Long Offset Simultaneous Inversion for Seismic Reservoir Characterisation a Case Study – Gryphon Field

Reiser, C.; Deschizeaux, B.; Freudenreich, Y.; Kirstetter, Olivier Hugues

doi:10.3997/2214-4609-pdb.1.f005

Cited by 3 publications

(2 citation statements)

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“…In parallel with the EMERGE re-run, a pre-stack inversion trial was carried out on 3 sub-areas of the 3D survey using the proprietary 3D algorithm described by Reiser et al (2005), andCoulon et al (2006). Input data consisted of well data and five angle stacks generated from the final PSDM gathers.…”

Section: Pre-stack Inversion Trialmentioning

confidence: 99%

Application of PSDM Imaging for Reservoir Characterisation in the Northern Malay Basin: A Case Study

2011

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Seismic imaging in the northern Malay Basin frequently suffers due to the limitations imposed on Kirchoff Time Migration by the complexities of structure, lithology, stratigraphy and fluid effects that occur in the area (Reilly et al., 2008 and Gosh et al., 2010). A recent Pre-Stack Depth Migration (PSDM) project not only enhanced the reservoir imaging, it enabled the production of amplitude preserved volumes that were used to improve reservoir characterisation studies for gas pay prediction. Reservoir characterisation studies within 4 producing gas fields of the northern Malay Basin have successfully used offset stacks and seismic inversion products Acoustic Impedance (AI) and Poisson's Ratio (PR) to target gas pay sands for development drilling. These sands display a weak type III AVO response. One field contains less of the type III AVO sand facies and displays lower seismic contrast; in an effort to improve reservoir prediction, the multi linear analysis EMERGE process was applied to generate target logs Volume of Sand, Porosity, Gas Saturation and Pay Flag. Although more successful in identifying pay sands, data quality issues hampered results. Shallow gas effects such as amplitude absorption and time distortion of underlying reflectors, in addition to fault shadow effects negatively impacted the pre stack and post stack data and the derivative inversion and EMERGE data. Although not a complex structural or velocity environment, PSDM processing was applied to 2 of the gas fields with the greatest data quality issues and generated improved pre and post stack data. The EMERGE process was rerun and delivered improved target attribute cubes. Simultaneously an inversion trial was run to test potential uplift in PSDM derived AI and PR data. The PSDM derived AI was of slightly better quality than the original while the PR was clearly superior; the data quality uplift is attributed predominantly to the improved PSDM pre stack data input. Acoustic Impedance and to a lesser extent PR form significant inputs to the EMERGE multi-attribute process and full re-inversion of the PSDM data is under consideration to use in future characterisation studies.

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Section: Pre-stack Inversion Trialmentioning

confidence: 99%

Application of PSDM Imaging for Reservoir Characterisation in the Northern Malay Basin: A Case Study

2011

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“…The 3-D and layered-based nature of our simultaneous inversion scheme (Reiser et al,2005 andLafet et al, 2005) is insensitive to random noise and is able to filter out spatially organized noise whose dip is inconsistent with the stratigraphic layering. Similarly, the angle dependence of the seismic frequency content is taken into account by using a different wavelet for each angle stack and the final inversion resolution is controlled by the bandwidth of the near angle stack.…”

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confidence: 99%

Stratigraphic elastic inversion for seismic lithology discrimination in a turbiditic reservoir

Coulon

Lafet

Deschizeaux

et al. 2006

SEG Technical Program Expanded Abstracts 2006

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An integrated workflow, including careful seismic data conditioning, pre-stack elastic inversion and seismic lithology classification has been applied to predict the distribution of channel sands in a complex turbiditic reservoir. Three partial stacks, with angles in the range 8-50 degrees, have been calibrated using elastic logs at three well locations. A well-based feasibility shows that reservoir sands can in theory be identified from a cross plot of Poisson's ratio versus P-wave impedance. In practice, seismic lithology discrimination is challenging due to a complex AVA response, which is affected by the difference in seismic frequency content between near and ultra far angles. Our simultaneous elastic inversion procedure is able to account for the angle-dependent change in seismic bandwidth and delivers high-resolution estimates of both Pand S-wave impedances, which have been used to calculate a sand lithology cube. The inversion was performed in a layered stratigraphic framework that has been automatically extracted from seismic dip information. This has yielded 3-D images of reservoir elastic properties that better conform to the complex shapes of the channelized sand deposits.

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Attenuation of seismic water-column noise, tested on seismic data from the Grane field

Landrø

2007

GEOPHYSICS

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Seismic analysis of long-offset data is gaining increased attention for several purposes: constraining three-parameter amplitude variation with offset ͑AVO͒ methods, 4D analysis, and imaging below salt and basalt. A major challenge for exploiting long-offset seismic data is that the water-column noise mixes with and distorts the reflected seismic signal from interfaces at the target level. Traditional processing methods such as f-k filtering often reduce this distortion problem. This article offers an alternative to conventional processing methods. The alternative exploits the difference in water depth and reservoir depth to subtract water-column noise. The proposed subtraction method works well where water depth is constant. The method was tested on a multicomponent seismic data set from the Grane field ͑North Sea͒. In this location, the water depth is fairly constant over the field. The fieldwise similarity level of water-column noise is high. A comparison of the water-column noise from various locations shows that the similarity is 10%, measured in normalized root mean squared error. The fact that the water-column noise is highly repeatable is a strong indication that the major part of it is harmonic waves that propagate in the water layer.

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Long Offset Simultaneous Inversion for Seismic Reservoir Characterisation a Case Study – Gryphon Field

Cited by 3 publications

References 0 publications

Application of PSDM Imaging for Reservoir Characterisation in the Northern Malay Basin: A Case Study

Application of PSDM Imaging for Reservoir Characterisation in the Northern Malay Basin: A Case Study

Stratigraphic elastic inversion for seismic lithology discrimination in a turbiditic reservoir

Attenuation of seismic water-column noise, tested on seismic data from the Grane field

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