Formation Porosity
and Saturation

Reservoir characterisation and understanding reservoir fluid dynamics is fundamental for effective reservoir management. Identifying active formation zones, distinguishing fracture and matrix flows, and understanding fluid movement from the reservoir to the wellbore is essential for optimal recovery

TGT’S Spectral Reservoir Platform is able to address multiple reservoir challenges through multiple completion strings deep into the formation. Our range of logging services can provide real Reservoir answers up to 5 meters away from well borehole. The answers TGT provides include: fluid breakthroughs, injection and production profile, stimulation flow efficiency as well as formation pressure behind multiple casings.

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Reservoir Saturation
Logging – Indigo PNN Suite*



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about PNN

TGT’s Indigo PNN Suite* is a pulsed neutron-neutron tool designed to determine the lithology of the near-wellbore zone, locate gas-water contact (GWC), oil-gas contact (OGC) and oil-water contact (OWC), and evaluate the porosity and oil saturation of reservoirs. TGT performs the interpretation using its proprietary modelling software.

Hardware tool


Example 1

The example below shows PNN SIGMA survey conducted through tubing.

The COUNT_NEAR and COUNT_FAR panels show the actual time decay of neutron density at near and far detectors. The COUNT_RATIO panel shows the distribution of ratio of cumulative counts during the survey. This panel is very sensitive to reservoir lithology and porosity. The further processing of this panel yields the synthetic TPHI log which usually has a very good correlation with reservoir porosity NPHI from open-hole data.

PNN SIGMA Flyer Pic1_sm

The SIGMA panel is derived from COUNT panels through the stabilised multi-exponential decomposition and correction for porosity impact on near and far responses. The panel is easily split into a borehole and reservoir responses with latter to be sensitive to reservoir lithology and water invasion. The consequent processing of this panel yields the reservoir capture cross-section (SIGMA_FRM) log which is further interpreted in terms of sweep (blue color on VOL MODEL panel). In this case the main water breakthrough ensues across the bottom perforations.

Example 2

The next example shows SIGMA survey in interchange of dolomite and anhydrite rocks. One can note a persistent quality of PNN SIGMA data both in casing and tubing.

The porosity developments in limestone streaks are clearly picked up by COUNT_RATIO panel. The TPHI log shows a very good correlation with open-hole porosity NPHI.

PNN SIGMA Flyer Pic2_sm

The SIGMA panel is very sensitive to anhydrite streaks which have high capture cross-section and extend the high values through all the channels.

Volumetric interpretation suggests that water invasion across perforations is not high and most of the produced water comes from the overlying non-perforated reservoir unit by downward channelling behind the casing, as confirmed by spectral noise logging and temperature simulations.