Prismatic grid inversion for oil saturation and 3-phase holdup
A method of determining downhole formation oil saturation and three-phase holdup is described. The method includes lowering a pulsed-neutron logging tool downhole with a near detector and a far detector. The method further includes measuring a carbon to oxygen ratio from the near detector, measuring a carbon to oxygen ratio from the far detector, measuring a ratio of inelastic count rates, and plotting the measured ratios in a prismatic grid. The method further includes visualizing the fluid volumetrics around the pulsed-neutron logging tool.
1 . A method comprising:
lowering a pulsed-neutron logging tool downhole comprising a near detector and a far detector;
measuring a carbon to oxygen ratio from the near detector;
measuring a carbon to oxygen ratio from the far detector;
measuring a ratio of inelastic count rates, wherein the ratio of inelastic count rates is a ratio of near detector inelastic count rates to far detector inelastic count rates; and
plotting the measured ratios in a prismatic grid.
2 . The method of claim 1 , wherein the prismatic grid has Cartesian coordinates.
3 . The method of claim 1 , further creating an inversion matrix to determine borehole holdup and oil saturation.
4 . The method of claim 1 , further determining a formation oil saturation and three-phase holdup.
5 . The method of claim 1 , further visualizing fluid volumetrics around the pulsed-neutron logging tool in real time.
6 . The method of claim 5 , further interpreting borehole and formation variations through representation of oil holdup (Y o ), gas holdup (Y g ), and oil saturation (S o ).
7 . The method of claim 1 , further analyzing dynamic density variations of the surrounding environment of the pulsed-neutron logging tool.
8 . The method of claim 1 , further representing boundaries of a relative change of a formation oil saturation (S o ) and an oil holdup (Y o ).
9 . A system for visualizing fluid volumetrics around a pulsed neutron logging tool comprising:
a pulsed-neutron logging tool comprising a near detector and a far detector; and
a prismatic grid with Cartesian coordinates, wherein one coordinate corresponds to a carbon to oxygen ratio from the near detector, another coordinate corresponds to a carbon to oxygen ratio from the far detector, and a third coordinate corresponds to a ratio of inelastic count rates, wherein the ratio of inelastic count rates is a ratio of near detector inelastic count rates to far detector inelastic count rates.
10 . A system for visualizing boundaries of a relative change of a formation oil saturation (S o ) and an oil holdup (Y o ) around a pulsed neutron logging tool comprising:
a pulsed-neutron logging tool comprising a near detector and a far detector; and
a prismatic grid with Cartesian coordinates, wherein one coordinate corresponds to a carbon to oxygen ratio from the near detector, another coordinate corresponds to a carbon to oxygen ratio from the far detector, and a third coordinate corresponds to a ratio of inelastic count rates, wherein the ratio of inelastic count rates is a ratio of near detector inelastic count rates to far detector inelastic count rates.