Fault reactivation potential of the Horda Platform, northern North Sea: Implications for successful storage of CO2

Introduction

The northern Horda Platform (Fig. 1) consists of multiple tilted fault blocks that formed by rifting in the Permo-Triassic and later reactivation in the Jurassic-Cretaceous. Towards the east of the Platform, shallow Mesozoic rocks (Triassic and Jurassic) provide potential fault-bound storage prospects for CO₂ injection and storage. These prospects are located within the Smeaheia and Aurora areas. This project will utilize a newly computed velocity model to depth convert and quantify the reactivation potential of key prospect bounding and intersecting faults within the aforementioned prospective areas.

Scientific Background

Pre-existing weaknesses (discontinuities such as faults and fractures) in a volume of rock are prone to reactivate if they are preferentially aligned with the in-situ stress regime (e.g., Andersonian-style faulting). Critically stressed faults are associated with along fault fluid leakage. Fault reactivation analysis considers several parameters in assessing reactivation potential, i) in-situ stresses (orientation and magnitude), ii) fault geometry and orientation, iii) hydrostatic or induced pressure gradients (where higher pressure favours reactivation) and the mechanical rock properties of the fault rock (e.g., cohesion and friction).

Aims

The primary aims of this project are to:

• Assess the reactivation potential for several northern Horda Platform fault blocks and associated second-order faults that bound or intersect potential CO₂ storage sites.
• Highlight areas of low/high risk for fault reactivation.
• Investigate the links between lithological/geomechanical host rock properties on fault dip and subsequent fault reactivation potential.

Objectives

• Add to an existing high-resolution fault model of the northern Horda Platform.
• Synthesize reactivation parameters (hydrostatic pressure, mechanical properties, in-situ directions and magnitudes) from literature, industry reports, well reports, and public databases (e.g. world-stress-map.org).
• Compute and visually display reactivation algorithms(e.g., Fig. 2)
• Derive lithological/geomechanical host rock properties from available well log data and compare with fault dip and reactivation potential.

Data

The project will utilize 2D regional seismic data of the greater Horda Platform area and 3D data of the northern Horda Platform (Figure 1). Well log data is accessible. Reactivation parameters will be synthesized from literature and industry reports.

Figure12D and 3D seismic data available for this study. The purple box outlines a newly computed velocity model which will be used for depth conversion in this project. Available wells also shown.

Tools and Method

Initial seismic interpretation will be conducted using SchlumbergerPetrel E&P software platform. Fault models will be exported to Petex Move and/or Badley’s T7 and/or Stanford University FSP software for fault characterization and reactivation analysis.

Learning Outcomes

Proficiency using Schumberger Petrel E&P Software Platform and PetexMove/Badley’s T7/Stanford University FSP. Statistical analysis of fault reactivation results. Independent research, academic writing and presentation skills.

Additional details

This project is affiliated with Task 9 of the NCCS centre, international research cooperation on CO₂ capture, transport and storage (CCS) and the associated FRISK project which investigates risk related to faults in reservoirs under consideration for CO₂ storage.