Porosity and permeability evaluation and geological interpretations from core data and geophysical well logs for 18 wells in the Paleozoic successions of eastern Canada and implications for hydrocarbon exploration

This paper describes a case study of the application of an improved method of formation evaluation from well logs in a pilot area of the Mardie Greensand reservoirs in the Carnarvon Basin of Western Australia. They are lithologically complex reservoirs with a high and highly variable content of glauconite and extensive micro- porosity. These facts, in addition to the presence of other lithological components, make traditional log analysis, in particular the estimation of log-derived values of permeability, difficult if not impossible. The aim of this project was mainly to determine electrofacies and evaluate porosity and permeability from conventional well logs in this area. The sequential steps in the log evaluation of these glauconite-rich reservoirs were as follows: log quality control (borehole environmental corrections and depth matching); analysis of the log response characteristics; determination of litho- parameters used to identify the electrofacies; identification of the so-called hard streaks and their subsequent elimination for the purpose of reading log responses largely unaffected by these horizons; electrofacies identification and classification; porosity and permeability evaluation. The paper presents examples from several wells in the pilot area of the Mardie Greensand to illustrate this study.

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NMR AND WELL LOGS PETROPHYSICAL CHARACTERIZATION OF SANDSTONE FROM THE MARACANGALHA FORMATION, BAHIA, BRAZIL

Revista de Geociências do Nordeste ◽

10.21680/2447-3359.2021v7n2id24562 ◽

2021 ◽

pp. 239-252

Author(s):

Nathália De Souza Penna ◽

Joelson Da Conceição Batista ◽

Suzan Sousa de Vasconcelos

Keyword(s):

Gamma Ray ◽

Production Capacity ◽

Clay Content ◽

Well Logs ◽

Depth Interval ◽

Porous Space ◽

Petrophysical Parameters ◽

Porosity And Permeability ◽

Using Data ◽

Geophysical Well Logs

The storage and production capacity of reservoir rocks can be estimated through some petrophysics characteristics involving the lithological identification of the constitute rocks, fluids nature in the porous space, porosity, permeability, saturation and clay content. The most popular tools for obtaining these petrophysical parameters are the conventional geophysical well logs. However, the determination of petrophysical parameters from tools based on the phenomenon of nuclear magnetic resonance (NMR) has gained prominence in recent decades. In this work, we analyzed rock samples from outcrops in Frades Island region, Bahia, Brazil, through laboratory NMR measurements, to estimate and evaluate the petrophysical properties of the Maracangalha Formation, one of the main hydrocarbons reservoirs in the Recôncavo Basin. The Sandstone samples were characterized in terms of porosity, permeability, saturation, and petrofacies. Finally, we calculated porosity, permeability, and clay content using data from gamma-ray, electrical and density logs, measured in a depth interval interpreted for Maracangalha Formation. These results corroborate with the obtained by NMR since, despite the effects of weathering and erosion on the samples used, the values of porosity and permeability obtained in NMR are in the range of values calculated from these profiles.

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