Deriving effects of pressure depletion on elastic framework moduli from sonic logs

Furre, Anne-Kari; Andersen, Mona; Moen, Anita; Tønnessen, Randi Kristin

doi:10.1111/j.1365-2478.2008.00744.x

Cited by 9 publications

(3 citation statements)

References 36 publications

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“…MacBeth () proposed an analogous equation to link dry‐rock elastic moduli to effective pressure with an exponential equation by fitting a set of lab measurements conducted on sandstone and shaley sandstone dry samples (see also Furre et al . ). Multi‐property relations are taken into account in the model proposed by Saul and Lumley ().…”

Section: Methodsmentioning

confidence: 97%

“…Shapiro (2003) provided some theoretical basis to the empirical velocity-pressure relations, using poroelasticity theory and empirical assumptions. MacBeth (2004) proposed an analogous equation to link dry-rock elastic moduli to effective pressure with an exponential equation by fitting a set of lab measurements conducted on sandstone and shaley sandstone dry samples (see also Furre et al 2009). Multi-property relations are taken into account in the model proposed by Saul and Lumley (2013).…”

Section: Rock Physics Modelmentioning

confidence: 99%

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Bayesian inversion of time‐lapse seismic data for the estimation of static reservoir properties and dynamic property changes

Grana

Mukerji

2014

Geophysical Prospecting

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Seismic conditioning of static reservoir model properties such as porosity and lithology has traditionally been faced as a solution of an inverse problem. Dynamic reservoir model properties have been constrained by time‐lapse seismic data. Here, we propose a methodology to jointly estimate rock properties (such as porosity) and dynamic property changes (such as pressure and saturation changes) from time‐lapse seismic data. The methodology is based on a full Bayesian approach to seismic inversion and can be divided into two steps. First we estimate the conditional probability of elastic properties and their relative changes; then we estimate the posterior probability of rock properties and dynamic property changes. We apply the proposed methodology to a synthetic reservoir study where we have created a synthetic seismic survey for a real dynamic reservoir model including pre‐production and production scenarios. The final result is a set of point‐wise probability distributions that allow us to predict the most probable reservoir models at each time step and to evaluate the associated uncertainty. Finally we also show an application to real field data from the Norwegian Sea, where we estimate changes in gas saturation and pressure from time‐lapse seismic amplitude differences. The inverted results show the hydrocarbon displacement at the times of two repeated seismic surveys.

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Section: Methodsmentioning

confidence: 97%

Section: Rock Physics Modelmentioning

confidence: 99%

Bayesian inversion of time‐lapse seismic data for the estimation of static reservoir properties and dynamic property changes

Grana

Mukerji

2014

Geophysical Prospecting

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“…The current state of the art requires that we calibrate the pressure dependence of velocity with core measurements. A major challenge is the fact that consolidated rocks often break up during coring and hence the stress sensitivity is likely to be over‐predicted in the laboratory relative to in situ conditions (e.g., Furre et al . 2009).…”

Section: Introductionmentioning

confidence: 99%

Rock physics modelling of 4D time‐shifts and time‐shift derivatives using well log data – a North Sea demonstration

Avseth

Skjei

Skålnes

2013

Geophysical Prospecting

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A B S T R A C TRock physics models for fluid and stress dependency in reservoir rocks are essential for quantification and interpretation of 4D seismic signatures during reservoir depletion and injection. For siliciclastic sandstone reservoirs, the Gassmann theory successfully predicts changes in seismic properties associated with fluid changes. However, our ability to predict the sensitivity to pressure from first principles is poor, especially for cemented sandstones. In this study, we demonstrate how we can use a patchy cement rock physics model to quantify the combined effect of stress and fluid changes in terms of seismic time-shifts and time-shift derivatives during depletion or injection. The time-shifts are estimated directly from well log data without core calibration of stress sensitivity. By assuming non-uniform grain contacts where some grain contacts are cemented and others are loose, we can combine the contact theory for cemented sandstones with the contact theory for loose sands in order to predict stress sensitivity in a patchy cemented sandstone reservoir. Time-shift derivatives are also useful estimates, as this parameter reveals which part of the reservoir is most stress sensitive and contributes most to the cumulative time-shift.We test out our new approach on well log data from Troll East, North Sea and compare the predicted time-shifts with observed 4D seismic time-shifts. We find that there are good agreements between predicted time-shifts and observed time-shifts. Furthermore, we confirm that there are local geological trends controlling the fluid and stress sensitivity of the reservoir sands on Troll East. In particular, we observe a lateral stiffening of the reservoir from west to east, probably associated with the tectonic and burial history of the area. The combined effect of a thinning gas cap and stiffening reservoir sands amplifies the eastward decrease in time-shifts associated with reservoir depletion. We manage to disentangle these two effects using rock physics analysis. It is essential to identify and map the static rock stiffness spatial trends before interpreting time-shifts and time-shift derivatives in terms of dynamic (i.e., 4D) pressure and fluid changes.

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A contribution to the petrophysical knowledge of the Lourinhã Formation as an analogue for the Statfjord Formation in the North Sea oil and gas fields

Ludovico-Marques¹

2020

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The Lourinhã Formation in the western region of Portugal is an analogue for the Statfjord Formation in the oil and gas fields of the Norwegian Northern North Sea. This petrophysics study encompasses a specific sandstone variety (M variety) of the Lourinhã Formation. This lithic arkose shows an average value of effective porosity of 18.5% and a permeability range of 20–30 mD, and is representative of the distribution range in the petrophysics models of the reservoirs of the Statfjord Formation. The petrographical, physical and mechanical characterization of the M variety sandstone is compared with the main features of the oil- and gas-producing sandstones of the Statfjord Formation in a reference well in the Norwegian Northern North Sea. Efficient enhanced oil recovery (EOR) projects in the oil and gas fields of the Norwegian Gullfaks hub are always needed, and this study intends to provide a contribution to that endeavour.

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Deriving effects of pressure depletion on elastic framework moduli from sonic logs

Cited by 9 publications

References 36 publications

Bayesian inversion of time‐lapse seismic data for the estimation of static reservoir properties and dynamic property changes

Bayesian inversion of time‐lapse seismic data for the estimation of static reservoir properties and dynamic property changes

Rock physics modelling of 4D time‐shifts and time‐shift derivatives using well log data – a North Sea demonstration

A contribution to the petrophysical knowledge of the Lourinhã Formation as an analogue for the Statfjord Formation in the North Sea oil and gas fields

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