Seismic Chronostratigraphy Research Articles

3-D seismic chronostratigraphy of reefs and drifts in the Browse Basin, NW Australia

Abstract In its subsurface, the Browse Basin on the Australian Northwest Shelf accommodates one of the largest Miocene–Pliocene carbonate platform provinces on Earth. This study presents a comprehensive three-dimensional (3-D) documentation and investigation of the Neogene Browse Basin carbonates based on the analysis of 15 3-D seismic reflection volumes covering ca. 33,000 km2 and 22 industry boreholes. Eight basin-wide seismic marker horizons tied to Sr isotope and biostratigraphic data provide a robust 3-D chronostratigraphic framework that (1) newly documents the occurrence of Miocene to recent carbonate systems in vast inboard basin areas; (2) presents the 3-D distribution and dynamic development of carbonate platforms through time constrained by absolute ages; and (3) supports the detailed 3-D interpretation of Miocene to recent depositional processes and key stratigraphic controls. Around 18.6 Ma, the extent of all Browse Basin carbonate platforms was ca. 8600 km2, rising to >10,000 km2 between 15.6 Ma and 12 Ma. By ca. 9.7 Ma, the total platform extent had decreased to ca. 5700 km2, waning to <2800 km2 in the Pliocene. The observed reef demise is less abrupt than previously thought and comprises two steps, with the first in the late Miocene on the outer shelf and the second in the Pliocene on the middle and inner shelf. The Miocene outer-shelf platform demise coincided with (1) strong subsidence that outpaced sedimentation, (2) an increase in NW–SE-oriented tidal current activity, (3) the development of NNE–SSW-oriented bottom currents, and (4) the onset of drift sedimentation. The Pliocene demise of middle-shelf reefs coincided with (1) an increase of clastic sediment input from land and (2) stalling of the Indonesian Throughflow around 3.7 Ma. The basin-wide, 3-D seismic chronostratigraphic analysis presented supports a re-evaluation of the key controls for Miocene and Pliocene reef growth and decay on the NW Shelf and highlights the complexity of interacting global, regional, and local processes and peculiarities in carbonate platform development.

Seismic chronostratigraphy at reservoir scale: Lessons from a realistic seismic modeling of mixed clastic-carbonate strata in the Permian Basin, West Texas and New Mexico, USA

We tested the validity of tracking seismic events as representations of chronostratigraphic surfaces at the subseismic, high-frequency-cycle level. A high-resolution geocellular model was generated from approximately 400 m of mixed clastic-carbonate sequences in the San Andres and Grayburg Formations in the Permian Basin, with 0.3–0.6 m layering and minimal upscaling. Realistic stratigraphic framework, facies, and velocity volumes were created by geostatistically mapping data from outcrop and subsurface sources while honoring state-of-the-art principles of stratigraphic and sedimentary analyses. Using the synthetic seismic data of different frequencies, the potential and pitfalls of using autotracked seismic horizons in building high-resolution reservoir models were tested. At the reservoir (meter) scale, the seismic reflections from flatter and thicker sediments with less facies and velocity heterogeneities tend to follow geologic-time surfaces; on the contrary, reflections from where thin sediments dip against flat strata with more facies and velocity heterogeneities tend to follow lithostratigraphy. For the latter seismic-guided reservoir modeling is not very precise, even with data as high as 140 Hz frequency. Therefore, for seismic-assisted reservoir prediction and modeling, the interpretation of seismic events is useful, but well calibration is critical.

The Rimthan Arch, basin architecture, and stratigraphic trap potential in Saudi Arabia

The Rimthan Arch, situated between the Arabian carbonate platform and the Gotnia intrashelf basin, represents a world class hydrocarbon province in Saudi Arabia. Middle to Upper Jurassic shallow-water depositional sequences are associated with productive hydrocarbon fields in which challenges exist in defining exploration targets, mainly stratigraphic trap plays. An attempt is made to investigate the basin depositional architecture on the flank of the Arch and also to model the stratigraphic trap potential of the youngest Arab third-order sequence. The basin architecture, stratal geometries, and impact of tectonics are explored using 3D seismic and well data. Seismic chronostratigraphy, seismic stratigraphy, seismic attribute, and log-based reservoir heterogeneity techniques are applied as an integrated approach to interpret the sequences from basin to reservoir scale. The study identifies two second-order sequences, SEQ 1 and SEQ 2, to frame a 3D geologic model and to examine basin development through time. Results derived from the integrated study indicate that although initial basin subsidence began later in SEQ 1 north of the Arch, it increased appreciably during SEQ 2. The Dhruma J20 maximum flooding surface, Lower Fadhili, and Hanifa provide clues in tracking major basin changes. Seismic stratigraphy applications highlight reflection terminations and prograding stratal geometries throughout the stratigraphic section to demonstrate tectonoeustatic influences. Tectonics impact SEQ 2 more intensely than SEQ 1 and may influence the migration of hydrocarbons across juxtaposed lithologies. A complex association between shallow marine tidal and ramp carbonates, and deeper basin halite beds, is linked to the subsiding Gotnia Basin. Log-facies analysis of the Arab third-order sequence demonstrates reservoir and seal trends, including the stratigraphic entrapment potential along a carbonate ramp profile. Seismic attributes support reservoir-depositional trends and salt-bed geometries. The integrated approach provides a targeted workflow to investigate the complex depositional systems and their stratigraphic trapping potential on the Arch.

Thickness imaging for high-resolution stratigraphic interpretation by linear combination and color blending of multiple-frequency panels

Despite routine demand from petroleum explorationists and field developers, interpreting (inverting) seismic data for reservoir thickness from acoustic impedance (AI) or lithology volume requires a high-quality, unbiased well database and the special skills of elite geophysicists. I have developed a new method, based on linear combination and color blending of multiple-frequency panels, to estimate AI and thickness without the strict implementation of complex mathematics and extensive well control. Aimed at readjusting the thin-bed tuning effect in a formation of normal thickness range (up to [Formula: see text]; [Formula: see text] = dominant wavelength), a linear combination of three frequency panels from [Formula: see text] data would lead to a reasonable visual match between a sandstone (shale) body and its seismic event, should the combined amplitude spectrum roughly match the AI spectrum. A red-green-blue blending of frequency panels further extends the interpretive benefits by illustrating the thickness in color, adding a sense of thickness cyclicity on the vertical view and that of sandstone thickness map on stratal-slice view. Tests using a simple wedge model and a complex, geologically realistic multi-thin-bed model demonstrate that the proposed workflow may achieve decent geometry (thickness) estimation and reasonably high correlation ([Formula: see text]) for AI prediction with minimal or no well control. The results are similar to colored inversion in the fast-track principle, with improved stability and less error (at least in this study). More complex procedures — such as linear regression and model-based inversion — may lead to minor to moderate improvement with adequate well control. An application to a field data set confirmed the value of the methods in high-resolution reservoir-thickness imaging, with a strong potential for stratigraphically oriented studies, such as seismic chronostratigraphy, sequence stratigraphy, and seismic sedimentology.

Seismic chronostratigraphy and basin development at a Mid-Cretaceous intrashelf basin margin

The Mid-Cretaceous Wasia Formation represents one of the most productive hydrocarbon carbonate sequences in the Middle East. In Saudi Arabia, limited integrated studies have assessed the complexity and spatial distribution of its reservoir depositional systems near to an intrashelf basin margin. This study was focused on an assessment of its 3D seismic chronostratigraphy by integrating key well and seismic data to evaluate the gross depositional history of the mixed carbonate-clastic system. A seismic chronostratigraphy approach was introduced to assess the geometric relationships of depositional cycles and lithologic associations in response to relative sea-level changes. The main step entailed the correlation of well log chronostratigraphy from core and biostratigraphy interpretations with closely spaced, semiautomatically generated seismic horizons from seismic reflection data. A 3D seismic chronostratigraphy cube was built to interactively assess the basin history through the Mid-Cretaceous stages. Seismic sequences were selected to assess isopachs and gross depositional trends for demarcation of shelf, shelf margin, and slope from horizon attributes including root-mean-square amplitude and frequency decomposition. The results found the oldest Albian Safaniya member to be a generalized low-angle ramp shelf slope with thinning of sequences toward an intrashelf basin. Later, in the Albian, Cenomanian, and Turonian, carbonate factories developed distinct seismic sequences with steepened prograding systems in the Mauddud, Ahmadi/Rumaila, and Mishrif members at the intrashelf basin margin. Generally, areas immediately landward of the shelf margin possessed the most favorable reservoir lithologies of rudist-bearing platform carbonates, with source-rock distribution confined to basinal equivalents of sequences. The seismic chronostratigraphy approach proved to be fundamental to understanding the Wasia carbonate depositional system because it provided a technique to assess the varied stratal architectures of the main productive sequences. The integrated technique represents a unique methodology for exploration targeting of conventional reservoirs and unconventional source rocks.

Introduction to special section: Seismic chronostratigraphy

Advances in seismic acquisition and processing have both improved the resolution of the seismic data and allowed a generation of increasingly sophisticated earth models. Volume-based and horizon-based assessments of 3D seismic “volumes” can be used to build 3D geologic models with the aid of

Stratal slice: The next generation

Vail and his colleagues (1977a, b) laid a foundation for seismic chronostratigraphy. By analyzing the relative rise of sea level indicated by coastal onlap, these workers invented a novel way of converting a stratigraphic cross section in the depth or traveltime domain to a chronostratigraphic chart in the Wheeler domain (Figure 1a and Figure 1b). With the widespread use of seismic data in the industry, such conversion can now be achieved conveniently with the proper software at the basinal, regional, or prospect scale (Figure 1c and Figure 1d).