Exploration Insights September 2020 - Page 28

Exploration Insights | 15
relative motion of continental land masses by GPS . These techniques have helped shape our comprehension of the Earth as a dynamic planet with its lithosphere segmented into plates .
In the late 1960s , the plate tectonic theory was formulated , showing that the relative motion of plates on a spherical Earth is accommodated along plate boundaries ( Mckenzie and Parker , 1967 ; Le Pichon , 1968 ). One implication of the theory is that the Earth preserves a constant volume by replacing the amount of lithosphere consumed at destructive plate boundaries ( e . g . volcanic arcs ) with the creation of lithosphere at mid-ocean ridges . This laid geometrical constraints on the motion of the tectonic plates at the Earth ’ s surface back through geological time ( e . g . Dewey and Bird , 1970 ).
Since the 1970s , full plate tectonic models have been developed . These are dynamic maps that represent the motions of discrete pieces of crust on the surface of a sphere — the Earth .
nter - Scientific Visualization Studio , Smithsonian Institution , Global Change se Advanced Research Projects Agency ( DARPA ), Dynamic Media Associates
In the second part of the 20 th century , the improvement of instrumental observations led to : the contextualization of magnetic anomalies on the ocean seafloor ( Hess , 1962 ); the recording of natural seismicity ; and the measuring of tectonic stress ( e . g . from borehole breakout ) or , more recently , observing the
The essential components of a plate tectonic model are :
A set of geodynamic units ( GDUs ), which represent fragments of the lithosphere ( present day ) which each have a singular tectonic evolution
A rotation pole table that associates each fragment with a series of rotation poles , enabling transformations (“ reconstructions ”) to be carried out from their present-day position to their paleo-positions
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Figure 1 > Initial attempts at plate reconstructions were essentially paleogeographic maps dealing with singular snapshots of time . A ) A fit between Africa and South America first proposed in 1587 , by Dutch map maker Abraham Ortelius . B ) Reconstruction of the continental fit before the opening of the Atlantic Ocean by Antonio Snider-Pellegrini , 1858 . C ) The well-known initial maps of Pangaea by Alfred Wegner , 1929 .
Exploration Handbook | 29 APPLICATIONS OF PALEOCLIMATE MODELS Why are paleoclimate models useful in exploration? Climate models, themselves, do not make petroleum systems elements predictions. However, paleoclimate simulations provide insights into a range of physical processes, such as wind strength, ocean temperatures, and rainfall patterns. These physical processes have a strong influence on sedimentary systems and, in turn, many aspects of petroleum systems, such as source rock, reservoir, and seal. To make paleoclimate simulations relevant to petroleum exploration, it is necessary to combine a range of simulated parameters provided by the model. Some features, such as tropical carbonates, are controlled by a small number of parameters. Other features, such as source rocks, are more complex. Paleoclimate models provide an independent, physics-based sense check of exploration concepts and have several direct applications for assisting successful hydrocarbon exploration. Examples include: » » Simulated ocean currents and oxygen values provide insights into the distribution of potential source rocks (figures 4 and 5). » » Vegetation modeling provides insights into the distribution of continent-derived organic matter. » » Information on ocean temperatures and clastic sediment flux enables the distribution of tropical carbonate factories to be predicted, providing better insights into carbonate play extents (Figure 3). » » Modeled precipitation patterns provide insights into source-to-sink relationships, helping to refine understanding of deep-water play extents. » » Evaporation and relative humidity can help evaluate the distribution of evaporite seals. » » Simulated seabed energy conditions (e.g. tidal currents) enable areas with potential for enhanced reservoir quality to be identified. » » Paleoclimate simulations can provide inputs into forward stratigraphic models. 2–5% TOC >5% TOC -0.004 -0.002 “Upwelling” 0 0.002 0.004 2 © 2 0 0 H b u a l l i n r t o FUTURE TRENDS Until recently, paleoclimate models were mainly developed by individual government bodies, such as the UK Met Office, the Japan Meteorological Agency, and the US National Oceanic and Atmospheric Administration Office. In recent years, there has been growing use of community-driven models developed by the wider research community, such as the Community Climate System Model (CCSM) and the Community Earth System Model (CESM). This may enable faster model development in the future, allowing additional parameters to be simulated. Such models may also allow climate simulations to be more easily generated. Simulating the climate is extremely computationally demanding and, as such, paleoclimate models are usually run on supercomputing facilities. However, the advent of powerful and easily accessible, cloud-based computing resources may allow simulations to be generated more easily and at a lower cost (Chen et al., 2017). The digital revolution poses many exciting new avenues for utilizing paleoclimate simulations within exploration. It may be possible to use techniques, such as machine learning, to make better predictions of petroleum systems elements. Such techniques even hold the promise of actually creating climate simulations without the need for a model, enabling simulations to be obtained more efficiently, allowing a greater range of uncertainties to be assessed. Data science techniques may also allow high-resolution simulations, akin to those created by the most sophisticated climate models, to be generated from low-resolution models (e.g. Rasp et al., 2018), providing greater insights into the distribution of petroleum systems elements. 0–2% TOC “Downwelling” Figure 5> A snapshot of upwelling predicted for a time-slice within the Early Jurassic. 0.006 0.008 Ocean vertical velocity (mm/s) Figure 4> Boxplot showing the distribution of modern day, grouped by total organic carbon (TOC) content, versus vertical velocity of the ocean. The vertical bars represent the median value for each group. This shows that higher TOC sediments are more likely to occur where there is a greater positive vertical velocity (known as upwelling). The digital revolution also makes a truly quantitative approach to stratigraphy and sedimentology possible. Paleoclimate simulations are the only means to understand many of the processes controlling depositional systems and, as such, will be central to such an approach. The seamless use of paleoclimate simulations to better constrain forward stratigraphic models and, thus, generate enhanced insights into play fairway extents and reservoir heterogeneity, is an obvious avenue to pursue. “Paleoclimate models provide an independent, physics-based sense check of exploration concepts and have several direct applications for assisting successful hydrocarbon exploration.” 28 | Halliburton Landmark