Use of rock properties and AVO in the Everest Field development, UKCS

Barrett, Ray; Margesson, R. W.; D‘Angelo, R. M.

doi:10.1144/petgeo.1.4.311

Cited by 2 publications

(1 citation statement)

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“…Re¯ected PP wave AVO is often used to discriminate between water and hydrocarbon-®lled rocks in a reservoir. Some recent examples include Barnett, Margesson and Dangelo (1995) and Reilly (1994) in the North Sea, Hall et al (1995) in the Gulf of Mexico, and Santoso et al (1996) in Indonesia.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of reflection seismic data to oil‐column height in high‐porosity sandstones

Ryan-Grigor¹,

Sayers²

2000

Geophysical Prospecting

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Tuning is the effect of interference between the reflections from the top and bottom of a thin layer on the amplitude of the composite reflection. For a homogeneous sandstone reservoir containing an oil column overlying brine, interference between the reflection from the top reservoir and the oil/water contact is a function of the height of the oil column. If the properties of the sandstone do not vary across the oil/water contact, the SS, PS and SP reflection coefficients from the oil/water contact are small in comparison to the PP reflection coefficient. This allows analytic expressions for the effective PP and PS reflection coefficients from the reservoir to be derived that include all P‐wave multiples within the oil column. For a given source/receiver offset, the component of the wavevector inside the oil column normal to the interface is larger for the PPPP reflection than for the PPPS reflection, due to the asymmetry in the raypath for the PPPS reflection. The PPPS reflection is therefore useful for determining oil‐column heights larger than that discriminated by the PPPP reflection, especially when used at wider offsets. A convenient classification of the AVO response of hydrocarbon‐bearing sandstone reservoirs overlain by shale is the scheme of Rutherford and Williams. Class 1 sands have higher acoustic impedance for normal incidence than the overlying shale, Class 2 sands have nearly the same acoustic impedance as the shale and Class 3 sands have lower acoustic impedance. Synthetic shot gathers calculated for these three classes as a function of oil‐column height show that a combination of the PPPP and the PPPS amplitudes can be plotted as a tuning trajectory, which can be used to determine the oil‐column height. This method is most sensitive for reservoirs that belong to AVO classes 1 and 2, and therefore may be useful in AVO analysis of Class 1 and 2 reservoirs where the traditional AVO indicators (developed for Class 3 reservoirs) do not work very well. These results demonstrate the usefulness of shear waves recorded in the marine environment at wide offsets.

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Section: Introductionmentioning

confidence: 99%

Sensitivity of reflection seismic data to oil‐column height in high‐porosity sandstones

Ryan-Grigor¹,

Sayers²

2000

Geophysical Prospecting

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Innovation and risk management in a small subsea-tieback: Arkwright Field, Central North Sea, UK

Kantorowicz

Andrews

Dhanani

et al. 1999

PGC

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Arkwright is a 50 × 106BBL oil field located within a single Forties Sandstone Member turbidite ‘channel’ system. Arkwright was discovered in 1990 and developed in 1996. Earlier start-up was precluded by reservoir risk and lack of export pipeline capacity. Reservoir definition improved after acquiring a 3D survey and applying imaging and attribute studies. This, combined with subsurface analogue, core, and carbon, oxygen and strontium isotopic studies, improved understanding of reservoir architecture and connectivity. Geostatistical techniques were used to quantify the STOIIP. The main risks identified were the absence of aquifer support, and possible vertical and lateral baffling. As these could not be tested by appraisal drilling it was decided to commence development.Low-cost, two-well development options were considered and rejected because of the subsurface risk. Without guaranteed aquifer support, the productivity from early sub-bubble point flow would be lost waiting for injection support to be added. Risk-weighting highlighted the advantage of initial expenditure to safeguard the project, and so a third initial production well was planned, in a location suitable for conversion to injection.Predicted rates were increased and the impact of lateral baffling minimized by drilling deviated producers on opposite sides of the structure, and not reusing the discovery well. Costs were reduced by using a drilling centre outside the field. The perforation strategy ensures drainage above and below potentially sealing abandonment shales, and facilitates future zonal isolation. Communication within the reservoir was tested at start-up with an interference test.

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Use of rock properties and AVO in the Everest Field development, UKCS

Cited by 2 publications

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Sensitivity of reflection seismic data to oil‐column height in high‐porosity sandstones

Sensitivity of reflection seismic data to oil‐column height in high‐porosity sandstones

Innovation and risk management in a small subsea-tieback: Arkwright Field, Central North Sea, UK

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