Applying high-resolution 3D CSEM and seismic for integrated reservoir characterization

Granli, J.R.; Daudina, D.A.; Robertson, Sarah; Morten, Jan Petter; Gabrielsen, Pål T.; Sigvathsen, Bård

doi:10.1190/segam2018-2995351.1

Cited by 4 publications

(4 citation statements)

References 5 publications

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“…This implies that both factors --nser receivers, and inclusion of H data-contribute to improving the resolution of 4-D CSEM. Our results are thus consistent with findings of Granli et al (2018) that a denser receiver and transmitter configuration can significantly improve the imaging resolution. In this section we have assumed identical survey parameters; investigations of the interplay between CSEM data density and non-repeatability effects are left for future work.…”

Section: M Pa C T O F Data D E N S I T Ysupporting

confidence: 92%

“…The survey consists of 6 parallel towlines spaced by 1 km and a grid of 57 seabed receivers spaced by 3 km along the towing direction. This is a relatively sparse survey as could be seen, for example by comparing it to a recent CSEM acquisition over the Gemini North discovery in the Barents Sea where the receiver spacing was 1 km and the towline spacing-500 m (Granli et al 2018). The present study therefore does not aim at probing the resolution limit for 4-D CSEM that would have required a much denser survey.…”

Section: S E M Datamentioning

confidence: 97%

“…The anomalous resistivity is defined with respect to the start model and integrated over the depth interval of 480-720 m. Note that these ATR maps are not meant for reservoir interpretation as they were obtained without any geological inputs and used down-sampled CSEM data. For high-resolution resistivity maps over Wisting and nearby area see analysis in Granli et al (2017) and Granli et al (2018) that combines several geophysical methods.…”

Section: F I E L D Data : W I S T I N Gmentioning

confidence: 99%

“…Alcocer et al 2013;Løseth et al 2014), as well as for imaging CO 2 plume at carbon storage sites (Park et al 2017). Recent years have seen a significant progress in various aspects of marine CSEM technology: launch of a new source with up to 10 000 A electrical current (Hanssen et al 2017), pushing acquisition frequencies up to 45 Hz to reach a record high spatial resolution (Granli et al 2018) and a common use of advanced Gauss-Newton optimization schemes for large-scale 3-D inversions (Nguyen et al 2016;Perez et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Time-lapse CSEM: how important is survey repeatability?

Shantsev

Nerland

Gelius

2020

Geophysical Journal International

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Summary An important concern for time-lapse studies using the controlled-source electromagnetic (CSEM) method is repeatability of acquisition parameters for the base and monitoring surveys. We consider a challenging case when variations in source and receiver positions, conductivity of seawater etc. will lead to differences in the recorded EM fields that exceed EM response due to production-induced changes in the reservoir resistivity. We show that even in that case, 4D response can often be clearly resolved if the base and monitor EM datasets are inverted to produce 3D resistivity distributions. More precisely, for a synthetic model of the Snøhvit gas field, changes in the inverted resistivity maps caused by such non-repeatability will be at least 10 times smaller than the time-lapse differences in the reservoir resistivity. By contrast, measurement errors and poor knowledge of background resistivity may reduce the resolution of 4D CSEM to a much stronger degree. Analysis of field CSEM data from the Wisting oil field supports our conclusion about strongly relaxed repeatability requirements when 4D effects are established by examining inverted resistivity volumes rather than by looking at raw EM data.

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Section: M Pa C T O F Data D E N S I T Ysupporting

confidence: 92%

Section: S E M Datamentioning

confidence: 97%

Section: F I E L D Data : W I S T I N Gmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Time-lapse CSEM: how important is survey repeatability?

Shantsev

Nerland

Gelius

2020

Geophysical Journal International

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Marine Electromagnetic Methods

MacGregor¹

2021

Integration of Geophysical Technologies in the Petroleum Industry

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Experience on controlled-source electromagnetic performance for exploration in Norway

et al. 2020

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We analyze the predictive performance of CSEM using a large statistical database. The prediction strength is quantified by comparing the CSEM interpretation to exploration drilling results for more than 100 wells in Norway. The comparison has been done by correlating inversion results for all surveys covering these wells with the well outcome, using a statistically driven anomaly detection workflow in order to avoid confirmation bias. The comparison is summarized by classifying the interpretations as true positives, true negatives, false positives or false negatives. We find that the CSEM interpretation correctly identified the true negative and positive cases for 79 % of the analyzed wells. We further show how integrated interpretation can provide more detailed predictions. This includes taking the sensitivity to the target into account, as well as integrating seismic data and rock physics parameters with the CSEM data in order to quantify the potential volumes in place. In some cases, we also see that the derived parameters are not compatible with hydrocarbon models, and prospects must be downgraded despite having clear CSEM anomalies associated with them. In addition to the statistics, our results are supported by several case examples.

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Applying high-resolution 3D CSEM and seismic for integrated reservoir characterization

Cited by 4 publications

References 5 publications

Time-lapse CSEM: how important is survey repeatability?

Time-lapse CSEM: how important is survey repeatability?

Marine Electromagnetic Methods

Experience on controlled-source electromagnetic performance for exploration in Norway

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