Reservoir Saturation Tool - Cased Hole Logging | SLB


Reservoir saturation tool

Reservoir formation

Saturation, lithology, and porosity through casing

The RSTPro reservoir saturation tool incorporates a pulsed neutron generator and a dual-detector spectrometry system to measure elemental concentrations, including carbon and oxygen, and the formation neutron-capture cross section (sigma) during a single trip in the well.

Oil volume is computed from the carbon/oxygen (C/O) ratio determined through full spectral analysis to eliminate any environmental bias and also from a windows-based C/O ratio. Proprietary alpha processing combines the two volume determinations to deliver a saturation answer that is both highly accurate and can be acquired at faster logging speeds. The accuracy of the resulting reserves estimates is comparable to that from core analysis.

The sigma measurement is used to determine porosity and differentiates between saline water and oil to calculate formation oil saturation. Where formation water is fresh or of unknown salinity, saturation is determined from the C/O ratio measurement, which is salinity independent.

A quantitative, mineral-based lithology interpretation is produced by inputting the elemental yields measured by the RSTPro tool to SpectroLith spectroscopy lithology processing.

302-degF temperature rating
15,000-psi pressure rating

The RSTPro tool can log flowing wells—no pulling tubing or killing the well is required, and reinvasion is avoided.

RSTPro reservoir saturation tool production logging

Production logging applications

The versatile RSTPro tool also provides answers for production logging.

The TPHL three-phase holdup log made with the RSTPro tool is a continuous measurement of the holdups of oil, water, and gas for wells at any deviation.

The WFL water flow log made with the RSTPro tool is conducted to locate and evaluate axial water migration behind pipe, measure the velocity of water flow in a well, and determine internal or behind-pipe crossflow between zones. The RSTPro tool is configured to measure both upward and downward flow, inside casing and behind pipe.

The PVL phase velocity log made with the RSTPro tool measures a marker element that is soluble in either oil or water only to calculate the velocity of that phase in a deviated well with segregated flow.