathon Dietz
- Jordan Martin
- Anthony Scott
- Elliot Foley
- Rachel Hardman
- Patrick Nixon
- Corrie Anderson
- Tom Martin
- The University of Basilicata
- Antonella Gatto
- Professor Andrew Hurst
- Consortium Members
- Aker BP
- JX Nippon
- Premier Oil
- Sval Energi
- Vår Energi
- Dana Petroleum
- Norsk Hydro
- Marathon Oil
Integration of outcrop and subsurface data is a pervasive theme of Phase 3 and our current research work. We have completed the mapping and logging of the World's largest known outcrops of giant injection complexes, The Lower Palaeocene Panoche Giant Injection Complex (PGIC) and the Mid Eocene Tumey Giant Injection Complex (TGIC). Both complexes share the tripartite architecture associated with other sand injectites but the relationships between parent (depositional) units and sandstone intrusions differs within the complexes and between them.
Why Study Outcrops?
During the last few decades, interest in Sand Injections, has been growing due to the recognition of several large-scale oil-bearing injected sandstone bodies. Subsurface sand injections were initially identified in the Paleogene deposits of the North Sea Basin by means exploration wells from 1969 onwards. They were initially considered to have no real significance for oil exploration. However, due to improved coring techniques and increases in 3-D seismic data quality, several large-scale sandstone intrusions have been discovered, containing large amounts of hydrocarbons. (e.g Aker BP recent discovery)
Sandstone intrusions have a large impact on oil reservoir connectivity and recovery. From this, fully understanding of subsurface large-scale injection complexes is key for efficient, economical, and optimizing well planning and hydrocarbon recovery. This is best completed through outcrop studies. To this aim we have located different outcrop areas in Europe, North Africa and North America. We have identified the best suited area to be Central California where sand injections complexes of different areas are the best exposed.
In particular, the Panoche and Tumey hills have been considered as outcrop equivalents for the North Sea sandstone injection reservoirs. In this area large-scale injected sandstone bodies, extending laterally for several kilometres, show sizes and geometries that are comparable with the equivalent bodies imaged in the North Sea seismic profiles. Detailed geological field mapping shows a complex network of sills and dikes belonging to two giant injection complexes named Panoche Giant Injection Complex (PGIC) and Tumey Giant Injection Complex (TGIC) respectively. Similarly to the North Sea, the main sandstone intrusions show a central bed-parallel portion and lateral stepped terminations giving rise to characteristic wing-like geometries. Although scattered in a hydrofractured mudstone host unit the main sandstone bodies are connected with the parent units and each other through innumerable vertical or high angle, centimetre to meters-scale dikes, forming complicated, often unpredictable 3D geometries.
As discerning between bed-parallel injected sandstones and depositional sandstones could be often challenging a series of detailed stratigraphic logs have been realized through the considered area. Discriminating features as well as upper erosional contacts, jig-saw geometries and the occurrence of mud clasts have been considered at this aim. The methods utilized for stratigraphic logs reconstructions can be successfully adopted to predict sand injection geometries in borehole cores.
Detailed field observations have been performed on well-exposed outcrops. This allowed examining the main sandstone injection features represented by the sand injection/host rock cross-cutting relationships and the control of fracturing/tectonics on the sand injections emplacement.
In parallel to our outcrop studies, the regional mapping of subsurface Tertiary era giant injection complexes from the North Sea is currently underway. Once completed this will give us a huge analogue data base to support subsurface interpretation. Mapping of 2D & 3D seismic data calibrated to wells adjacent to the outcrop areas within California has been completed and has provided additional insight to the regional development of the injection complexes. It has also defined a new and still untested play in the San Joaquin Valley.
The Injected Sand Group, over the course of the project, has been studying several case-studies proposed by the supporting companies. The case-studies mainly come from the Paleogene deep-water reservoirs of the North Sea, but the project had the chance to embrace also examples from the Angolan offshore Mid-Cenozoic deep-water channels.
Some of the fields or discoveries, which have been studied, are displayed in the above picture. They are all characterised by extensive remobilisation features: 1. Grane; 2.Gryphon, Leadon; 3. Jotun; 4. Alba
The most obvious characteristic of injected sand units in cores is the cross-cutting relations with the background fine-grained sequence. Other common features which may help in the recognition are the sharp, fracture-defined boundaries, the deformation of surrounding shales and the occurrence of heterometric, angular, often platy shale-fragments. This example comes from the Gryphon Field (K. Purvis, in publication), one of the first fields in the North Sea where the relevant effect of sand remobilisation was recognised. The appearance of injected sands can be very different: brecciated units or tiny sndstones with ptygmatic folds are as common as this example and indicate different conditions at the moment of injection.
(core pictures of injected sands - courtesy of Kerr-McGee)
Image courtesy of Chevron U.K.
Reservoirs characterised by large-scale fluidisation and injection are often difficult to image, even on 3D seismic data. However, recent acquisition of multi-component 3D seismic data using ocean bottom cable (OBC) technology have vastly improved the subsurface image of the Alba Field, leading to revised reservoir models and development plans (see fig. on the left; from MacLeod et al. 1999). Hence, the application of OBC technology may provide a key to properly imaging injected reservoir sands elsewhere. In any case, it would seem that wide-angle stacks should be interpreted alongside the conventional 3D cube for improved reservoir imaging.
Interpretation of converted-wave seismic data reveal substantial modifications by remobilisation and injection of the original depositional geometry of the reservoir, some of which may also be visible on conventional 3D seismic or wide-angle stacks. These features include mounds, lateral wings, ridges and partly detached sand bodies, which cross-cut original stratigraphic relationships.
The increasing amount of 3D seismic and well data from the NW European Atlantic margin has led to an increased recognition of injection features, especially in the Faeroe-Shetland Basin. Although less well studied, this example from the Atlantic margin shows that large-scale remobilisation and injection are common phenomena, also outside the North Sea.
The injected features interpreted on seismic data are often high amplitude or "bright". This could be related to higher impedance of the disturbed sands, relative to in situ sands and shales, confirming the well logs and core observations, but other factors such as pore-fluid or tuning effects could also be in effect.
The lower Paleogene turbidite reservoirs of the North Sea frequently display a typical stratigraphic organization which is represented in the conceptual diagram on the right. Gamma-ray log and lithological section are completed with representative core photographs of remobilization and injection features. The thin ("ratty") sands above the main reservoir are mainly thought to be of injected (dykes and sills) rather than depositional origin. Core picture of dykes and sills is from Purvis et al. (2002). Injection breccias are usually found close to the top of an underlying massive sand, while homogenized sands, giant pillars and over-steepened laminae are found in the top of the massive sand. Each core section is 3 feet (~0.9 m long).
Conventional P-wave seismic section across a Balder age sand body, showing development of crosscutting wing-like reflections at its sides. These are interpreted as large-scale injected sand bodies.
Three-dimensional visualization of the top of the anomalous amplitudes seen in the figure on the left (location indicated by white line) and the top Balder reflection (grey) displaying a polygonal fault pattern. Bluish colours coincide with the top of the largely in situ Balder sand; green-yellow correspond to the crosscutting part of the wing, whilst orange-red colours correspond to anomalous amplitudes (sill or extrusion?). The total relief on the coloured horizon is about 250 ms TWT (from c. 1700 ms to c. 1950 ms TWT), corresponding to c. 300 m.
Typical cross-section of an isolated Balder-age sand body displaying differential compaction mound and marginal wings. Borehole data show that the eastern wing reflection correspond to a 41.5 massive sand, whilst cores from the crest, 150-200 m above the Balder sand body display decimetre to metre thick sand injectites.
Models of sand distribution and geometries vary depending on data quality and interpretation mind set: Upper model shows a massive sand confined to an erosional scour with "ratty" sands on gamma-ray logs interpreted as thin-bedded turbidites in the overburden shales. The lower model shows a massive sand with no apparent confinement and mounding due to differential compaction. The "ratty" sands are interpreted as sand injectites in the overburden shales, whilst wing-like reflections at the edges of the sand are interpreted as low-angle sand dykes and sills/extrusions. The lower model is fully applicable to the mound shown in the previous figure. Over the past decade, increased quality of core and 3D seismic data has changed the interpretation of many fields of the North Sea Paleogene from the upper to the lower model.
Digital Outcrop Modelling
Terrestrial lidar and photogrammetric data as well as airborne UAV photogrammetry has been acquired to a high resolution to facilitate, statistically-supported reservoir modelling. This is used to provide crucial geostatistical data including geometric and volumetric relationships for sandstone intrusions from outcrop analogues.
A current research project being undertaken by Dr. Brian Burnham and Dr. Antonio Grippa uses the current (and continually increasing) digital outcrop analogue database, along with seismic data, to produce a library of multiple-resolution (e.g. cm - 100's of metres) deterministc reservoir and 3D forward seismic models. The methods and workflow under development will improve the constraints on reserve estimation as the resultant models are used to cross validate and cross correlate subsurface interpretation. The project results will aid reservoir modellers, reservoir engineers and production geologists to better understand reservoir behaviour and development with the goal of allowing operators to “see” more of the missing (not resolvable on seismic) reservoir volume and thereby enhance reserve estimates and, specifically, allow optimal placement of wells.
This will naturally fall into a larger workflow being developed to mose accurately model and predict sand intrusion geometry for subsurface reservoir modelling and production.
Seismic Forward Modelling and Industry collaboration
Through direct collaboration with sponsors and utilizing MSc student projects, we are seeking to transfer learning from outcrop analogue characterization into subsurface interpretation. Above simply increasing our sponsors' familiarity with intrusions and their host strata, we have identified two main areas of focus: Enhancing core description/interpretation, and seismic forward modelling. Several studies have utilized our outcrop data to better constrain subsurface interpretation and to support the planning of production wells. Using the SeisRox modelling platform, we have added a new level of sophistication to seismic forward modelling that provides enhanced constraint to subsurface interpretation.
Coupled Hydro-Mechanical Reservoir Simulation
Coupled hydro-mechanical model could be used to predict the evolution of fracture and matrix permeability, porosity, which are impacted by the stress state variation. Providing the distribution and evolution of reservoir conductivity and the resulted production due to sand dyke propagation and interaction are key deliverables for our sponsors.
The main deliverable in this part of work is the development of more comprehensive reservoir simulator for modelling the evolution of fracture permeability and its influence in the hydrocarbon production.
Currently, we are using the continuum coupled simulator FLAC3D-Tough to model rock deformation and fluid flow problem, we are working towards to develop a new modelling that will better represent the constitutive process of sand fluidization and distribution of dykes in models.
Research articles in press
Hu, Yu.; Gan, Quan. et al. Evolution of Stress-Dependent Permeability in Sand Injectite Systems. International Journal of Rock Mechanics (accepted Feb, 2018).
Research articles in preparation and/or review
Zivrtes, Gustavo; Hurst, Andrew et al. Intrusive geometries and petrogenetic relationships in the Tumey Giant Injection Complex, Tumey Hill, California (USA). In: Subsurface Sand Remobilization and Injection: Implications for Oil and Gas Exploration and Development eds. Lovelock, C.E., Silcock, S., Hurst, A. and Huuse, M. Geological Society of London Special Publication (submission early May).
Hurst, Andrew; Zvirtes, Gustavo et al. Diagnostic petrographic and mineralogical criteria for identifying sandstone intrusions. In: Subsurface Sand Remobilization and Injection: Implications for Oil and Gas Exploration and Development eds. Lovelock, C.E., Silcock, S., Hurst, A. and Huuse, M. Geological Society of London Special Publication (submitted early March).
Grippa, Antonio; Lecomte, Isobelle; et al. Detecting and constraining the geometry of subsurface sandstone intrusions by seismic forward modeling of analogue outcrop data. Earth and Planetary Science Letters (submission in early May)
Palladio, Giuseppe; Alsop, Ian; et al. Sandstone intrusions along faults: a new element in fault seal analysis of multi-layered siliciclastic reservoirs. In: Subsurface Sand Remobilization and Injection: Implications for Oil and Gas Exploration and Development eds. Lovelock, C.E., Silcock, S., Hurst, A. and Huuse, M. Geological Society of London Special Publication (submitted early March).
Published research articles by year
Hurst, Andrew; Wilson, Michael Jeffrey; Grippa, Antonio; Palladino, Giuseppe. Provenance and Sedimentary Context of Clay Mineralogy in an Evolving Forearc Basin, Upper Cretaceous-Paleogene and Eocene Mudstones, San Joaquin Valley, California. Minerals
Zvirtes, Gustavo; Philipp, Ruy; Hurst, Andrew; Palladino, Giuseppe; Grippa, Antonio. Petrofacies of Eocene sand injectites of the Tumey Giant Injection Complex, California (USA). Sedimentary Geology
Grippa, Antonio; Hurst, Andrew; Palladino, Giuseppe; et al. Seismic imaging of complex geometry: Forward seismic modeling of sandstone intrusions. Earth and Planetary Science Letters
Zvirtes, Gustavo; Hurst, Andrew; Philipp, Ruy; Palladino, Giuseppe; Grippa, Antonio. The Tumey Giant Injection Complex, Tumey Hill, California (USA). Geologial Society of London Special Publications
Palladino, Giuseppe; Alsop, Ian; et al., Sandstone-filled normal faults: A case study from central California. Journal of Structural Geology.
Hurst, Andrew; Morton, Andrew, et al. Heavy-Mineral Assemblages in Sandstone Intrusions: Panoche Giant Injection Complex, California, U.S.A. Journal of Sedimentary Research.
Hurst, Andrew; Vigorito, Mario. Saucer-shaped sandstone intrusions: An underplayed reservoir target. AAPG Bulletin
Wu, Feng; Hurst, Andrew; Grippa, Antonio, Grain and pore microtexture in sandstone sill and depositional sandstone reservoirs: preliminary insights. Petroleum Geoscience
Palladino, Giuseppe; Grippa, Antonio; et al. Emplacement of sandstone intrusions during contractional tectonics. Journal of Structural Geology.
Hurst, Andrew; Huuse, Mads; et al., Application of outcrop analogues in successful exploration of a sand injection complex, Volund Field, Norwegian North Sea. Geological Society, London, Special Publications
Lecomte, I.; Lavadera, P.L. et al. 2 (3) D convolution modelling of complex geological targets - beyond 1D convolution. First Break
Hurst, Andrew; Huuse, Mads et al. Application of outcrop analogues in successful exploration of a sand injection complex, Volund Field, Norwegian North Sea. In: Bowman, M, et al. (eds) Geological Society of London, Special Publication