The MacCulloch Field: improving reservoir characterization through time-lapse analysis

Abstract

The MacCulloch oilfieldliesinBlock 15/24b inthe UK CentralNorthSea.The fieldisproduced usinga floatingproduction storage andofftake facility from two sub-sea centresandhasbeenonproduction since 1997.The originalgeophysicalmappingofthe fieldwasbased on 3Dseismic dataacquired in1993. InApril2002,a repeat3Dsurveywasacquired overthe fieldwiththe aimofbetterunderstandingthe depletion ofthe fieldusing time-lapseseismic analysis.The MacCulloch Fieldreservoirs areturbiditesofthe UpperBalmoralSandstoneUnitinthe ListaFormation of the UpperPaleocene, which areconnected to alarge aquiferinthe underlyingLowerBalmoralSandstoneUnit. Connection to such alarge aquifermeans thatpressuresupport overfieldlife hasbeenvery good( , 100 psidrop overfieldlife). Thisfact,coupled withthe lack ofagascap,means thatfor the time-lapseanalysisany change shouldprimarily be dueto asubstitution ofwaterfor oil.The MacCulloch Fieldreservoirismade up offivediscreteturbiditesandstone-dominated sandbodies,which canbe distinguished on the seismic data.Examination ofthe time-lapseresponseinthesebodiesshows thatthey haveacted asaprimary control on the depletion ofthe field.The individualbodieshavebeenanalysed using3D visualization andi nterpretation techniques,a ndi ncorporated into the geologicalm odelw ithd ifferingrock propertiesassigned to each.Withinthe reservoirsimulation model,the assignment ofdirectionalpermeabilitiesto theseunits andthe placingoftransmissibility barriers attheirboundariessubstantially improved the history match ofthe field, therebyenhancingour ability to predictfutureperformance andi dentifyp ossiblei nfill drilling locations.

The Brenda Field development: A multi‐disciplinary approach

“…On the MacCulloch field, 12 km NW of Brenda, Conoco have noted that the seismic event representing the top of the reservoir illustrates that this event is characterized by a "Class III" (weak trough -near offset, strong troughfar offset) AVO anomaly (Scorer, et al, 2003). Scorer claims that this technique has been a good "oil indicator" with an oil/water contact evident.…”