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Durham University

Department of Earth Sciences

Profile

Publication details for Professor Richard Hobbs

Oughton, R.H., Wooff, D.A., Hobbs, R.W., O'Connor, S.A. & Swarbrick, R.E. (2015). Quantifying uncertainty in pore pressure estimation using Bayesian networks, with application to use of an offset well. Petroleum Geostatistics 2015. Biarritz, France, European Association of Geoscientists and Engineers (EAGE).

Author(s) from Durham

Abstract

Pore pressure estimation is a crucial yet difficult problem in the oil industry. If unexpected overpressure
is encountered while drilling it can result in costly challenges and leaked hydrocarbons.
Prediction methods often use empirical porosity-based methods such as the Eaton ratio method, requiring
an idealised normal compaction trend and using a single wireline log as a proxy for porosity.
Such methods do not account for the complex and multivariate nature of the system, or for the many
sources of uncertainty. We propose a Bayesian network approach for modelling pore pressure, using
conditional probability distributions to capture the joint behaviour of the quantities in the system
(such as pressures, porosity, lithology, wireline logs). These distributions allow the inclusion of
expert scientific information, for example a compaction model relating porosity to vertical effective
stress and lithology is central to the model. The probability distribution for each quantity is updated
in light of data, producing a prediction with uncertainty that takes into account the whole system,
knowledge and data. Our method can be applied to a setting where an offset well is used to learn
about the compaction behaviour of the planned well, and we demonstrate this with two wells from
the Magnolia field.