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.
Classification of Seismic Windows Using Artificial Neural Networks
We examine the plausibility of using an Artificial Neural Network (ANN) and an Importance-Aided Neural Network (IANN) for the refinement of the structural model used to create full-wave tomography images. Specifically, we apply the machine learning techniques to classifying segments of observed data wave seismograms and synthetic data wave seismograms as either usable for iteratively refining the structural model or not usable for refinement. Segments of observed and synthetic seismograms are considered usable if they are not too di erent, a heuristic observation made by a human expert, which is considered a match. The use of the ANN and the IANN for classification of the data wave segments removes the human computational cost of the classification process and removes the need for an expert to oversee all such classifications. Our experiments on the seismic data for Southern California have shown this technique to be promising for both classification accuracy and the reduction of the time required to compute the classification of observed data wave segment and synthetic data wave segment matches.
The Venezuelan hydrocarbon habitat
Abstract Venezuela has produced some 40 billion barrels of oil. Remaining recoverable reserves are currently in the order of 60 billion barrels of oil and 92 trillion cubic feet of gas. The Orinoco Heavy Oil Belt, the world’s largest known oil accumulation, has some 1.2 trillion barrels of oil-in-place. Only part of the 267 billion barrel, ultimate recoverable of this belt is included in the current reserves. Most of Venezuela’s hydrocarbon reserves are located in the Maracaibo, Eastern Venezuela, and Barinas—Apure Basins, and most are derived from Upper Cretaceous, marine source rocks. Tertiary, terrestrial source rocks have also contributed hydrocarbons in the Maracaibo and Eastern Venezuela basins, and Tertiary marine and terrestrial source rocks have generated hydrocarbons in the Falcon and offshore Venezuelan basins. The hydrocarbon habitat has been profoundly influenced by Mesozoic—Recent platetectonics. Many of the structural traps are the consequence of Carribbean—South America dextral relative movements. Some of these structures, mainly in the northwest, were enhanced by stress generated in the Pacific. The northern part of the country has suffered considerable shortening and inversion. The resultant mountain chains limit the modern hydrocarbon basins. Reconstruction of late Cretaceous source rock palaeogeography, of Late Cretaceous to Palaeocene kitchens (now metamorphosed), and of Eocene to Recent kitchens, shows that the latter are remnants of a much larger petroliferous province and provides an explanation for the great abundance of hydrocarbons in the area. Significant volumes of hydrocarbons remain to be discovered in extrapolations of traditional and developing plays.