Presenter
Carlos Torres-Verdin, PhD, Professor from The University of Texas at Austin
Co-authors
Wardana Saputra, UT Austin; Weichen Zhan, UT Austin; Joaquin Ambia, UT Austin; Bruce Klappauf, UT Austin; Nazanin Jahani, NORCE; Jörn Zimmerling , Uppsala University; Vladimir Druskin, 3D EM Modeling & Inversion JIP, Sofia Davydycheva, 3D EM Modeling & Inversion JIP; Ivan Davydychev, 3D EM Modeling & Inversion JIP
Abstract
We summarize our recent algorithmic and software developments concerning the rapid modeling and inversion of borehole UDAR measurements. The algorithms are designed for their efficient implementation on multi-CPU computer clusters and are explicitly coupled to a pre-defined local 3D geological model where measurements are acquired along an arbitrary 3D well trajectory. Modeling is performed via a finite-volume implementation of Maxwell’s equations with a self-adaptable Lebedev grid for efficient and accurate assimilation of arbitrary electrical conductivity anisotropy, operating frequency, and coplanar-coaxial transmitter-receiver couplings. Furthermore, effective-medium averages are used for discretization of local anisotropic conductivity across non-conforming boundaries separating large conductivity contrasts. Inversion is carried out using both deterministic and stochastic inversion methods which explicitly render estimates of the uncertainty of inversion results. Determinist inversion methods are implemented with gradient-based strategies where the Jacobian matrix is efficiently calculated and updated by the modeling algorithm, while stochastic inversion methods are implemented with multi-grid and multi-resolution simulating annealing procedures. Furthermore, the inversion is implemented with a data-weighting quadratic data misfit term and a penalty term for stabilization (regularization) in the presence of inadequate and noisy measurements (Occam-type inversion). The regularization term is adaptively adjusted as measurements are progressively matched with numerical simulations. Inversion results are described as pixelized spatial distributions of anisotropic electrical conductivity. The inversion method progressively increases the complexity (dimensionality) of the estimated spatial distribution of anisotropic electrical conductivity around and ahead of the well trajectory in the natural sequence 0D-1D-2D-3D stemming from localized dimensionality of both measurement and model complexity. This progression of local model complexity along the well trajectory enables (a) biasing of local and near-well-trajectory electrical conductivity with LWD measurements and (b) enforces spatial variability (and its energy) of electrical conductivity around the well trajectory only when warranted by the measurements, hence mitigating the possibility of false inferences of electrical conductivity, or inferences beyond the scope of resolution-vs.-depth of investigation available from the measurements. Verifications of the new rapid modeling and inversion methods are performed with both challenging synthetic models inspired by field data, and field measurements acquired in the North Sea by various service companies. It is found that the inversion algorithms are efficient, stable, and reliable; they enable the automatic control of model complexity vs. measurement complexity when estimating spatial distributions of anisotropic electrical conductivity around and ahead of the well trajectory. This is possible by enforcing data compression and reduced-order modeling constraints in the inversion method which not only reduce CPU times but also actively calculate both data misfit (together or separately for coaxial and coplanar induction measurements) and model uncertainty to adaptively control the spatial variability of inversion results from smooth to locally 3D anisotropic variability. Furthermore, inversion results are readily projectable to the coupled 3D geological model for their assimilation in the joint interpretation of geological, seismic, reservoir, and multi-well measurements.
Biography
Carlos Torres-Verdín received a BSc degree in Engineering Geophysics from the National Polytechnic Institute of Mexico, a MSc degree in Electrical Engineering from the University of Texas at Austin, and a PhD degree in Engineering Geoscience from the University of California at Berkeley in 1991. During 1991-1997, he held the position of Research Scientist with Schlumberger-Doll Research. From 1997-1999, he was Reservoir Specialist and Technology Champion with YPF (Buenos Aires, Argentina). Since 1999, he has been affiliated with the Hildebrand Department of Petroleum and Geosystems Engineering of the University of Texas at Austin, where he is currently Full Professor, holds the Brian James Jennings Memorial Endowed Chair in Petroleum and Geosystems Engineering, and conducts research on borehole geophysics, formation evaluation, petrophysics, well logging, and integrated reservoir description. Dr. Torres-Verdín is the founder and director of the Research Consortium on Formation Evaluation at the University of Texas at Austin, which has been in operation for 24 years and is currently sponsored by 20 companies. He has published over 260 refereed journal papers and over 270 conference papers, two book chapters, co-authored one book, is co-inventor of 6 U.S. patents. Dr. Torres-Verdín is recipient of the 2020 Virgil Kauffman Gold Medal from the SEG, 2019 Anthony Lucas Gold Medal from the SPE, 2017 Conrad Schlumberger Award from the EAGE (European Association of Geoscientists and Engineers), 2014 Gold Medal for Technical Achievement from the SPWLA, 2008 Formation Evaluation Award from the SPE, 2006 Distinguished Technical Achievement Award from the SPWLA, Distinguished Member of the SPE, and Honorary Member of the SEG. He also received the 2003, 2004, 2006, and 2007 Best Paper Awards in Petrophysics (SPWLA), 2020 Best Paper Award published in Geophysics, 2006 and 2014 Best Presentation Awards and the 2007 Best Poster Award by the SPWLA. Dr. Torres-Verdín has supervised 43 PhD and 47 Master’s students, conducted numerous industry training courses, co-chaired several technical workshops and conference sessions, and has served as member of multiple SPE, SPWLA, and SEG committees in the past.