US 9,869,792 B2Granted

Inversion-based workflow for processing nuclear density images in high-angle and horizontal wells

AssigneeSchlumberger Technology Corporation

InventorsSushil Shetty, Dzevat Omeragic, Tarek M. Habashy, John Rasmus, Jeffrey Miles

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Abstract

Methods and apparatus for characterizing a subterranean formation traversed by a wellbore including collecting data from the formation using a tool wherein the tool collects data to form an azimuthal image, characterizing a section of the formation comprising data and images acquired in a high angle wellbore section or horizontal wellbore section using a parametric model, and performing an inversion using apparent densities and volumetric photoelectric factor images to build a formation model wherein the inversion is tailored for high angle wellbore sections and/or horizontal wellbore sections.

Claims22

Dependent claims

A method for characterizing a subterranean formation traversed by a borehole, the method comprising:

collecting data in a borehole section for the formation using a nuclear density tool or sensor, wherein the data includes long spacing density data and short spacing density data, and wherein both the long spacing density data and the short spacing density data are combined to form density images of the formation as a function of azimuth around the tool or sensor;
segmenting the borehole section into a plurality of segments based on features of said density images of the formation;
identifying a segment of said plurality of segments as a high angle segment;
defining an initial formation model of the formation for said high angle segment;
defining an initial borehole model for said high angle segment, wherein the borehole model comprises a standoff distance between the tool or sensor and a wall of the borehole, the standoff distance varying as a function of azimuth around the tool or sensor;
and
for said high angle segment, performing inversion operations using the initial formation model, the initial borehole model, and the density images to determine at least one formation parameter for the formation;
wherein the inversion operations involve:
i) inverting for borehole geometry of said high angle segment using at least short spacing density data for said high angle segment, wherein the borehole geometry of said high angle segment is defined in terms of the standoff distance between the tool or sensor and the wall of the borehole as a function of azimuth, and
ii) inverting for at least one formation parameter using at least long spacing density data for said high angle segment.

7 more elements

A method for characterizing a subterranean formation traversed by a borehole, the method comprising:

collecting data in a borehole section for the formation using a nuclear density tool or sensor, wherein the data includes long spacing density data and short spacing density data, and wherein both the long spacing density data and the short spacing density data are combined to form density images of the formation as a function of azimuth around the tool or sensor;
segmenting the borehole section into a plurality of segments based on features of said density images of the formation;
identifying a segment of said plurality of segments as a horizontal segment;
defining an initial formation model of the formation for said horizontal segment;
defining an initial borehole model for said horizontal segment, wherein the initial borehole model comprises a standoff distance between the tool or sensor relative to a wall of the borehole, the standoff distance varying as a function of azimuth around the tool or sensor;
and
for said horizontal segment, performing inversion operations using the initial formation model, the initial borehole model, and the density images to determine at least one formation parameter for the formation;
wherein the inversion operations involve:
i) inverting for borehole geometry of said horizontal segment using at least short spacing density data for said horizontal segment, wherein the borehole geometry of said horizontal segment is defined in terms of the standoff distance between the tool or sensor and the wall of the borehole as a function of azimuth, and
ii) inverting for at least one formation parameter using at least long spacing density data for said horizontal segment.

7 more elements

Dependencies are inferred from the claim text.