Hydrocarbon saturation from total organic carbon logs derived from inelastic and capture nuclear spectroscopy

US9851468B2 · kind B2 · utility

Assignee

• SCHLUMBERGER TECHNOLOGY CORPORATION · US

Inventors

• Michael M. Herron · Ridgefield, US
• Susan Herron · Danbury, US
• James A. Grau · Ridgefield, US
• John P. Horkowitz · Sugar Land, US
• Paul Ryan Craddock · Scituate, US
• Robert Badry · Calgary, CA

Key dates

• Filing date: Oct 4, 2013
• Grant date: Dec 26, 2017
• Expiry date: Oct 4, 2033

Classification

• Technology area (CPC G): Physics
• CPC primary: G01V5/101
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

The accurate determination of formation hydrocarbon or water saturation is a useful step in the petrophysical evaluation of petroleum reservoirs. This disclosure presents a new method for estimating hydrocarbon saturation directly from a porosity log and a total organic carbon (TOC) log. The method is enabled by the recent development of a geochemical spectroscopy logging tool that combines inelastic and capture gamma ray measurements to provide a robust and accurate TOC log. The method differs from the prior approach of using carbon-to-oxygen ratios that is most often applied in cased hole evaluation. The main advantages of this method are that it does not use knowledge of formation water resistivity, it does not rely on a resistivity model, it does not use an extensive calibration database, and it is largely independent of clay or other lithology effects. Here, the principles of the method and the main challenges are described, and calculations that explore uncertainties in the saturation estimates arising from uncertainties in the log inputs are presented. The statistical uncertainty in the estimate of hydrocarbon saturation is as good as 10 saturation units (s.u.) in convention…