Structural, stratigraphic and thermal basin modelling In collaboration with Prof. Nick Kusznir Liverpool University

Structural, stratigraphic & thermal basin modelling Background and history Since the late 1980s we have worked with Prof. Nick Kusznir to develop a set of software tools and workflow practices which use state-of-the-art academic research to produce geodynamic models with a direct application and relevance to predictive exploration of rifts and continental margins No-one else in the UK or overseas can offer these services or facilities, they are unique to Badleys Past and present customers include –BP, Shell, Conoco, Phillips, Anadarko, KMG, Norsk Hydro, Statoil We are constantly keeping these services at the leading edge by collaborating in new research, such as the government and industry-funded iSIMM Atlantic Margin project, running from

Structural, stratigraphic & thermal basin modelling What do we offer ? 2D modelling of cross-sections and structural profiles –FlexDecomp for backstripping through the thermal-subsidence history of rifts and continental margins, using 2D flexural backstripping –Stretch for forward modelling the structure and subsidence history of rifts and continental margins, using the flexural cantilever model 3D modelling of maps and grids –FlexDecomp 3D for backstripping and restoration of maps and grids, using 3D flexural backstripping. Powerful palaeobathymetric prediction. Thermal modelling of wells and transects –Heat for whole-lithosphere thermal modelling, works in conjunction with structural predictions from Stretch or FlexDecomp –2DHeat and 3DHeat for modelling thermal transfer in 2D profiles or 3D volumes, includes igneous and oceanic heating

Structural, stratigraphic & thermal basin modelling What are the applications ? Interpretation QC: Constrain and help the seismic interpretation of difficult-to-interpret faulted structure in basins. An alternative to traditional section balancing. Understanding basin dynamics: Understand and predict the large-scale process driving extension, subsidence, uplift and heat-flow in a basin. Palinspastic Restoration: Produce sequential isostatically- balanced cross-sections or maps, depicting stratigraphic, fault and basin geometries. Palaeostructure. Palaeobathymetry: Predict variation of bathymetry, basin- floor slope and depocentre location through time. Applicable both to 2D cross-sections and 3D maps & grids Cont …

Structural, stratigraphic & thermal basin modelling What are the applications ? Depositional & Erosional Analysis: Model syn-rift elevation (footwall uplift) highlighting sediment source areas and predict amounts of erosion of fault blocks. Quantify the effects of sediment loading and compaction on stratigraphy. Generate burial history plots across a basin. Thermal History: Evaluate a basin's temperature history by generating beta factor and heat-flow profiles from both forward and reverse models. Predict top basement and top sediment heat-flow and horizon temperatures through time. Calibrate vitrinite and downhole temperature against a tectonic/thermal model. Other specialised applications also. Gravity modelling: Compare structurally-derived predictions of gravity anomaly with measured gravity data.

Structural, stratigraphic & thermal basin modelling Who can benefit ? Almost anyone in the exploration team Seismic interpreter, wanting to check the validity of a fault interpretation Sedimentologist, wanting to know whether a depositional model is tenable Biostratigrapher, wanting to know whether their bathymetric estimates are reasonable Structural geologist, wanting to know the morphology of the syn-rift basin Stratigrapher, wanting to investigate the generation of unconformities in the basin Geophysicist, wanting to know the magnitude of stretching (beta) in the basin Geochemist, wanting a constrained estimates of heat-flow and temperature through time Team leader, wanting his staff better trained in understanding fundamental processes

FlexDecomp 2D – backstripping of cross-sections The modelling involves: Layer-by-layer removal of the stratigraphic sequence, accompanied by sediment decompaction and incorporating long-term eustasy Isostatic unloading, applying flexural isostasy in 2D. Key to the methodology and much more robust than applying Airy isostasy Reverse thermal-subsidence modelling of one or two rift events Regional uplift/subsidence related, for example, to the plume dynamics Calibration against geological data, bathymetry, emergence, erosion The main sensitivities, which can be iterated or tested: Rift ages and rift magnitudes (beta factors) Flexural isostatic parameters Decompaction parameters, overpressure, location of basement Section validation, palaeobathymetry, depocentres, topography, beta factors, burial history

FlexDecomp 2D – backstripping of cross-sections Backstrip from present to near syn-rift Acknowledge two rift events Jurassic (150Ma) beta profile from Stretch Constant value for Triassic (250Ma) beta Allow for Palaeocene uplift by Iceland plume Regional 2D model Northern Viking Graben – Magnus Basin, across Snorre horst to Sogn Graben

FlexDecomp 2D – backstripping of cross-sections Northern Viking Graben – Magnus Basin, across Snorre horst to Sogn Graben Backstripped to: Top Cretaceous Top Lower Cretaceous Base Cretaceous

FlexDecomp 2D – backstripping of cross-sections Northern Viking Graben – More detail over Dunlin, Statfjord, Gullfaks Backstrip from present to near syn-rift Acknowledge two rift events Constant values for Jurassic and Triassic beta Allow for Palaeocene uplift by Iceland plume Present-day section Top Palaeocene With plume support Top Cretaceous No plume support More detailed 2D model

FlexDecomp 2D – backstripping of cross-sections Northern Viking Graben – More detail over Dunlin, Statfjord, Gullfaks Backstrip from present to near syn-rift Acknowledge two rift events Constant values for Jurassic and Triassic beta Top Lower Cretaceous Base Cretaceous Upper Jurassic Syn-rift Note the variable timing and amount of footwall emergence for the three fault blocks

FlexDecomp 2D – backstripping of cross-sections Vøring Basin, Norwegian Atlantic margin – Nyk High and Hel Graben Base Tertiary With plume uplift Syn-rift Near breakup Present-day section Large beta values Passive margin model

FlexDecomp 2D – backstripping of cross-sections Published map of beta stretching factor for the Vøring basin, Norway Roberts et al 1997 JGS Multiple 2D models produce constrained maps of beta factor, which are a proxy for maps of heat flow Mapping beta factor

Stretch – forward modelling of cross-sections The modelling involves: Application of the Flexural-cantilever model of continental lithosphere extension, an established model for investigating rift geometries. Flexural isostasy in 2D applied to all faulting and loading processes. Key to the methodology, much more robust than applying Airy isostasy. Multiple rifting and re-faulting capability. Forward thermal-subsidence modelling of one or two rift events. Calibration against the results of flexural backstripping. The main sensitivities, which can be iterated or tested: Fault extension, fault position, fault dip. Erosion of topography and deposition in basinal areas Flexural isostatic parameters Section validation, fault geometry, footwall uplift & erosion, beta factors, heat flow, gravity model

Stretch – forward modelling of cross-sections Northern Viking Graben – Magnus Basin, across Snorre horst to Sogn Graben Whole crustal model of Late Jurassic rift basin. Single rift model. 1:1 Beta stretching-factor and corresponding syn-rift heat-flow anomaly for Late Jurassic rift Upper-crustal detail view of Late Jurassic rift basin. Note repeated and varied footwall uplift. 4:1 Regional model

Stretch – forward modelling of cross-sections Northern Viking Graben – Magnus Basin, across Snorre horst to Sogn Graben 50% erosion at syn-rift stage50% further erosion at Base Cretaceous, 15Ma Base Cretaceous forward model with corresponding backstripped template

Stretch – forward modelling of cross-sections Northern Viking Graben – Magnus Basin, across Snorre horst to Sogn Graben Model of Triassic early rift basin after 100Ma thermal subsidence, prior to re-rifting in the Late Jurassic Multiple rifting Triassic-rift template re-rifted on the same faults during the Late Jurassic. Note the variable thickness of pre-rift

Stretch – forward modelling of cross-sections Northern Viking Graben – Magnus Basin, across Snorre horst to Sogn Graben Gravity anomaly associated with syn-rift multiple rift model, gravity highs associated with structural highs and vice versa Beta profiles, Late Jurassic and combined Combined heat-flow anomaly, in Late Jurassic Multiple rift model 150Ma thermal subsidence after Jurassic rift

Stretch – forward modelling of cross-sections Northern Viking Graben – More detail over Dunlin, Statfjord, Gullfaks Detail of syn-rift model + template Detail of base Cret model + template Detailed whole-crustal model, includes small faults within the major structures Maximum erosion from the syn-rift model More focussed local model

FlexDecomp 3D – backstripping of maps & grids The modelling involves: Layer-by-layer removal of the stratigraphic sequence, accompanied by sediment decompaction and incorporating long-term eustasy Isostatic unloading, applying flexural isostasy in 3D, allowing 3D variations in stratigraphic and structural geometry to be acknowledged Reverse thermal-subsidence modelling of one or two rift events Regional uplift/subsidence related, for example, to the plume dynamics Calibration against geological data, bathymetry, emergence, erosion The main sensitivities, which can be iterated or tested: Rift ages and rift magnitudes (beta factors) Flexural isostatic parameters Decompaction parameters, overpressure, location of basement Palaeobathymetry, depocentres, topography, palaeostructure, decompacted isochores, beta factors,

FlexDecomp 3D – backstripping of maps & grids Regional depth maps Lithology mix by interval Multi stage rifting Input Beta map Output Palaeobathymetric maps to aid depositional modelling Palaeostructure maps to aid structural understanding and migration modelling Thermal balance McKenzie model Flexural isostatic balancing Decompaction of underlying sediment Sea-level variation Load removal Neogene uplift Plume effects Map-based restorations QC agaist 2D sections Beta map Iterations to match well and seismic paleobathymetric markers Model of the uncertainty arising from the interpretation range Illustration courtesy of Richard Corfield, BP 3D-backstripping method and iterations

FlexDecomp 3D – backstripping of maps & grids Seabed Accurate seabed topography is essential for deeper restoration Intermediate horizons With folds, compaction features and bathymetric markers Deep horizons With fault-block structure and rift bathymetry Input requirements – example present-day depth maps and grids Norwegian Atlantic margin

FlexDecomp 3D – backstripping of maps & grids Reverse thermal-subsidence modelling is constrained either by applying constant values of beta stretching-factor, or more rigorously by applying a map of stretching factor, typically constrained by multiple 2D sections Published map of beta stretching factor for the Vøring basin, Norway Roberts et al 1997 JGS

FlexDecomp 3D – backstripping of maps & grids Extrusive basalts (B) restored to sea-level Lower Tertiary present day Lower Tertiary at seabed Base Cretaceous fault-blocks restored to sea-level Base Cretaceous deep structure present day Base Cretaceous at seabed Restoration and bathymetric calibration B B

FlexDecomp 3D – backstripping of maps & grids Subsurface palaeostructural restorations Basal Tertiary back to seabed Preferred geodynamic model sequentially restoring the Basal Tertiary back in time from the present day to contemporary seabed. Full 3D model and N-S serial sections Norwegian Atlantic margin

FlexDecomp 3D – backstripping of maps & grids Subsurface palaeostructure below Lower Tertiary Palaeostructure section between horizon surfaces Base Cretaceous palaeostructure structure below Base Eocene palaeobathymetry Multiple subsurface Cretaceous horizons below Base Eocene at seabed

FlexDecomp 3D – backstripping of maps & grids Decompacted isochores highlight structural growth and sediment depocentres Upper Tertiary Upper Cretaceous Lower Tertiary Basal Tertiary Stratigraphic sequence sufficiently thick to avoid differential compaction over basement highs Isochore variation in Tertiary and Upper Cretaceous reflects structure or relict seabed topography Upper isochores show Tertiary domes Deeper isochores show Vøring fault-blocks and basins

Heat – whole-lithosphere thermal modelling The modelling is very fast and incorporates: Whole-lithosphere thermal perturbation, with adjustable lithosphere parameters Burial history, defined by input stratigraphy and lithology, incorporating compaction Tectonic thermal history, the ability to model the thermal perturbation from multiple rift events and their subsequent relaxation. Calibrated by Stretch and FlexDecomp Crustal and lithosphere thinning, defined by the tectonic history. Lithosphere thinning can be considered as uniform with depth or depth-dependent Crustal and sediment radiogenic heat input The thermal consequences of igneous intrusion into the sediment pile Calibration against downhole temperature and %VR data The main sensitivities, which can be iterated or tested: Rift ages and rift magnitudes (beta factors) Background radiogenic parameters, particularly crustal Rad Gen Lithological parameters Heat is a 1D forward modelling program for predicting heat-flow, maturation and horizon temperature histories from well or cross-section data.

Heat – whole-lithosphere thermal modelling The modelling is computationally intensive and incorporates: Whole-lithosphere thermal perturbation, with adjustable lithosphere parameters Lateral thermal input into the basin or margin from new oceanic crust or igneous intrusion, 2D or 3D model Tectonic thermal history, the thermal perturbation from tectonic rift events and their subsequent relaxation. Calibrated by Stretch and FlexDecomp Crustal radiogenic heat input Lithological control The main sensitivities, which can be iterated or tested: Oceanic spreading rate, thermal passage of hot ridge Thickness of igneous intrusion Lithological and Rad Gen parameters Heat 2D and Heat 3D are new bespoke applications for modelling heat transfer and temperature profiles across continental margins

Heat – whole-lithosphere thermal modelling Heat is a 1D forward modelling program for predicting heat-flow, maturation and horizon temperature histories, incorporating tectonic thermal input Heat-flow and temperature history Heat – basic output for model QC, model with multiple rift events

Heat – whole-lithosphere thermal modelling Maturation and burial history Heat is a 1D forward modelling program for predicting heat-flow, maturation and horizon temperature histories, incorporating tectonic thermal input Heat – basic output for model QC, model with multiple rift events

Heat – whole-lithosphere thermal modelling Detailed heat-flow history and multi-model sensitivity tests Heat is a 1D forward modelling program for predicting heat-flow, maturation and horizon temperature histories, incorporating tectonic thermal input Small rift 1 250Ma Large rift 2 140Ma Large rift 3 55Ma Small rift 1 250Ma Large rift 2 140Ma Large rift 3 55Ma

Heat – whole-lithosphere thermal modelling Burial and temperature history and multi-model sensitivity tests Heat is a 1D forward modelling program for predicting heat-flow, maturation and horizon temperature histories, incorporating tectonic thermal input

Heat – whole-lithosphere thermal modelling Heat 2D and Heat 3D are new bespoke applications for modelling heat transfer and temperature profiles across continental margins Temperature Section at time = 5 Ma Ridge Duration = 0 Ma Depth (km) X (km) Transform margin Continental Oceanic Time (Ma) Depth (km) Temperature History at x = -20 km Ridge Duration = 0 Ma 2D and 3D Thermal Models Whole lithosphere thermal model Includes sediments, basement, lithospheric mantle Steady state initial continental temperature Oceanic lithosphere emplaced at t = 0 Ma 2D or 3D (vertical and horizontal) conductive heat transfer Compaction dependent sediment conductivity (k r = k m 1-f.kw f ) for shale, sand or shaly sand Upper crustal radiogenic heat productivity Lithosphere thickness = 125 km T o = 1333 o C Transform margin at X=0 km Sensitivities ridge duration time continental crustal thickness oceanic crustal thickness continental sediment thickness oceanic sediment thickness continental sediment composition oceanic sediment composition

Structural, stratigraphic & thermal basin modelling Resumé At Badleys we offer a range of basin-modelling products and services integrated across the following disciplines: Structural geology Stratigraphy Geophysics Thermal modelling In this way we draw upon our own expertise in tectonic analysis and collaborate with Prof. Nick Kusznir on the application of quantitative geophysical and thermal modelling techniques to provide a unique portfolio of experience. This capability distinguishes us very clearly from both traditional structural analysis and traditional geochemical basin modelling, and provides the logical bridge between these two normally-separate areas of study. Badleys