133 results found
Jackson WA, Hampson GJ, Jacquemyn C, et al., 2022, A screening assessment of the impact of sedimentological heterogeneity on CO2 migration and stratigraphic-baffling potential: Johansen and Cook formations, Northern Lights project, offshore Norway, International Journal of Greenhouse Gas Control, Vol: 120, Pages: 103762-103762, ISSN: 1750-5836
We use a method combining experimental design, sketch-based reservoir modelling, and single-phase flow diagnostics to rapidly screen the impact of sedimentological heterogeneities that constitute baffles and barriers to CO2 migration in the Johansen and Cook formations at the Northern Lights CO2 storage site. The types and spatial organisation of sedimentological heterogeneities in the wave-dominated deltaic sandstones of the Johansen-Cook storage unit are constrained using core data from the 31/5-7 (Eos) well, previous interpretations of seismic data and regional well-log correlations, and outcrop and subsurface analogues. Delta planform geometry, clinoform dip, and facies-association interfingering extent along clinoforms control: (1) the distribution and connectivity of high-permeability medial and proximal delta-front sandstones, (2) effective horizontal and vertical permeability characteristics of the storage unit, and (3) pore volumes injected at breakthrough time (which approximates the efficiency of stratigraphic baffling). In addition, the lateral continuity of carbonate-cemented concretionary layers along transgressive surfaces impacts effective vertical permeability, and bioturbation intensity impacts effective horizontal and vertical permeability. The combined effects of these and other heterogeneities are also influential. Our results suggest that the baffling effect on CO2 migration and retention of sedimentological heterogeneity is an important precursor for later capillary, dissolution and mineral trapping.
Jacquemyn C, Hampson GJ, Jackson MD, et al., 2021, Rapid Reservoir Modelling: Sketch-Based Geological Modelling with Fast Flow Diagnostics, Abu Dhabi International Petroleum Exhibition & Conference, Publisher: Society of Petroleum Engineers
Rapid Reservoir Modelling (RRM) is a software tool that combines geological operators and a flow diagnostics module with sketch-based interface and modelling technology. The geological operators account for all interactions of stratigraphic surfaces and ensure that the resulting 3D models are stratigraphically valid. The geological operators allow users to sketch in any order, from oldest to youngest, from large to small, or free of any prescribed order, depending on data-driven or concept-driven uncertainty in interpretation. Flow diagnostics assessment of the sketched models enforces the link between geological interpretation and flow behaviour without using time-consuming and computationally expensive workflows. Output of RRM models includes static measures of facies architecture, flow diagnostics and model elements that can be exported to industry-standard software. A deep-water case is presented to show how assessing the impact of different scenarios at a prototyping stage allows users to make informed decisions about subsequent modelling efforts and approaches. Furthermore, RRM provides a valuable method for training or to develop geological interpretation skills, in front of an outcrop or directly on subsurface data.
Collins DS, Avdis A, Wells MR, et al., 2021, Prediction of shoreline–shelf depositional process regime guided by palaeotidal modelling, Earth-Science Reviews, Vol: 223, ISSN: 0012-8252
Ancient shoreline–shelf depositional systems are influenced by an unusually wide array of geological, biological and hydrodynamic processes, with sediment transport and deposition primarily determined by the interaction of river, wave (including storm) and tidal processes, and changes in relative sea level. Understanding the impact of these processes on shoreline–shelf morphodynamics and stratigraphic preservation remains challenging. Numerical modelling integrated with traditional facies analysis provides an increasingly viable approach, with the potential to quantify, and thereby improve understanding of, the impact of these complex coastal sedimentary processes. An integrated approach is presented here that focuses on palaeotidal modelling to investigate the controls on ancient tides and their influence on sedimentary deposition and preservation – one of the three cornerstones of the ternary process classification scheme of shoreline-shelf systems. Numerical tidal modelling methodology is reviewed and illustrated in three palaeotidal model case studies of different scales and focus. The results are synthesised in the context of shoreline–shelf processes, including a critique and modification of the process-based classification scheme.The emphasis on tidal processes reflects their global importance throughout Earth’s history. Ancient palaeotidal models are able to highlight and quantify the following four controls on tidal processes: (1) the physiography (shape and depth) of oceans (1000s km scale) determines the degree of tidal resonance; (2) the physiography of ocean connections to partly enclosed water bodies (100–1000s km scale) determines the regional-scale flux of tidal energy (inflow versus outflow); (3) the physiography of continental shelves influences shelf tidal resonance potential; and (4) tides in relatively local-scale embayments (typically 1–10s km scale) are influenced by the balance of tidal amplification
Lyster SJ, Whittaker AC, Hampson GJ, et al., 2021, Reconstructing the morphologies and hydrodynamics of ancient rivers from source to sink: Cretaceous Western Interior Basin, Utah, USA, Sedimentology, Vol: 68, Pages: 2854-2886, ISSN: 0037-0746
Quantitative reconstruction of palaeohydrology from fluvial stratigraphy provides sophisticated insights into the response, and relative impact, of tectonic and climatic drivers on ancient fluvial landscapes. Here, field measurements and a suite of quantitative approaches are used to develop a four-dimensional (space and time) reconstruction of palaeohydrology in Late Cretaceous palaeorivers of central Utah, USA – these rivers drained the Sevier mountains to the Western Interior Seaway. Field data include grain-size and cross-set measurements and span five parallel fluvial systems, two of which include up-dip to down-dip transects, across seven stratigraphic intervals through the Blackhawk Formation, Castlegate Sandstone and Price River Formation. Reconstructed palaeohydrological parameters include fluvial morphologies (flow depths, palaeoslopes, palaeorelief and planform morphologies) and various hydrodynamic properties (flow velocities, water discharges and sediment transport modes). Results suggest that fluvial morphologies were similar in space and time; median flow depths spanned 2 to 4 m with marginally greater flow depths in southerly systems. Meanwhile palaeoslopes spanned 10−3 to 10−4, decreasing downstream by an order of magnitude. The most prominent spatio-temporal change is an up to four-fold increase in palaeoslope at the Blackhawk–Castlegate transition; associated alluvial palaeorelief is tens of metres during Blackhawk deposition and >100 m during Castlegate Sandstone deposition. This study observed no change in unit water discharges at the Blackhawk–Castlegate transition, which argues against a climatically driven increase in palaeoslope and channel steepness. These findings instead point to a tectonically driven palaeoslope increase, although one limitation in this study is uncertainty in palaeochannel widths, which directly influences total water discharges. These reconstructions complement and expand on extensive p
Jacquemyn C, Pataki MEH, Hampson GJ, et al., 2021, Sketch-based interface and modelling of stratigraphy and structure in three dimensions, Journal of the Geological Society, Vol: 178, Pages: 1-17, ISSN: 0016-7649
Geological modelling is widely used to predict resource potential in subsurface reservoirs. However, modelling is often slow, requires use of mathematical methods that are unfamiliar to many geoscientists, and is implemented in expert software. We demonstrate here an alternative approach using sketch-based interface and modelling, which allows rapid creation of complex three-dimensional (3D) models from 2D sketches. Sketches, either on vertical cross-sections or in map-view, are converted to 3D surfaces that outline geological interpretations. We propose a suite of geological operators that handle interactions between the surfaces to form a geologically realistic 3D model. These operators deliver the flexibility to sketch a geological model in any order and provide an intuitive framework for geoscientists to rapidly create 3D models. Two case studies are presented, demonstrating scenarios in which different approaches to model sketching are used depending on the geological setting and available data. These case studies show the strengths of sketching with geological operators. Sketched 3D models can be queried visually or quantitatively to provide insights into heterogeneity distribution, facies connectivity or dynamic model behaviour; this information cannot be obtained by sketching in 2D or on paper.
Costa Sousa M, Silva J, Silva C, et al., 2020, Smart modelling of geologic stratigraphy concepts using sketches, Smart Tools and Applications in computer Graphics (STAG) 2020, Publisher: The Eurographics Association, Pages: 89-100
Several applications of Earth Science require geologically valid interpretation and visualization of complex physical structures in data-poor subsurface environments. Hand-drawn sketches and illustrations are standard practices used by domain experts for conceptualizing their observations and interpretations. These conceptual geo-sketches provide rich visual references for exploring uncertainties and helping users formulate ideas, suggest possible solutions, and make critical decisions affecting the various stages in geoscience studies and modelling workflows. In this paper, we present a sketch-based interfaces and modelling (SBIM) approach for the rapid conceptual construction of stratigraphic surfaces, which are common to most geologic modelling scales, studies, and workflows. Our SBIM approach mirrors the way domain users produce geo-sketches and uses them to construct 3D geologic models, enforcing algorithmic rules to ensure geologically-sound stratigraphic relationships are generated, and supporting different scales of geology being observed and interpreted. Results are presented for two case studies demonstrating the flexibility and broad applicability of our rule-based SBIM approach for conceptual stratigraphy.
Lupin J, Hampson G, 2020, Sediment-routing controls on sandstone bulk petrographic composition and texture across an ancient shelf: example from Cretaceous Western Interior Basin, Utah and Colorado, USA, Journal of Sedimentary Research, Vol: 90, Pages: 1389-1409, ISSN: 1527-1404
Sediment-routing controls on sandstone texture and bulk petrography have been evaluated in linked alluvial-coastal-shelfal deposits of the Upper Cretaceous Castlegate Sandstone, Blackhawk Formation, Star Point Sandstone, and Mancos Shale (Western Interior Basin, Utah and Colorado, USA) using thin-section analysis of representative outcrop samples in the context of a high-resolution sequence stratigraphic and paleogeographic framework. The studied strata record deposition from two styles of sediment-routing system within an overfilled foredeep and contiguous intra-continental seaway. First, multiple transverse drainages supplied sand to fluvial, shoreline, and shelf segments of sediment-routing systems characterized by down-dip transport distances of 150-450 km and significant strike-oriented sediment transport along the shoreline. Second, the distal shoreline-shelf segment of an axially supplied sediment-routing system was characterized by sand transport for a distance of c. 300 km.Bulk petrographic composition indicates that transverse sediment-routing systems were sourced from catchments that supplied quartz-rich sand with a subordinate lithic component, while the large axial sediment-routing system was sourced from a catchment(s) supplying slightly more feldspathic sand. Thin-section measurements of mean grain size, sorting, skewness, and ratio of minimum-to-maximum diameter (a proxy for sphericity) are similar for sandstones deposited in fluvial, shoreline and shelf segments of the transverse sediment-routing systems and in the shoreline-shelf segment of the axial sediment-routing systems, although hydrodynamic sorting is important in locally segregating grain-size populations within each segment. Further, textural analysis of detrital quartz, feldspar, and lithic sand-grain populations shows little evidence of relative change in mean grain size or apparent grain sphericity with downsystem distance, implying that sand-grain populations of different petrographic
Sahoo H, Gani MR, Gani ND, et al., 2020, Predictable patterns in stacking and distribution of channelized fluvial sandbodies linked to channel mobility and avulsion process, Geology (Boulder), Vol: 48, Pages: 903-907, ISSN: 0091-7613
Despite the importance of channel avulsion in constructing fluvial stratigraphy, it is unclear how contrasting avulsion processes are reflected instratigraphic-stacking patterns of channelized fluvial sandbodies, asa proxy for how riverdepocentersshifted in time and space. Using an integrated, geospatially-referenced 3D dataset that includesoutcrop, core, and LiDAR data, we identify for the first time in an outcropstudy a predictive relationship between channelized-sandbodyarchitecture, paleochannel mobility, and stratigraphic-stacking pattern. Single-story sandbodies tend to occur in vertically-stacked clusters that are capped by a multilateral sandbody, indicating an upward change from a fixed-channelsystem to a mobile-hannelsystem in each cluster.Vertical sandbody stacking in the clusters implies reoccupation of abandoned channelsafter “local” avulsion.Reoccupational avulsion may reflect channel confinement, location downstream of a nodal avulsion point that maintained its position during development of the sandbody cluster, and/or aggradation and progradation of a backwater-mediated channel downstream of a nodal avulsion point. Sandbody clusters and additional multilateral sandbodies are laterallyoffset or isolated from each other, implying compensational stackingdue to “regional” switching of a nodal avulsion point to anew, topographically-lowersite on the floodplain.The predictive links between avulsion mechanisms, channel mobility,and resultant sandbody distributions and stacking patterns shown in our findings haveimportant implications forexploringand interpreting spatio-temporal patterns of stratigraphic organizationin alluvial basins.
Brewer C, Hampson G, Whittaker A, et al., 2020, Comparison of methods to estimate sediment flux in ancient sediment routing systems, Earth-Science Reviews, Vol: 207, ISSN: 0012-8252
The need to predict accurately the volume, timing and location of sediments that are transported from an erosional source region into a basin-depocentre sink is important for many aspects of pure and applied sedimentological research. In this study, the results of three widely used methods to estimate sediment flux in ancient sediment routing systems are compared, using rich input datasets from two systems (Eocene South Pyrenean Foreland Basin, Spain and late-Pleistocene-to-Holocene Gulf of Corinth Rift Basin, Greece) for which mapped, dated sediment volumes provide an independent reference value of sediment accumulation rates. The three methods are: (1) the empirical BQART model, which uses values of drainage basin area, relief, temperature, lithology and water discharge; (2) empirical scaling relationships between characteristic geomorphological parameters of sediment-routing-system segments; and (3) the “fulcrum” model, which uses the palaeohydrological parameters of trunk river channels to estimate downsystem sediment discharge. The BQART model and empirical geomorphological scaling relationships were originally developed using modern sediment routing systems, and have subsequently been applied to ancient systems. In contrast, the “fulcrum” model uses hydrological scaling relationships from modern systems, but was developed principally for application in ancient systems.Our comparative analysis quantifies the sensitivity of the three methods to their input parameters, and identifies the data required to make plausible estimates of sediment flux for ancient sediment routing systems. All three methods can generate estimates of sediment flux that are comparable with each other, and are accurate to at least one order of magnitude relative to independent reference values. The BQART model uses palaeoclimatic and palaeocatchment input data, which are accurate for sub-modern systems but may be highly uncertain in deep-time systems. Corresponding
Zhang Z, Geiger S, Rood M, et al., 2020, Fast flow computation methods on unstructured tetrahedral meshes for rapid reservoir modelling, Computational Geosciences, Vol: 24, Pages: 641-661, ISSN: 1420-0597
Subsurface reservoir models have a high degree of uncertainty regarding reservoir geometry and structure. A range of conceptual models should therefore be generated to explore how fluids-in-place, reservoir dynamics, and development decisions are affected by such uncertainty. The rapid reservoir modelling (RRM) workflow has been developed to prototype reservoir models across scales and test their dynamic behaviour. RRM complements existing workflows in that conceptual models can be prototyped, explored, compared, and ranked rapidly prior to detailed reservoir modelling. Reservoir geology is sketched in 2D with geological operators and translated in real-time into geologically correct 3D models. Flow diagnostics provide quantitative information for these reservoir model prototypes about their static and dynamic behaviours. A tracing algorithm is reviewed and implemented to compute time-of-flight and tracer concentrations efficiently on unstructured grids. Numerical well testing (NWT) is adopted in RRM to further interrogate the reservoir model. A new edge-based fast marching method is developed and implemented to solve the diffusive time-of-flight for approximating pressure transients efficiently on unstructured tetrahedral meshes. We demonstrate that an implementation of the workflow consisting of integrated sketch-based interface modelling, unstructured mesh generation, flow diagnostics, and numerical well testing is possible.
Angus L, Hampson G, Palci F, et al., 2020, Characteristics and context of high-energy, tidally modulated, barred shoreface deposits: Kimmeridgian–Tithonian sandstones, Weald Basin, southern UK and northern France, Journal of Sedimentary Research, Vol: 90, Pages: 313-335, ISSN: 1527-1404
The influence of tides on the sedimentology of wave-dominated shorefaces has been emphasized in recent studies of modern shorelines and related facies models, but few ancient examples have been reported to date. Herein, we use a case study from the stratigraphic record to develop a revised facies model and predictive spatio-temporal framework for high-energy, tidally modulated, wave-dominated, barred shorefaces.Kimmeridgian–Tithonian shallow-marine sandstones in the Weald Basin (southern England and northern France) occur as a series of laterally extensive tongues that are 5–24 m thick. Each tongue coarsens upward in its lower part and fines upward in its upper part. The lower part of each upward-coarsening succession consists of variably stacked, hummocky cross-stratified, very fine- to fine-grained sandstone beds and mudstone interbeds that are moderately to intensely bioturbated by a mixed Skolithos and Cruziana ichnofacies. This lower part of the succession is interpreted to record deposition on the subtidal lower shoreface, between effective storm wave base and fairweather wave base. The upper part of each upward-coarsening succession comprises cross-bedded, medium- to coarse-grained sandstones that are pervasively intercalated with mudstone-draped, wave-rippled surfaces (including interference ripples) which mantle the erosional bases of trough cross-sets. Bioturbation is patchy, and constitutes a low-diversity Skolithos ichnofacies. Cross-bedded sandstones are arranged into cosets superimposed on steeply dipping (up to 10˚) clinoforms that dip offshore and alongshore, and extend through the succession. These deposits are interpreted to record shallow subtidal and intertidal bars on the upper shoreface, which likely contained laterally migrating rip channels or formed part of a spit. The lower, upward-coarsening part of each sandstone tongue represents an upward-shallowing, regressive shoreface succession in which the internal bedding of upper-shor
Le Blevec T, Dubrule O, John C, et al., 2020, Geostatistical Earth modeling of cyclic depositional facies and diagenesis, AAPG Bulletin, Vol: 104, Pages: 711-734, ISSN: 0149-1423
In siliciclastic and carbonate reservoirs, depositional facies are often described as being organized in cyclic successions that are overprinted by diagenesis. Most reservoir modeling workflows are not able to reproduce stochastically such patterns. Herein, a novel geostatistical method is developed to model depositional facies architectures that are rhythmic and cyclic, together with superimposed diagenetic facies. The method uses truncated Pluri-Gaussian random functions constrained by transiograms. Cyclicity is defined as an asymmetric ordering between facies, and its direction is given by a three-dimensional vector, called shift. This method is illustrated on two case studies. Outcrop data of the Triassic Latemar carbonate platform, northern Italy, are used to model shallowing-upward facies cycles in the vertical direction. A satellite image of the modern Bermuda platform interior is used to model facies cycles in the windward-to-leeward lateral direction. As depositional facies architectures are modeled using two Gaussian random functions, a third Gaussian random function is added to model diagenesis. Thereby, depositional and diagenetic facies can exhibit spatial asymmetric relationships. The method is applied in the Latemar carbonate platform that experiences syn-depositional dolomite formation. The method can also incorporate proportion curves to model non-stationary facies proportions. This is illustrated in Cretaceous shallow-marine sandstones and mudstones, Book Cliffs, Utah, for which cyclic facies and diagenetic patterns are constrained by embedded transition probabilities.
Onyenanu G, Hampson G, Fitch P, et al., 2019, Characterisation of effective permeability in heterolithic, distal lower shoreface sandstone reservoirs: Rannoch Formation, Brent Group, UK North Sea, Petroleum Geoscience, Vol: 25, Pages: 519-531, ISSN: 1354-0793
The reservoir properties of distal lower-shoreface and distal wave-dominated delta-front deposits, which consist of sandstone beds with locally scoured bases and mudstone interbeds, are poorly understood. The lower Rannoch Formation (Middle Jurassic Brent Group) forms an interval of such heterolithic sandstones in many North Sea reservoirs, and is used to illustrate a workflow for rapid estimation of reservoir properties and their sensitivity to key parameters. Mudstone-interbed thickness distributions in cored reservoir successions are compared to the thickness distribution of sandstone scour-fills in an outcrop analogue(s) in order to identify mudstones with the potential to form laterally extensive barriers to vertical flow. Effective kv/kh at the scale of several typical reservoir-model grid cells (200 × 100 × 20 m) is estimated in intervals bounded by these mudstone barriers via a simple analytical technique that is calibrated to previously documented reservoir-modelling experiments, using values of sandstone proportion measured in cored reservoir successions. Using data from the G2 parasequence (Grassy Member, Blackhawk Formation, east-central Utah, USA) outcrop analogue, mudstones bounding 3–8 m-thick, upwards-coarsening successions in the lower Rannoch Formation may define separate stratigraphic compartments in which grid-cell-scale effective kv/kh is estimated to be 0.0001–0.001 using a streamline-based analytical method.
Dean CD, Collins DS, van Cappelle M, et al., 2019, Regional-scale paleobathymetry controlled location, but not magnitude, of tidal dynamics in the Late Cretaceous Western Interior Seaway, USA, Geology, Vol: 47, Pages: 1083-1087, ISSN: 0091-7613
<jats:title>Abstract</jats:title> <jats:p>Despite extensive outcrop and previous sedimentologic study, the role of tidal processes along sandy, wave- and river-dominated shorelines of the North American Cretaceous Western Interior Seaway remains uncertain, particularly for the extensive mid-Campanian (ca. 75–77.5 Ma) tidal deposits of Utah and Colorado, USA. Herein, paleotidal modeling, paleogeographic reconstructions, and interpretations of depositional process regimes are combined to evaluate the regional-scale (hundreds to thousands of kilometers) basin physiographic controls on tidal range and currents along these regressive shorelines in the “Utah Bight”, southwestern Western Interior Seaway. Paleotidal modeling using a global and astronomically forced tidal model, combined with paleobathymetric sensitivity tests, indicates the location of stratigraphic units preserving pronounced tidal influence only when the seaway had a deep center (∼400 m) and southern entrance (>100 m). Maximum tidal velocity vectors under these conditions suggest a dominant southeasterly ebb tide within the Utah Bight, consistent with the location and orientation of paleocurrent measurements in regressive, tide-influenced deltaic units. The modeled deep paleobathymetry increased tidal inflow into the basin and enhanced local-scale (tens to hundreds of kilometers) resonance effects in the Utah Bight, where an amphidromic cell was located. However, the preservation of bidirectional, mudstone-draped cross-stratification in fine- to medium-grained sandstones requires tides in combination with fluvial currents and/or local tidal amplification below the maximum resolution of model meshes (∼10 km). These findings suggest that while regional-scale controls govern tidal potential within basins, localized physiography exerts an important control on the preservation of tidal signatures in the geologic record.</jats:p>
Dean C, Allison P, Hampson G, et al., 2019, Aragonite bias exhibits systematic spatial variation in the late Cretaceous Western Interior Seaway, North America, Paleobiology, Vol: 45, Pages: 571-597, ISSN: 0094-8373
Preferential dissolution of the biogenic carbonate polymorph aragonite promotes preservational bias in shelly marine faunas. Whilst field studies have documented the impact of preferential aragonite dissolution on fossil molluscan diversity, its impact on regional and global biodiversity metrics is debated. Epicontinental seas are especially prone to conditions which both promote and inhibit preferential dissolution, which may result in spatially extensive zones with variable preservation. Here we present a multi-faceted evaluation of aragonite dissolution within the late Cretaceous Western Interior Seaway of North America. Occurrence data of molluscs from two time intervals (Cenomanian-Turonian boundary, early Campanian) are plotted on new high-resolution paleogeographies to assess aragonite preservation within the seaway. Fossil occurrences, diversity estimates and sampling probabilities for calcitic and aragonitic fauna were compared in zones defined by depth and distance from the seaway margins. Apparent range sizes, which could be influenced by differential preservation potential of aragonite between separate localities, were also compared. Our results are consistent with exacerbated aragonite dissolution within specific depth zones for both time slices, with aragonitic bivalves additionally showing a statistically significant decrease in range size compared to calcitic fauna within carbonate-dominated Cenomanian-Turonian strata. However, we are unable to conclusively show that aragonite dissolution impacted diversity estimates. Therefore, whilst aragonite dissolution is likely to have affected the preservation of fauna in specific localities, time averaging and instantaneous preservation events preserve regional biodiversity. Our results suggest that the spatial expression of taphonomic biases should be an important consideration for paleontologists working on paleobiogeographic problems.
Onyenanu G, Hampson GJ, Fitch P, et al., 2019, Effects of erosional scours on reservoir properties of heterolithic, distal lower shoreface sandstones, Petroleum Geoscience, Vol: 25, Pages: 235-248, ISSN: 1354-0793
Distal intervals of interbedded sandstones and mudstones in shallow-marine, wave-dominated shoreface and deltaic reservoirs may contain significant hydrocarbon resources, but their reservoir properties are difficult to predict. Relatively small-scale (200 × 100 × 20 m) three-dimensional object-based reservoir models, conditioned to outcrop analogue data, have been used to investigate the controls on the proportion of sandstone, the proportion of sandstone beds that are connected by sandstone-filled erosional scours and the effective vertical-to-horizontal permeability ratio (kv/kh) of such intervals. The proportion of sandstone is controlled by sandstone-bed and mudstone-interbed thickness, and by parameters that describe the geometry, dimensions and lateral-stacking density of sandstone-filled scours. Sandstone-bed connectivity is controlled by the interplay between the thickness of mudstone interbeds and sandstone-filled erosional scours. Effective kv/kh is controlled by the proportion of sandstone, which represents the effects of variable distributions and dimensions of mudstones produced by scour erosion, provided that scour thickness is greater than mudstone-interbed thickness. These modelling results provide a means of estimating the effective kv/kh at the scale of typical reservoir-model grid cells using values of mudstone-interbed thickness and the proportion of sandstone that can potentially be provided by core data.
Jacquemyn C, Jackson MD, Hampson GJ, 2019, Surface-based geological reservoir modelling using grid-free NURBS curves and surfaces, Mathematical Geosciences, Vol: 51, Pages: 1-28, ISSN: 1874-8953
Building geometrically realistic representations of geological heterogeneity in reservoir models is a challenging task that is limited by the inflexibility of pre-defined pillar or cornerpoint grids. Surface-based modelling workflow uses grid-free surfaces that allows efficient creation of geological models without the limitations of pre-defined grids. Surface-based reservoir modelling uses a boundary representation approach in which all heterogeneity of interest (structural, stratigraphic, sedimentological, diagenetic) is modelled by its bounding surfaces, independent of any grid. Volumes bounded by these surfaces are internally homogeneous and thus no additional facies or petrophysical modelling is performed within these geological domains and no grid or mesh discretization is needed during modelling. Any heterogeneity to be modelled within such volumes is incorporated by adding surfaces. Surfaces and curves are modelled using a parametric NURBS (non-uniform rational B-splines) description. These surfaces are efficient to generate and manipulate, and allow fast creation of multiple realizations of geometrically realistic reservoir models. Multiple levels of surface hierarchy are introduced to allow modelling of all features of interest at the required level of detail; surfaces at one hierarchical level are constructed so as to truncate or conform to surfaces of a higher hierarchical level. This procedure requires joining, terminating and stacking of surfaces to ensure that models contain “watertight” surface-bounded volumes. NURBS curves are used to represent well trajectories accurately, including multi-laterals or side-tracks. Once all surfaces and wells have been generated, they are combined into a reservoir model that takes into account geological relationships between surfaces and preserves realistic geometries.
van Cappelle M, Hampson GJ, Johnson HD, 2018, Spatial and temporal evolution of coastal depositional systems and regional depositional process regimes: Campanian Western Interior Seaway, USA, Journal of Sedimentary Research, Vol: 88, Pages: 873-897, ISSN: 1527-1404
This paper provides a critical review and regional synthesis of Late Cretaceous shallow-marine deposits along part of the western margin of the Western Interior Seaway of North America, which contains the most extensively documented outcrop-based studies of siliciclastic coastal depositional systems in the world. The results of this synthesis are presented in the form of paleogeographic maps (covering present-day New Mexico, Utah, Colorado, and Wyoming, USA) for five timeslices in the Campanian. These maps are used to evaluate the spatial and temporal evolution of regional depositional process regimes along a large (> 1000 m) stretch of coastline. The evolution of regional depositional process regimes is linked to tectonic and paleoceanographic controls on the Western Interior Seaway, which enables the results of this synthesis to be applied to prediction of depositional process regimes in other, less intensively studied basins.Six gross depositional environments have been mapped for each timeslice: (1) alluvial to coastal-plain sandstones; (2) coastal-plain coals, mudstones, and sandstones; (3) shoreline sandstones; (4) marine mudstones; (5) gravity-flow siltstones and sandstones; and (6) marine marls and chalk. Shoreline sandstones in each timeslice are interpreted in further detail using documented evidence for the three principal classes of depositional process (wave, tidal, and fluvial) and published reconstructions of coastal morphology, which is widely considered to reflect depositional process regime. Based on these interpretations, shoreline sandstones are assigned to five categories of depositional process regime: (1) regressive wave-dominated shorefaces and delta fronts; (2) regressive river-dominated delta fronts; (3) regressive mixed tide- and wave-influenced delta fronts; (4) regressive tide-dominated delta fronts; and (5) transgressive barrier islands, back-barrier lagoons, and estuaries. The accuracy of and uncertainty in classification of deposit
Onyenanu GI, Jacquemyn CEMM, Graham GH, et al., 2018, Geometry, distribution and fill of erosional scours in a heterolithic, distal lower shoreface sandstone reservoir analogue: Grassy Member, Blackhawk Formation, Book Cliffs, Utah, USA, Sedimentology, Vol: 65, Pages: 1731-1760, ISSN: 0037-0746
Many shoreface sandstone reservoirs host significant hydrocarbon volumes within distal intervals of interbedded sandstones and mudstones. Hydrocarbon production from these reservoir intervals depends on the abundance and proportion of sandstone beds that are connected by erosional scours, and on the lateral extent and continuity of interbedded mudstones. Cliff‐face exposures of the Campanian ‘G2’ parasequence, Grassy Member, Blackhawk Formation in the Book Cliffs of east‐central Utah, USA, allow detailed characterization of 128 erosional scours within such interbedded sandstones and mudstones in a volume of 148 m length, 94 m width and 15 m height. The erosional scours have depths of up to 1·1 m, apparent widths of up to 15·1 m and steep sides (up to 35°) that strike approximately perpendicular (N099 ± 36°) to the local north–south palaeoshoreline trend. The scours have limited lateral continuity along strike and down dip, and a relatively narrow range of apparent aspect ratio (apparent width/depth), implying that their three‐dimensional geometry is similar to non‐channelized pot casts. There is no systematic variation in scour dimensions, but ‘scour density’ is greater in amalgamated (conjoined) sandstone beds over 0·5 m thick, and increases upward within vertical successions of upward‐thickening conjoined sandstone beds. There is no apparent organization of the overall lateral distribution of scours, although localized clustering implies that some scours were re‐occupied during multiple erosional events. Scour occurrence is also associated with locally increased amplitude and laminaset thickness of hummocky cross‐stratification in sandstone beds. The geometry, distribution and infill character of the scours imply that they were formed by storm‐generated currents coincident with riverine sediment influx (‘storm floods’). The erosional scours increase the vertical and lateral connectivity
Deveugle PEK, Jackson MD, Hampson GJ, 2018, A comparative study of reservoir modeling techniques and their impact on predicted performance of fluvial-dominated deltaic reservoirs: reply, AAPG Bulletin, Vol: 102, Pages: 1664-1667, ISSN: 0149-1423
Le Blévec T, Dubrule O, John CM, et al., 2018, Geostatistical modelling of cyclic and rhythmic facies architectures, Mathematical Geosciences, Vol: 50, Pages: 609-637, ISSN: 1874-8961
A Pluri-Gaussian method is developed for facies variables in three dimensions to model vertical cyclicity related to facies ordering and rhythmicity. Cyclicity is generally characterised by shallowing-upward or deepening-upward sequences and rhythmicity by the repetition of facies at constant intervals along sequences. Both of these aspects are commonly observed in shallow-marine carbonate successions, especially in the vertical direction. A grid-free spectral simulation approach is developed, with a separable covariance allowing a dampened hole-effect to capture rhythmicity in the vertical direction and a different covariance in the lateral plane along strata, as in space-time models. In addition, facies ordering is created by using a spatial shift between two latent Gaussian functions in the Pluri-Gaussian approach. Rapid conditioning to data is performed via Gibbs sampling and kriging using the screening properties of separable covariances. The resulting facies transiograms can show complex patterns of cyclicity and rhythmicity. Finally, a three dimensional case study of shallow-marine carbonate deposits at outcrop shows the applicability of the modelling method.
Jacquemyn C, Jackson MD, Hampson GJ, et al., 2018, Geometry, spatial arrangement and origin of carbonate grain-dominated, scour-fill and event-bed deposits: Late Jurassic Jubaila Formation and Arab-D Member, Saudi Arabia, Sedimentology, Vol: 65, Pages: 1043-1066, ISSN: 0037-0746
Outcrop analogues of the Late Jurassic lower Arab-D reservoir zone in Saudi Arabia expose a succession of fining-upward cycles deposited on a distal middle-ramp to outer-ramp setting. These cycles are interrupted by erosional scours that incise up to 1·8 m into underlying deposits and are infilled with intraclasts up to boulder size (1 m diameter). Scours of similar size and infill are not commonly observed on low-angle carbonate ramps. Outcrops have been used to characterize and quantify facies-body geometries and spatial relationships. The coarse grain size of scour-fills indicates scouring and boulder transport by debris or hyperconcentrated density flows strengthened by offshore-directed currents. Longitudinal and lateral flow transformation is invoked to produce the ‘pit and wing’ geometry of the scours. Scour pits and wings erode up to 1·8 m and 0·7 m deep, respectively, and are on average 50 m wide between wing tips. The flat bases of the scours and their lack of consistent aspect ratio indicate that erosion depth was limited by the presence of cemented firmgrounds in underlying cycles. Scours define slightly sinuous channels that are consistently oriented north–south, sub-parallel to the inferred regional depositional strike of the ramp, suggesting that local palaeobathymetry was more complex than commonly assumed. Weak lateral clustering of some scours indicates that they were underfilled and reoccupied by later scour incision and infill. Rudstone scour-fills required reworking of material from inner ramp by high-energy, offshore-directed flows, associated with storm action and the hydraulic gradient produced by coastal storm setup, to generate erosion and sustain transport of clasts that are generally associated with steeper slopes. Quantitative analysis indicates that these coarse-grained units have limited potential for correlation between wells as laterally continuous, highly permeable rese
Debbabi Y, Jackson M, Hampson G, et al., 2018, Impact of the buoyancy–viscous force balance on two-phase flow in layered porous media., Transport in Porous Media, Vol: 2018, ISSN: 0169-3913
Motivated by geological carbon storage and hydrocarbon recovery, the effect of buoyancy and viscous forces on the displacement of one fluid by a second immiscible fluid, along parallel and dipping layers of contrasting permeability, is characterized using five independent dimensionless numbers and a dimensionless storage or recovery efficiency. Application of simple dimensionless models shows that increased longitudinal buoyancy effects increase storage efficiency by reducing the distance between the leading edges of the injected phase in each layer and decreasing the residual displaced phase saturation behind the leading edge of the displacing phase. Increased transverse buoyancy crossflow increases storage efficiency if it competes with permeability layering effects, but reduces storage efficiency otherwise. When both longitudinal and transverse buoyancy effects are varied simultaneously, a purely geometrical dip angle group defines whether changes in storage efficiency are dominated by changes in the longitudinal or transverse buoyancy effects. In the limit of buoyancy-segregated flow, we report an equivalent, unidimensional flow model which allows rapid prediction of storage efficiency. The model presented accounts for both dip and layering, thereby generalizing earlier work which accounted for each of these but not both together. We suggest that the predicted storage efficiency can be used to compare and rank geostatistical realizations, and complements earlier heterogeneity measures which are applicable in the viscous limit.
Debbabi Y, Stern D, Hampson GJ, et al., 2018, Use of dimensionless scaling groups to interpret reservoir simulation results, Journal of Petroleum Science and Engineering, Vol: 163, Pages: 270-282, ISSN: 1873-4715
In conducting studies to make reservoir management decisions, it is important to efficiently interpret results of reservoir simulations. An understanding of how and why predicted reservoir performance changes with model parameters guides evaluation of production strategies as well as exploration of the impact of uncertainty in reservoir description. The aim of this work is to demonstrate the use of dimensionless scaling groups to interpret and qualitatively predict simulation results of multiphase flow in subsurface reservoirs with a large number of wells. Dimensionless scaling groups which quantify the balance between the forces causing fluid flow were computed between well pairs to rationalize simulation results. The data required to partition the model according to injector-producer pairs and estimate the scaling groups were obtained within minutes using simplified, single-phase numerical experiments. We show that scaling groups can be used to classify multiphase flow behaviours observed over the field into a small set of flow regimes characterized by the combination of their dominant forces. Changes in fluid distribution and reservoir performance with the model parameters can be analyzed in terms of changes in the force balance, and qualitatively predicted using the scaling groups. Predictions made using scaling groups may guide, and thereby reduce the use of, time-consuming multiphase flow simulations to optimize field development plans, to improve the calibration of reservoir models to production data and interpreted subsurface heterogeneity, and to assess the impact of reservoir uncertainties on production.
Madjid M, Vandeginste V, Hampson GJ, et al., 2018, Drones in carbonate geology: opportunities and challenges, and application in diagenetic dolomite geobody mapping, Marine and Petroleum Geology, Vol: 91, Pages: 723-734, ISSN: 1873-4073
Unmanned aerial vehicles (UAVs) or drones have become widely available for use in a broad range of disciplines. Despite the decreased cost and technological developments of platforms, sensors and software, the use of drones in carbonate geology has yet to be exploited. Nevertheless, drones offer multiple advantages over traditional field work or high-altitude remote sensing techniques, in that they enable the reconstruction of three dimensional models of inaccessible or unsafe outcrops, and can bridge the spatial scale gap in mapping between manual field techniques and airborne, high-altitude remote sensing methods. In this contribution, we present our methodology of structure from motion photogrammetry on drone-captured images and highlight opportunities and challenges of using drones in carbonate geological studies. Moreover, we apply this method to document the spatial distribution and dimensions of diagenetic dolomite geobodies in Carboniferous limestone host rock of the Picos de Europa, northern Spain. The results of our study indicate that dolomite geobodies occur preferentially near to strike-slip faults, rather than thrust faults or specific types of limestone host rock lithology, in the study area. The geobody dimensions appear to be related to the strain magnitude of the strike-slip faults. We propose that these identified links and controls are applicable to structurally-controlled dolomitization on a more general basis. Our study has demonstrated the potential for using drones in carbonate geological studies.
Zhang Z, Geiger S, Rood M, et al., 2017, A Tracing Algorithm for Flow Diagnostics on Fully Unstructured Grids With Multipoint Flux Approximation, SPE Journal, Vol: 22, Pages: 1946-1962, ISSN: 1930-0220
Flow diagnostics is a common way to rank and cluster ensembles of reservoir models depending on their approximate dynamic behavior before beginning full-physics reservoir simulation. Traditionally, they have been performed on corner-point grids inherent to geocellular models. The rapid-reservoir-modeling (RRM) concept aims at fast and intuitive prototyping of geologically realistic reservoir models. In RRM, complex reservoir heterogeneities are modeled as discrete volumes bounded by surfaces that are sketched in real time. The resulting reservoir models are discretized by use of fully unstructured tetrahedral meshes where the grid conforms to the reservoir geometry, hence preserving the original geological structures that have been modeled.This paper presents a computationally efficient work flow for flow diagnostics on fully unstructured grids. The control-volume finite-element method (CVFEM) is used to solve the elliptic pressure equation. The flux field is a multipoint flux approximation (MPFA). A new tracing algorithm is developed on a reduced monotone acyclic graph for the hyperbolic transport equations of time of flight (TOF) and tracer distributions. An optimal reordering technique is used to deal with each control volume locally such that the hyperbolic equations can be computed in an efficient node-by-node manner. This reordering algorithm scales linearly with the number of unknowns.The results of these computations allow us to estimate swept-reservoir volumes, injector/producer pairs, well-allocation factors, flow capacity, storage capacity, and dynamic Lorenz coefficients, which all help approximate the dynamic reservoir behavior. The total central-processing-unit (CPU) time, including grid generation and flow diagnostics, is typically a few seconds for meshes with O (100,000) unknowns. Such fast calculations provide, for the first time, real-time feedback in the dynamic reservoir behavior while models are prototyped.
Hampson GJ, Premwichein K, 2017, Sedimentologic character of ancient muddy subaqueous-deltaic clinoforms: Down Cliff Clay Member, Bridport Sand Formation, Wessex Basin, UK, Journal of Sedimentary Research, Vol: 87, Pages: 951-966, ISSN: 1527-1404
Muddy subaqueous clinoforms are a common feature of many modern deltas, particularly those developed in basins with strong waves, tides, or oceanographic currents. Ancient examples have only rarely been reported, implying that they are under-recognized. Herein, the sedimentological characteristics of muddy subaqueous-deltaic clinoforms from the Lower Jurassic Down Cliff Clay Member of the Bridport Sand Formation, Wessex Basin, UK, are described and interpreted, as a reference to re-evaluate other ancient shallow-marine mudstone successions.Deposits below the Down Cliff Clay clinoforms consist of erosionally based, bioclastic sandy limestone beds intercalated with upward-thickening fossiliferous claystones and siltstones (facies association A), which record upward-increasing water depth under conditions of minor input of clastic sediment and reworking by storm waves. These deposits are downlapped by foreset-to-toeset deposits of the subaqueous-deltaic clinoforms, which comprise claystones and siltstones that contain calcareous nodules and are variably bioturbated by a low-diversity trace-fossil assemblages dominated by Chondrites (facies association B). These foreset-to-toeset deposits record slow deposition (undecompacted sediment accumulation rate of c. 4.4 m/Myr) from suspension fall-out and distal sediment gravity flows under conditions of intermittent and/or poor oxygenation of bottom waters. Clinoform foreset deposits dip paleoseaward at 2°, and consist of siltstones and sandy siltstones that are moderately to completely bioturbated by a high-diversity trace-fossil assemblage (facies association C). Thin (< 1 cm), erosionally based, parallel-laminated and current-ripple cross-laminated siltstone and very fine-grained sandstone beds in the foreset deposits record episodic sediment gravity flows and tractional currents. Foreset deposits record relatively rapid deposition (undecompacted sediment accumulation rate of c. 194 m/Myr) above effective storm wave
Debbabi Y, Jackson MD, Hampson GJ, et al., 2017, Capillary Heterogeneity Trapping and Crossflow in Layered Porous Media, Transport in Porous Media, Vol: 120, Pages: 183-206, ISSN: 0169-3913
We examine the effect of capillary and viscous forces on the displacement of one fluid by a second, immiscible fluid across and along parallel layers of contrasting porosity, and relative permeability, as well as previously explored contrasts in absolute permeability and capillary pressure. We consider displacements with wetting, intermediate-wetting and non-wetting injected phases. Flow is characterized using six independent dimensionless numbers and a dimensionless storage efficiency, which is numerically equivalent to the recovery efficiency. Results are directly applicable to geologic carbon storage and hydrocarbon production. We predict how the capillary–viscous force balance influences storage efficiency as a function of a small number of key dimensionless parameters, and provide a framework to support mechanistic interpretations of complex field or experimental data, and numerical model predictions, through the use of simple dimensionless models. When flow is directed across layers, we find that capillary heterogeneity traps the non-wetting phase, regardless of whether it is the injected or displaced phase. However, minimal trapping occurs when the injected phase is intermediate-wetting or when high-permeability layers contain a smaller moveable volume of fluid than low-permeability layers. A dimensionless capillary-to-viscous number defined using the layer thickness rather than the more commonly used system length is most relevant to predict capillary heterogeneity trapping. When flow is directed along layers, we show that, regardless of wettability, increasing capillary crossflow reduces the distance between the leading edges of the injected phase in each layer and increases storage efficiency. This may be counter-intuitive when the injected phase is non-wetting. Crossflow has a significant impact on storage efficiency only when high-permeability layers contain a smaller moveable volume of fluid than low-permeability layers. In that case, capillary he
Flood YS, Hampson GJ, 2017, Analysis of floodplain sedimentation, avulsion style and channelised fluvial sandbody distribution in an upper coastal plain reservoir: Middle Jurassic Ness Formation, Brent Field, UK North Sea, Sedimentology of Paralic Reservoirs: Recent Advances, Editors: Hampson, Reynolds, Kostic, Wells, Publisher: Geological Society of London, Pages: 109-140
Numerical models and recent outcrop case studies of alluvial-to-coastal-plain strata suggest that autogenic avulsion can control the stacking density and architecture of channelized fluvial sandbodies. The application of these models to subsurface well data was tested by the analysis of upper coastal plain deposits of the late Bajocian Ness Formation in the Brent Field reservoir, UK North Sea. These coastal plain deposits accumulated during the progradation and retrogradation of the wave-dominated ‘Brent Delta’. Sedimentological facies analysis and palaeosol characterization in cores were used to interpret the styles of palaeochannel avulsion. These results were then compared with the dimensions and distributions of channelized fluvial sandbodies that had been quantified by spatial statistical tools (lacunarity, Besag’s L function) applied to interpretative correlation panels between closely spaced wells. The results indicate that the distributions of channelized sandbodies may plausibly have been generated by avulsions and that they influence sandbody connectivity and pressure depletion patterns. Intervals of upper coastal plain strata with relatively wide sandbodies that display some clustering in their stratigraphic architecture are associated with a high proportion of avulsions by incision and annexation in core samples. Such intervals display relatively good vertical pressure communication and relatively slow, uniform pressure depletion.
Hampson GJ, Reynolds AD, Kostic B, et al., 2017, Introduction to the sedimentology of paralic reservoirs: recent advances, Sedimentology of Paralic Reservoirs: Recent Advances, Editors: Hampson, Reynolds, Kostic, Wells, Publisher: Geological Society of London, Pages: 1-6, ISBN: 9781786202741
Paralic reservoirs reflect a range of clastic depositional environments developed along or near coastlines, including deltas, shoreline–shelf systems and estuaries. Such reservoirs provide the backbone of production in many mature basins around the world, and contribute significantly to global conventional hydrocarbon production. Strata that host these reservoirs are shaped by a wide variety of depositional processes and controls which reflect the upstream supply of sediment and water, the characteristics of the receiving basin, relative sea level, tectonic setting, and the internal dynamics of depositional systems. Consequently, they exhibit much variability in their stratigraphic architecture and sedimentological heterogeneity, which translates into complex patterns of reservoir distribution and reservoir performances that are challenging to predict, optimize and manage. This Special Publication presents new research and developments in established approaches to exploration and production of paralic reservoirs. It arises from the conference and associated core workshop titled ‘Sedimentology of Paralic Reservoirs: Recent Advances and their Applications’, which was organized by the Petroleum Group of the Geological Society of London and held in London from 18 to 21 May 2015.
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