Investigation of the Various Spectral Decomposition Methods to Detect and Explore Hidden Complex Reef Reservoir Structures and Their Hydrocarbon Potentials in Northwestern Part of the Persian Gulf

Abstract

The Persian Gulf and its coastal areas are recognized as one of the biggest hydrocarbon basins in the world as world's largest petroleum reservoirs are located through its offshore and onshore oil and gas fields. Coastline countries of the Persian Gulf produce about 25% of the world's oil yearly and they have nearly two-thirds and one-third of the world's crude oil and natural gas reserves, respectively. In the Persian Gulf and south of Iran, Zagros orogeny process has a most important structural role as it causes many petroleum reservoirs into folds with northwest-southeast trends that are parallel with Zagros orogeny direction. However, there is good potential to explore new petroleum reservoirs in the Persian Gulf yet. One of these potential oilfields located northwestern of the Persian Gulf includes high petroleum potential, but with structural complexity and this investigation is focused to explore reservoir in its other horizons, specially Sarvak formation as the famous reservoir in the area. To achieve essential information from reservoir and locating it, we applied two useful seismic methods. Authors considered different advantages of the fast Fourier transform (FFT) and the continuous wavelet transform (CWT) as the most commonly applicable spectral analysis of seismic methods in an experimental investigation besides geological new findings. We found that the FFT can provide a good image from reservoir stratigraphic characteristics; it has specifically proven efficient even in carbonate reservoirs allowing individualization of geological bodies not easily defined in amplitude maps. Besides that, the CWT can provide an accurate and clear image from reservoir structural characteristics and low frequency shadows under petroleum reservoirs. We will prove our claims by using theoretical and experimental evidences. Objectives of this paper, beside geological evidences, are to show abilities of these two methods and to describes how, (1) the FFT method shows the distribution of the hidden reef boundaries and (2) the CWT shows the probable presence of hydrocarbons in purpose structure much better than the original seismic data and others methods.