FISH Seminar: Dr. Ángel Rodríguez Rozas (BCAM)

Friday, December 01, 2017 at 12:00pm to 1:00pm

Building 54, 209
21 AMES ST, Cambridge, MA 02139

"Fast Simulation and Inversion of Borehole Resistivity Measurements"

Accurate inversion methods are needed to provide a precise quantitative estimation of the subsurface's resistivity distribution, enabling the identification and assessment of hydrocarbon-bearing formations. In this seminar, I will focus on the fast simulation and inversion of logging-while-drilling (LWD) and extra-deep azimuthal resistivity measurements for geosteering.

In well geosteering, interpretation of resistivity measurements has to be performed in real-time, and the use of general 3D inversion methods becomes prohibitively expensive. In order to reduce the computational cost, it is possible to decrease the problem dimensionality by means of a Fourier or a Hankel series expansion along one or two spatial dimensions, leading to the so-called 2.5D and 1.5D formulations, respectively.

1.5D simulations can be rapidly accomplished either semi-analytically or numerically; however, the use of 1D transversely isotropic (TI) models is insufficient to grant accurate simulations when dealing with geological faults and/or other high-dimensional spatial features that may appear in complex rock formations. For 2D TI models, efficient 2.5D simulations for real-time well geosteering inversion require spatial discretizations (grids) that are often challenging to design.

In the first part of this seminar, I will focus on some of the latest developments in our 1.5D+2.5D inversion library, namely: (a) an algorithm for the fast simulation of 2.5D Finite Element simulations of borehole resistivity measurements using distributed memory parallel machines, and (b) the use of a rescaling strategy for modeling different logging instruments.

In the second part of this seminar, I will present the capabilities of our library to simultaneously invert measurements acquired at different wells and/or with different commercial LWD and deep azimuthal co-axial and tri-axial logging instruments. The inversion is made for the positions of the bed boundaries in addition to the horizontal and vertical layer resistivities.

Numerical experiments performed over synthetic examples and a field example will illustrate the need for combining 1.5D and 2.5D measurements in order to properly invert borehole resistivity measurements acquired in 3D formations.

Prior knowledge:
- Essential: numerical methods for solving PDEs, Inverse Problems, Geophysics.
- Recommended: Finite Element Method, Maxwell's equations, Formation Evaluation, Borehole Geophysics, Resistivity Measurements, Well Logging.

About the Series

The Friday Informal Seminar Hour [FISH, Earth Resources Laboratory] is a postdoc-run weekly seminar series within the ERL. Topics include research relating to geophysics, and in particular seismology, with applications in Earth resources exploration such as e.g. seismics exploration, microseismicity, earthquake physics, and Earth imaging techniques. The seminars usually take place on Fridays at 12 noon in 54-209 (term-time only).

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