Compaction Within the South Belridge Diatomite

Chase, Chevy; Dietrich, J.K.

doi:10.2118/17415-pa

Cited by 24 publications

(10 citation statements)

References 8 publications

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“…Water weakening of chalk has been known for a long time (Simon et al, 1982 andNewman, 1983). Similar chemical related water weakening effects have also been reported to take place in a similar low permeable reservoir rocks with large grain surface area, the diatomite (Chase and Dietrich, 1989). The effect was brought up again in relation to compaction during waterflood (Andersen et al, 1992 andCook et al, 2001).…”

Section: Water Weakeningmentioning

confidence: 54%

History Matched Full Field Geomechanics Model of the Valhall Field Including Water Weakening and Re-Pressurisation

Kristiansen

Plischke²

2010

SPE EUROPEC/EAGE Annual Conference and Exhibition

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Valhall is a large chalk field in the Norwegian sector of the North Sea. The reservoirs consist of highly overpressured (0.84 psi/ft) chalk. The high overpressure and early oil migration has resulted in very well preserved porosity, exceeding 50% in parts of the field. This highly porous chalk is extremely weak, which results in liquefaction of the chalk at certain conditions during production. The weak nature of the chalk does also result in significant reservoir compaction, exceeding 10 meters in some locations in the reservoir. The compaction is providing an excellent source of reservoir energy, accounting for 50-60% in certain areas of the field. The compaction is transferred to the seafloor in the form of subsidence and is currently exceeding 6 meters below the central platform complex.The seafloor subsidence has resulted in a diminishing air gap for the platforms at Valhall, resulting in demobilisation of personnel during very rough winter storms. Water injection started in the field in 2004 with a gradual step up in rate. An offset chalk field in the area have experienced an increasing subsidence rate due to water weakening of the chalk. The micro-scale physical and chemical processes involved in water weakening of chalk have not been quantitatively determined, but a strategy to handle this had to be developed. This paper documents the development of a prediction model for the subsidence at Valhall between 2002 and 2008. The paper covers the development of a suitable and effective constitutive model to account for strain rate dependent reservoir compaction during depletion, re-pressurisation and waterflooding. The constitutive deformation model is driven by pore pressure and watersaturation calculated in a reservoir flow model and imported into the geomechanics model.It will be described how the constitutive model for the reservoir was populated. The overburden, underburden and sideburden were also modelled and required properties. The initialisation requires an initial stress state and it will be presented how this was defined. We also included faults in the model and check for re-activation and amount of slip on them. The Valhall model can also be constrained by a relative large amount of field and surveillance data. It will be presented how this data was used in the history matching process. The data used for the history matching process includes vertical and horizontal platform movements from GPS, time lapse seafloor bathymetry maps, radioactive markers in the reservoir and overburden as well as 4D seismic. It will be presented how the model matched the observed data from the field, showing a gradual decrease in subsidence rate from around 25 cm/year with the risk to increase due to water weakening, to the current reduced rate at 11 cm/year. This response is different to the one reported from the offset field. We will also present other high impact business applications of the model prediction, besides seafloor subsidence forecasting.

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Section: Water Weakeningmentioning

confidence: 54%

History Matched Full Field Geomechanics Model of the Valhall Field Including Water Weakening and Re-Pressurisation

Kristiansen

Plischke²

2010

SPE EUROPEC/EAGE Annual Conference and Exhibition

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“…a linear steamdrive, obtained by use of the volatile-oil steamflood simulator described by Chase and Dietrich (1989). The method is novel and is easy to apply, requiring only a hand calculator or spreadsheet software.…”

Section: Discussionmentioning

confidence: 99%

Saturated-Steam Pressure Drop in Flow Through Porous Media

Closmann¹

2010

SPE Reservoir Evaluation &Amp; Engineering

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This note provides a simple steady-state method for estimating the pressure drop for steam vapor flowing at a constant mass rate through porous media. The derived formula includes the relevant properties of saturated steam and allows for their distribution along the zone of pressure variation. It also eliminates the need for steam tables within the applicable pressure range (10-2,900 psia). The method can also be extended to cases in which the rate varies in a known manner because of heat loss or other factors.* Results with Chase and Dietrich (1989), steam zone length = 92 ft, absolute permeability = 1 darcy, injection pressure = 726.5 psia, steam injection rate = 30.294 B/D, injection time = 20 days, block length = 4 ft, block height = 10 ft, block width = 10 ft.

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“…Since its development in 1980, this simulator has been used extensively within the petroleum industry to design and analyze field projects worldwide. [3][4][5][6][7][8][9] Steam distillation, steam additives, hydraulically induced fractures, and reservoir compaction were important elements in many of these field applications.…”

Section: Pilot Design Simulationsmentioning

confidence: 99%

The Kern River Horizontal-Well Steam Pilot

Dietrich¹

1988

SPE Reservoir Engineering

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Sluggish oil response in the Kern River horizontal-well steam pilot was caused by placement of the wells in a reservoir environment unfavorable for application of either conventional oil recovery processes or novel oil-mining techniques. Encouraging pilot operational experience and the tremendous potential for improved ultimate oil recovery shown by preliminary simulations suggest that future pilot testing of horizontal-well steam technology is warranted in a more favorable environment.

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Compaction Within the South Belridge Diatomite

Cited by 24 publications

References 8 publications

History Matched Full Field Geomechanics Model of the Valhall Field Including Water Weakening and Re-Pressurisation

History Matched Full Field Geomechanics Model of the Valhall Field Including Water Weakening and Re-Pressurisation

Saturated-Steam Pressure Drop in Flow Through Porous Media

The Kern River Horizontal-Well Steam Pilot

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