Quantitative Interpretation of Seismic Facies - A case study, Oriente Basin Ecuador
Summary Interpretation of several 3D volumes from the Oriente basin suggests that faults define the extent of a given field. Additionally, the subtle stratigraphic boundaries characterised by the clay-filled zones of low porosity compartmentalise oil pools within a field. Identification of these zones is critical. In our experience, neural network based waveform classification has proven to be a successful tool to identify these zones. Qualitative analysis of seismic facies derived from the classification is a common practice. However, we demonstrate in this paper that the quantitative interpretation of seismic facies is possible provided a geological understanding of the seismic signatures is achieved. This paper discusses the extensive 1D-modeling carried out to comprehend the trace shape variations due to changing isopach of the sand/shale sequences, which was fundamental in assigning a realistic geological model to each facies. Also described in the paper is the workflow and a key methodology developed to derive “Net thickness” of reservoir sands from the seismic facies. Rigorous study of this technique on several 3D data sets from Ecuador’s Oriente Basin has produced results, which have established the foundation for understanding the depositional environments and the reservoir models, validated by subsequent drilling.
Classic petroleum provinces
In recent years there has been a proliferation of international meetings and publications with themes such as ‘Frontier Areas for Exploration’, ‘Future Petroleum Provinces’ and ‘Future Potential for Exploration in Frontier Basins’ in the hope that new exploitable hydrocarbon reserves will be discovered. Many of these geologically interesting areas, usually with limited hydrocarbon potential, have been promoted and often over emphasized in efforts to obtain investment monies into the regions. With the 1986 oil-price crash, there has been and will continue to be only limited funds available to explore in these frontier areas: deep water, jungles, mountain terrain, ice-covered lands and remote continental interiors. The oil industry’s present and likely future existence will continue to be focussed in the classic petroleum provinces of the world. Which company would choose not to explore in the mature petroleum provinces (Middle East, North and off-shore West Africa, West and East Texas, Mexico, Venezuela, Siberia, Western Canada, Gulf Coast, Niger Delta, North Sea) if they had the opportunity? The concept of a petroleum province, composed of one or several sedimentary basins having common geological features and a comparable history was first suggested by Perrodon (1980). It generally includes several petroleum zones. The classic petroleum provinces are still the world’s major producers of hydrocarbons and will continue to be so well into, and through, the 21st century. The world’s hydrocarbon supplies, oil company profits and major exploration and production activities will continue to be principally from these mature provinces. In recent years much new data, new understandings, new interpretations
Global Basin Classification System
A proposed system classifies sedimentary basins, worldwide, into specific as well as general categories. The geologic history of each basin may be subdivided into cycles using three parameters: basin-forming tectonics, depositional sequences, and basin-modifying tectonics. Sedimentary basins may be simple, with one or two tectonic/sedimentary cycles, or they may be complex polyhistory basins with many different cycles and events. There are eight simple cycle types in this classification, which cover continental, continental-margin, and oceanic areas. The eight basic cycle types, their depositional fills, and tectonic modifiers have been given letter and number symbols so that the specific geologic history of each basin may be written as a formula. These formulas may then e compared and similarities or differences between basins noted.