Evaluating petrophysical properties of volcano-sedimentary sequences: A case study in the Paraná-Etendeka Large Igneous Province

Rossetti, Lucas de Magalhães May; Healy, David; Hole, Malcolm; Millett, John; Lima, Evandro Fernandes de; Jerram, Dougal A.; Rossetti, Marcos

doi:10.1016/j.marpetgeo.2019.01.028

Cited by 22 publications

(22 citation statements)

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“…The distribution and type of porous and mineral phases are key for understanding waves speeds and rock strength. Although igneous volcanic rocks have been studied in terms of their porosity, permeability and seismic character (Adam and Otheim ; Adelinet et al ; Benson et al ; Heap et al ; Rossetti et al ; Vanorio et al ; Vinciguerra et al ), and alteration (Adam et al, ; Christensen & Salisbury, ; Heap et al, ; Kanakiya et al, ; Mordensky et al, ; Navelot et al, ; Pola et al, ; Wyering et al, ), little knowledge involves the effect of rock alteration and fractures on elastic waves speed for volcaniclastic rocks. Here we study at atmospheric and reservoir pressures how rock alteration influences the development of porosity and rock density and its impact on wave speeds for volcaniclastic and intrusive rocks within the Ngatamariki geothermal field, New Zealand (Figure ).…”

Section: Introductionmentioning

confidence: 99%

Mineral Alteration and Fracture Influence on the Elastic Properties of Volcaniclastic Rocks

et al. 2019

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In geothermal environments, the physical properties of rocks, such as porosity and alteration, are highly variable and control the reservoir's elastic and hydraulic properties. Elastic wave velocity in volcaniclastic rocks and their relation to fractures, pore shapes, and mineral alteration is mostly unknown. We measure ultrasonic P and S wave speeds on volcanic rocks from the Ngatamariki Geothermal Reservoir, New Zealand. Data clustering of wave speed versus porosity and density allow us to classify lithotypes of variable propylitic and phyllic mineral alteration. Wave speeds increase first due to porosity reduction as a result of mineral alteration and welding and, second, due to the high elasticity of alteration minerals (epidote, chlorite, and carbonates). We model the rock porosity as composed of equant pores and oblate-spheroidal microfractures following an elastic effective medium model. For our samples, microfracture porosities range from 4% in the volcaniclastic tuffs to less than 1% in the ignimbrites, which we validate with pycnometer porosity data under effective pressure. We quantify that within one geological volcaniclastic formation, wave speeds vary up to 47% due to rock alteration and welding, while the effect of microfractures and changes in effective stress on wave speeds is secondary (up to 11%) but not negligible. From the experimental and numerical results we show that equant pores remain open at reservoir conditions (2,000 m) and can retain considerable porosity (10%). Our analysis has implications for microfracture and pore network characterization in geothermal reservoirs, in particular, in vapor-dominated systems where matrix porosity and permeability play a role.

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Section: Introductionmentioning

confidence: 99%

Mineral Alteration and Fracture Influence on the Elastic Properties of Volcaniclastic Rocks

et al. 2019

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“…To better understand such elements, there is a consensus among several researchers about the importance of seeking to improve our understanding on volcanic facies (e.g. Nelson et al, 2009;Jerram et al, 2009;Jerram, 2015;Millett et al, 2016;Rossetti et al, 2019). Volcanic reservoirs are more frequent in Mesozoic and Cenozoic periods (Zou, 2013), where Jurassic, Cretaceous, Paleogene, Neogene and Quaternary rocks represent 70% of the reservoirs, with few occurrences of older ages.…”

Section: Geological Aspectsmentioning

confidence: 99%

“…Physical properties such as velocity and density in igneous rocks are highly dependent on the type of volcanic facies (Planke et al, 1994;Nelson et al, 2009;Rossetti et al, 2019) and, mainly, of considerable dimensions so that it is possible to detect them in seismic and well data. The last authors also highlight the variation in the velocity of seismic waves, in the same igneous unit, due to geochemical factors and the presence of fluids, which can vary from 5.80 to 4.30 km/s and density from 2.69 to 2.89 g/cm 3 , obtained by petrophysics in samples from igneous provinces of the North Atlantic.…”

Section: Geophysical Aspectsmentioning

confidence: 99%

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Volcanic reservoirs: historic and current context

et al. 2021

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Within the oil and gas industry, igneous rocks are still seen as exploration and production challenges, due to their diverse petrogenesis and the wide range of values of some important petrophysical properties. This petrophysical variability depends on both primary and secondary processes. These facts made these rocks unattractive for decades. This condition is still observed in many fields around the world. This article has as main objective to make a historical review of studies developed globally with a focus on igneous rocks that act as a reservoir in petroleum systems. The review covered in this article was developed from a compilation of global data, thus allowing an overview of the countries that produce hydrocarbons in volcanic rocks, what types of rocks, geological age, and size of the reserve. Countries such as China and Indonesia stand out with higher daily production, exceeding orders of quantities of 108 cubic meters of gas and 104 tons of barrels of oil. In these countries, geological patterns are already being noticed in volcanic reservoirs, such as more recent geological ages and typical lithologies. Also, this work seeks to emphasize the importance of studying this type of reservoir, as its knowledge can lead to the solution of real problems within the world oil and gas industry.

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“…For a more realistic approach to quantify the porosity of basalt and to improve estimations thereof, we developed an empirical model based on sonic velocity data. To this end, experimental data relating porosity and sonic velocities in basaltic rocks, compiled from previous works (Al-Harthi et al 1999;Zamora et al 1994, Planke et al 1999, Chen et al 2015, Vedanti et al 2018, Rossetti et al 2019, were employed in a regression analysis. As noted by Helm-Clark et al (2004), the use of neutron logs can potentially result in porosity overestimation in the presence of hydrous minerals, making velocity logs a better approach for porosity estimation.…”

Section: Porosity and Permeability Derived From Empirical Modelsmentioning

confidence: 99%

Assessing hydrofacies and hydraulic properties of basaltic aquifers derived from geophysical logging

2020

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Basaltic aquifers are an important source of water supply in many regions worldwide. Because of their cooling process, flood basalts normally have complex internal structures and unpredictable permeable zone distribution. Geophysical profiling is a reliable tool used to identify the vertical variations of physical properties within the flood basalts, mainly to distinguish between low and high permeability intervals. In this study, a detailed analysis of drill cuttings, and geophysical logging of two depth wells helped to identify the typical response of main facies of flood basalts in the Serra Geral aquifer system. The evidence obtained from this work confirms that flood basalts may be classified as multilayer aquifer systems in which a highly permeable top covers a center with low permeability as a result of recurrent floods. In several cases, permeable layers are represented by a weathering horizon developed between two flood events. This study uses an empirical model to estimate the porosity based on acoustic velocity logging. A useful model based on a well-established Kozeny-Carman model was developed to predict the permeability of basaltic rocks using porosity data. The results obtained allow to identify the permeable intervals of basaltic aquifers and to estimate their hydraulic properties.

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Evaluating petrophysical properties of volcano-sedimentary sequences: A case study in the Paraná-Etendeka Large Igneous Province

Cited by 22 publications

References 103 publications

Mineral Alteration and Fracture Influence on the Elastic Properties of Volcaniclastic Rocks

Mineral Alteration and Fracture Influence on the Elastic Properties of Volcaniclastic Rocks

Volcanic reservoirs: historic and current context

Assessing hydrofacies and hydraulic properties of basaltic aquifers derived from geophysical logging

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