The Njord Field: a dynamic hydrocarbon trap

Lilleng, Trond; Gundesø, R.

doi:10.1016/s0928-8937(97)80018-5

Cited by 6 publications

(2 citation statements)

References 2 publications

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“…Both segments are broadly planar in cross section and dip towards the NW. The two NE‐SW‐striking segments are linked by a central, WNW‐ESE‐striking segment, which is located immediately to the south of the Njord Field and which has a ramp‐flat‐ramp geometry in cross section (Lilleng & Gundesco, ; Ehrlich & Gabrielsen, ) (Figs and c). The hangingwall rollover‐related structural high located in the hangingwall of the E‐W‐striking segment results from the ramp‐flat‐ramp geometry of the fault complex at this particular location (Fig.…”

Section: Study Area Structure and Syn‐rift Distributionmentioning

confidence: 99%

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Late syn‐rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models

et al. 2015

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Rift basin tectono-stratigraphic models indicate that normal fault growth controls the sedimentology and stratigraphic architecture of syn-rift deposits. However, such models have rarely been tested by observations from natural examples and thus remain largely conceptual. In this study we integrate 3D seismic reflection, and biostratigraphically constrained core and wireline log data from the Vingleia Fault Complex, Halten Terrace, offshore Mid-Norway to test rift basin tectono-stratigraphic models. The geometry of the basin-bounding fault and its hangingwall, and the syn-rift stratal architecture, vary along strike. The fault is planar along a much of its length, bounding a half-graben containing a faultward-thickening syn-rift wedge. Locally, however, the fault has a ramp-flat-ramp geometry, with the hangingwall defined by a fault-parallel anticline-syncline pair. Here, an unusual bipartite syn-rift architecture is observed, comprising a lower faultward-expanding and an upper faultward-thinning wedge. Fine-grained basinfloor deposits dominate the syn-rift succession, although isolated coarse clastics occur. The spatial and temporal distribution of these coarse clastics is complex due to syn-depositional movement on the Vingleia Fault Complex. High rates of accommodation generation in the fault hangingwall led to aggradational stacking of fan deltas that rapidly (<5 km) pinch out basinward into offshore mudstone. In the south of the basin, rapid strain localization meant that relay ramps were short-lived and did not represent major, long-lived sediment entry points. In contrast, in the north, strain localization occurred later in the rift event, thus progradational shorefaces developed and persisted for a relatively long time in relay ramps developed between unlinked fault segments. The footwall of the Vingleia Fault Complex was characterized by relatively low rates of accommodation generation, with relatively thin, progradational hangingwall shorelines developed downdip of the fault block apex, sometime after the onset of sediment supply to the hangingwall. We show that rift basin tectono-stratigraphic models need modifying to take into account along-strike variability in fault structure and basin physiography, and the timing and style of syn-rift sediment dispersal and facies, in both hangingwall and footwall locations.

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Section: Study Area Structure and Syn‐rift Distributionmentioning

confidence: 99%

“…The hangingwall rollover‐related structural high located in the hangingwall of the E‐W‐striking segment results from the ramp‐flat‐ramp geometry of the fault complex at this particular location (Fig. c) (Lilleng & Gundesco, ; Ehrlich & Gabrielsen, ).…”

Section: Study Area Structure and Syn‐rift Distributionmentioning

confidence: 99%

Late syn‐rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models

et al. 2015

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Three-dimensional visualization for well placement and geosteering: Njord Field, offshore mid-Norway

Dart

Denichou

Bridger

et al. 2005

PGC

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NjordisastructurallycomplexLowerJurassic oilfieldlocated on the HaltenTerrace, offshoremidNorway. The fieldwasdiscovered in1986andhasbeenunderproduction since 1997. The fieldisproduced bya combination ofdepletion andcrestalgasinjection. Difficultiesinfindingneweconomically viabledrillingtargets led to adrillingstop in2001-2002 andproduction isnow indecline.Aseconddrillingphasecomprisingthree infill wells beganinlate2002. Production results from thesethree wells will be criticalfor determiningNjord's futureb eyond2005.Duringthe drillingstop,a dvanced 3Dvisualization techniquesw ereused to unravelt he field's complexextensionalfault pattern. Neww ell targets werei dentified usingmultipleseismic datasets and multipleinterpretations. 3Dvisualization wasalso used duringdrillingto keepthe wells withinthe reservoirand to avoid anunstableformation.Reservoirs imulation models wereused to identifyareasw ithundrained potential,a nd4 Dseismic data indicated fault blockswherechangesingassaturation had occurred.The reservoiroilisinitially under-saturated, but gashasalso comeout ofsolution inareaswithsignificant pressuredepletion. Gashasalso beenre-injected. Newwells wereplanned to avoid thesefault blocks. Targetpoints wereplaced using3Dvisualization software andwell pathd og-leg anglesw erec alculated.The process continued iteratively untilawell pathh ad been achieved withmaximum reservoirp enetration andrealistic dog-leg angles( , 3.5 8 ). Realt imed atawere transmitted to shored uringd rillingusingaweb service.Thesed atai ncluded survey,petrophysicall og, biostratigraphicalandboreholeimage datathatwereused alongside the 3Dvisualizations.Inthisway,drilling progress through the G&G interpretation wascontinuouslymonitored.Similarly,geosteering, or plugback and sidetrack, decisionsw erequickly evaluated.

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A 3D stochastic model integrating depth, fault and property uncertainty for planning robust wells, Njord Field, offshore Norway

Rivenæs

Otterlei

Zachariassen

et al. 2005

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The Njord Field, situated in the Haltenbanken area, is one of the most challenging reservoirs on the Norwegian shelf. The structural complexity is high, with numerous intersecting faults compartmentalizing the reservoir. The reservoir is dominated by alternating shale and sand intervals of tidal, estuarine and deltaic depositional origin. One of the main segments on Njord – the Central Area – was the target for a one-year improved oil recovery study. The Central Area reservoir is produced by depletion, with a current recovery factor of only 6%, as most faults appear to seal during production. The previous drilling experience revealed quite large uncertainty with respect to both depth and missing faults due to poor seismic data quality. In order to plan further wells in this area a model that comprises the full uncertainty with respect to both structural components (depth uncertainty and faults) and property components (facies, permeability, porosity) was made. The model was built by combining commercial modelling software (IRAP RMS and STORM:HORIZON) with an R&D tool (HAVANA) in a manner that has not been attempted previously, and 200 stochastic realizations were run. Each realization has a different structural 3D grid (depth and fault pattern) and different petrophysical properties. A streamline simulator in IRAP RMS was applied to rank the realizations and ten realizations were chosen for further well screening in the flow simulator (ECLIPSE). The model was applied to propose two new well targets that were robust economically (given all uncertainty). In addition, the model was applied in testing various unconventional well types, for example so-called ‘connector-wells’, which are open holes in the reservoir (but not connected to the surface), in order to connect fault blocks bounded by sealing faults. Drilling and subsequent seismic interpretation after the model had been built revealed that the structural uncertainty was even greater than predicted. It is crucial to capture the full interpretation uncertainty and, in particular, to address the problem of jump-correlation across fault blocks. Despite this, however, the observed cumulative production from the new oil producer compares well with the prognosis from the model.

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The Njord Field: a dynamic hydrocarbon trap

Cited by 6 publications

References 2 publications

Late syn‐rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models

Late syn‐rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models

Three-dimensional visualization for well placement and geosteering: Njord Field, offshore mid-Norway

A 3D stochastic model integrating depth, fault and property uncertainty for planning robust wells, Njord Field, offshore Norway

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