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Deciphering the relative roles of allogenic versus autogenic controls on deltaic depositional systems

Dr Nigel Mountney (SEE), Dr Luca Colombera (SEE), Prof. Bill McCaffrey (SEE) and Prof. David Hodgson (SEE)

Project partner(s): Petrotechnical Data Systems Ltd

Contact email: n.p.mountney@leeds.ac.uk

A PhD studentship to be run under the auspices of the Shallow Marine Research Group (SMRG) and the Fluvial Research Group (FRG) in the School of Earth and Environment at the University of Leeds

Background

The preserved sedimentary architecture of deltaic successions serves as a valuable archive that records factors that govern the morphodynamic behaviour of deltas and associated shoreline sedimentary systems. A fundamental challenge in rock-record interpretations and in the compilation of models for subsurface predictions is posed by the difficulty in filtering the record of allogenic processes, such as changes in climate, tectonics and base-level, from autogenic factors, such as delta-lobe switching and backwater hydrodynamics. Development of novel and innovative techniques for deciphering the complexity of this rock-record archive represents an active research avenue that has potential for gaining a better understanding of the interdependence between extrinsic and intrinsic controls, and the relative importance of different factors on the accumulation and preservation of deltaic successions in both lacustrine and marine settings. One promising approach to addressing this issue is the quantitative characterization of depositional systems using a database, whereby many aspects of sedimentary and geomorphic architecture from many different deltaic-system types (both ancient and modern), and from different sedimentary settings (e.g. rift versus foreland basins) are stored in a relational database that can be queried in a sophisticated manner to identify common trends (Colombera et al., 2013; 2015). Such an approach can be used to assess shoreline response to changing relative sea-level and changing climate, for example; it therefore serves as a tool with which to predict the effects of future environmental change.

From an applied standpoint, the development of a database of sedimentary heterogeneity is significant because it offers the opportunity to develop quantitative models of sedimentary architecture that can be used to make informed predictions regarding likely sand-body distribution, size, lateral extent, connectivity, and overall net-to-gross for a variety of economic purposes: reservoir characterization in oil and gas exploration; assessment of the hydrogeological potential of ground-water aquifers; selection of underground sites that are potentially suitable for long-term sequestration of carbon dioxide to mitigate against future anthropogenically driven climate change. Lithological heterogeneity presents significant challenges for characterizing subsurface reservoir successions, including: (i) meso-scale prediction of sand-body architecture and connectivity; (ii) stacking patterns of reservoir-quality channel bodies or parasequence sandstones; and (iii) predicting the effects of macro-scale controls on system-scale spatial variability and stratigraphic evolution at the basin scale.

Aim and objectives

The aim of this project is to devise a novel database-driven approach for the development of quantitative facies and sequence stratigraphic models to assess the impact of external and intrinsic controls on deltaic system development within a range of environmental settings and sedimentary basin types.

Specific research objectives of this research are as follows: (i) to demonstrate evidence to show that primary allogenic and autogenic controls on preserved deltaic strata are interdependent and interrelated via a series of complex feedback mechanisms; (ii) to encapsulate facies and sequence stratigraphic models, and the data that underpin them, within a database that can be used to predict sedimentary architecture based on knowledge of system boundary conditions. The research will involve development and employment of the Shallow Marine Architecture Knowledge Store (SMAKS) and the Fluvial Architecture Knowledge Transfer System (FAKTS), two relational databases conceived and designed in the School of Earth and Environment at the University of Leeds. These databases will be used to address the following research questions.

  1. What is the 3D facies architecture, internal and external heterogeneity, and connectivity of sand-bodies within fluvial-dominated delta tops subject to different climatic settings?

  2. How does the geometry, connectivity and stacking pattern of distributary channel fills vary spatially and temporally within delta tops, and how well do these variations match with what is predicted by recent models that invoke backwater controls?

  3. How do allogenic factors, such as climate and relative sea-level change, influence and dictate autogenic behaviour in deltaic systems, such as frequency of delta-lobe avulsion, and how are such changes manifest in the preserved stratigraphic record?

  4. Are there scaling relationships between sub-components of deltaic systems that can be used predictively (e.g. mouth-bar size as a function of distributary-channel size)?

  5. Are there commonalities in the way attributes (e.g. geometry, timescale) of Quaternary delta-lobes and deltaic parasequences in the ancient stratigraphic record are controlled by specific boundary conditions (e.g. accommodation: sediment-supply ratio)?

  6. Is it possible to establish how the hierarchy of deltaic constructional units (e.g. lobes at multiple scales) vary as a function of the size of a delta and its controls (e.g. drainage area, mean yearly discharge)? Can such hierarchical stacking patterns be identified through analysis of bounding surface arrangements and stratal trends in ancient systems, and on drainage orders in modern systems?

  7. Do we see any relationships between the direction of seismic-scale shoreline trajectories and the potential sedimentary characteristics of the different physiographic elements of a delta (top, front, prodelta)?

The studentship is not limited to any of these themes, and the particular research topics will be defined in accordance with the interests of the candidate.

Methodology

A range of methods will be employed to fulfil the aim of this project and answer the stated research questions.

  1. Fieldwork to examine the sedimentology and architecture of deltaic deposits accumulated in a range of basin types, and to examine the stratigraphic evolution of such systems over time. The choice of study areas and case studies is open, but could include the Jurassic of the Yorkshire coast, the Carboniferous of Ireland and Britain, or the Cenozoic in the Spanish Pyrenees. Some of these successions are exceptionally well-exposed such that they will provide excellent opportunity for field-based study to examine and document deltaic architectural heterogeneity and stratigraphic evolution.

  2. Population of SMAKS and FAKTS – two databases storing aspects of fluvial, paralic and shallow-marine stratigraphic architecture developed in-house by SMRG and FRG at Leeds – for the quantitative characterization of sedimentary units within a range of sedimentary basin types and settings.

  3. Use of satellite imagery for the collation of a database of attributes describing the plan-form morphology and scale of deltaic systems developed in a range of environmental settings and possibly associated with river-, wave- and tide-dominated seas.

Potential for high-impact outcome

A major outcome of this project will be the development of quantitative, predictive facies and sequence stratigraphic models, which will improve our understanding of factors controlling fluvio-deltaic sedimentary architecture and response to environmental controls. Results have implications for the prediction of future coastal landform response to currently on-going environmental change. From an applied standpoint, the method to be developed will aid the lithological characterization of subsurface fluvio-deltaic hydrocarbon reservoirs, ground water aquifers and sites currently being considered for long-term carbon sequestration. Past and on-going research on similar topics to this and undertaken at Leeds have been funded by NERC to address their mission aims. The appointed candidate will be encouraged to publish the results of their research in leading pure and applied research journals such as Nature Geoscience, Geology, Sedimentology, Journal of Sedimentary Research, AAPG Bulletin, Basin Research and others. Previous projects using Leeds-developed proprietary database technology similar to that proposed here have resulted in publications in leading international journals.

Eligibility

Applicants should have a BSc degree (or equivalent) in geology, geology-geography, earth sciences, geophysics or a similar discipline. An MSc or MGeol in applied geoscience or petroleum geoscience (or similar) is desirable. Skills in field-based geological data collection and field sedimentology and stratigraphy are desirable. Experience of using GIS software would be useful, though is not essential.

Training

The project will involve field-based data collection (e.g., UK, Ireland or Spain) over a series of field seasons. There will be opportunities for the appointed applicant to spend time in the offices of our chosen project partner, Petrotechnical Data Systems (PDS), and one or more SMRG or FRG sponsor companies. Such placements will involve working with a team of applied geology professionals. Training will be provided in advanced concepts and techniques in clastic sedimentology and stratigraphy, in approaches to basin analysis, and in the use and development of geological databases. The mixed pure- and applied-science nature of this research project will enable the appointed applicant to consider a future career in either academia or industry. The successful applicant will join a team of academic staff and PhD research students who collectively form two applied-facing industry-supported research consortia based at the University of Leeds: SMRG and FRG. The groups currently have 16 on-going PhD students, with 14 others having successfully completed their PhD studies in recent years. The groups also currently comprise 4 PDRAs and a team of like-minded academics working on a range of applied-facing research questions in sedimentology. The two groups are currently supported our chosen project partner (PDS), with whom we work closely, by 12 international sponsor companies, plus a number of other companies who have commissioned stand-alone research projects.

Examples of modern deltas with markedly different morphologies. A range of extrinsic (allogenic) and intrinsic (autogenic) processes govern how sediment is distributed within deltas and how such sediments ultimately accumulate and become preserved in the stratigraphic rock record. The 11 km-long Ural River Delta (left) and the Volga River Delta (right), Kazakhstan and Russia, both prograde into the Caspian Sea. Part of this project will attempt to classify the range of processes and form known from modern deltas to help build improved facies and sequence stratigraphic models that may be used to account for the sedimentary architecture of ancient successions. Images courtesy of NASA Earth Observatory.

CASE Partner

The proposal has been agreed as a “Partnership Project” (a potential CASE project) with Petrotechnical Data Systems (PDS) Ltd, who design and deliver innovative software technologies, R&D and consulting services to the Exploration and Production Industry. This CASE partnership provides extra funding additional to the NERC student stipend. The project aligns with an existing collaboration between Leeds PDS to develop innovative geotechnical database technologies for better characterization of subsurface sedimentary successions.

Recommended Reading

  1. Colombera, L., Felletti, F., Mountney, N.P. and McCaffrey, W.D., 2012. A database approach for constraining stochastic simulations of the sedimentary heterogeneity of fluvial reservoirs. American Association of Petroleum Geologists Bulletin, 96, 2143-2166. doi: 10.1306/04211211179

  2. Colombera, L., Mountney, N.P., Hodgson, D.M. and McCaffrey, W.D., 2016. The Shallow-Marine Architecture Knowledge Store: a database for the characterization of shallow-marine and paralic depositional systems. Marine and Petroleum Geology, 75, 83-99. doi: 10.1016/j.marpetgeo.2016.03.027

  3. Colombera, L., Mountney, N.P. and McCaffrey, W.D., 2013. A quantitative approach to fluvial facies models: methods and example results. Sedimentology, 60, 1526-1558. doi: 10.1111/sed.12050

  4. Colombera, L, Mountney, N.P. and McCaffrey, W.D., 2015. A meta-study of relationships between fluvial channel-body stacking pattern and aggradation rate: implications for sequence stratigraphy. Geology, 43, 283-286. doi:10.1130/G36385.1.

  5. Colombera, L., Mountney, N.P., McCaffrey, W.D. and Felletti, F., 2014. Models for guiding and ranking well-to-well correlations of channel bodies in fluvial reservoirs. American Association of Petroleum Geologists Bulletin, 98, 1493-1965. doi: 10.1306/05061413153

Further Information

For more information about this project and other Sedimentology Group research activities at the University of Leeds contact:

Nigel Mountney, +44 (0)113 3435249, n.p.mountney@leeds.ac.uk, http://frg.leeds.ac.uk/

Related undergraduate subjects:

  • Earth science
  • Geography
  • Geology