IAP2-22-473

Investigating the role of structural and stratigraphic heterogeneities in regionally extensive mudstones in controlling vertical and lateral fluid migration in sedimentary basins

In sedimentary basins mudstones and shales, which are often termed sealing lithologies, are critical in controlling vertical and lateral fluid migration pathways. These sealing lithologies can be regionally extensive and can be centimeters to hundreds of meters thick. The burial, compaction, and deformation history of sealing lithologies are determined by the physical properties of the sediment, along with the stress regime and pore fluid pressure (cf. Maltman, 1994). Understanding the breaching of these seals, sometimes referred to as seal bypass (Cartwright et al., 2007) is key to containing possible escape pathways to the seabed. Alongside the vertical leakage through the propagation of hydraulic fractures, it has been shown (e.g., Streit & Hillis, 2004) that rising fluid pressure can induce fault slip, temporarily increasing the permeability in the fault zone allows for vertical migration. Understanding the dominant flow pathways and the redistribution of fluid pressures through time is to understand at what point fluid pressures could create fault permeability that could lead to vertical escape. Improving our understanding of the vertical and lateral flow (including cross-flow at fault juxtapositions) within sedimentary basins is important in understanding the distribution of pore fluid pressures,

Using 2-D and 3-D seismic reflection data, integrated with well data from the North West Shelf of Australia, this project will investigate the controls of fluid flow pathways from the scale of individual faults (10’s meters), up to the regional (100’s kilometers). These interpretations will be used to constrain both 2-D and 3-D numerical models to which investigate the timing of episodic changes in fluid flow pressure. Changes in modeled fluid pressures will be used in turn for evaluating the likelihood of fault slip. The key aims of the project will be to investigate:

1) Constrain the structural and stratigraphic structural and stratigraphic heterogeneities in sealing lithologies;

2) Constrain pathways and mechanisms for increasing pore pressure prior to vertical leakage at, or close to structural discontinues, including investigating the transient changes in pore pressures before, during, and after vertical leakage;

3) Investigate the likelihood of changes in pore fluid pressure resulting in fault slip at different depths and pressures within the basin;

4) Consider the implications of vertically connected seal bypass systems for the storage of CO2 in geological sequestration projects.

Methodology

• Interpretation of 2D and 3D seismic data with the integration of well data.
• 2D and 3D basin modeling coupled with pore pressure estimation
• Fault slip modeling

Project Timeline

Year 1

Literature review, data identification and management, training in seismic interpretation and pore pressure principles, training transferable skills. Specific focus on seismic and well interpretation to define structural and stratigraphic frameworks, and of fluid escape features and pathways.

Year 2

Integrated basin modeling underpinned by interpretations from year 1. Models will be dynamic and include aspects of structural evolution and pressure history, and be used to investigate seal bypass through geologic time.

Year 3

Evaluate both the hydrofracturing plays in the rate and direction of fluid migration. Analyse the likely fault stability of overburden faults under in situ stresses and under increased pore pressures due to vertical fluid migration.

Year 3.5

Write up and completion of thesis
Preparation of Journal articles

Training
& Skills

Newcastle University has a faculty-run postgraduate research development programme that follows the Vitae Researcher Development Framework focusing on knowledge and intellectual abilities, personal effectiveness, research governance and organisation, engagement, and influence and impact. Each PhD student has a tailor-made Personal Development Plan, with the expectation of them to take 60 credits in the first year and 40 credits in the second year.

The student will be part of the energy geosciences research group at Newcastle working alongside other researchers across a range of geo-energy projects and have the opportunity to be involved with Newcastle University’s Centre for Energy.

The student will be part of the IAPETUS DTP which offers a multidisciplinary package of training focused on meeting the specific needs and requirements of each student, benefitting from the combined strength and expertise that is available across the partner organisations.

The project and student will be affiliated with the GeoPOP research group led by Durham University (http://www.geopop.org.uk/) and attend the weekly meetings/seminars on various topics – pressure related

References & further reading

Cartwright, J., Huuse, M. and Aplin, A., 2007. Seal bypass systems. AAPG bulletin, 91(8), pp.1141-1166.

Streit, J.E. and Hillis, R.R., 2004. Estimating fault stability and sustainable fluid pressures for underground storage of CO2 in porous rock. Energy, 29(9-10), pp.1445-1456.

Maltman, A., 1994. Deformation structures preserved in rocks. In The geological deformation of sediments (pp. 261-307). Springer, Dordrecht.

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