none 10.1190/geo2018-0781.1 Society of Exploration Geophysicists Society of Exploration Geophysicists 186 107719373 5981 2025121211013543500 10.1190 2025-12-12T16:01:44Z 2019-06-19T03:52:24Z 3 Geophysics 0016-8033 1942-2156 09 1 2019 84 5 Mingqi Wu Shell 1 , 150 North Dairy Ashford Road, Houston, Texas 77079, . E-mail: send2mqwu@gmail.com ; neilkunal.panchal@shell.com ; jeremy.vila@shell.com . USA Yinsen Miao Rice University 2 , Department of Statistics, Houston, Texas 77005, . E-mail: yinsen.miao@rice.edu ; daniel.kowal@rice.edu ; marina@rice.edu . USA Neilkunal Panchal Shell 1 , 150 North Dairy Ashford Road, Houston, Texas 77079, . E-mail: send2mqwu@gmail.com ; neilkunal.panchal@shell.com ; jeremy.vila@shell.com . USA Daniel R. Kowal Rice University 2 , Department of Statistics, Houston, Texas 77005, . E-mail: yinsen.miao@rice.edu ; daniel.kowal@rice.edu ; marina@rice.edu . USA Marina Vannucci Rice University 2 , Department of Statistics, Houston, Texas 77005, . E-mail: yinsen.miao@rice.edu ; daniel.kowal@rice.edu ; marina@rice.edu . USA Jeremy Vila Shell 1 , 150 North Dairy Ashford Road, Houston, Texas 77079, . E-mail: send2mqwu@gmail.com ; neilkunal.panchal@shell.com ; jeremy.vila@shell.com . USA Faming Liang Purdue University 3 , Department of Statistics, West Lafayette, Indiana 47907, . E-mail: fmliang@purdue.edu . USA ABSTRACT We have developed a Bayesian statistical framework for quantitative geosteering in real time. Two types of contemporary geosteering approaches, model based and stratification based, are introduced. The latter is formulated as a Bayesian optimization procedure: The log from a pilot reference well is used as a stratigraphic signature of the geologic structure in a given region; the observed log sequence acquired along the wellbore is projected into the stratigraphic domain given a proposed earth model and directional survey; the pattern similarity between the converted log and the signature is measured by a correlation coefficient; then stochastic searching is performed on the space of all possible earth models to maximize the similarity under constraints of the prior understanding of the drilling process and target formation; finally, an inference is made based on the samples simulated from the posterior distribution using stochastic approximation Monte Carlo in which we extract the most likely earth model and the associated credible intervals as a quantified confidence indicator. We extensively test our method using synthetic and real geosteering data sets. Our method consistently achieves good performance on synthetic data sets with high correlations between the interpreted and the reference logs and provides similar interpretations as the geosteering geologists on four real wells. We also conduct a reliability performance test of the method on a benchmark set of 200 horizontal wells randomly sampled from the Permian Basin. Our Bayesian framework informs geologists with key drilling decisions in real time and helps them navigate the drilling bit into the target formation with confidence. 08 24 2019 09 1 2019 06 19 2019 ID13 ID24 1 10.1190/crossmark-policy library.seg.org true 2018-11-13 2019-04-28 2019-05-30 2019-08-24 https://creativecommons.org/licenses/by-nc-nd/4.0/ 10.1190/geo2018-0781.1 https://pubs.geoscienceworld.org/geophysics/article/84/5/ID13/580134/Stochastic-clustering-and-pattern-matching-for https://pubs.geoscienceworld.org/seg/geophysics/article-pdf/84/5/ID13/6376287/geo-2018-0781.1.pdf https://pubs.geoscienceworld.org/seg/geophysics/article-pdf/84/5/ID13/6376287/geo-2018-0781.1.pdf https://pubs.geoscienceworld.org/geophysics/article/84/5/id13/580134/stochastic-clustering-and-pattern-matching-for Berg C. R. , 2012, Calculating true stratigraphic and true vertical thickness: Technical report, ResDip Systems. 1061-8600 Journal of Computational and Graphical Statistics Brooks 7 434 1998 10.1080/10618600.1998.10474787 General methods for monitoring convergence of iterative simulations 0003-1305 The American Statistician Chib 49 327 1995 10.1080/00031305.1995.10476177 Understanding the Metropolis-Hastings algorithm 0016-8033 Geophysics Eidsvik 71 4 F79 2006 10.1190/1.2212268 Positioning drill-bit and look-ahead events using seismic traveltime datapositioning drill-bit and look-ahead events 10.15530/urtec-2018-2902891 Fierstien J. Winkler H. Strauss P. Klokov A. , 2018, Optimization and drilling of horizontal wells using a Bayesian network: Unconventional Resources Technology Conference, 23–25, doi: http://dx.doi.org/10.15530/URTEC-2018-2902891. Well placement fundamentals Griffiths 2009 Guennebaud G. Jacob B. , and others, 2010, Eigen v3, http://eigen.tuxfamily.org, accessed 16 July 2019. 0006-3444 Biometrika Hastings 57 97 1970 10.1093/biomet/57.1.97 Monte Carlo sampling methods using Markov Chains and their applications 1064-6671 SPE Drilling and Completion Kullawan 29 36 2014 10.2118/167433-PA A decision analytic approach to geosteering operations 0003-1305 The American Statistician Lee Rodgers 42 59 1988 10.1080/00031305.1988.10475524 Thirteen ways to look at the correlation coefficient Journal of the American Statistical Association Liang 102 305 2007 10.1198/016214506000001202 Stochastic approximation in Monte Carlo computation OpenMP application program interface version 3.0 OpenMP Architecture Review Board 2008 PetroWiki, 2012, Gamma ray logs, https://petrowiki.org/Gamma_ray_logs, accessed 16 July 2019. 0969-8043 Applied Radiation and Isotopes Qin 123 114 2017 10.1016/j.apradiso.2017.02.042 A fast forward algorithm for real-time geosteering of azimuthal gamma-ray logging SPE Drilling and Completion Sawaryn 20 24 2005 10.2118/84246-PA A compendium of directional calculations based on the minimum curvature method Multivariate density estimation: Theory, practice, and visualization Scott 2015 10.1002/9781118575574 Stoner 2007 Technical geosteering finds the sweet spot SES user manual Stoner 2015 Applied subsurface geological mapping with structural methods Tearpock 2002 0016-8033 Geophysics Winkler 82 5 D279 2017 10.1190/geo2016-0569.1 Geosteering by exact inference on a Bayesian network 0969-8043 Applied Radiation and Isotopes Yuan 96 63 2015 10.1016/j.apradiso.2014.11.015 A novel method for quantitative geosteering using azimuthal gamma-ray logging