--> Predicting Oil Quality in Present Day Deepwater Drilling Environments, by W. Owen BeMent; #90037 (2005)

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Predicting Oil Quality in Present Day Deepwater Drilling Environments

W. Owen BeMent
Shell International Exploration & Production, Houston, TX

The prediction of crude oil quality is essential to the economic assessment of exploration prospects drilled in present day water depths >1000 where drilling costs can exceed $100,000 USD/day and follow-up developments costs can reach one billion USD. One of the key physical properties of crude oil that controls production well flow rates is viscosity while the crude oil acid number has a significant impact on the potential market price of the crude oil. Exploration success of significant quantities of what could be described as low quality crude oil (defined here as having API's < 20 and TAN acid numbers > 0.5) may not result in commercial success unless the crude oil can eventually be produced, sold and refined to recover costs.

It is generally accepted that crude oil quality is a function of both source rock maturity and post-reservoir hydrocarbon charge transformation processes. Even with the advancements in basin modeling, our ability to accurately predict a specific numerical value for crude oil properties is still limited.

One approach has been to develop a set of cumulative curves of these crude oil properties as a function of reservoir temperature. These distributions can then used to predict P10, PSO and P90 values which can be subsequently used in economic evaluations to determine scenarios that are described as the "low", "base" and "high" case. This allows us to better evaluate the economic sensitivity of a project given that we are unable to predict a specific value for these crude oil properties.