- Elin Skurtveit
- Senioringeniør, Petroleumsgeomekanikk og geofysikk (PGG)
- Norges Geotekniske Institutt - NGI
Structural derisking (Task 9)
Task 9 focuses on reducing the risks related to the injection and storage of CO₂ on the Norwegian Continental Shelf, with a focus on the geology and faults in the Horda Platform area. Site specific knowledge building for the Smeaheia fault block within the Horda Platform area is combined with observations from field analogies and experimental investigation in order to address fault seal integrity and develop an improved workflow for dynamic up-along-fault fluid migration.
The ambitions for this Task are to reduce risk related to injecting and storing CO2 in the continental shelf, and contribute to maximize the CO2 injection volume for the Smeaheia region (Norwegian Continental Shelf storage region) as well as develop techniques to address fault-sealing and integrity.
The Task was developed in collaboration with industry partners to ensure optimal contribution to the research of the Northern Lights project (Statoil, Shell and Total's carbon storage project) as well as contribution to optimization of CO2-storage fault risk procedures.
E.g. the Task will investigate:
- Faults and migration pathways in the Smeaheia region
- How to improve geological and geomechanical models for the area
- Challenges related to pressure depletion prior to injection
- Improved models for along fault flow and fault reactivation
- The possibility of additional storage volumes related to satellite storage sites (additional injection wells) in the Smeaheia region
The Task will contribute to the Northern Lights project through knowledge sharing of in depth research related to the derisking of CO2 storage on the continental shelf.
Important industry partners to the Task are Statoil, Shell, Total (as representatives for the Northern Lights Project) and Gassnova (As provider of Smeaheia data set etc.). The potential for acquiring new partners is currently investigated.
Detailed mapping of sedimentary units, faults and CO₂ traps in Horda Platform area has improved the geological understanding of the area and resulted in new geo-models for the Smeaheia and Aurora sites. Detailed characterisation of the Permian-Triassic alluvial rift system in the Horda Platform provides valuable lessons on how faulting influences reservoir deposition. This work provides new and relevant information for evaluating storage capacity in the deeper formations of the Smeaheia fault blocks and has been published as a research article in Basin Research. Identification of structural traps and assessment of top and fault seals for the Horda area is discussed in a paper currently being reviewed by the American Association of Petroleum Geologists (AAPG), and shows promising potential for expanding CO₂ storage in the North Sea.
Analyses of fault stability and reactivation of the Vette fault zone show that fault rock cohesion and horizontal stress acting on the fault are of high importance for the fault stability during injection. A 3D finite element geomechanical model for Smeaheia has been completed and provides an important tool for assessing the horizontal stress development in a reservoir during injection, and quantifies the uncertainties of stress within fault zones. This study indicates that if the fault stability results can be calibrated with a small safety margin, an analytical approach assuming uniaxial strain condition seem to be still a relatively accurate method to screen critically oriented faults. The new 3D geomechancial model was presented as an open webinar and will be used to further address effects of uncertainties in stress conditions and mechanical properties on fault and seal integrity.
Experimental work has been carried out based on a need for improved mechanical understanding of shale caprock and clay rich faults. Frictional properties in fault gouges are found to vary systematically with clay-sand mixing ratios, from around 20-degree friction angles in clay-dominated gouges and above 30 degrees in sand-dominated gouge, whereas interfaces between clay and sand seems to be controlled by the higher sand friction. A comprehensive experimental study on Draupne Shale that provides a thorough description of its elastic properties, anisotropy and shear strength has been published in Geosciences. The work provides an important reference study for the evaluation of seal integrity of other caprocks on the Norwegian Continental Shelf.
An improved workflow for quantification of fault leakage risk during CO2 injection in saline aquifers is an important contribution for identification and qualification of additional storage volume in the Horda Platform area, where the Northern Lights project currently develops the Aurora site for CO2 injection.
New datasets released from Eos well drilled in Aurora site have resulted in improved geological models for the area. Close collaboration between Northern Lights, NCCS and the University of Oslo on reservoir characterisation, building on existing sedimentological models as a basis for reservoir simulations, has improved the confidence in the storage capacity for the Johansen Formation.
Screening of fault stability in the Horda Platform area showed that the local stress regime around the fault as well as the internal strength of the fault zone is highly important for the determination of fault slip stability. To address these findings in more detail, we have initiated laboratory testing to better understand the deformation processes in shale dominated units and the development of faults in these units. The ongoing test programs provide new data on frictional strength comparing intact Draupne shale material properties and synthetic mixtures of fault gouge (Intact material that is crushed down).
Results provide systematic frictional properties with clay content and will provide new and valuable input for modelling fault slip stability in the overburden of the CO2 storage reservoirs.
Main results 2019
The Horda Platform area is already selected for CO2 injection within the Northern Lights project. We have therefore conducted a detailed seismic interpretation of two supplementary sites in the same area, the Smeaheia fault block and Triassic Lunde Formation. This has resulted in improved geological understanding of the Horda Platform area, by demonstrating new findings on age relationships, timing and basement involvement for the faults in the area, as well as identifying good reservoir sands in the Triassic.
Our new knowledge on the geology of the Platform has the potential to identify and qualify additional storage volume in this area. More specifically, age relationships and extent of faulting provides important input for the maturation of the area and can help quantify the risk related to fault sealing and reactivation. Identification and qualification of additional reservoir units in areas where storage infrastructure is developed can provide an important step towards large-scale CO2 storage. Two main uncertainties related to the Horda Platform area, the juxtaposition seal for the Vette fault and the origin of the pockmarks in the overburden have been addressed to further reduce the risk. The seal properties of the Vette fault zone have been demonstrated by comparing the Vette fault with the Tusse fault, a sealing fault within the Troll gas reservoir. The comparison suggests that the geometry and juxtaposition is comparable and similar sealing properties can be expected for Vette fault as for Tusse fault. The most likely source for pockmarks is found to be laterally migrating fluids (from gas chimneys) near the Troll Field, and not from the underlying reservoir-seal system at Smeaheia.
- Extensive fault mapping using Gassnova 3D seismic completed for Alpha structure providing a detailed (academic) fault dataset as basis for further fault seal analysis and migration models
- Complexity for polygonal faults and faulting of beta structure documented and detailed interpretation in progress
- Fault slip stability screening performed identifying the fault rock properties as the most critical parameter for fault slip risk
- Machine learning algorithm for evaluation of leak of test (LOT) data established
Impact and innovations
- The extensive fault mapping and geological system characterization for the Smeaheia area was shared with Northern Lights project.
- The fault derisking work has resulted in an increasing awareness of the need for better understanding of risk related to faults in order to utilize the large potential of storage volume within faulted reservoirs.
Main activities are related to establishing a good platform for collaboration between research partners, industry and the Northern Lights project.
The workshop in fall 2017 was an important arena for knowledge shearing and defining important research tasks related to fault seal and integrity evaluations for the Norwegian CCS project (NORCCS).
Detailed mapping of faults in the Smeaheia area has started focusing on both sealing potential of major faults in the area and leakage risk into the polygonal fault system in the overburden.
Tools for screening of critical stressed faults is under development together with a more detailed assessment of fault rock properties based on the spares data available.
Workshop viewing the core from Smeaheia
NCCS Task 9 - Structural Derisking - started the new year with a very successful workshop viewing the core from well 32/4-1 of Smeaheia.
The workshop was led by Anja Sundal, UiO and gathered participants from UiO, NGI, Statoil, Northern Lights Project, Gassnova and Sintef for an interesting discussion on the geological model of Smeaheia.
- Digital Drill Core Models: Structure-from-Motion as a Tool for the Characterisation, Orientation, and Digital Archiving of Drill Core Samples - P. Betlem, T. Birchall, K. Ogata, J. Park, E. Skurtveit, K. Senger
- Demonstrating the potential of CO2 hydrate self-sealing in Svalbard, Arctic, Norway - S. Almenningen, P. Betlem, A. Hussain, S. Roy, K. Senger, G. Ersland
- You learn as long as you drill; research synthesis from the Longyearbyen CO2 Laboratory, Svalbard, Norway - S. Olaussen, K. Senger, A. Braathen, S. Grundvåg, A. Mørk
- Discovery of shale gas in organic-rich Jurassic successions, Adventdalen, Central Spitsbergen, Norway - S. E. Ohm, L. Larsen, S. Olaussen, K. Senger, T. Birchall, T. Demchuk, A. Hodson, I. Johansen, G. O. Titlestad, D. A. Karlsen, A. Braathen
- Sedimentology and palynology of the Lower Cretaceous succession of central Spitsbergen: integration of subsurface and outcrop data - S. A. Grundvåg, M. E. Jelby, K. K. Sliwinska, H. Nøhr-Hansen, T. Aadland, S. E. Sandvik, I. Tennvassås, T. Engen, S. Olaussen
- Seismic modelling of metre-scale normal faults at a reservoir-cap rock interface in Central Spitsbergen, Svalbard: implications for CO2 storage - P. Lubrano-Lavadera, K. Senger, I. Lecomte, M. J. Mulrooney, D. Kühn
- Fluid flow properties of the Wilhelmøya Subgroup, a potential unconventional CO2 storage unit in central Spitsbergen - M. J. Mulrooney, L. Larsen, J. Van Stappen, B. Rismyhr, K. Senger, A. Braathen, S. Olaussen, M. B. E. Mørk, K. Ogata, V. Cnudde
- Facies, palynostratigraphy and sequence stratigraphy of the Wilhelmøya Subgroup (Upper Triassic–Middle Jurassic) in western central Spitsbergen, Svalbard - B. Rismyhr, T. Bjærke, S. Olaussen, M. J. Mulrooney, K. Senger
- Integrating subsurface and outcrop data of the Middle Jurassic to Lower Cretaceous Agardhfjellet Formation in central Spitsbergen - M. J. Koevoets, Ø. Hammer, S. Olaussen, K. Senger, M. Smelror
- Comparison between two Late Jurassic CO2 storage prospects with respect to structural derisking Smeaheia area, Norwegian North Sea - J.L. Osmond, M.J. Mulrooney, E. Skurtveit, A. Braathen. NGWC
- Analogous juxtaposition of mixed litologles against a sillciclastic hydrocarbon reservoir and proposed CO2 storage formation in the Norwegian North Sea - J.L. Osmond, M.J. Mulrooney, E. Skurtveit, A. Braathen. ACE 2019, San Antonio, Texas
- 3D geologic framework and structural derisking of two offshore CO2 storage prospects in the Smeaheia area, Norwegian North Sea - J.L. Osmond, M.J. Mulrooney, E. Skurtveit, A. Braathen. 2019 CLIMIT PhD and PostDoc Seminar, Oslo
- Probabilistic Seismic Hazard Analysis of a CO2 Storage Prospect Using the NGA East Ground Motion Models - B. Carlton, E. Skurtveit, K. Atakan, A. M. Kaynia. SECED 2019 Conference: Earthquake risk and engineering towards a resilient world
- Deep Neural Network Based Prediction of Leak-Off Pressure in Offshore Norway - J.C. Choi, E. Skurtveit, L. Grande, Offshore Technology Conference
- Effect of CO2 injection-induced stress rotation in overburden on the fault stability and induced seismicity: Numerical investigation - J. C. Choi, E. Skurtveit, L. Grande, J. Park. TCCS-10. The 10th Trondheim Conference on Carbon Capture, Transport and Storage
- A reduced capacity Smeaheia prospect – Structural risks associated with an Alpha-only storage scenario - M. J. Mulrooney, J. L. Osmond, E.H. Leon, A. Braathen. The 10th Trondheim Conference on CO2 Capture, Transport and Storage
- Distribution and spatial statistics of pockmarks in Quaternary sediments above the Smeaheia CO2 storage area - E. H. Leon, J. L. Osmond, M. J. Mulrooney, A. Braathen. NGF Vinterkonferansen
- Experimental and analytical assessment of Draupne shale seal integrity for CO2 storage sites - M. Soldal, E. Skurtveit, B. Bohloli, H. Wilkinson, J. C. Choi, L. Griffiths, H. Smith. DECOVALEX 2019 Symposium on Coupled Processes in Radioactive Waste Disposal and Subsurface Engineering Applications
- Smeaheia, a potential northern North Sea CO2 storage site: structural description and de-risking strategies - M. Mulrooney, J. Osmond, E. Skurtveit, L. Wu, A. Braathen.
- 3D falut integrity screening for Smeaheia CO2 injection site - E. Skurtveit, J.C. Choi, M. Mulrooney, J. Osmond, A. Braathen. GHGT-14, Melbourne
- First-pass 3D geologic interpretation and structural modelling of the alpha CO2 storage prospect in the Smeaheia area, Norwegian North Sea - J.L. Osmond, M.J. Mulrooney, E. Skurtveit, A. Braathen. NFIP PhD Seminar, Stavanger
- Prediction of leak-off pressure in Norwegian offshore using NPD factpages and deep neutral network - J.C. Choi, E. Skurtveit, L. Grande. SEG 2018