Global Classification of Shallow Marine Systems
Shallow marine systems are traditionally classified on a ternary diagram that compares the relative importance of tidal, wave and fluvial processes at the coastline. The different processes produce markedly different shoreline types with distinct sandbody geometries, which in turn have a significant impact on hydrocarbon reservoir performance. The advent of modern remote sensing data (GoogleEarth and similar) has revolutionsied modern analogue studies allowing reservoir geologists to very quickly access high quality satallite imagary of depositional systems which can be used to improve reservoir models of the subsurface. Identifying the correct analogues remains a challenge. Global data on mean wave height and mean tidal range have been combined with estimates of fluvial discharge from watershed analysis to classify the World's coastline in 5 km increments by dominant and secondary process. This database can then be filtered by parametres such as climate, latitude and tectonic setting to identify potential reservoir analogues. The first order classification is whether the shorelines are erosional (rocky shorelines) or depositional. 36% of the Earth's shorelines are depositional. Within the depsotional shorelines 65% are wave dominated of which 8% are fluvial influenced and 14% are tidally influenced. 34% of shorelines are tide dominated of which 4 and 11% are fluvially and tidally influenced respectively. Fluvial domainted shorelines make up 1% of the global depositional coastlines. The distribution of process appears to correlate with a variety of controlling parametres. Wave dominated systems are more common at higher latitudes and in regions with narrow shelves. A far greater abundance of tidal systems occurs close to equator. Wave dominated systems are most abundant on erosional coastalines. Extensional and foreland basins show the highest proprotion of tidal infleunce. The database that has been compiled allows suitable analogues to oil fields to be quickly indentified. In addition a robust emprical description of the current distribution of moden systems is the first stage towards a detailed predictive model for the ancient.
AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016