Structural analysis of Triassic units in the Smeaheia CO2 storage site, Northern Horda Platform

Introduction

Smeaheia is a prospective subsurface CO2 storage site located on the Northern Horda Platform in the Norwegian sector of the North Sea, 10 km east of the Troll East gas field and 30 km offshore mainland Norway (Figure 1). The storage site is bounded by two basement-involved faults, the Vette and Øygarden, which developed during Permo-Triassic rifting and reactivated during an additional phase of Mid Jurassic – Early Cretaceous rifting.

To date, studies have focussed on assessing the suitability of the Jurassic Viking Group as a suitable storage unit. These results have, however, yielded significant uncertainties regarding storage formation depletion due to Troll field production that may render the storage capacity inadequate, and concern for potential loss of injected fluid upsection along the Øygarden fault as the storage unit is juxtaposed across this fault with Caledonian basement which may be weathered and fractured.

This project will focus on deeper potential Triassic storage units comprised of thick continental facies deposited in arid to semi-arid environments e.g. the Upper Triassic Lunde Fm. Primarily, the focus will be on defining potential structural traps that would allow storage of CO2, a detailed fault analysis to establish the potential for these faults to contain a CO2 column, and identify any other structural heterogeneities that may be problematic to CO2 containment. If time permits, the analysis will extend to the fault blocks to the west of Smeaheia.

Figure 1. Structural elements and oil/gas fields of the northern Horda Platform. Blue outline highlights the extent of the GN1101 3D seismic survey that covers a portion of the Smeaheia area. The prospect is bounded by the Vette and Øygarden faults (From Mulrooney et al., In Prep). Click here for a bigger picture

Aims

  • Generate a 3D model of the Triassic interval of Smeaheia.
  • Discern if trapping structures and continuous caprock are present within the Triassic.
  • Discern how faults will influence injected CO2, i.e., seal capacity, baffling and potential compartmentalisation within the target formation, and influence on CO2 migration pathways.
  • Discern injection-related pressure increases that faults can withstand before reactivation occurs, and compare the stability of the faults with existing results from the shallower Jurassic storage prospect.
  • Categorise results of fault analysis and effects on fluid flow into statistical criteria based on, e.g. fault orientation, length, displacement, nature of juxtaposition, probability of reactivation etc. These results will contribute towards a large database of northern North Sea faults aimed at outlining improved de-risking techniques for fault affected CO2 reservoirs.

Objectives

  • High-resolution mapping of faults intersecting Triassic units.
  • Computing juxtaposition of Triassic units across faults using interpreted seismic horizons.
  • Generate and visualise comprehensive fault displacement and attribute (e.g. strike, dip, curvature) analyses in order to inform fault complexity and segmentation history.
  • Classify individual faults based on deformation style, orientation and geometry, the timing of activity and influence on CO2 migration. 
  • Conduct fault reactivation analysis and compare results to those already computed for the shallower Jurassic prospect.

Data

The project will utilise a high-resolution 3D seismic survey (GN1101) that images a portion of the Smeaheia fault block. Additional 2D seismic lines with more regional coverage are also available. Well log information from two exploration wells cover the area and both penetrate the Triassic. Additional well data from the adjacent Troll area are also available.

Tools and Method

The method will follow a comprehensive fault analysis derived from 3D fault and horizon interpretation of seismic data. Schumberger Petrel E&P Software Platform will be utilised for seismic interpretation and generation of a 3D geomodel. The geomodel will be imported into Midland Valley Move which for fault analysis. Figure 2 shows a typical fault analysis based on seismic interpretation.

Figure 2. Workflow diagram illustrating seismic investigation and fault analysis methods being applied to the structural de-risking of the Smeaheia prospect. Click here for a bigger picture

Learning outcomes

Proficiency using Schumberger Petrel E&P Software Platform and Midland Valley Move. Statistical analysis of fault displacement and attributes. Independent research, academic writing and presentation skills.

Contact Details

For further information or to register interest in projects, please contact Alvar Braathen (alvar.braathen@geo.uio.no) or Mark Mulrooney (mark.mulrooney@geo.uio.no).

Tags: Triassic, CCS, seismic interpretation, fault analysis, juxtaposition, fault reactivation, North Sea, Structural geology
Published Oct. 3, 2019 10:43 AM - Last modified Oct. 3, 2019 10:43 AM

Scope (credits)

60