Anisotropic depth migration: Reducing lateral‐position uncertainty of subsurface structures in thrust‐belt environments

1999 ◽  
Author(s):  
Robert W. Vestrum ◽  
Don C. Lawton
Keyword(s):  
Lateral Position ◽  
Thrust Belt ◽  
Position Uncertainty ◽  
Depth Migration ◽  
Subsurface Structures

High-Precision Drill Bit Tracking

2021 ◽  
Author(s):  
Marianne Houbiers ◽  
Sascha Bussat ◽  
Florian Schopper ◽  
Fredrik Hansteen
Keyword(s):  
High Precision ◽  
Lateral Position ◽  
Optimal Placement ◽  
Drill Bit ◽  
Noise Sources ◽  
Position Uncertainty ◽  
Passive Seismic ◽  
Continuous Stream ◽  
Well Trajectory ◽  
Passive Measurements

Abstract The lateral well position uncertainty of magnetic/gyro MWD measurements can often exceed the requirements regarding anti-collision, for optimal placement of infill wells between existing producers, or for hitting targets with limited geological extent. The positional uncertainty can be significantly reduced by implementing high-precision drill-bit localization using passive seismic data. Consequently, not only drilling risks can be reduced, but optimal reservoir drainage is ensured as well. By utilizing passive seismic recordings from the seafloor, we can "listen" to the noise generated by the BHA while drilling. Despite various noise sources in the vicinity (e.g. vessels and rigs), advanced data processing and the combination of hundreds of seafloor receivers spread above the ongoing drilling, enable us to detect the drilling signal and locate the drill bit. Whereas the magnetic and gyro MWD tools have errors that accumulate with measured depth, each bit position derived from seismic (usually every 90 seconds) is completely independent. For horizontal sections, the error does not increase with measured depth, and hence can provide improved lateral accuracy. No additional BHA tool is required and the measurements are neither dependent on the magnetic nor gravitational field. Moreover, the passive seismic measurements can be used to obtain an improved lateral well position estimate. This is done by optimizing the azimuth information of the well trajectory in the minimum curvature method. A lateral uncertainty measure can be derived from the residuals between the passive measurements and the updated well path. Since 2018, we have used the continuous stream of passive data from permanent seafloor sensors at the Grane field with its reservoir depth of around 1800 m TVDSS to follow all wells with this drill bit tracking scheme. Lateral deviations from the magnetic/gyro measurements of up to 20m have been observed. The lateral position uncertainty can be as low as a couple of meters under optimal conditions.

Key seismic exploration techniques for foreland thrust belt: A case from the complex deep subsalt structure of Kuqa, Tarim Basin, Western China

2016 ◽  
Vol 4 (3) ◽  
pp. T337-T346 ◽  
Author(s):  
Yang Ping ◽  
Sun Longde ◽  
Qi Jiafu
Keyword(s):  
Tarim Basin ◽  
Signal To Noise Ratio ◽  
Research Effort ◽  
Complex Structure ◽  
Western China ◽  
Seismic Exploration ◽  
Burial Depth ◽  
Thrust Belt ◽  
Structure Mapping ◽  
Depth Migration

The Kuqa area of the Tarim Basin is a typical foreland thrust belt. Abundant petroleum resources are stored in the complex subsalt structures at depths greater than 6500 m. The extremely rugged surface, the severely deformed gypsum-salt cap above the reservoir, and the large burial depth of the overthrust target make it difficult to accurately delineate the target structures. Those geologic challenges translate into geophysical difficulties of complex seismic wavefields, low signal-to-noise ratio (S/N), and poor imaging accuracy, which compound the exploration challenge in the Kuqa area. To meet the exploration challenge, a research campaign has been conducted since 2005 to integrate seismic acquisition, processing, and interpretation. After almost a decade of research effort and pilot applications, a set of techniques, comprised of wide-line large-array acquisition, anisotropic prestack depth migration under rugged topography, complex structure modeling, and structure mapping with varying velocities, was developed. The use of these techniques has much improved the S/N, imaging accuracy, subsequent interpretation, and well placement. As a result, the success ratio of exploration drilling has increased from less than 25% to more than 64% in the Kuqa area of the Tarim Basin.

scholarly journals The Application of Depth Migration for Processing GPR Data

2018 ◽  
Vol 35 ◽  
pp. 03004
Author(s):  
Dang Hoai Trung ◽  
Nguyen Van Giang ◽  
Nguyen Thanh Van
Keyword(s):  
Significant Role ◽  
Ground Penetrating Radar ◽  
Field Data ◽  
Velocity Model ◽  
Radar Data ◽  
Energy Diagram ◽  
Depth Migration ◽  
Subsurface Structures ◽  
Calculated Velocity ◽  
Ground Penetrating

Migration methods play a significant role in processing ground penetrating radar data. Beside recovering the true image of subsurface structures from the prior designed velocity model and the raw GPR data, the migration algorithm could be an effective tool in bulding real environmental velocity model. In this paper, we have proposed one technique using energy diagram extracted from migrated data as a criterion of looking for the correct velocity. Split Step Fourier migration, a depth migration, is chosen for facing the challenge where the velocity varies laterally and vertically. Some results verified on field data on Vietnam show that migrated sections with calculated velocity from energy diagram have the best quality.

A simple way for producing holographic filters suitable for image improvement

1978 ◽  
Vol 36 (1) ◽  
pp. 226-227
Author(s):  
K.-H. Herrmann ◽  
E. Reuber ◽  
P. Schiske
Keyword(s):  
Transfer Functions ◽  
Diffraction Order ◽  
Lateral Position ◽  
Simple Method ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Wiener Filters ◽  
Image Improvement ◽  
Optical Reconstruction ◽  
Set Up

Aposteriori deblurring of high resolution electron micrographs of weak phase objects can be performed by holographic filters [1,2] which are arranged in the Fourier domain of a light-optical reconstruction set-up. According to the diffraction efficiency and the lateral position of the grating structure, the filters permit adjustment of the amplitudes and phases of the spatial frequencies in the image which is obtained in the first diffraction order.In the case of bright field imaging with axial illumination, the Contrast Transfer Functions (CTF) are oscillating, but real. For different imageforming conditions and several signal-to-noise ratios an extensive set of Wiener-filters should be available. A simple method of producing such filters by only photographic and mechanical means will be described here.A transparent master grating with 6.25 lines/mm and 160 mm diameter was produced by a high precision computer plotter. It is photographed through a rotating mask, plotted by a standard plotter.

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