Schlumberger

Water Saturation and Movable Fluids

Integrating wellbore software, logs, and multimineral matrix solving with expert interpretation

Unconventional plays and deepwater arenas may require advanced interpretation of many different log types, including magnetic resonance and neutron-induced gamma ray spectroscopy. To perform such interpretation, Schlumberger petrotechnical experts use the Techlog wellbore software platform, which uses advanced interpretation workflows that can incorporate the latest logging technologies.

Water saturation

For the determination of water saturation, Schlumberger petrophysical experts have the knowledge and expertise to use any industry-standard equation you prefer—Archie, Juhasz, Simandoux, Dual-Water, Indonesia, or Waxman-Smits. Familiar with virtually every basin and formation in the world, our experts can build a petrophysical model that will suit your particular environment and accurately calculate lithology, porosity, and water saturation. In carbonates, we can calculate a continuous M value from the Dielectric Scanner multifrequency dielectric dispersion service for an improved Archie water saturation.

Immovable versus producible fluids

We can quantify bound fluid compared with movable fluid when magnetic resonance logs are obtained. When laboratory magnetic resonance measurements are made on cores, specific T2 cutoffs can be determined for your given formation and fluid types. Then, these cutoffs can be applied to the continuous log information so that fluid types and movable versus immovable fluids can be identified over the entire logged section.

Non-resistivity-based water saturation

Using the Dielectric Scanner multifrequency dielectric dispersion service, it is possible to measure directly the volume of water present in a formation in fresh or unknown formation water salinity. When combined with the total porosity from another source, water saturation in the near-wellbore region is determined. This technique works very well in fresh or variable salinity formation waters where traditional resistivity based techniques to calculate water saturation are problematic.

Another method of determining water saturation is by magnetic resonance fluid characterization. Schlumberger MR Scanner expert magnetic resonance service can measure total porosity and determine the volumes of bound water, free water, and hydrocarbons in the near-wellbore region. These answers are independent of Archie analysis and can be derived without having to input water salinity.

Laminated sand analysis

One of the most difficult challenges in petrophysics is evaluating laminated pay where the sand lenses are thinner than the vertical resolution of standard logging tools. Schlumberger petrotechnical experts have three methods to solve this problem.

  • FMI fullbore formation microimager, used to delineate thin beds that are thicker than 0.5 in for a net sand count. The OBMI oil-base microimager can be used for beds that are thicker than 1.2 in.
  • Dielectric Scanner service, used to delineate beds thicker than 1 in and determine water-filled porosity
  • Rt Scanner triaxial induction service, used to measure vertical and horizontal resistivities. Combining both resistivities with porosity and clay volume measurements allows us to determine water saturation and net pay for beds of any thickness.

Technical challenges

 
 
 
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Direct Measurement of
Water Volume and Salinity

Dielectric Scanner multifrequency dielectric dispersion service measured water-filled porosity of individual thin beds in Venezuela to determine high-quality reservoir zones.The proVISION Plus MR log helps characterize two additional laminated sand–shale sequences.Quality control of Schlumberger multimineral evaluation of LWD data shows error to be extremely low.Logging showed a highly laminated interval with net to gross 40% to 60% in the lower setion and 30% to 40% in the upper section. Porosity in the sand laminations is 30%.
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