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Fourth EAGE Borehole Geophysics Workshop
- Conference date: November 19-22, 2017
- Location: Abu Dhabi, United Arab Emirates
- Published: 19 November 2017
21 - 29 of 29 results
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Single- and Multi Well Imaging Field Survey With the SPWD-wireline Prototype at the Piana di Toppo Test Site in Italy
Authors R. Giese, K. Krüger, K. Jaksch, C. Virgil, M. Neuhaus, F. Poletto, A. Schleifer, M. Amro and S. ReichmannSummaryIn 2015 the SPWD-wireline prototype incorporating a phased array vibration source and two three component receivers has been tested at the “Piana di Toppo” test site in Italy. The test aims to demonstrate its applicability, the estimation of the exploration range and to calibrate the sonde for its application in a sedimentary rock environment. To ensure a safe operation during the well test a temperature monitoring system, tool azimuth measuring system and a trigger-system for combined downhole and surface measurements were integrated. Besides single frequency transmission tests between 120 Hz and 1920 Hz a borehole survey applying linear sweeps from 120 Hz to 2600 Hz were executed in 5 m and 10 m steps to image structures around and below the three test wells. Three-component Fresnel Volume Migration were used to image shear wave reflections of the three different wavefield amplification directions
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Key Considerations In 4DVSP Survey Design and Acquisition
Authors B. Al-Ajmi, K. S. Eldin, W. Zahran, D. Inala, S. Anwar, R. Stott, J. Tinnin and A. HamiltonSummaryNo summary available.
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Extracting More Information from Rig Source 3C-VSPs
Authors C. Naville, A Rivet and V. LesnivovSummaryDifferent VSP datasets studied by surface seismic geophysicists inspired three short notes, illustrating aspects seldom related by borehole seismic geophysicists:
- The first arrival times constitute the basic information from VSP’s, considered as the modern form of checkshots: therefore, the surface seismic processing operators would like to read the root mean square stacking velocity (Vrms) and the divergence factor (V2T), expressed versus vertical two way times (twt) in the VSP reports.
- Signal-to-Noise conditions in deep boreholes can be an issue in open hole sections: a critical case of noisy hole conditions during VSP acquisition has been analysed, concluding to the presence of infiltration microseismic noise near-linearly polarized into the preferred permeability azimuth in the plane radial to the borehole axis.
- Complex, interfered downgoing wavetrain obverved in borehole seismic indicates multipath seismic propagation in a heretogeneous medium. Time pick of “first arrival” is rendered approximate, at best, and signature deconvolution is often impossible, except in the case where the spatial distribution of the multipath wavetrain remains within a small solid angle, as verified from oriented 3C VSP records. In such case, a depth variant downgoing incident signature can be defined to properly compress the VSP data corridor stack domain.
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Orientation Method Applied to onshore 3-Component VSP’s Recorded with a Relative Bearing Sensor in Partially Low Deviated Boreholes
Authors K. Kazemi and C. NavilleSummaryMany Iranian rig-source VSP datasets are recorded with the multilevel versatile seismic imager (VSI) VSP tool. Each shuttle of the VSI toolstring contains a Relative Bearing (RB) sensor measuring the roll angle made by the VSP tool arm with the vertical plane locally tangent to the deviated borehole trajectory. The 3C VSP data actually look correctly oriented using the roll angle provided by the RB sensor where the hole vertical inclination is over 8°. The whole orientation into geographical system was done using the hole inclination and azimuth angles provided by the borehole survey recorded during the wireline logging operations. A method was designed at the preprocessing stage to orientate the VSP data recorded below the 8° hole inclination threshold, by finding the RB angle differences level to level so as to render the downgoing Shear VSP wavetrain coherent on adjacent VSP stations. This was followed by calibrating the true RB angle on the VSP levels located in the hole intervals with inclination over 8°, whether the hole is cased or not. The present paper focuses on the principles of this orientation method, successfully tested on a couple of 3 component onshore VSP datasets made available by NIOC.
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Walkaway VSP Velocity Tomography Modeling and Prestack Depth Migration Imaging of Complex Surface
Authors J.G. Li, J.H. Huang, Y.P. Li, Z.D. Cai and Y.Z. ChenSummaryThe foreland basin of piedmont belt is one of the oil prospects and a current hotspot for exploration in western China. Complex surface and structures put forward higher requirements for surface correction and migration imaging. Usually, static correction only solves the vertical component of travel time, and conventional time migration can’t accommodate the lateral changes in velocity.
Based on the Walkaway VSP data of one well in western China, we studied the Walkaway VSP velocity tomography modeling, wave field continuation and prestack depth migration imaging of complex surface in this paper. The core idea includes updating the velocity model, extending the wave field, realizing the near-surface correction, and completing the f-x prestack depth migration. Know from the test of model data and measured data, the velocity modeling from reflection travel time tomography can provide an accurate velocity model for prestack depth migration, and the one-way wave field continuation and f-x prestack depth migration migration imaging, can effectively solve the wave field correction problem of complex surface. The results show that this method can be applied to prestack depth migration imaging of complex surface and lateral varied velocity medium with universal applicability.
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Orientation of a 3-C VSP Dataset Acquired by Integrated Geophone Sensor and MEMS Inclinometer Devices
Authors W. Wills, C. Naville, M. Nott-Bower and G. TubridySummaryThis paper seeks to gauge the performance of a new commercial downhole VSP tool electronics module, which has been recently implemented with a 3C solid state inclinometer system called a High Side Indicator (HSI). The HSI measures the direction of the pull of gravity and calculates the angles of roll and vertical inclination in each shuttle of the borehole seismic toolstring. By so doing, the VSP tool manufacturer expects to (a) replace the previous gimbal settings systems, which proved voluminous, fragile, inaccurate at low inclination, and mechanically difficult to maintain through the lifetime of a VSP tool, and (b) encourage full 3C processing of all downhole datasets, even those acquired within rig source VSP survey geometries. The first objective of this test was to check that the VSP hardware and acquisition software worked as expected, and secondly to define a minimal field QC procedure which includes at least the roll angle rotation and associated 3C VSP displays. From this the field engineer and the client supervisor can be reassured as soon as possible about the overall VSP data quality and usability for advanced full 3C VSP processing by the geophysicists and interpreters.
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Application of Dual Walkaway VSP Technology in Oilfield Development
More LessSummaryThe oil and gas reservoirs in LH oilfield in eastern China are deep and thin, and the resolution of 3D seismic data is poor. This paper introduces the dual Walkaway VSP technologies and apply them in the LH oilfield to conduct fine structural evaluation and reservoir characterization including identification of minor faults and low-relief structures, prediction of oil-bearing sand body distribution, and solving reservoir development problems of the study area.
In the study, the high quality Walkaway VSP data is firstly obtained by three component digital geophone array in two wells. And then study the imaging technology to optimize the common imaging point gathers to obtain the high resolution VSP profile. Finally, fine structure interpretation and impedance inversion were conducted to predict oil and gas between the two wells. We demonstrate through the consistency of well data and prediction result that dual Walkaway VSP technology could be very helpful in oil and gas development.
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Application of Adaptive Time-frequency Distribution for Reservoir Prediction: A Case Study of the VSP in Tarim Basin, China
More LessSummaryAs one of several time-frequency analysis methods for VSP data, W-V distribution has widely been used and provides better time-frequency concentration and reliable distribution edges, but s seriously impacted by the cross-term interference. An adaptive W-V distribution method is proposed to suppress the cross-term interference of VSP data based on spectrum decomposition W-V distribution. We apply the method to the field VSP data of Tarim Basin and the adaptive W-V distribution result are significantly related to oil-gas characteristics.
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Complex Geologic Modeling Using Walkaway-VSP Imaging: a Case Study from Jiuquan Basin,China
More LessSummaryComplex structure, fragmentized strata and the lack of drilling data make it difficult to modeling geological structure in the complicated structural belt. Dispite some oilfield had completed the large area 3D-seismic with high-steep structures, the imaging at structural main portion still necessary to improve. In recent years, we realized that borehole seismic have the natural advantage in observation of the high-steep targets. In this paper, we implemented a synchronous dual-well acquisition Walkaway-VSP with large array geophone in Jiuquan basin. And then we studied the complex geologic modeling with Walkaway-VSP imaging. Finally, we formed a system of complicated geological modelling with overthrust nappe stratum based on high quality Walkaway-VSP imaging. It is a very useful application of borehole seismic technology in complex areas.
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