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Geology-guided pore space quantification for carbonate rocks

First Break, March, 2020
Reza Saberi
©2020 EAGE

The heterogeneity in geological properties of carbonate rocks makes their acoustical behaviour more difficult to model and predict than siliciclastics. This uncertainty in prediction normally is attributed to their pore structure complexity and heterogeneity. Pore structure in carbonate is a result of the place they are deposited combining with subsequent post-depositional processes to form the final carbonate rock. Carbonates can form in different depositional environments and subsequently can undergo into various diagenesis regimes. This combination along with their chemically active mineralogy makes them susceptible for complex and heterogeneous pore structures. This study investigates variation of carbonates depositional environment on their velocity behavior. It, furthermore, uses this information to quantify a more comprehensive pore model for carbonate rocks. This geology dependent workflow is tested on a number of carbonate core-plugs from two exploration wells with ultrasonic measurements. The results confirm application of this workflow for defining a more comprehensive pore model compared with the routine approach using only Wyllie time average by defining maximum two pore types. This study uses another reference curve from depositional environment in addition to the routine approach to derive a more general (geology oriented) pore aspect ratio spectrum.

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Fluid detection in carbonate rocks by integrating well logs and seismic attributes

Interpretation (SEG+AAPG), February, 2020
Reza Saberi

It has been well documented that the pre-stack seismic attributes can be an efficient tool for hydrocarbon exploration and pore fluid detection using techniques like Amplitude Versus Offset (AVO) analysis. These studies mainly focus on siliciclastics rather than carbonates as fluid effects in carbonate rocks can be masked by their complex pore structure. These fluid detection seismic attributes usually reside on a linear background model for P- and S-velocities of the water-saturated rocks, and any deviation from this trend is assigned to the possible pore fluid changes. This means that fake (or even missed) fluid effects can be detected in carbonate rocks if the fluid detection seismic attributes, which designed for siliciclastics, are used. This can mainly be related to the nonlinearity of background model in carbonates due to their varying pore structure. In this study, both well logs and seismic data from a carbonate sequence are used to show that the correlation between P- and S-velocities in water-saturated carbonates becomes more linear when considering P-velocity squared versus the product of the P- and S-velocities. Furthermore, this linear version is used for detecting the fluid anomalies, and being compared with other various fluid factors to highlight the gas saturated interval. The modified fluid attribute displays the gas-saturation brighter than the alternatives, although, in this case, all the studied indicators perform well and consistently.

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Facies – The Drivers for Modern Inversions

The Leading Edge, February, 2020
John Pendrel | Henk Schouten
©2020 SEG

We address the problem of creating low frequency models for AVO inversions, investigating two workflows, neither of which involve well log interpolation. The first workflow creates a constant but structurally-compliant low frequncy model from averages over available logs. Facies analysis is done from the inversion outcomes. The second workflow takes the facies from the first workflow and together with per-facies trends creates a new model for a second pass of inversion. The results of the subsequent facies analysis are compared with the first in several ways and found to be superior. Notable in the analysis is the inclusions of several types of uncertainty which becomes useful in assessing risk.

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Norway: New play models for Patch Bank Ridge, east of Utsira High

Geo Expro, December, 2019
Marit Stokke Bauck | Idar Kjorlaug | Silje Rogne | Anna Rumyantseva
©2019 GeoPublishing Ltd

NVGS, a recently acquired southward extension of the NVG survey in the northern Norwegian North Sea, is a high-quality broadband seismic data set, which reveals detailed stratigraphy from the Permian Salt to the Quaternary section for stratigraphic and lithological interpretation. In the deeper parts, old basin configurations can be mapped. Including Caledonian fold and faults and Paleozoic basins. The regional scale of the data set makes it ideal for establishing a geological model for this region. Including prediction of potential source and reservoir rocks. Although the North Sea is a mature region, the Patch Bank Ridge area is under-explored.

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Advanced imaging solutions for tailored multi-source and multi-vessel surveys

First Break, November, 2019
Gordon Poole | Vetle Vinje | Ewa Kaszycka | Thomas Elboth | Risto Siliqi | Anne Camerer | Hari Krishna | Erling Frantzen | Thomas Mensch
©2019 EAGE

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