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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
29 results
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3D Reflectivity-Guided Joint Migration Inversion of Multi-Well Borehole Data
Authors B. El Marhfoul and D.J. VerschuurSummary3D borehole-related seismic data has superior quality and higher-frequency content compared to surface seismic data. These unique properties make it possible to produce high-resolution images and accurate velocity models especially around the borehole. However, using conventional imaging algorithms, that assume primary reflection energy, will retrieve only a limited area around the borehole. This problem can be overcome by including surface-related and internal multiples in the imaging algorithm to enhance the illumination of the. In addition, on-the-fly the velocity model can be updated using the so-called Joint Migration Inversion (JMI) process, which explains the full wavefield seismic data in terms of reflectivity and a propagation velocity model. To augment the results, datasets from different wells in the area can reinforce each other by simultaneous inversion to assure the consistency and improve the quality of the results. To steer and constrain the velocity estimation, the estimated reflectivity in the JMI process can be used as additional constraint for the velocity updating process.
In this paper we have deployed the full wavefield of the 3D borehole data, from two different wells, containing all orders scattering, both up- and down-going wavefields, in one integrated inversion-imaging process as proposed by the JMI methodology. The final result is a smooth accurate background velocity model along with a true amplitude reflectivity image with high resolution and maximum lateral extent.
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Interferometric VSP Multiples Imaging: A Case Study from Saudi Arabia
Authors A. Aldawood, S. Alsaadan and N. PalaciosSummaryWe utilized interferometric datuming to convert VSP first-order surface-related multiples into virtual surface-seismic primary reflections. These reflections are subsequently imaged using a Kirchhoff-based migration to obtain representative subsurface structures. Tests on both synthetic and field datasets demonstrate the ability of imaging with VSP multiples to extend the spatial resolution of the migrated images. We concluded that imaging with VSP multiples could potentially provide a wider subsurface illumination compared with conventional imaging with VSP primaries.
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Characterization of a Fractured Reservoir Using DAS VSP—A Model-Based Reflection Amplitude Study
Authors R. Zhou, M.E. Willis, D. Cheng and K. GreenSummaryDistributed acoustic sensing (DAS) technology offers the time-lapse capability of monitoring hydraulic fracturing and reservoir depletion processes. This paper uses a model-based study to explore the feasibility of using DAS vertical seismic profiling (VSP) to detect and characterize fracture-induced azimuthal variation in P-wave reflection amplitude. The study particularly focuses on seismic amplitude vs. offset and azimuth (AVOAz) to answer two questions. First, which fracture-induced seismic responses can be detectable by a three-dimensional (3D) DAS VSP survey. Second, how shots can be arranged to detect such seismic responses and image the extent of the fractures. Waveform data were simulated for two types of fractured reservoir models using full-elastic anisotropic algorithms. P-wave reflection amplitude was mapped in incidence angle intervals for the top of each reservoir model. Analyses of the amplitude variation with AVOAz revealed distinctive patterns for the two fracture models. These patterns of amplitude variation can be used to detect fractures, if the fractures have uniform density and similar orientation around the well.
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VSP Anisotropic NMO Correction and Its Application to Attenuate Noise
Authors M. Lou and H. SimpsonSummaryNormal moveout (NMO) correction is an important data processing step for VSP CDP transform and other applications. Most of the previously used VSP NMO correction methods are valid for isotropic media, but can cause significant errors in multi-layered and/or anisotropic (VTI) media. We present a new methodology to accurately and efficiently perform VSP anisotropic NMO correction for walkaway VSP (WVSP) or 3DVSP data. We adapt the Fomel and Stovas’ NMO correction formulation originally developed for surface seismic data, to NMO correction for WVSP or 3DVSP data in multi-layered VTI media. We employ a simulated annealing (SA) algorithm to automatically search for four parameters in the Fomel and Stovas’ formulation. In the SA algorithm, we use semblance coherence analysis in the VSP common receiver gather domain as an object function. That is, after a correct NMO correction, a reflection event is aligned and its semblance coherence coefficient is maximized. To attenuate both coherent and incoherent noise in the reflection wavefield of VSP data, we utilize a three-step processing flow consisting of NMO correction, median filtering, and reverse NMO correction. We demonstrate a significant improvement in the image quality of a field WVSP data after attenuating noise by this new methodology.
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From VSP Optimum Imaging to Reservoir Characterization
Authors N. El Yadari, A. Suleiman, C. Planchart Marquez, S. Saadan and M. AhmedSummaryThe past twenty years have witnessed significant developments in the way that seismic data are used in oil and gas exploration and production. Arguably, the most important has been the use of surface seismic, not only to map structures in detail but also to infer reservoir properties from an analysis of seismic amplitude and other attributes. Improvement in seismic amplitude fidelity coupled with advances in the understanding and application of seismic inversion and rock physics have made quantitative description of the reservoir and risk evaluation not only a possibility but an expectation in certain geological contexts. To benefit from the superior quality of the VSP image over the surface seismic one, we extend the reservoir characterization workflow to borehole data and show its application to a 2D walkaway VSP data recorded in Saudi Arabia.
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Imaging Salt Flank by a Rig-source VSP
By M. LouSummaryAccurately delineating a salt flank or base is critical to evaluate the extent of reservoir rock and to successfully place development wells in many salt-trap oil reservoirs. Due to the severe distortion and obstruction of seismic waves by the salt body, surface seismic imaging often fails to clearly define the salt flank or base boundary. Borehole seismic salt proximity surveys (SPS) have historically played an important role in delineating and mapping the salt flank/base adjacent to a borehole by either calculating the salt exit points from first break travel times or directly migrating the first arrival waveforms. In a conventional SPS, a seismic source is positioned above the salt body. In an offshore environment, deploying a source boat adds significant cost for the acquisition of a conventional SPS. Through modelling a real case of rig-source VSP survey, this paper suggests for certain salt-trap reservoirs such as those in Gulf of Mexico (GOM), a rig source VSP can also serve as a salt proximity survey to delineate the salt flank as done by a conventional offset source SPS. By removing the need to deploy a source boat, a rig-source SPS is more efficient and cost-effective than a conventional offset-source SPS.
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Subsalt Imaging Using Walkabove and Walkaway VSP in the Transition Zone of the Red Sea
Authors C. A. Planchart, M.J. Vega, J. Jiao, N. El Yadari and Y. K. FadolalkaremSummaryThe transition zone in the Red Sea contains challenges for seismic imaging related to the complex bathymetry and presence of reefs. Also, the presence of salt bodies overlying the potential reservoirs causes weak illumination due to the defocusing of the energy and the weak reflectivity.
While drilling a well, it was necessary to drill a side track due to operational reasons. Some unexpected lateral variations at the same depth were found between both wells separated by only 130 ft. As part of the exploratory efforts, several VSP surveys were acquired. We present a case study where several migration algorithms were evaluated to perform subsalt imaging. The image from walkaway VSP found the cause of the unexpected lateral variation. We also used the VSP data to explain the possible reasons of the poor imaging of the 2D surface seismic data.
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Estimation of Maximum Horizontal Stress Direction using a Walkaround VSP dataset: A Case Study from the Red Sea, Saudi Arabia
Authors N. Palacios, C. Planchart and M. VegaSummaryA Walkaround VSP (WARVSP) dataset has been acquired and analyzed to estimate the principal stress direction at the target formation, using various methods such as shear wave splitting analysis, Alford rotation analysis, and azimuthal amplitude analysis. As results of these analyses the different methods for determining the maximum stress direction concurred in the results and confirming the maximum stress direction in the field. WARVSP data also provided a qualitative characterization of the salt body shape around the well. This study recommend to combine different techniques to measure the principal stress directions and achieve characterization of a known presence of irregular salt bodies in geological complex fields.
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Vertical Cable Seismic (VCS) Processed Using VSP Methods
Authors J. Bailey, E. Asakawa, M. Humphries and K. TaraSummaryA VCS case study for the shallow marine imaging of seafloor massive sulphides. The processing workflow, using borehole seismic techniques, will be discussed. An interpretation and examination of the final 3D imaging results will be presented.
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DAS Versus Geophones: a Quantitative Comparison of a VSP Survey at a Dedicated Field Laboratory
Authors J. Correa, L. Van Zaanen, K. Tertyshnikov, T. Dean, R. Pevzner and A. BonaSummaryDistributed Acoustic Sensing (DAS) is a novel technology to acquire acoustic data. DAS is noticeably promising for Vertical Seismic Profiling (VSP) applications as it offers highly sampled data, acquired simultaneously at all levels, at relatively low cost. In this study, DAS data is acquired using two different cable deployments: cemented behind the casing, and deployed suspended in the well. Both datasets were compared to conventional 3-component geophone VSP. DAS acquired with cemented cable presented similar quality and signal to noise ratio as geophone data, although it suffers from loss of high frequencies. The suspended cable presented predominantly tube noise, however reflections can still be recognized. We hope the results from this study contribute to a broader use of DAS for VSP acquisition.
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The Merits of DAS Acquisition on Multimode Optical Fiber
Authors A. Constantinou, A. Hartog, P. Dickenson and G. LeesSummaryCollecting Distributed Acoustic Sensing (DAS) data with multi-mode (MM) optical fiber is a challenge but not impossible. This paper presents the effect of MM fiber on DAS data for several oil and gas applications. These include borehole seismic surveying and downhole flow monitoring. The business need to acquire DAS on MM is high given the considerable installed base of MM fiber. This MM fiber was originally installed for Distributed Temperature Sensing (DTS) and communications. However, it is now possible to re-purpose this fiber for DAS acquisition, making a considerable saving over the installation of a new fiber. We present promising results acquired using this approach.
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Offset VSP for the Reservoir Monitoring
Authors K. Tertyshnikov, A. Egorov, R. Pevzner and A. BonaSummaryOffset Vertical Seismic Profile (VSP) is often used for time-lapse seismic monitoring in oil/gas exploration or CO2 geosequestration. Standard offset VSP processing technologies allow the imaging and qualitative interpretation of time-lapse changes in the medium. However, quantification of the observed time-lapse anomalies is often needed. We suggest using Full Waveform Inversion (FWI) for quantitative interpretation of the offset VSP data. We apply conventional time-lapse processing and time-lapse FWI to the offset VSP dataset acquired in the Otway field and compare the results. We observe a match in the images of the CO2 plume obtained by both methods and suggest that using FWI increases the value of offset VSP data.
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Application of 4D VSP for Monitoring Of Small-Scale Supercritical CO2 Injection: Stage 2C of CO2CRC Otway Project Case Study
Authors H. AINasser, R. Pevzner, K. Tertyshnikov, D. Popik and M. UrosevicSummaryTime-lapse VSP seismic can be used in addition to land seismic to increase the repeatability in reservoir characterization. As a part of the monitoring program within the Stage 2C of the Otway Project, CO2CRC conducted the acquisition of offset Vertical Seismic Profile (VSP) data before injection (baseline) and three monitoring surveys after injection of every 5kT of CO2. The objective of this study is to evaluate the repeatability of 4D VSP onshore seismic and compare the results with surface seismic data. To this end, we develop an optimal workflow for VSP data processing of the CRC-1 well 2015 baseline and the 2016 monitor surveys to produce 3D migrated images of the subsurface.
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Elastic Anisotropy Estimation in the North Sea from Walkaway VSP and Sonic Data
Authors C. Mogensen, M.L. Khaitan, R. Guerra, L. Dahlhaus, S. Leaney, J. Jocker and E. WielemakerSummaryThe Hejre oil and gas field is located in the Danish Central Graben, a shallow water part of the central North Sea. The reservoir lies at depths below 5 km in a high-temperature (172°C) and high-pressure (1 kbar) environment. Seismic resolution is relatively poor due to absorption in the overburden, multiples and distortion from a complex structure. Anisotropic depth processing improved the seismic quality but the anisotropy uncertainty remained high.
In order to measure elastic anisotropy in-situ, reduce the velocity model uncertainties and allow improvements in anisotropic surface seismic processing, comprehensive Walkaway VSP and modern wireline sonic logging surveys were planned in a new deviated production well drilled in 2016.
This project represents a first step in the velocity model calibration workflow and highlights the importance of integrating measurements taken at different scales: cores, sonic, borehole and surface seismic, in order to understand the elastic anisotropy of the rocks drilled and allow reducing the uncertainties in the seismic velocity models used for depth imaging.
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High Resolution Imaging Using Crosswell Seismic with Complex Stratum in Western China
Authors J. J. Wu, Y. P. Li, Q. H. Zhang, J. H. Huang, Y. Z. Chen, C. Chen, Y. H. Wang and Z. D. CaiSummaryThe crosswell seismic has the characteristics of high frequency and high resolution. It can provide more accurate velocity information because of its depth domain data. The crosswell seismic is known as the link of well logging, conventional 3D seismic and reservoir geology. Because the shot and geophone of crosswell-seismic are both inside the well, seismic waves avoid be attenuation of propagating through the surface with low velocity. So we can get higher quality data theoretically. In the other hand, the source of crosswell seismic usually radiates high frequency wave, which is typically several times higher than surface seismic. These features make the reflected imaging can obtain more insider information. Then we can get small sand group, which surface seismic hardly resolved. Multi-attribute parameters were extracted based on amplitude preserving imaging. Comprehensive analysis of a variety of attribution information can achieve fine structure interpretation and reservoir cognition. In this paper, we acquired three pairs of crosswell seismic data in a western China oilfield. And then data processing and corresponding geological interpretation give us good results.
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Application of Walkaway-VSP Technology in Volcanic Rocks
More LessSummaryVolcanic rock, as a kind of special reservoir, has gradually become an important target for oil and gas exploration. Because of the complex geological conditions in the volcanic rock exploratory area, the poor layering of rock mass, irregular development of rock mass, and quick changes of thickness, the conventional seismic methods can not to satisfy the requirements for fine exploration and development for volcanic rock, due to the low data resolution and the uncertain velocity information. This paper gives an application of Walkaway-VSP data processing and interpretation in Tuha Oilfield Malang Sag Santanghu basin, with high resolution, high fidelity of Walkaway-VSP longitudinal wave imaging, the volcanic rock of M68 well area is described exactly, based on the imaging, vertically the lithologic interface of volcanic rock reservoir and source rock reservoir is carefully identified, horizontally the shape and distribution range of volcanic rock are fine described,which achieves very good application effect.
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Utilizing the Uniqueness of Vertical Seismic Profiling (VSP) for Deepwater Exploration
Authors M.L. Khaitan, P. Ranjan, S. Chandrasekhar and B. KumarSummaryWe plan to present two case studies from deepwater drilling wherein we performed look-ahead VSP inversion. The cases elaborated in this paper are unique in the sense that these are examples wherein look-ahead VSP was the only possible alternative that could lead to viable planning of risk mitigation associated with the drilling and aid decision making in the drilling program in the deepwater environment for avoidance of major financial losses
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3D VSP Processing and Imaging: A Case Study in Eastern China
Authors Y. Z. Chen, Y. H. Wang, H. Y. Zhao, Y. P. Li and J. H. HuangSummaryComplex structure, fault development and thin reservoirs are three main characteristics of Liaohe oilfield in Eastern China. And the development is difficult due to the low resolution of surface seismic data in this area. To accurately evaluate and predict the reservoir, identify small faults and implement the micro structure, as well as predict the distribution range of the oil sand body, a 3D VSP survey was conducted. In this paper, the 3D VSP project in Liaohe oilfield is taken as an example to demonstrate the 3D VSP technology and its application in structural imaging. After interpretation and fault recognition, small faults which were not seen on surface seismic data are shown up on VSP image. Analysis shows that the 3D VSP has a good impact on oil and gas exploration and development.
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Characterisation and Imaging of a Near-vertical Fault Zone in Crystaline Rock from Hydrophone VSP Data
Authors A. Greenwood, E. Caspari, J. Hunziker, L. Baron, T. Zahner, D. Egli and K. HolligerSummaryA shallow near-vertical hydrothermally active fault zone embedded in fractured crystalline rocks of the central Alps has been drilled and geophysically explored in view of its potential analogies to planned deep petrothermal reservoirs in the Alpine foreland. Hydrophone-based zero-offset vertical seismic profiling (VSP) data were found to be highly effective for detecting open fractures and determining seismic velocity changes due to deformation. Walk-away hydrophone VSP data were acquired with a 45-degree crooked-line survey geometry with respect to the borehole plane, which requires 3D processing methods for seismic imaging. For imaging purposes, a laterally changing velocity cube was generated from the ZVSP velocities and projected along the strike of the fault. The subsequent, pre-stack-depth-migration imaging has been successful in delineating vertical structures, the target fault core, and an as of yet unknown, and correspondingly enigmatic, sub-horizontal structural feature.
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Application of Far Field Shear Wave Reflection Imaging To Identify The Precise Location Of A Horizontal Well In A Formation
Authors T. Bradley, A. Przebindowska and N. AarsethSummaryIn recent years imaging of near wellbore structures using reflected shear wave energy from full waveform wireline acoustic logging tools has become an accepted technology in formation evaluation.
The technique enables imaging and identification of geological features up to approximately 30 metres from the borehole axis on a scale and resolution between those of borehole images and vertical seismic profiles, so filling the resolution gap between these two techniques. High resolution borehole images resolve features located millimetres to centimetres from the borehole wall, whereas vertical seismic profiles image geological features on a metre to tens of metre scale and located between tens and hundreds of metres from the wellbore.
In this extended abstract we present the application of single well imaging using shear energy to visualize the location of a horizontal well in a formation, and a technique to easily visualize the data. We then present a case study where the location of a horizontal well in a formation has been precisely identified using the technique.
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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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