Talk Title: “Estimating, Benchmarking and Managing Subsurface Uncertainty: Principles and Examples”
Speaker: Kurt Rudolph, University of Houston and Rice University
Subsurface risk and uncertainty are recognized as very important considerations in petroleum geoscience. And even when volume estimates are relatively accurate, the reservoir characteristics that determine well placement and performance can remain highly uncertain.
Even more important than minimizing error, is avoiding bias. Programmatic overestimation of success rates and volumes can put a company out of business. Underestimating leads to the regret of significant missed opportunities. Especially in exploration, one should expect to be disappointed; but you should never be surprised.
Context matters too. For example, exploration play maturity has a strong influence on performance. Generally, chance of success increased and prospect success case volumes decreased with play maturity. For very mature plays, success rate decreased again. So, optimizing the efficient frontier, on a risk-reward basis, ensures a diverse and successful portfolio.
Seismic technologies also have had a significant influence on success rates. Wildcats drilled based on 3D seismic data had about a +10% higher success rate than those based on 2D data.
For improved decision making, incorporating subsurface uncertainty into economic evaluations is critical. Expected Monetary Value (EMV) is an especially useful approach to address uncertainty.
Another consideration is the impact of technical or business dependencies. These tend to be underappreciated and can result in a wider range of outcomes. Such dependencies are important in considering aggregate assets, when linkages can reduce the protection afforded by the portfolio effect.
These principles and work practices of using scenario-weighted economic analyses will be demonstrated using an example from a deep-water West Africa oil prospect/development (Girassol). Based on ample public domain data, Girassol illustrates the application of probability-weighted economics across a spectrum of business stages.
Kurt Rudolph received a B.S. in Geology from Rensselaer Polytechnic Institute and an M.A. in Geology from the University of Texas. He began his career as an Exploration Geologist with Unocal in 1978, until he joined Exxon Production Research in 1981. He held a variety of positions at Exxon/ExxonMobil, including Research Geologist, Chief Interpreter in Kuala Lumpur, Technical Advisor for the Africa and Middle East Region, and Hydrocarbon Systems Resource Manager. From 2002 until his retirement in 2015, he was Chief Geoscientist with ExxonMobil Exploration Company in Houston. Since then, Kurt has been an Adjunct Professor at the University of Houston and Rice University.
His interests include seismic attributes/DHI analysis, risking and assessment, sequence stratigraphy, and tectonics and sedimentation. Current research includes the Cretaceous Western Interior, Paleozoic orogenic systems of North America and northern Europe, and integrating subsurface uncertainty into assessment and economic analysis.He won Wallace Pratt Awards for the best AAPG Bulletin paper in 1994 and 2017, was an AAPG-SEG Distinguished Lecturer for 2001-2002, was the AAPG Michael Halbouty Lecturer for 2007, won best paper award for the Mountain Geologist (RMAG) in 2015, and will be an AAPG Distinguished Lecturer for 2023-2024.
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