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
Cretaceous to Eocene volcanic arc activity in the Andes of northern Ecuador
During the Cretaceous to Eocene the W. part of N. Ecuador received the tholeiitic and calk-alkaline magmatic products of one volcanic arc, which built up on a thin or dense basement, at least partly of oceanic origin. Accumulation of this arc was preceded by early Cretaceous volcanicity and flexuring in the E. and was brought to a close by late Senonian to Eocene orogenic movements. The partly ensimatic arc of N. Ecuador contrasts markedly with the totally ensialic arc of S. Ecuador and Peru, and suggests an important change in basement type near 2°30'S (the latitude of Guayaquil). Oceanic basement in N. Ecuador was probably trapped in the Lower Cretaceous by initiation of subduction at a trench in approximately the same relative offshore position as at present.