4D Seismic Response of Primary Production and Waste Injection at the Valhall Field

Geophysical Prospecting

Barkved

et al. 2005

A B S T R A C TLegacy streamer data and newer 3D ocean-bottom-cable data are cross-matched and analysed for time-lapse analysis of geomechanical changes due to production in the Valhall Field. The issues relating to time-lapse analysis using two such distinctly different data sets are addressed to provide an optimal cross-matching workflow that includes 3D warping. Additionally an assessment of the differences between the imaging using single-azimuth streamer and multi-azimuth ocean-bottom-cable data is provided. The 3D warping utilized in the cross-matching procedure is sensitive to acquisition and processing differences but is also found to provide valuable insight into the geometrical changes that occur in the subsurface due to production. As such, this work also provides a demonstration of the use of high-resolution 3D interpreted warping to resolve the 3D heterogeneity of the compaction and subsidence. This is an important tool for Valhall, and possibly other fields, where compaction and subsidence (and monitoring thereof) are key factors in the reservoir management since the predominant observed production-induced changes are compaction of the soft, high-porosity chalk reservoir, due to pore-pressure reduction, and the resultant overburden subsidence. Such reservoir compaction could have significant implications for production by changing permeabilities and production rates. Furthermore the subsidence effects could impact upon subsea installations and well-bore stability. Geomechanical studies that have previously been used to model such subsidence and compaction are only constrained by observed surface displacements and measured reservoir pressure changes, with the geological overburden being largely neglected. The approaches suggested herein provide the potential for monitoring and assessment in three dimensions, including the probable heterogeneity and shearing, that is needed for full understanding of reservoir compaction and the resultant effects on the overburden to, for example, mitigate well-bore failures.

Section: Resultssupporting

confidence: 83%

Cross‐matching with interpreted warping of 3D streamer and 3D ocean‐bottom‐cable data at Valhall for time‐lapse assessment

Hall

Geophysical Prospecting

Barkved

et al. 2005

“…The recovery factor is influenced by our knowledge of the zones of depletion and the performance of individual perforations connecting long horizontal wells in the formation (Barkved et al . ).…”

Section: Introductionmentioning

confidence: 97%

Estimation of pore‐pressure change in a compacting reservoir from time‐lapse seismic data

Corzo

Geophysical Prospecting

Barkved

2013

A B S T R A C TAn approach is developed to estimate pore-pressure changes in a compacting chalk reservoir directly from time-lapse seismic attributes. It is applied to data from the south-east flank of the Valhall field. The time-lapse seismic signal of the reservoir in this area is complex, despite the fact that saturation changes do not have an influence. This complexity reflects a combination of pressure depletion, compaction and stress re-distribution throughout the reservoir and into the surrounding rocks. A simple relation is found to link the time-lapse amplitude and time-shift attributes to variations in the key controlling parameter of initial porosity. This relation is sufficient for an accurate estimation of pore-pressure change in the inter-well space. Although the time-lapse seismic estimates mostly agree with reservoir simulation, unexplained mismatches are apparent at a small number of locations with lower porosities (less than 38%). The areas of difference between the observations and predictions suggest possibilities for simulation model updating or a better understanding of the physics of the reservoir.

“…Indeed, the value of 4D seismic in inferring the nature and location of faults has been demonstrated at a qualitative level by several previous studies. For example, Barkved et al (2003) showed that small scale faulting in the Valhall field could be detected by differential pressure changes in fault blocks monitored with seismic. Parr and Marsh (2000) detected the position of a breakdown in a fault-related pressure barrier on the Schiehallion field using 4D seismic data.…”

Section: Introductionmentioning

confidence: 99%

A method to update fault transmissibility multipliers in the flow simulation model directly from 4D seismic

Benguigui

Yin

Journal of Geophysics and Engineering

2014

We propose a new approach to update fault seal estimates in fluid flow simulation models by direct use of 4D seismic amplitudes calibrated by a well geological constraint. The method is suited to compartmentalized reservoirs and based on metrics created from differences in the 4D seismic signature on either side of major faults. The effectiveness of the approach is demonstrated by application to data from the fault controlled Heidrun field in the Norwegian Sea. The results of this application appear favourable and show that our method can detect variations of fault permeability along the major controlling faults in the field. Updates of the field simulation model with the 4D seismic-derived transmissibilities are observed to decrease the mismatch between the predicted and historical field production data in the majority of wells in our sector of interest.