A Class IV AVO response was seen at the top of the Avalon Formation, which is typical of an unconventional reservoir.
We determined the layering and rock fabric anisotropy using empirical relationships or modeled in the rock property characterization process because reflectivity effects are often seen in the observed seismic used for well tie and wavelet estimation. Using calibrated RPM templates, we found that TOC is driving the elastic property variations in the Avalon Formation. In organic mudrock reservoirs, the computed TOC log was used as an input to compute porosity and calibrate rock-physics models (RPMs), which are needed for understanding the potential of source rocks or finding sweet spots and their contribution to the amplitude variation with offset (AVO) changes in the seismic data. TOC was calculated as a weighted average of Passey’s (empirical) and the bulk density-based (theoretical) methods. We used TOC estimation to aid the process of determining the best pay zones for development of such reservoirs. This includes accurate computation of mineral volumes, total organic carbon (TOC), porosity, and saturations. Drilling data acquired through intrusions provide valuable insight into the problems exploration wells can encounter, often unexpectedly, many of which can be detrimental to safe drilling practice and result in prolonged non-productive time.Petrophysical analysis of unconventional plays that are comprised of organic mudrock needs detailed data QC and preparation to optimize the results of quantitative interpretation. These silicic intrusions are difficult to recognise in seismic and petrophysical data due to their low density and compressional velocity and have historically been misidentified on seismic reflection data as exploration targets.
Furthermore, analysis of petrophysical data shows that within the FSB there are silicic intrusions such as diorite and rhyolite, in addition to the commonly encountered mafic intrusions. Examination of cores reveals additional igneous material in individual wells, compared to estimates using seismic or petrophysical data alone, leading to potential underestimation of the volume of the igneous component in a basin. Utilising 29 FSB wells (with 251 intrusions) and 3D seismic data, this study presents new insights into the impacts that igneous intrusions have on hydrocarbon exploration. The Faroe-Shetland Basin (FSB), NE Atlantic Margin, has been the focus of exploration for over 45 years, with many wells penetrating igneous intrusions. Igneous sills and dykes that intrude pervasively into prospective sedimentary basins are a common occurrence in volcanic margins, impacting the petroleum system and causing geological and technical drilling challenges during hydrocarbon exploration.
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