Jandyr M. Travassos

Magnetotellurics as a modeling tool in the extensive magmatic context of Paraná Basin, Brazil

Parana Basin is a huge oval-shaped basin covering the southern portion of Brazil and parts of Argentina, Paraguay, and Uruguay, with an area of more than 1,700,000 km2 (Figure 1). Hydrocarbon exploration in Parana Basin has been a challenge due to the worlds second-most-extensive inshore flood basalt complex overlying the Paleozoic sedimentary rocks (Figure 1), which in turn are extensively intruded by swarms of diabase dikes and sills, making seismic imaging a difficult task. The basin itself represents approximately one-half of the sedimentary rock volume of onshore Brazilian basins and is still underexplored. No major discovery for oil or gas has been made to date.

High-resolution facies modeling of presalt lacustrine carbonates reservoir analog: Morro do Chaves Formation example, Sergipe-Alagoas Basin, Brazil

AbstractBarremian lacustrine carbonates, mainly coquinas, are the reservoir rocks of the large presalt petroleum discoveries in deep to ultradeepwaters, at the southeast Brazilian margin, namely, the Santos, Campos, and Espirito Santo Basins. The complex geologic setting of those discoveries, with massive overburden of salt bodies, makes the seismic imaging of the carbonate reservoirs an expensive and challenging issue. In this setting, accurate facies models are a requirement to the predictability of the carbonate reservoir intervals. We have developed an analog high-resolution coquinas facies model based on an interpretation of a pseudo-3D ground penetrating radar survey. We relied not only on the trace amplitude analysis, but also on trace attributes to reduce the ambiguity of the interpretation due to possible visual biases, which may relate electromagnetic reflection amplitude to geologic relevance. We have used the dip and texture attributes to help us better understand the subsurface and to focus o...

High resolution radar mapping of the Cierva Point, Antarctic

The excellent penetration of the electromagnetic field in ice favors the radar and the radio-echo sounding methods for the study of ice masses laying on Earths surface. In particular the ground penetrating radar has proved to be very effective for surface-based studies of land and sea ice. The most ubiquitous radar signatures are reflections from the internal structure of ice, the so-called stratigraphic layers, or from the bedrock. In this paper we concentrate on some reflection phenomena other than on ice stratigraphy revealed on the ice cover of the Cierva Point, Antarctic Peninsula. We acquired 25 SW-NE and NE-SE profiles in an area of 140 × 175 m2 with an acquisition train of 2 Nansen sledges dragged by a ski-doo. Radar sections revealed internal reflection horizons are caused by changes in dielectric properties as well as density fluctuations and preferred crystal orientation fabric.

Comment on “Frequency-domain Green’s functions for radar waves in heterogeneous 2.5D media” (

We call the reader9s attention to a recent paper by Ellefsen et al. (2009) in which the authors use the following equation for the magnetic field H expressed in the frequency domain:

Comment on “Frequency-domain Green's functions for radar waves in heterogeneous 2.5D media” (K. J. Ellefsen, D. Croizé, A. T. Mazzella, and J. R. McKenna, 2009, GEOPHYSICS, 74, no. 2, J13–J22)

We call the reader9s attention to a recent paper by Ellefsen et al. (2009) in which the authors use the following equation for the magnetic field H expressed in the frequency domain:

Comment on “Frequency-domain Green's functions for radar waves in heterogeneous 2.5D media” (K. J. Ellefsen, D. Croizé, A. T. Mazzella, and J. R. McKenna, 2009, GEOPHYSICS, 74, no. 2, J13–J22)Discussion and Reply

We call the reader9s attention to a recent paper by Ellefsen et al. (2009) in which the authors use the following equation for the magnetic field H expressed in the frequency domain:

EM phase velocity dispersion in a surficial concrete slab

It is know that surface layers may act as waveguides to the propagation of EM energy. Here we analyze the case where a concrete pavement can act as a guide of EM waves over a higher permittivity soil. This situation cannot be described as a true waveguide as the steady state is never reached. We estimate a phase velocity dispersion curve from the F-K panel of a common-shot profile. That curve is then used in an inversion procedure to obtain waveguide refractive index and thickness through a minimization strategy that seeks models where the numerical dispersion curve matches the picked dispersion curve.

Imaging the central portion of Parana Basin with 3‐D MT modeling

A geoelectric model is proposed for the central part of Parana Basin. A major part of that intracratonic basin has one of the most voluminous flood basalt inshore complex up to 2 km thick, covering an area of some 800,000 km. The basalt overlies a series of Paleozoic sediments including hydrocarbon source rocks. This paper presents a three-dimensional geoelectric model for the central portion of the basin, based on a data set comprising 231 broadband MT sites with a frequency range spanning 0.001s to 600s, covering an area of 120,000 km2. Sites were deployed along 9 profiles running SW-NE, and one NW-SE. Site spacing is compatible to a regional study. The model reveals basin structure through its basement to lower crustal depths. In particular it has revealed a more complex structure for the Ponta Grossa Arch than previously thought. The results emphasize the feasibility of 3-D forward modeling in practice.