Julian David Clark

Architectural Elements and Growth Patterns of Submarine Channels: Application to Hydrocarbon Exploration

Modern and ancient submarine channels show a wide range of architectural styles. Architectural element analysis is a useful descriptive means to characterize the type of channel fill, show the interconnectivity and lateral continuity of sand bodies, and interpret the causal sedimentary processes. This paper combines a review of the literature on submarine channels with new observations and analysis, and proposes architectural element models for submarine channels, in particular, demonstrating how these models can be applied to interpreting the sequential fill of ancient submarine channels. Data for the dimensions and degrees of lateral continuity and vertical connectivity of channel elements, such as those giving rise to reservoir heterogeneities in hydrocarbon exploratio , are presented for a variety of examples of architectural elements, providing quantitative information for reservoir analog models.

3D high-resolution digital models of outcrop analogue study sites to constrain reservoir model uncertainty: an example from Alport Castles, Derbyshire, UK

Advances in data capture and computer technology have made possible the collection of 3D high-resolution surface and subsurface digital geological data from outcrop analogues. This paper describes research to obtain the 3D distribution and internal sedimentary architecture of turbidite channels and associated sediments at a study site in the Peak District National Park, Derbyshire, UK. The 1D, 2D and 3D digital datasets included Total Station survey, terrestrial photogrammetry and remote sensing, sedimentary logs and a Ground Penetrating Radar (GPR) dataset. A grid of 2D GPR profiles was acquired behind a cliff outcrop; electromagnetic reflection events correlated with cliff face sedimentary horizons logged by Vertical Radar Profiling. All data were combined into a Digital Solid Model (DSM) dataset of the site within reservoir modelling software. The DSM was analysed to extract 3D architectural geometries for petroleum reservoir models. A deterministic base model was created using all information, along with a suite of heterogeneous turbidite reservoir models, using 1D, 2D or 3D information. The model suite shows significant variation from the deterministic model. Models built from 2D information underestimated connectivity and the continuity of geobodies, but overestimated channel sinuosity. Advantages of using 3D digital outcrop analogue data for 3D reservoir models are detailed.

Outcrop-based stochastic modelling of turbidite amalgamation and its effects on hydrocarbon recovery

In sandstone-dominated successions of sheet-like turbidites, erosion of thin shale horizons during deposition of the overlying turbidite may lead locally to vertical amalgamation of sandstone beds, resulting in discontinuous thin fine-grained beds or, in the extreme case, thoroughly amalgamated sandstone. Measurements of discontinuous shale lengths from very well exposed turbidite successions have enabled the development of a mixed rule-based/stochastic model for the erosion of shales. Monte Carlo realizations of 2D cross-sections were used to examine the effects of shale discontinuities on both single-and two-phase flow, at the genetic sedimentary unit scale. Results demonstrate that the flow is strongly dependent on the balance of viscous, capillary and gravity forces, which can vary according to the distribution of amalgamation surfaces. The single-phase upscaled ratio of horizontal to vertical permeability and the fraction of mobile oil recovered can be related to the fraction of shale removed (amalgamation ratio) by log-linear and linear relationships respectively.

Quantitative outcrop characterization of an analog to weakly confined submarine channel systems: Morillo 1 member, Ainsa Basin, Spain

Weakly confined channel systems are common in low-relief minibasins on continental margins and are important hydrocarbon reservoirs. They are characterized by channels that diverge in the proximal part of the basin and converge because of topographic confinement in the distal part of the basin. The Morillo 1 member, in the Ainsa Basin, Spain, is an excellent outcrop analog of a weakly confined submarine channel system. Data from the Morillo 1 member are used to quantitatively document how reservoir characteristics vary laterally and longitudinally in weakly confined submarine channel reservoirs. The key axis-to-margin patterns are the proportions of channel elements, channel complexes, channel-complex sets, reservoir facies, and net sand content; static connectivity decreases laterally from the axis to the margins of the system. The key longitudinal patterns in the updip area are channel elements that have levees, are spatially dispersive, and have a radially divergent map pattern. In the downdip area, channel elements are spatially focused and have uniform orientations, and the proportion of channel elements does not change along the longitudinal profile. However, the size of channel elements, percentage of reservoir facies, and connectivity of channel elements are higher in the downdip area. Patterns identified herein are significant because they cannot be resolved using subsurface or sea-floor data. Results of this study can therefore be used to reduce uncertainty in the interpretation of subsurface data, provide input to constrain rule-based forward stratigraphic models, and provide input to constrain reservoir models.

The ancestral Mississippi drainage archived in the late Wisconsin Mississippi deep-sea fan

The response of continental-scale drainage systems to short-term (i.e., millennial-scale) climate change is unknown but has wide implications for understanding climate feedbacks and terrestrial-marine fluxes. The late Wisconsin Mississippi River to deep-sea fan of North America was one of Earth’s largest sediment-routing networks during the most recent glacio-eustatic cycle. To understand late Pleistocene sediment production and dispersal related to the partly glaciated, ancestral Mississippi system, we sampled late Wisconsin deep-sea fan channel-fill and lobe deposits for detrital zircon U-Pb and (U-Th)/He double-dating analyses, from Deep Sea Drilling Project (Leg 96) cores and U.S. Geological Survey piston cores. Our results suggest a late Pleistocene glacial Mississippi system that forced a larger transfer of sediment from Cordilleran magmatic provinces and the Canadian Shield when compared to the modern drainage. This indicates a potentially more expansive and/or erosive ancestral Mississippi catchment, and the efficient dispersal of terrigenous sediment, nutrients, and solutes into the deep-sea via high-discharge meltwater and glacial-lake outbursts during ice retreat.

The Charo/Arro canyon-mouth sheet system, south-central Pyrenees, Spain; a structurally influenced zone of sediment dispersal

ABSTRACT Detailed field and photogeological mapping of the Charo Canyon and Arro Sandbody, which can be traced directly into the canyon, shows the relationships between shelf, slope, canyon, and base-of-slope deposition. The Charo Canyon is incised into slope and shelf facies of the Castisent Group (50.5-49.5 Ma), and was a sediment conduit for turbidity currents and their deposits during the upper part of the Castisent Group, and the Santa Liestra Group (49.5-44 Ma). The Arro Sandbody, downslope from the Charo Canyon, belongs to the upper part of the Castisent Group. Unlike the overlying Santa Liestra channel complex, the Arro Sandbody, shows few features typical of a channel-fill deposit, but is characterized by a base-of-slope facies association in front of the canyon mouth. The key factors influencing the internal architecture of the Arro Sandbody were variations in slope angle and an increase in sediment supply, both factors being largely controlled by mid-Castisent thrust activity. This paper describes the composite fill of the Charo Canyon and investigates its relationship to the depositional setting of the downcanyon deposits.

Event-Based Geostatistical Modeling: Description and Applications

Event-based methods provide unique opportunities to improve the integration of geologic concepts into reservoir models. This may be accomplished over a continuum of rule complexity from very simple geometric models to complicated dynamics. Even the application of simple rules, including few conceptual interactions based on an understanding of stratigraphic relationships and parametric geometries for event scale depositional and erosion features, have been shown to efficiently produce complicated and realistic reservoir heterogeneities. In more complicated applications, initial and boundary conditions from analysis of paleobathymetry and external controls on sediment supply and the event rules may be informed by process models. These models have interesting features that depart from typical geostatistical model; they demonstrate emergent behaviors and preserve all information at all scales during their construction. These models may be utilized to produce very realistic reservoir models and their unique properties allow for novel applications. These modeling applications include; impact of model scale, seismic resolvability, value of information, flow relevance of advanced architecture, iterative and rule-based conditioning to sparse well and seismic data, numerical analogs for architectural concepts, statistical analysis and classification of architectures, unstructured grid construction and utilization as training and visualization tools.

The Marnes Brunes Inférieures in the Grand Coyer remnant: characteristics, structure and relationship to the Grès d’Annot

Abstract Part of the Alpine foreland basin, the Grand Coyer remnant lies in a NW-SE-trending syncline and contains turbidity current deposits derived from the south. Palaeotopography of the Marnes Bleues surface is complex but there is generally a NE-dipping confining slope in the west of the area. Palaeocurrent data suggest that aside from localized alteration of flow paths, the mean direction of flow was parallel to this slope. Three sections (Vallon de Fouès & Carton, Laupon and Sommet de la Mole) are used to illustrate the nature of the Marnes Brunes Inférieures—a transitional facies between the Marnes Bleues and the Grès d’Annot. The Marnes Brunes Inférieures is typically thin-bedded, sharp-based and sharp-topped, non-graded, predominantly very fine-grained sands, with planar and ripple lamination, interbedded with thin marls and shale. The finer grained Marnes Brunes Inférieures in the Grand Coyer area is interpreted as a distal and lateral equivalent of the coarser Grès d’Annot, which is generally thought to represent deposition along the main axis of flow. Examples are provided of how these characteristics change away from the onlap slope. Evidence is presented to illustrate the connection between syndepositional structural alteration and the common slumping observed within the Marnes Brunes Inférieures.

Detecting eustatic and tectonic signals with carbon isotopes in deep-marine strata, Eocene Ainsa Basin, Spanish Pyrenees

We explore the potential of high-resolution carbon isotope stratigraphy to provide an independent record of global sea-level changes in a 1600-m-thick succession representing ∼5 m.y. of slope sedimentation in the Eocene Ainsa Basin of Spain. The restricted physiographic setting of the basin results in a bulk δ 13 C carb signal that accurately correlates with the coeval eustatic curve from the New Jersey (USA) passive margin. We show that much of the deep-water sediment gravity flow (SGF) deposits are emplaced during eustatic lowstands and fine-grained marly intervals between SGFs correlate with rising and highstand sea levels. However, we also detect a substantial interval of SGF deposition during a sea-level highstand, confirming the nonuniqueness of the controls on clastic deposition. This approach provides a new way to assess the origin of depositional sequences and improve stratigraphic predictions in basins with limited chronostratigraphic control.

The use of vertical radar profiling (VRP) in GPR surveys of ancient sedimentary strata

Abstract Vertical radar profiling (VRP) is an application of ground penetrating radar (GPR) technologies that can extract important subsurface information from suitable outcrops. Using standard GPR equipment, a site-specific time-depth calibration can be obtained, along with correlation of observed sedimentological horizons exposed on cliff-faces. These horizons may then be correlated with subsurface reflection events imaged on fixed-offset profiles. Summaries of six GPR study sites, where the VRP technique was used, are detailed. Where possible, CMP and VRP velocities have been compared, and show good correlations. Geochemical analysis of selected sedimentary rocks shows that increasing grain size and quartz mineral percentages generally lead to increased GPR velocities. Reflection events tend to be associated with sandstone/shale boundaries.