Overpressure prediction using converted mode reflections from base of salt

Miley, Monica P.; Kessinger, Walter

doi:10.1190/1.1821201

Cited by 6 publications

(5 citation statements)

References 4 publications

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“…In this approach, the reflection coefficients as function of angle of incidence (or offset) show a different trend for normally consolidated sediments compared to those that are overpressured (e.g. Miley and Kessinger, 1999;Dutta, 2002;Dash et al, 2004). All elastic properties (P-and S-wave velocities and density) are significantly altered by the increase in pore pressure (e.g.…”

Section: Amplitude-versus-offset Processingmentioning

confidence: 99%

First results on velocity analyses of multichannel seismic data acquired with the icebreaker RV Araon across the southern Beaufort Sea, offshore Yukon

Riedel

Hong²,

Jin³

et al. 2016

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Abstract:One thousand two hundred twenty kilometres of multichannel seismic data were acquired in the Beaufort Sea in 2013 and 2014 to interpret shallow sedimentary structures associated with the upper Cenozoic Iperk and Shallow Bay depositional sequences. Seismic velocity analyses suggest a remarkably consistent regional velocity-depth trend on the slope within the upper 4 s two-way traveltime. A separate velocity trend was not defined beneath the shelf in this region, where data are influenced by the occurrence of permafrost. Deviations from this trend were noted at unconformities including an upper erosional unconformity.The seismic data in the Mackenzie Trough region suggest a different velocity-depth trend within the upper section and the region is marked by a large erosional unconformity, likely the base of the Shallow Bay sequence. Velocity analyses suggest the removal of up to 425 m of overburden; however, this is an overestimate of erosion as differential compaction from the glacial history has not yet been taken into account. In deeper water (>750 m) a bottom-simulating reflector is present, characterized by the occurrence of free gas and a low-velocity zone.Analyses of three fluid-expulsion features on the slope indicate that the Pokak fluid-expulsion feature and the Triple-Mound fluid-expulsion feature are linked to underlying anticline structures. A flat-topped fluidexpulsion feature at the flank of an equivalent anticline was also examined, but the occurrence of shallow gas creates a blank zone beneath this structure. Pronounced changes in the velocity-depth function at these fluid-expulsion features are linked to occurrence of free gas, and/or fluidized mud extrusions. Résumé :En 2013 et 2014, des données sismiques multicanal ont été acquises sur 1220 km dans la mer de Beaufort afin d'interpréter les structures sédimentaires à faible profondeur associées aux séquences sédimentaires d'Iperk et de Shallow Bay du Cénozoïque supérieur. Des analyses de la vitesse sismique indiquent une tendance vitesse-profondeur remarquablement constante à l'échelle régionale sous le talus pour les quatre premières secondes de temps de trajet double. Dans cette région, nous n'avons pas défini une tendance vitesse-profondeur distincte pour le secteur sous-jacent à la plate-forme continentale, un endroit où les données sont influencées par la présence de pergélisol. Des écarts par rapport à la tendance ont été relevés au niveau de discordances, notamment d'une discordance d'érosion supérieure.Dans la région de la cuvette de Mackenzie, les données sismiques révèlent une tendance vitesseprofondeur différente dans la partie supérieure de la coupe et la région est marquée par la présence d'une importante discordance d'érosion, qui correspond vraisemblablement à la base de la séquence de Shallow Bay. Les analyses de la vitesse laissent croire à la suppression de terrains de couverture sur une épaisseur pouvant atteindre 425 m. Cependant, il s'agit là d'une surestimation de l'importance de l'érosion, étant donné que la compac...

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Section: Amplitude-versus-offset Processingmentioning

confidence: 99%

First results on velocity analyses of multichannel seismic data acquired with the icebreaker RV Araon across the southern Beaufort Sea, offshore Yukon

Riedel

Hong²,

Jin³

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Best et al (1990) use AVO analysis to treat these cases. Modeling analysis of AVO signatures of pressure transition zones is given in Miley (1999), Miley and Kessinger (1999), and Carcione (2001). This type of analysis should complement the present prediction method on the basis of geological information of the study area.…”

Section: Fig 2 Flowchart Illustrating the Pore-pressure Predictionmentioning

confidence: 99%

“…AVO-based verification.-In some cases, velocity information alone is not enough to distinguish between a velocity inversion resulting from overpressure and a velocity inversion from pore fluid and lithology [e.g., base-of-salt reflections (Miley, 1999;Miley and Kessinger, 1999)]. Occasionally, overpressuring is not associated with large velocity variations, as in smectite/illite transformations.…”

Section: Fig 2 Flowchart Illustrating the Pore-pressure Predictionmentioning

confidence: 99%

Pore pressure estimation in reservoir rocks from seismic reflection data

et al. 2003

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A method is used to obtain pore pressure in shaly sandstones based upon an acoustic model for seismic velocity versus clay content and effective pressure. Calibration of the model requires log data-porosity, clay content, and sonic velocities-to obtain the dry-rock moduli and the effective stress coefficients as a function of depth and pore pressure. The seismic P-wave velocity, derived from reflection tomography, is fitted to the theoretical velocity by using pore pressure as the fitting parameter. This approach, based on a rock-physics model, is an improvement over existing pore-pressure prediction methods, which mainly rely on empirical relations between velocity and pressure. The method is applied to the Tune field in the Viking Graben sedimentary basin of the North Sea. We have obtained a high-resolution velocity map that reveals the sensitivity to pore pressure and fluid saturation in the Tarbert reservoir. The velocity map of the Tarbert reservoir and the inverted pressure distribution agree with the structural features of the Tarbert Formation and its known pressure compartments.

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“…Effective stress, used to predict pore pressure after the overburden stress has been determined, is just one of them. Miley and Kessinger (1999) demonstrated how to use this effect for subsalt pore pressure prediction using shear velocities that were determined from seismic converted wave reflections. In order to determine effective stress from seismic velocity, the other variables have to be either modeled as well, or kept constant, for example, by considering shales only.…”

Section: Rock Modelmentioning

confidence: 99%

A New Petrophysically Constrained Predrill Pore Pressure Prediction Method for the Deepwater Gulf of Mexico: A Real-Time Case Study

Nader¹,

Stephan²,

Mike³

et al. 2001

Proceedings of SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractImproper planning and execution of deepwater drilling programs can lead to high costs and unsafe conditions. Proper well planning requires reliable estimates of the expected pore fluid pressure and formation strength prior to drilling. Such pressure predictions are based on integrated seismic and offset well data. A new, rock model-based approach especially suited for deepwater pore pressure imaging is introduced here and applied in an example of a deepwater Gulf of Mexico well. P-and S-velocities were determined both at an offset well and for the future drilling location, using prestack seismic full waveform inversion. Both predicted velocities were later verified with log measurements. Using the new model, a significant pore pressure increase at depth was predicted before drilling the well and verified while drilling (Figure 1). For the entire well, the predicted and measured pore pressure gradients agree within half a pound per gallon equivalent mudweight (Figure 1). The shear velocity, and the extracted shear modulus, proved to be excellent indicators of low effective stresses, corresponding to overpressured formations ( Figure 2).

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Overpressure prediction using converted mode reflections from base of salt

Cited by 6 publications

References 4 publications

First results on velocity analyses of multichannel seismic data acquired with the icebreaker RV Araon across the southern Beaufort Sea, offshore Yukon

First results on velocity analyses of multichannel seismic data acquired with the icebreaker RV Araon across the southern Beaufort Sea, offshore Yukon

Pore pressure estimation in reservoir rocks from seismic reflection data

A New Petrophysically Constrained Predrill Pore Pressure Prediction Method for the Deepwater Gulf of Mexico: A Real-Time Case Study

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