Deep-Water Sandstone Facies and Ancient Submarine Fans: Models for Exploration for Stratigraphic Traps: DISCUSSION

Walker, Roger G.

doi:10.1306/2f9182e3-16ce-11d7-8645000102c1865d

Cited by 97 publications

References 57 publications

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Seascape Evolution on Clastic Continental Shelves and Slopes

Pratson

Nittrouer

Wiberg

et al. 2007

Continental Margin Sedimentation

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The morphology of clastic continental margins directly reflects their formative processes. These include interactions between plate movements and isostasy, which establish the characteristic stairstep shape of margins. Other factors are thermal and loading-induced subsidence, compaction and faulting/folding, which create and/or destroy accommodation space for sediment supplied by rivers and glaciers. These processes are primary controls on margin size and shape. Rivers and glaciers can also directly sculpt the margin surface when it is subaerially exposed by sea-level lowstands. Otherwise, they deposit their sediment load at or near the shoreline. Whether this deposition builds a delta depends on sea level and the energy of the ocean waves and currents. Delta formation will be prevented when sea level is rising faster than sediment supply can build the shoreline. Vigorous wave and current activity can slow or even arrest subaerial delta development by moving sediments seaward to form a subaqueous delta. This sediment movement is accomplished in part by wave-supported sediment gravity flows. Over the continental slope, turbidity currents are driven by gravity and, in combination with slides, cut submarine canyons and gullies. However, turbidity currents also deposit sediment across the continental slope. The average angle of continental slopes (~4°) lies near the threshold angle above which turbidity currents will erode the seafloor and below which they will deposit their sediment load. Therefore, turbidity currents may help regulate the dip of the continental slope. Internal waves exert a maximum shear on the continental-slope surface at about the same angle, and may be another controlling factor.

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Seascape Evolution on Clastic Continental Shelves and Slopes

Pratson

Nittrouer

Wiberg

et al. 2007

Continental Margin Sedimentation

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Explorational Rock Physics – The Link Between Geological Processes and Geophysical Observables

Avseth

2010

Petroleum Geoscience

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The field of rock physics represents the link between qualitative geological parameters and quantitative geophysical measurements. Increasingly over the last decade, rock physics has become an integral part of quantitative seismic interpretation and stands out as a key technology in petroleum geophysics. Ultimately, the application of rock physics tools can reduce exploration risk and improve reservoir forecasting in the petroleum industry.This chapter covers basic rock physics principles and practical recipes that can be applied in the field. The importance and benefit of linking rock physics to geological processes, including depositional and compactional trends, is demonstrated. It is further documented that lithology substitution can be of equal importance to fluid substitution during seismic reservoir prediction. It is essential in exploration and appraisal to be able to extrapolate away from existing wells, taking into account how the depositional environment changes, together with burial depth trends. In this way rock physics can better constrain the geophysical inversion and classification problem in underexplored marginal fields, surrounding satellite areas, or in new frontiers.Finally, practical examples and case studies are presented to demonstrate a best-practice workflow and associated limitations and pitfalls. Rock physics models are combined with well log and pre-stack seismic data, sedimentological information, inputs from basin modelling and statistical techniques, to predict reservoir geology and fluids from seismic amplitudes.P. Avseth ( ) Odin Petroleum, Bergen; NTNU, Trondheim, Norway e-mail: pavseth@yahoo.com Quantitative Seismic Interpretation Using Rock PhysicsThe main goal of conventional, qualitative seismic interpretation is to recognise and map geological elements and/or stratigraphic patterns from seismic reflection data. Often hydrocarbon prospects have been defined and drilled entirely on the basis of this qualitative information. Today, however, quantitative seismic interpretation techniques have become common oil industry tools for prospect evaluation and reservoir characterisation. The most important of these techniques include post-stack amplitude analysis (brightspot and dim-spot analysis), offset-dependent amplitude analysis (AVO-analysis), acoustic and elastic impedance inversion, and forward seismic modelling. These techniques seek to extract additional information about the subsurface rocks and their pore fluids from the reflection amplitudes and, if used properly, they open up new doors for the seismic interpreter. Seismic amplitudes primarily represent contrasts in elastic properties between individual layers and contain information about lithology, porosity, pore fluid type and saturation, as well as pore pressure -information that cannot be gained from conventional seismic interpretation. Seismic amplitude maps are increasingly important in prospect evaluation and reservoir delineation. As shown in Fig. 18.1, the amplitude patterns often provide a good insight into depo...

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