Time-lapse seismic observations of regional gas blowdown at Teal South

Ezawi, Mohamed A.; Pennington, Wayne D.; Islam, Nayyer

doi:10.1190/segam2012-0784.1

Cited by 4 publications

(20 citation statements)

References 3 publications

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“…There are several reservoirs within the 4500-ft sand at Teal South, as shown in Figure 1. Here, we discuss those changes observed in reservoirs A (the only reservoir under production at the time of the surveys), B, and C (the primary little neighbors referenced by Pennington et al [2001] and Ezawi et al [2012], respectively), as well as one "tiny" reservoir lying between reservoirs B and C.…”

Section: Observationsmentioning

confidence: 99%

“…In this study, we use volume visualization techniques to examine Pennington et al's (2001) prediction in some detail. Ezawi et al (2012) demonstrate that a specific seismic attribute, squared instantaneous amplitude, evaluated on time slices of stacked data can be used to help identify leakage of the oil and gas from neighboring reservoirs. They confirm the initial prediction by Pennington et al (2001): The oil and gas from a neighboring reservoir is leaking into the adjacent sandstone from where it may be lost forever if not trapped by a secondary feature.…”

Section: Introductionmentioning

confidence: 99%

“…Pennington et al (2001) qualitatively explain time-lapse changes in Teal South using inversion of the legacy stacked data set, amplitude-variation-with-offset (AVO) analysis of the two time-lapse data sets, and rock-physics models. Ezawi et al (2012) use volume visualization of attributes using stacked data from the two later surveys to identify details of fluid movement. This study extends the analyses of Pennington et al (2001) and Ezawi et al (2012) to investigate the time-lapse effects of all three surveys using poststack data to better evaluate predictions of fluid migration.…”

Section: Introductionmentioning

confidence: 99%

“…Ezawi et al (2012) use volume visualization of attributes using stacked data from the two later surveys to identify details of fluid movement. This study extends the analyses of Pennington et al (2001) and Ezawi et al (2012) to investigate the time-lapse effects of all three surveys using poststack data to better evaluate predictions of fluid migration. Pennington et al (2001) discover that the pressure drop caused by production from the reservoir is communicated across the fault to at least one "little neighbor" reservoir not under production.…”

Section: Introductionmentioning

confidence: 99%

“…The semblance attribute is shown in the figure to highlight the faults separating these reservoirs. The primary little neighbor in that paper is referred to here as reservoir C, and another neighboring reservoir is referred to here and by Ezawi et al (2012) as reservoir B. The studies by Pennington et al (2001) and Ezawi et al (2012) are concerned only with changes in the seismic responses between the OBC surveys of phases I and II.…”

Section: Introductionmentioning

confidence: 99%

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Imaging of phase changes and fluid movement in and between reservoirs at Teal South

2015

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We have reexamined the poststack seismic legacy and time-lapse data sets from the Teal South field in the Gulf of Mexico for insight into regional pressure changes from production at one reservoir and its effects on neighboring unproduced reservoirs. We support previous predictions of oil and gas leakage from neighboring reservoirs by providing direct evidence for leakage through 3D mapping of the hydrocarbons themselves. The use of the squared instantaneous amplitude as an attribute allowed visualization of the large amplitude changes while minimizing the appearance of noise. The use of translucency in the 3D time-lapse difference volumes assisted in identifying features of interest that had been unrecognized in earlier studies. For example, this investigation found that hydrocarbons appeared to have escaped from one small (unproduced) reservoir through its spill point, only to be trapped in a nearby structure, from which it ultimately escaped through that trap's spill point. Such fluid migration can occur in a period of a few years due to production, not geologic time. Time-lapse studies such as the one presented here can be very helpful in identifying such fluid movement, particularly in highly porous and unconsolidated reservoirs that are highly sensitive to pore-fluid type and stress changes.

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Section: Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Imaging of phase changes and fluid movement in and between reservoirs at Teal South

2015

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Compaction-induced anisotropy and time-lapse AVO analysis

Islam

Pennington

2015

Interpretation

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Hydrocarbon reservoirs are often monitored using repeated seismic observations to track fluid movement and other changes. Here, we present a study of compaction-induced anisotropy in an unconsolidated overpressured sandstone reservoir from Teal South field in the Gulf of Mexico. Previous work at Teal South had demonstrated that the time-lapse observations could not be satisfied through models of fluid changes without strong pressure effects acting on the formation rock framework. However, those studies are not highly quantitative, and some minor inconsistencies appear on closer examination. We have examined the effect of the pressure-sensitivity of elastic moduli in the formation and carefully examined the offset-dependence of amplitudes in light of several rock-physics models, empirical and theoretical. The amplitude-variation-with-offset behavior for the interface between overlying shale and the hydrocarbon sand is best modeled under the assumption that this overpressured reservoir becomes anisotropic because it undergoes compaction during production, which reduces the reservoir pressure from highly overpressured to nearly normal for this depth. Although the results obtained here are only weakly constrained due to the limited offset ranges and low fold, this strongly suggests that anisotropic effects in poorly consolidated overpressured reservoirs undergoing primary depletion may in fact dominate over fluid effects after the bubble point has been reached.

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