High-Resolution, Reflection Mode Tomographic Imaging Part II: Application to Echography

1989 ◽  
Vol 11 (1) ◽  
pp. 22-41
Author(s):  
A. Herment ◽  
J.P. Guglielmi ◽  
P. Péronneau ◽  
Ph. Dumée
Keyword(s):  
Signal Processing ◽  
High Resolution ◽  
Data Acquisition ◽  
Ultrasonic Imaging ◽  
Synthetic Data ◽  
Computation Time ◽  
Propagation Speed ◽  
Tomographic Imaging ◽  
Reflection Mode ◽  
Using Data

Principles of high-resolution, ultrasonic imaging using data acquisition by a compound scanning with a sector echograph are presented. The signal processing is based on both deconvolution and reflection mode tomography. Three of the methods that can be derived from these principles are selected due to their lower computation costs. Applications of these methods to synthetic data and test targets demonstrate that, with respect to 2D deconvolution, they offer: a gain in computation time of more than 8, an improvement in resolution of the order of 10 and an increase of S/N ratio of the order of 4. Finally, both the effects of limited acquisition angular window and of a variable propagation speed are illustrated.

High-Resolution, Reflection Mode Tomographic Imaging Part I: Principles and Methods

1989 ◽  
Vol 11 (1) ◽  
pp. 1-21
Author(s):  
A. Herment ◽  
J.P. Guglielmi ◽  
P. Péronneau ◽  
Ph. Dumée
Keyword(s):  
High Resolution ◽  
Image Reconstruction ◽  
Computation Time ◽  
Tomographic Imaging ◽  
Image Resolution ◽  
Square Root ◽  
Two Dimensional ◽  
Reflection Mode ◽  
Reconstruction Process ◽  
General Method

A general method for improving image resolution is derived and applied to ultrasound signals; it combines the principles of both reflection mode tomography and deconvolution. The different possibilities of applying these principles allow two types of approaches to be defined, depending upon whether image reconstruction is achieved on radiofrequency or detected signals. A thorough description of three methods that are of particular interest due to their lower computation costs is presented, and their results quantified. They permit a gain in resolution of the order of ten with respect to two-dimensional deconvolution of images, as well as an improvement of the S/N ratio, which is related to the square root of the number of projections used in the reconstruction process, and a decrease of about four in computation time.

High‐resolution velocity and attenuation logs from long‐spaced sonic data

Geophysics ◽  
1991 ◽  
Vol 56 (7) ◽  
pp. 1071-1080 ◽  
Author(s):  
Mark Sams
Keyword(s):  
High Resolution ◽  
Conjugate Gradient ◽  
Layered Medium ◽  
Synthetic Data ◽  
Real Data ◽  
Tomographic Imaging ◽  
Gradient Technique ◽  
Special Case

A long‐spaced sonic survey may be thought of as a special case of ray theoretical tomographic imaging. With such an approach estimates of borehole properties at a resolution of 6 inches (0.15 m) have been obtained by inversion compared with a resolution of 2 ft (0.6 m) from standard borehole‐compensated techniques (BHC). The inversion scheme employs the conjugate gradient technique which is fast and efficient. Unlike BHC, the method compensates for variable refraction angles and provides estimates of errors in the measurements. Results from synthetic data show that these factors greatly improve the imaging of the properties of a finely layered medium, though amplitude decay and coupling are less well defined than velocity and mud traveltime. Results from real data confirm the superior quality of logs from inversion. Furthermore, they indicate that measured amplitudes can be dominated by errors that cause deterioration of BHC estimates of amplitude decay and coupling.

EVALUATION OF LWD HIGH RESOLUTION ULTRASONIC IMAGING TECHNOLOGY AND APPLICATIONS IN SLIM HOLE SIZE

2021 ◽  
Author(s):  
Mohamed M. Hashem ◽  
◽  
Ahmed Taher ◽  
Mohamed Fouda ◽  
Rehab Al-Khalifah ◽  
...  
Keyword(s):  
High Resolution ◽  
Data Acquisition ◽  
Imaging Techniques ◽  
Drilling Fluid ◽  
Ultrasonic Imaging ◽  
Wellbore Stability ◽  
Hole Size ◽  
Time Dependency ◽  
Measurement Sensitivity ◽  
Water Based

Logging while drilling (LWD) ultrasonic imaging tools have been recently introduced for slim hole size. Due to fundamental differences in data acquisition methodologies with other previously utilized LWD and wireline imaging techniques, field trials have been performed with the objective of validating and evaluating the new ultrasonic tool’s measurement. Ultrasonic imagers have been deployed in multiple wells of different environments and formation characteristics to evaluate the tool’s measurement quality and potential applications. The trials were performed in carbonate and clastic formations, horizontal and vertical trajectories, oil- and water-based drilling fluid systems, and in drilling and wipe operations. An LWD ultrasonic imager has also been deployed back to back with wireline. Multiple passes were performed to evaluate the time dependency and hole deterioration effect. In water-based mud, an ultrasonic imaging tool was run in the same bottomhole assembly with the proven LWD laterolog resistivity imager for the comparison of both technologies. In addition to stratigraphic dips, bed boundaries, fractures, faults, and other geological features usually detected by other imaging techniques, ultrasonic imaging tools also provided high measurement sensitivity for detecting geometric features relating to wellbore shape and wellbore stability. LWD microresistivity-based image comparisons indicated a robust correlation of the fractured zones contributing to lost circulation while drilling. Multiple passes for drilling and wipe images with wireline comparisons logged days after the LWD run clearly illustrated the time-dependency of the image quality due to borehole deterioration, invasion, and progression of geomechanical effects used to benchmark future data acquisition requirements. This paper evaluates the capabilities and performance of ultrasonic imaging tools in comparison with other LWD and wireline high-resolution imaging sensors.

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