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Bulletin Article

Handling natural complexity in three-dimensional geomechanical restoration, with application to the recent evolution of the outer fold and thrust belt, deep-water Niger Delta

Volumetric restoration can provide crucial insights into the structural evolution of three-dimensional (3-D) petroleum systems. A major limitation to its widespread application is the need to include complex architectures and realistic mechanics such as flexural slip. We apply an implicit approach that allows for, including unconformities, thin and/or pinched-out layers in the models but that cannot explicitly localize slip along horizons. To take advantage of this approach while accounting for flexural slip in 3-D restoration, we investigate new geomechanical properties. We consider flexural slip folding as a result of stacked rigid and thin weak layers, which can be modeled using transversely isotropic properties. We compare restorations of an anticline using transversely isotropic properties, isotropic properties, and a stack of rigid isotropic layers with nonfrictional slip between the layers. Our results show that transversely isotropic properties reasonably approximate flexural slip folding. We use these new tools to model the evolution of a complex system located in the Niger Delta toe. The system includes a detachment fold, a fault-bend fold, and a structural wedge formed in series. Growth stratigraphy and erosional surfaces delimit the kinematics of deformation. Regional erosive surfaces, 3-D gradients of fault slip, and vertical variations in mechanical strength motivated the use of our new restoration techniques. Restoring two growth units results not only in reinforcing the interpretation that the area is behaving as a deforming thrust sheet at critical taper, but also in highlighting coeval activity on both the hinterland structures and the toe of the thrust belt.

Added on 31 December, 2012

Bulletin Article

Assessing the extent of carbonate deposition in early rift settings

Select lacustrine and marine depositional settings show a spectrum of styles of carbonate deposition and illustrate the types of carbonates, with an emphasis on microbialites and tufa, to be expected in early rift settings. Early rift lake examples examined in this review article are all from East Africa: Lakes Turkana, Bogoria, Natron and Magadi, Manyara, and Tanganyika. Other lake examples include four from the western United States (Great Salt Lake and high lake level Lake Bonneville, Mono Lake and high lake level Russell Lake, Pyramid Lake and high lake level Lake Lahontan, and Searles Lake) and two from Australia (Lakes Clifton and Thetis). Marine basin examples are the Hamelin Pool part of Shark Bay from Australia (marginal marine) and the Red Sea (marine rift). Landsat images and digital elevation models for each example are used to delineate present and past lake-basin margins based on published lake-level elevations, and for some examples, the shorelines representing different lake levels can be compared to evaluate how changes in size, shape, and lake configuration might have impacted carbonate development. The early rift lakes show a range of characteristics to be expected in lacustrine settings during the earliest stages of continental extension and rifting, whereas the Red Sea shows well advanced rifting with marine incursion and reef–skeletal sand development. Collectively, the lacustrine examples show a wide range of sizes, with several of them being large enough that they could produce carbonate deposits of potential economic interest. Three of the areas—Great Salt Lake and high lake level Lake Bonneville, Pyramid Lake and high lake level Lake Lahontan, and the Red Sea—are exceedingly complex in that they illustrate a large degree of potential depositional facies heterogeneity because of their size, irregular pattern, and connectivity of subbasins within the overall basin outline.

Added on 31 December, 2012

Bulletin Article

Subsidence controls on foreland basin development of northwestern offshore Cuba, southeastern Gulf of Mexico

We reviewed the tectonostratigraphic evolution of the Jurassic–Cenozoic collision between the North American and the Caribbean plate using more than 30,000 km (18,641 mi) of regional two-dimensional (2-D) academic seismic lines and Deep Sea Drilling Project wells of Leg 77. The main objective is to perform one-dimensional subsidence analysis and 2-D flexural modeling to better understand how the Caribbean collision may have controlled the stratigraphic evolution of the offshore Cuba region. Five main tectonic phases previously proposed were recognized: (1) Late Triassic–Jurassic rifting between South and North America that led to the formation of the proto-Caribbean plate; this event is interpreted as half grabens controlled by fault family 1 as the east-northeast–south-southwest–striking faults; (2) Middle–Late Jurassic anticlockwise rotation of the Yucatan block and formation of the Gulf of Mexico; this event resulted in north-northwest–south-southeast–striking faults of fault family 2 controlling half-graben structures; (3) Early Cretaceous passive margin development characterized by carbonate sedimentation; sedimentation was controlled by normal subsidence and eustatic changes, and because of high eustatic seas during the Late Cretaceous, the carbonate platform drowned; (4) Late Cretaceous–Paleogene collision between the Caribbean plate, resulting in the Cuban fold and thrust belt province, the foreland basin province, and the platform margin province; the platform margin province represents the submerged paleoforebulge, which was formed as a flexural response to the tectonic load of the Great Arc of the Caribbean during initial Late Cretaceous–Paleocene collision and foreland basin development that was subsequently submerged during the Eocene to the present water depths as the arc tectonic load reached the maximum collision; and (5) Late Cenozoic large deep-sea erosional features and constructional sediment drifts related to the formation of the Oligocene–Holocene Loop Current–Gulf Stream that flows from the northern Caribbean into the Straits of Florida and to the north Atlantic.

Added on 31 December, 2012

Explorer President’s Column By Ted Beaumont

'Communities' Concept Starts to Grow

One of the AAPG Executive Committee’s priorities during the first five months of this fiscal year has been to study the Association’s science program with the goal of creating new conduits for generating and disseminating scientific content.

Added on 01 December, 2012

Explorer Emphasis Article By Louise Durham

Geosteering Keeps Drillers On the Right Track

It’s all about staying on target: Technological advances are helping to make geosteering an increasingly valuable tool for geologists involved in horizontal wells.

Added on 01 December, 2012

Explorer Emphasis Article By David Brown

Oklahoma Geologists are Basement-Bound

A new well in Oklahoma may be the most historic and geologically interesting project in the entire country – and for a bonus, it may involve a new helium province.

Added on 01 December, 2012

Explorer Article By Susan Eaton

Scientists Will Explore a Frozen Classroom

One more time: The AAPG Foundation’s “explorer-in-residence,” Susan Eaton, is returning to Antarctica again on a scientific expedition to study the geology and the climate found at the Bottom of the World.

Added on 01 December, 2012

Explorer Emphasis Article By Louise Durham

Tomography a Hit

Taking a closer look at the fracture networks in reservoirs has become a reality through tomography, a new seismic sector of the industry.

Added on 01 November, 2012

Explorer Article

ICE Awardees Announced

Added to the 'first-time-ever” list was the announcing of paper and poster awards at the end of the event.

Added on 01 November, 2012

Explorer Regions and Sections By Abeer Al-Zubaidi,Carol McGowen

Middle East Region Sets GTW Lineup

In an effort to continue serving the geosciences community in the Middle East, AAPG Middle East Region will be offering a number of Geosciences Technology Workshops (GTWs) where the attendees, practitioners and scientists will have an opportunity to discuss real cases, issues and experiences.

Added on 01 October, 2012

Hot Items

Explorer Article By David Brown

What Will it Take to Get CCUS Ready for Prime Time?

Nihal Darraj, carbon capture and storage researcher at Imperial College, London shares barriers to CCUS commercialization, including costs, technology, permitting and more.

Added on 01 March, 2024

Explorer Historical Highlights By Bernard Duval,Jean Laherrere,Jean-Jacques Biteau,Jean-Marie Masset

From Outcrops to the Champs-Elysées: Petroleum Exploration in the Paris Basin

The Paris Basin offers times of both discoveries and failures, from its first well drilled near Normandy in the 1920s to today.

Added on 01 March, 2024

Explorer Article By Barry Friedman

How the U Adds Value in CCUS

Carbon capture and sequestration reduces emissions, but it cannot work past cost barriers without the revenue opportunities provided by utilization and storage.

Added on 01 March, 2024

Explorer Director’s Corner By David Curtiss

Introducing the New EXPLORER, New Digital Newsletters

Perhaps you did a double take pulling the April issue of EXPLORER from the mailbox. What is this? If you joined AAPG in the last 40 years, you’ve only known EXPLORER in its long-standing tabloid format. It worked well for many years as our advertisers – particularly seismic companies – loved the large format and the ability to display their data on a sweeping canvas. For readers, it was a little more awkward.

Added on 01 April, 2024

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