METHOD FOR USING VOXELATED X-RAY DATA TO ADAPTIVELY MODIFY ULTRASOUND INVERSION MODEL GEOMETRY DURING CEMENT EVALUATION

Abstract

A combining mechanism for borehole logging tool data that uses density data from a logging tool to inform the geometry of an acoustic-based or ultrasound-based data inversion is provided, comprising: at least one mechanism for converting three-dimensional density data into a three-dimensional density model; at least one mechanism for converting three-dimensional density model into a three-dimensional acoustic impedance model; and, at least one mechanism for processing acoustic data using said three-dimensional acoustic impedance model to produce an interpretable data log. A method of using density data from a logging tool to inform the geometry of an acoustic-based or ultrasound-based data inversion is also provided, comprising: converting three-dimensional density data into a three-dimensional density model; converting three-dimensional density model into a three-dimensional acoustic impedance model; and, processing acoustic data using said three-dimensional acoustic impedance model to produce an interpretable data log.

Claims

1. A combining mechanism for borehole logging tool data that uses density data from a logging tool to inform the geometry of an acoustic-based or ultrasound-based data inversion, comprising: at least one mechanism for converting three-dimensional density data into a three-dimensional density model; at least one mechanism for converting three-dimensional density model into a three-dimensional acoustic impedance model; and, at least one mechanism for processing acoustic data using said three-dimensional acoustic impedance model to produce an interpretable data log.

2. The combining mechanism of claim 1, wherein said mechanism is configured to process ultrasound or acoustic data from a borehole logging tool.

3. The combining mechanism of claim 1, wherein said mechanism is configured to process x-ray data from a borehole logging tool.

4. The combining mechanism of claim 1, wherein said mechanism is configured to include the processing of neutron porosity data from a borehole logging tool to improve the accuracy of x-ray data from a borehole logging tool.

5. The combining mechanism for borehole logging tool data of claim 1, wherein said borehole tool is a wireline-based tool.

6. The combining mechanism for borehole logging tool data of claim 1, wherein said borehole tool is a logging-while-drilling-based tool.

7. The method of using density data from a logging tool to inform the geometry of an acoustic-based or ultrasound-based data inversion, comprising: converting three-dimensional density data into a three-dimensional density model; converting three-dimensional density model into a three-dimensional acoustic impedance model; and processing acoustic data using said three-dimensional acoustic impedance model to produce an interpretable data log.

8. The method of claim 7, wherein said method processes ultrasound or acoustic data from a borehole logging tool.

9. The method of claim 7, wherein said method processes x-ray data from a borehole logging tool.

10. The method of claim 7, wherein said method further comprises the processing of neutron porosity data from a borehole logging tool to improve the accuracy of x-ray data from a borehole logging tool.

11. The method for borehole logging tool data of claim 7, wherein said borehole tool is a wireline-based tool.

12. The method for borehole logging tool data of claim 7, wherein said borehole tool is a logging-while-drilling-based tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 illustrates an ultrasonic wellbore tool combined with an x-ray-based wellbore tool being lowered into a well by means of wireline conveyance, in addition to the cement masses surrounding the cased wellbore.

[0038] FIG. 2. illustrates one example of how ultrasound data is typically inverted based upon a highly homogeneous and radially symmetric model, to produce a data log or cement image.

[0039] FIG. 3 illustrates one example of how ultrasound data mat inverted based upon an adaptive model, the geometry of which has been informed by the three-dimensional cement density data provided by x-ray cement evaluation logs, to produce a more accurate data log or cement image.

BRIEF DESCRIPTION OF SEVERAL EXAMPLE EMBODIMENTS

[0040] The methods described herein use the output of an x-ray-based borehole cement logging/mapping tool to inform the inversion model geometry used to invert the raw data collected by an acoustic/ultrasonic tool deployed to collect data within the same borehole.

[0041] With reference now to FIG. 1, an example embodiment comprising an ultrasonic tool [101] is deployed into a borehole upon the same string as a x-ray-based cement evaluation tool [102], or a x-ray-based borehole mapping tool, or an isotope-based cement evaluation tool, or an isotope-based borehole mapping tool. The ultrasonic logging tool [101] is accompanied by an x-ray cement evaluation and/or neutron porosity tool [102] by wireline conveyance [103] into a cased borehole, wherein the cemented section of the well [104] is logged through the inner-most casing or tubing [105].

[0042] The example embodiment of FIG. 2 illustrates how during a typical ultrasound inversion, the raw ultrasound log data [201] is inverted and processed [202] through the use of a geometric model [203] which assumes the geometry of the casing, cement, and formation, along with their mechanical properties. The geometric model [203] is not adapted to the well geometry, such that the eccentricity of the casing, ovality of the casing, or ovality of the wellbore itself, as a function of depth, is not considered. The mechanical properties include acoustic impedance coefficients which are used the match the empirically) collected speed of sound (time of flight) data and signal attenuation, such that the actual mechanical properties of the cement can be determined to produce an image of cement homogeneity as a function of depth [204]. The output is typically represented as an ultrasonic image or variable density display [204].

[0043] The example embodiment of FIG. 3 illustrates how raw ultrasound log data [301] may inverted and processed [302] through the use of a geometric model [305] which is unique for each depth interval (measurement according to logged depth). Three-dimensional x-ray density logs [303] are processed to create a voxelated three-dimensional density map of the cement as a function of depth [304]. The result is an accurate model including actual cement geometries, three-dimensional density variations, and any casing or formation eccentricitieswhich is computed for each depth interval. Acoustic impedance properties can be created from comparison with a database of known cement impedances for a known density, and the three-dimensional density model [305] reprocessed as necessary to create a three-dimensional model of acoustic impedance variations. As such, the model [305] which serves to inform the inversion [302] is based upon the physical geometries and attributes of the well that has been logged. The output is typically represented as an ultrasonic image or variable density display [306] that has now been corrected for wellbore geometry variations (as a function of depth) by use of the three-dimensional x-ray data.

[0044] In another embodiment, raw ultrasound log data [301] is inverted and processed [302] through the use of a geometric model [305] which is unique for each depth interval. Three-dimensional x-ray density logs [303] are processed along with neutron porosity logs to ensure that regions of the x-ray data which indicate a void or channel can be further corroborated by a relative increase in cement porosity (in the near-field region surrounding the casing). The three-dimensional x-ray density logs [303] once pre-processed to create a voxelated three-dimensional density map of the cement as a function of depth [304], are enhanced by the accuracy or confidence-interval of which has been improved dramatically by automated/processed comparison with neutron-porosity logs. The result is an accurate model including actual cement geometries, three-dimensional density variations (corroborated with porosity data), and any casing or formation eccentricities computed for each depth interval. Acoustic impedance properties can be created from comparison with a database of known cement impedances for a known density, and the three-dimensional density model [305] reprocessed as necessary to create a three-dimensional model of acoustic impedance variations. As such, the model [305] which serves to inform the inversion [302] is based upon the physical geometries and attributes of the well that has been logged. The output is typically represented as an ultrasonic image or variable density display [306].

[0045] In a further embodiment, machine learning can be employed to analyze the results of the inversion and quality index flags (produced from the inversion) to determine whether the selection of mechanical properties a specific cement depth interval was optimal, or whether the result would have a higher confidence level if an alternative set of cement characteristics had been used for the adaptive model.

[0046] In a further embodiment, machine learning can be employed to analyze the results of the inversion and quality index flags (produced from the inversion) to determine whether the three dimensional density model geometry adequately matches the anticipated results of the acoustic inversionand to what degree other, alternative geometric model interpretations of the x-ray or neutron data would better fit the model behavior, thereby serving as an additional re-processing step for the ultrasound inversion.

[0047] In another embodiment, the data collected was from borehole tools deployed by wireline.

[0048] In a still further embodiment, the data collected was from borehole tools deployed by logging-while-drilling.

[0049] The foregoing specification is provided only for illustrative purposes, and is not intended to describe all possible aspects of the present invention. While the invention has herein been shown and described in detail with respect to several exemplary embodiments, those of ordinary skill in the art will appreciate that minor changes to the description, and various other modifications, omissions and additions may also be made without departing from the spirit or scope thereof.