US 5,854,991 A · Method for inversion processing of transverse electromagnetic induction well logging measurements

Abstract

A method for determining the 2-dimensional distribution of horizontal and vertical electrical conductivities of earth formations surrounding a wellbore using measurements made by a transverse electromagnetic induction well logging instrument. A model is generated of the axial distribution of the horizontal and vertical conductivities, from induction signals acquired by the instrument using two-frequency alternating current. The model is generated by calculating an initial estimate of the conductivity distribution and axially inverting the estimate with respect to the measurements made using the two-frequency alternating current. Shoulder correction is applied to measurements made by the instrument using single-frequency alternating current. An estimate of the radial distribution of the conductivities is generated from the shoulder corrected induction signals acquired using the single-frequency alternating current. A 2-dimensional model is made of the conductivity distribution from the model of axial distribution and from the estimate of radial distribution. The two-frequency induction signals are corrected for near wellbore effects using two-frequency whole space responses calculated using the 2-dimensional model. The corrected two-frequency signals are then axially inverted to generate a 2-dimensional model. Using the corrected two-frequency signals in place of the acquired signals, all the previous steps are repeated until differences between the corrected two-frequency induction signals from successive repetitions (iterations) of the steps fall below a predetermined threshold. The two-dimensional model extant when process is halted becomes the final two-dimensional model.

Claims39

Dependent claims

A method for determining distribution of horizontal and vertical electrical conductivities of earth formations surrounding a wellbore using measurements made by a transverse electromagnetic induction well logging instrument, comprising:

generating a model of axial distribution of said horizontal and vertical conductivities from induction signals acquired by said instrument using two-frequency alternating current;
shoulder correcting measurements made by said instrument using single frequency alternating current;
generating an estimate of radial distribution of said horizontal and vertical conductivities from said shoulder corrected measurements;
constructing a 2-dimensional model of conductivity distribution from said model of axial distribution and from said estimate of radial distribution;
correcting said two-frequency induction signals for near wellbore effect using two-frequency whole space responses calculated using said 2-dimensional model;
generating a final model of said conductivity distribution by axially inverting said corrected two-frequency induction signals and combining with said estimate of radial distribution;
and
using said corrected two-frequency signals in place of said acquired two-frequency signals, repeating said steps of shoulder correcting measurements, generating an estimate of radial distribution, constructing a 2-dimensional model, and correcting said two-frequency induction signals until differences between said corrected two-frequency induction signals calculated in successive repetitions of said steps fall below a predetermined threshold.

5 more elements

A method for determining distribution of horizontal and vertical electrical conductivities of earth formations surrounding a wellbore, comprising:

measuring electromagnetic induction signals along three mutually orthogonal axes by passing alternating current through transmitter coils each oriented along one of said axes, and detecting induction voltages in receiver coils as a result of said alternating current passing through said transmitter coils, first ones of said receiver coils each oriented along the same axis as a corresponding one of said transmitter coils, second ones of said receiver coils each oriented along one of said axes perpendicular to said corresponding one of said transmitter coils, said alternating current including two-frequency alternating current and single frequency alternating current;
generating a model of axial distribution of said horizontal and vertical conductivities from induction signals acquired by said instrument using said two-frequency alternating current;
shoulder correcting signals measured by said instrument using said single frequency alternating current;
generating an estimate of radial distribution of said conductivities from said shoulder corrected measurements;
constructing a 2-dimensional model of conductivity distribution from said model of axial distribution and from said estimate of radial distribution;
correcting said two-frequency induction signals for near wellbore effect using two-frequency whole space responses calculated using said 2-dimensional model;
generating a final model of said conductivity distribution by axially inverting said corrected two-frequency induction signals and combining with said estimate of radial distribution;
and
using said corrected two-frequency signals in place of said acquired two-frequency signals, repeating said steps of generating a model of said axial distribution, shoulder correcting measurements, generating an estimate of radial distribution, constructing a 2-dimensional model, correcting said two-frequency induction signals until differences between said corrected two-frequency induction signals calculated for successive repetitions of said steps fall below a predetermined threshold.

6 more elements

A method for determining a 2-dimensional distribution of conductivities of earth formation penetrated by a wellbore from measurements made by a transverse electromagnetic induction logging instrument, comprising:

generating a model of axial conductivity distribution by inverting measurements made by said instrument using two-frequency alternating current;
generating an estimate of radial conductivity distribution by inverting measurements made by said instrument using single-frequency alternating current;
generating a model of said 2-dimensional distribution by combining said model and said estimate.

A method for determining distribution of horizontal and vertical electrical conductivities of earth formations surrounding a wellbore, comprising:

measuring electromagnetic induction signals along three mutually orthogonal axes by passing alternating current through transmitter coils each oriented along one of said axes, and detecting induction voltages in receiver coils as a result of said alternating current passing through said transmitter coils, first ones of said receiver coils each oriented along the same axis as a corresponding one of said transmitter coils, second ones of said receiver coils each oriented along one of said axes perpendicular to said corresponding one of said transmitter coils, said alternating current including two-frequency alternating current and single frequency alternating current;
generating a model of axial conductivity distribution by inverting measurements using said two-frequency alternating current;
generating an estimate of radial conductivity distribution by inverting measurements made using said single-frequency alternating current;
generating a model of said 2-dimensional distribution by combining said model and said estimate.

1 more element

Dependencies are inferred from the claim text.

Method for inversion processing of transverse electromagnetic induction well logging measurements

Life of this patent

Method for inversion processing of transverse electromagnetic induction well logging measurements

Life of this patent

Abstract

Claims39