Suitability of vibrators for time-lapse monitoring in the Middle East

Jervis, Michael; Bakulin, Andrey; Burnstad, Roy; Berron, Cécile; Forgues, Éric

doi:10.1190/segam2012-0948.1

Cited by 16 publications

(4 citation statements)

References 3 publications

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“…Lower frequencies require very long total sweep durations to make the signal-to-noise ratio high enough for processing while each sweep already takes more than 20 s to record. While the timing of the peaks on the source signatures matches almost perfectly, a significant variation in the signal shape is observed, which is well supported by previous studies of [ 34 ] where they proved for the desert environment that running the source at the same location at different times, gives large variations in the source signature measured by a nearby geophone. The geophone data in this study were acquired with a source that is located in a different position and at a different time.…”

Section: Source Signature and Das Instrument Response Estimationsupporting

confidence: 87%

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Quality Control of DAS VSP Data in Desert Environment Using Simulations and Matching Filters

Alzamil,

Kazei,

Zhou

et al. 2024

Sensors

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The unconsolidated near surface and large, daily temperature variations in the desert environment degrade the vertical seismic profiling (VSP) data, posing the need for rigorous quality control. Distributed acoustic sensing (DAS) VSP data are often benchmarked using geophone surveys as a gold standard. This study showcases a new simulation-based way to assess the quality of DAS VSP acquired in the desert without geophone data. The depth uncertainty of the DAS channels in the wellbore is assessed by calibrating against formation depth based on the concept of conservation of the energy flux. Using the 1D velocity model derived from checkshot data, we simulate both DAS and geophone VSP data via an elastic pseudo-spectral finite difference method, and estimate the source and receiver signatures using matching filters. These field geophone data show high amplitude variations between channels that cannot be replicated in the simulation. In contrast, the DAS simulation shows a high visual similarity with the field DAS first arrival waveforms. The simulated source and receiver signatures are visually indistinguishable from the field DAS data in this study. Since under perfect conditions, the receiver signatures should be invariant with depth, we propose a new DAS data quality control metric based on local variations of the receiver signatures which does not require geophone measurements.

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Section: Source Signature and Das Instrument Response Estimationsupporting

confidence: 87%

“…The source signature in a desert environment has typically poor repeatability [ 34 ], hence, it must be estimated for every vibrating point. Figure 6 b,d shows two gathers of field DAS data for 50 m and 250 m offsets corrected for geometrical spreading, respectively.…”

Section: Source Signature and Das Instrument Response Estimationmentioning

confidence: 99%

Quality Control of DAS VSP Data in Desert Environment Using Simulations and Matching Filters

Alzamil,

Kazei,

Zhou

et al. 2024

Sensors

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“…The near‐surface changes also impact the repeatability of ghosts and multiples. In desert conditions, additional considerations arise due to dune movement (shifts of up to 1 m) and a very complex near‐surface of varying sand thickness, highly variable near‐surface velocities and underlying limestone karsts (see, e.g., Bakulin et al., 2012; Jervis et al., 2012). Such effects spread across the pre‐stack volume and contaminate the measurement of subsurface time‐shifts estimated post‐stack unpredictably.…”

Section: Acquisition and Processing‐related Errorsmentioning

confidence: 99%

A review and analysis of errors in post‐stack time‐shift interpretation

MacBeth

Izadian

2023

Geophysical Prospecting

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This study complements two earlier papers on the interpretation and estimation of post‐stack time‐shifts that detail the most popular measurement methods to date. In this current work, the focus is on describing the magnitude and identifying the origin of the uncertainty present in these time‐shift values. We also consider how the underlying assumptions behind conventional time‐shift estimation methods can contribute to the inadequate resolution of the subsurface time‐lapse changes. The various errors fall into three broad categories: (1) those related to intrinsic data limits that cannot be avoided; (2) those associated with seismic measurement methods that can be corrected with some effort; and finally (3) those that arise due to approximations to the wave physics made during the design or implementation of the methods. In the first category are limitations due to sampling rate and signal‐to‐noise ratio, and wavelet interferences resulting from the narrow band nature of the seismic data and the heterogeneous nature of the geology itself. The effects produce errors of typically a fraction of a millisecond, but exceptionally in 4D data with poor repeatability up to 1 ms. In the second category are acquisition and processing errors. These are usually of the order of a few milliseconds but can reach up to 10s of milliseconds and are, therefore, essential to correct. It is possible to correct the effects of tides and seawater variations in marine acquisition if these changes are monitored and measured. Navigation and timing are identified as issues to consider carefully. For land data, daily and seasonal near‐surface variations are still problematic, and source and sensors must be buried to deliver interpretable time‐shifts. The impact of choices made during processing can be significant but is specific to the workflow and dataset and thus cannot be generically assessed. However, the effects from residual multiples can be identified and treated. Of moderate importance is the third category of errors, which consists of four items. Of these, the effect of lateral image shifts and amplitude effects are judged to play a minor role. Deviation from the assumption of vertical ray‐paths during post‐stack analysis appears to be of concern only for reservoirs with noticeably dipping structures and strong contrasts. The effect of pre‐stack variations on the post‐stack measurements remains a topic to be more thoroughly examined, and the conclusion is unclear. Finally, it is apparent that uncertainties in all categories are strongly dependent on the field setting and geographical location.

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“…To improve repeatability, permanent sensors have been utilized in both marine (van Gestel et al, 2008) and land projects (Roach et al, 2015). However, these studies were done with mobile sources, which, in the case of land projects, can be affected by nonrepeatability of source coupling and near-surface conditions (Jervis et al, 2012). Optimizing the source component of permanent reservoir monitoring systems poses a significant challenge, especially in onshore time-lapse seismic monitoring for carbon capture and storage projects.…”

Section: Introductionmentioning

confidence: 99%

The appraisal of surface orbital vibrators with buried geophone array for permanent reservoir monitoring

Yavuz

Pevzner

Popik

et al. 2021

Geophysical Prospecting

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Time-lapse seismic is one of the main methods for monitoring changes in reservoir conditions caused by production or injection of fluids. One approach to time-lapse seismic is through permanent reservoir monitoring, whereby seismic sources and/or receivers are permanently deployed. Permanent reservoir monitoring can offer a more cost-effective and environmentally friendly solution than traditional campaign-based surveys that rely on temporarily deployed equipment while facilitating more frequent measurements. At the CO2CRC Otway Project, surface orbital vibrators were coupled to a buried geophone array to form a permanent reservoir monitoring system. These are fixed position seismic sources that provide both P and S waves using induction motor-driven eccentric masses. After an initial injection of CO 2 in February 2016, five months of continuous seismic data were acquired, and reflection imaging was used to assess the system performance. Analysis of the data showed the effects of weather variations on the near-surface conditions and the sweep signatures of surface orbital vibrators. Data processing flows of the continuous data was adapted from Vibroseis four-dimensional data processing flows. Ground roll proved a significant challenge to data processing. In addition, variations in the surface wave pattern were linked to major rainfall events. For the appraisal of surface orbital vibrators in imaging, a Vibroseis four-dimensional monitor survey data with similar geometry was also processed. Surface orbital vibrators are observed to be reliable sources with a potential to provide a repeatable signal, especially if the ground roll should fall outside the target window of interest. To guide future permanent reservoir monitoring applications, a repeatability analysis was performed for the various key data processing steps.

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Suitability of vibrators for time-lapse monitoring in the Middle East

Cited by 16 publications

References 3 publications

Quality Control of DAS VSP Data in Desert Environment Using Simulations and Matching Filters

Quality Control of DAS VSP Data in Desert Environment Using Simulations and Matching Filters

A review and analysis of errors in post‐stack time‐shift interpretation

The appraisal of surface orbital vibrators with buried geophone array for permanent reservoir monitoring

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