Network of Offshore Records of Geology and Stratigraphy

NORLEX

Lysing Member [new status]

Introduction

The Lysing Member is mainly a unit of sandstones attributed to the uppermost Blålange Formation of predominantly Coniacian to latest Turonian age developed on the Halten and Dønna Terraces along the margins of the Nordland Ridge and within parts of the Vøring Basin.

Name

English/ Norwegian and any previous names: The name "Lysing Formation" was introduced by Dalland et al. (1988) as the only sandstone unit recognised in the Norwegian Sea area at that time, the other formations being dominated by mudstones. This study reduces the unit to member status within the Blålange Formation on the basis of being detached sandstone bodies and for consistency with other new sandstone members recognised in the area. It is also reassigned to the Shetland Group (formerly Cromer Knoll Group of Dalland et al., 1988) following the revised group definitions in the Norwegian Sea area.

Derivatio nominis: The name Lysing is derived from the Norwegian word for the fish species Merluccius merluccius or hake.

Publication: Dalland et al. (1988)

Lithology

The Lysing Member consists predominantly of clear to white-grey or grey-greenish quartzitic sandstones with subordinate interbedded mudstones. The sandstone grain size is fine to medium or occasionally coarse, with moderately sorted sub-angular to sub-rounded grains, occasionally sub-spherical. The sandstones are frequently glauconitic (imparting the grey-green colouration) or have traces of mica and are calcite cemented. The subordinate mudstones are medium dark grey, firm to hard, weakly laminated, sub-fissile, micro-micaceous and non- to slightly calcareous with traces of fine crystalline pyrite and mica. In cores of the reference well 6506/12-4 (figures XX), the sandstones form thick 0.3 to 1.5 m beds or thin sandstone laminae within the subordinate interbedded mudstones.

Basal stratotype

Sandstones of the Lysing Member rest on mudstones of the underlying Blålange Formation. In the type well 6507/7-1, the basal stratotype is defined by a gradual decrease in the gamma-ray log and an upward increase in sonic velocities response at the onset of a more serrate pattern on the resistivity and sonic logs.

Sample depository

Palynological preparations (organic matter depository)

Type well 6507/7-1: 1 slide from the ditch cuttings sample at 2930 m at NPD.

Reference well 6506/12-4: 15 slides, of which 14 are core samples and 1 ditch cuttings sample, covering the interval 3129.1 m - 3144.3 m are available at the NPD. Note that these fall in the (+5.9 m) corrected core range of the member.

Core photographs

Type well 6507/7-1: no cores were taken in this formation.

Reference well 6506/12-4: core #1, interval 3129 m - 3150 m (3142.9 m uncorrected core depth). Note there is at least a +5.9 m core correction to this core.

Reference well 6506/3-1 (new additional reference well): core #1 3101.5 m - 3171.5 m (uncorrected core depth). The lowermost part of the member is cored including the base of the member at 3109.41 m (uncorrected core depth). Note that core #1 has a +1.07 m core to log correction.

6506/12-4:

6506/12-4, 3129-3133 m	6506/12-4, 3134-3138 m
6506/12-4, 3139-3143 m	6506/12-4, 3144-3148 m

6506/3-1 (selected core details only):

6506/3-1: Base of the Lysing Member. The base is marked by the first (up-section) sandstone bed and is characterised by scattered glauconite grains at 3109.41 m MD RKB.

6506/3-1 Lysing Member 3106.96 m MD RKB. Normal graded 27 cm thick sandstone bed. Note the glauconite grains at the base and possible low angle cross lamination.

6506/3-1 Lysing Member, 3106.69 m MD RKB. Cross-laminated sandstone with glauconite lining the lamination.

6506/3-1 Lysing Member 3104.8 m MD RKB. Thin massive and ripple laminated glauconitic sandstone beds inter-bedded with pin-striped mudstones.

Thickness

The Lysing Member varies in thickness from 1 m e.g. 6608/10-1 to 120 m e.g. 6506/11-4 S with an average of approximately 35 m based on released well data. These figures exclude the informal 'lower Lysing sandstones' of late Turonian age developed below this member in some wells.

Regional isochore of the Lysing Member thickness in the Norwegian Sea based on released well data. The isochore map is generated from Norlex data using thin plate splines (thickness constrained to original range). Thicknesses in metres. Circled wells contain both top and base horizons. The red wells have Norlex biostratigraphy. Click for large version.
Interactive Function: Note that this map is only a regional interpretation and the user can generate more specific, local area isochore maps interactively within Norlex using the link below.
Interactive Norlex isochore map for the Lysing Member

Geographical distribution

The member is widely distributed on the Halten and Dønna Terraces, particularly along the margin of the Nordland Ridge, but it is generally thin (< 5 m) e.g. 6507/2-1 and 6507/5-5 or absent on the Trøndelag Platform. It is also variably developed in wells that have penetrated the deeper parts of the Vøring Basin e.g. 6605/8-1 (Stetind) but was not present in the 6504/5-1 well (Gemini prospect) that was also drilled in the Vigrid syncline (Heskestad et al. 2009). In this well, the time-equivalent section was represented by mainly mudstones with thin sandstones, siltstone and limestone stringers. Maximum thicknesses of over 100 m (gross) are on the westerly flank of the Halten Terrace in block 6506/11 (Morvin Field) e.g. 6506/11-4 S (120 m) and 6506/11-7 (111 m).

Occurrences of member tops in wells

Type well

Well name: 6507/7-1

WGS84 coordinates: N 65°27'16.7", E 07°12'52.6"
UTM coordinates: 7260481.16 N 417247.40 E
UTM zone: 32
Drilling operator name: Conoco Norway
Completion date: 01.12.1984
Status: P & A
Interval of type section (m) & thickness in type well: 3000 m - 2926 m, 74 m thickness.

Reference wells

Well name: 6506/12-4

WGS84 coordinates: N 65°12'46.97"N, E 06°43'30.37"
UTM coordinates: 7234298.14 N 393591.29 E
UTM zone: 32
Drilling operator name: Den norske stats oljeselskap a.s. (Statoil AS)
Completion date: 13.08.1985
Status: P & A
Interval of type section (m) & thickness in type well: 3150 m to 3132.5 m, 17.5m thickness. The lower 15 m of the formation are cored, including the base at 3142.87 m MD RKB (uncorrected core depth). Note core #1 has a +6.9 m core to log correction.

It was considered appropriate to define an additional reference well 6506/3-1 in order to see the log variation within the Lysing Member.

Well name: 6506/3-1

WGS84 coordinates: N 65°48'20.75"N, E 06°44'32.64"
UTM coordinates: 7200300.07 N 396769.02 E
UTM zone: 32
Drilling operator name:Norsk Chevron AS
Completion date: 9.08.2001
Status: P & A
Interval of type section (m) & thickness in type well: 3110.5 m MD RKB (3109.41 m uncorrected core depth) - 3090 m MD RKB, 20.5 m thickness.

Upper and lower boundaries

Upper boundary

The Kvitnos Formation usually overlies the Lysing Member and the boundary is usually characterised by an upward increase in gamma ray values and a decrease in sonic velocities representing the change from sandstones to mudstones.

Lower boundary

Sandstones of the Lysing Member usually rest on mudstones of the underlying (and surrounding) Blålange Formation.

In the type well 6507/7-1, the basal stratotype is defined by a gradual decrease in the gamma-ray log and an upward increase in sonic velocities response at the onset of a more serrate pattern on the resistivity and sonic logs. In other wells, e.g. 6506/6-1, 3080 m MD RKB, the base of the member may be sharp and reflects the abrupt input of sandstones. In some instances, the base of the Lysing Member has been defined at a prominent high gamma marker (informal k58a) within the upper part of the Blålange Formation e.g. 6506/12-10 (6580 m MDRKB), but the position of this regional correlative event may be as much as 30 m below the first development of sandstones and is not recommended, e.g. 6506/3-1 (3110.5 m MD RKB). In the type well 6507/7-1 the informal k58a marker is almost coincident with the base of the Lysing Member, presumably due to local erosion at the base of the unit. However, this useful marker, which may represent a synchronous ash bed, provides a means of distinguishing Lysing Member sandstones from older sandstones of the underlying Blålange Formation based only on wireline log information.

Well log characteristics

The wireline log response of the Lysing Member is variable. In the type well 6507/7-1, the member is characterised by a serrate but generally blocky gamma-ray profile with a funnel shaped basal section. Dalland et al. (1988) in their original description also noted that the resistivity and sonic log patterns were generally serrate with respect to the underlying and overlying intervals, but these probably relate to zones of calcite cementation within the sandstones or thin limestone stringers. In the reference well 6506/12-4, however, the Lysing Member has a generally irregular gamma-ray log profile and in the 6506/3-1 well, a lower irregular unit is divided from an upper, funnel shaped, cleaning upward unit by a unit of mudstones . This variation in log profile reflects local differences in the depositional style of the member.

A prominent high gamma ray feature (informal k58a event) e.g. 6507/7-1 (3002 m MD RKB) provides a useful and regionally correlatable event below the member.

Biostratigraphy

In the type well 6507/7-1, the Lysing Member can be considered for practical purposes to be Coniacian age since the late Turonian dinocyst marker LO Stephodinium coronatum (Zone 27) is recorded 2 m above the base of the member in sidewall samples at 2998 m. In the type well there is an increase in Heterosphaeridium difficile at the same level, although the lack of separation of these two events may suggest some minor (local) erosion at the base of the member. The FO Chatangiella 'spinosa' appears to be within the middle part of this member and suggests an age no older than Coniacian, e.g. 6507/7-1, 2964.5 m swc. The Lysing Member is generally within the abundance ranges of the Palaeoperidinium pyrophorum and Palaeohystrichophora infusorioides palynoevents that are regionally typical of the early Coniacian (Zone 26).

Planktonic foraminifera are generally absent in the Lysing Member but pyritised diatoms such as Stellarima spp. and radiolarians (cenosphaerid and spumellarian types) are frequent, particularly towards the base.

In the reference well 6506/12-4, the dating maybe confused by reworking, since Triassic palynomorphs are present and suggests a source origin for the sediments. It is uncertain whether the sporadic occurrences of S. coronatum throughout the member are in situ or reworked.

More meaningful biostratigraphic data are derived from the additional reference well 6506/3-1 where LO S. coronatum is in the mudstones immediately below the member (3111.04 m corrected core), but the increase in H. difficile (from 3100 m dc and extending within the lower cored interval of the member to 3108.98 m corrected core) suggests that in this well, the Lysing Member straddles the Turonian-Coniacian boundary if this event can be considered reliable.

Additional, less reliable dinocyst events to constrain the Lysing sandstones are the LO Psaligonyaulax deflandrei, LO Spiniferites porosus and acme C. 'spinosa' in the overlying Kvitnos mudstones and the LO Cyclonephelium membraniphorum either within or below the member.

In summary, it appears that the Lysing Member in the majority of wells appears to be (early) Coniacian age but some sandstones developed within the lower part of the member may be latest Turonian age. This is dependant on location and depositional fill history (see comments on correlation below).

Age (redefined)

Late Cretaceous, latest Turonian - (early) Coniacian.

The main sandstones of the Lysing Member are usually (early) Coniacian age but the member may straddle the Turonian/Coniacian stage boundary in some wells. In some instances, the biostratigraphic dating is complicated by syn-sedimentary reworking. This review suggests a considerable reduction in the age uncertainty than presented earlier by Dalland et al. (1988).

Correlation

In the deeper locations of the Vøring Basin, e.g. wells 6607/5-1 and 6605/8-1, an informal three fold reservoir zonation of the Lysing Member is proposed for practical purposes. The 'upper' Lysing Member is typical of wells on the Dønna terrace and is Coniacian age. The Turonian/Coniacian boundary lies within a middle unit dominated by mudstones. The informal 'lower' Lysing member is typically late Turonian age and represents an earlier phase of deposition, possibly deserving of separate member status, although without biostratigraphic control this could be difficult to formally recognise on lithological criteria alone.

Depositional environment

When Dalland et al. (1988) first formally described the unit there was considerable uncertainty on the depositional processes and setting of these sandstones. Interpretations varied from shallow to deep marine and possibly sandstone dominated fan lobe deposits as suggested for the type well 6507/7-1 by Hastings (1987) and Vergara et al. (2001). Since that time, there has been a steady amount of data published on the depositional setting of the Lysing sandstones from most areas of the Norwegian Sea, and this review of the current literature suggests deposition in a variety of settings on the upper slope, lower slope and basin floor. Significantly there are no interpretations that support an in situ shallow marine, tidal interpretation in spite of the development of a sedimentary facies in core e.g. 6506/12-5 that is characterised by cross stratified, glauconitic sandstones. These have interpreted as being a slumped unit of tidal sediments (Shanmugan et al., 1994) that may be related to the slumping identified by seismic facies mapping in the southern Halten Terrace south of Quadrant 6406 (Vergara et al., 2001), or atypical in situ deep marine sediments emplaced by episodic bottom traction currents (oceanic contourites) in a deep, basin floor setting (Hastings 1986; Walker 1998 unpubl.). Significantly, in their argument to support slumping and mass transport complexes, Vergara et al. (2001) undertook backstripping of sections across the Halten Terrace to indicate palaeo-water depths of several hundred metres during their K80 (Lysing time) sequence. Although not a period of tectonic activity, Lien (2005) in his development of the Cretaceous to Eocene deep-water hydrocarbon reservoirs of the Norwegian Sea recognised that the Lysing (Sequence K60) was part of the late post-rift phase representing a time of passive infill, high subsidence rates and subsequent sediment loading in the basin causing basin margin uplift and tilting.

For a general overview of the various depositional settings of the Lysing sandstones, the reader is referred to Fugelli and Olsen (2005 a,b). Some details are given in the following summary. In their basin screening study of deep marine reservoirs and associated risk assessment and play fairway analysis of the Vøring and Møre Basins, the Lysing sandstones and time equivalent sediments (K72 sequence) were cited as examples and the main focus for comparison with outcrop analogues from the early Cenozoic Ainsa Basin, Spain and Permian Delaware Basin in Texas, USA. These outcrops studies were used to construct a (composite) shelf-slope to basin floor transect. They documented the seismic character, gross facies elements, reservoir architecture and inferred scale and geometry of the various depositional systems of the Lysing sandstones and time equivalent sediments. They interpreted their K72 sequence as being deposited in medial basin-floor fans within the Vøring Basin (example 2) e.g. 6706/11-1 area; lower slope basin floor fans on the margin of the Trøndelags platform (example 3) e.g. down-dip of 6507/5-3 (Snadd Field) and 6507/2-3 wells; upper slope basin floor fan conduit (example 4) e.g. 6507/5-3 (Snadd Field) representing the main sediment fairway into the down-dip fan complex; slope deposits (example 5) e.g. 6204/11-1; and slope-channel deposits (example 6) e.g. 6204/10-1 located in the Slørebotn sub-basin. Examples 5 and 6 are time equivalent to the Lysing sandstones that are present on the eastern margin of the Møre Basin and are included within the Rødspette Member in this study. In a more area specific study, Fugelli and Olsen (2007) described how the tectonically confined sub-basins on the Dønna Terrace controlled the deposition of the "Lysing Formation". Based on an integrated, multidisciplinary approach, they constructed a detailed depositional model for the deposition of the Lysing sandstones as turbidite complexes within a series of slope (sub) basins.

In terms of details of the sedimentary facies, in the cored 6506/12-4 reference well, located in the Smørbukk Field area, the Lysing Member consists mainly of fine grained sandstones with thin mudstones. The sandstone beds (average thickness 50 cm within a range 17-105 cm) typically have sharp bases and are characterised by fluid escape structures (vertical or inclined pipes and contorted internal structures) suggesting rapid deposition from turbidity currents. However, these sandstones do not show the range of features typically associated with 'classical' turbidites such as the alternation of thin sandstones and mudstones. The sandstones are in some instances interbedded with hemipelagic, generally non- or rarely bioturbated black mudstones with a similar character to those of the underlying interval with rare Planolites, Teichichnus and Zoophycos traces suggesting a relatively deep-water, quiet environmental setting. The boundary with the underlying Blålange mudstones is transitional and does not represent a sharp contact or abrupt facies change. The background mudstones become progressively more bioturbated upwards and sandstone beds appear below the boundary at 3142.87 m MD RKB (uncorrected core depth). This supports the interpretation that the Lysing Member is genetically linked to the Blålange Formation. Elsewhere in the Smørbukk Field area, seven sedimentary facies have been identified from cores within the Lysing Member (Walker unpublished report, 1998) namely, thick structureless sandstones (facies 1), sandstones with fluid escape structures (facies 2 as per 6506/12-4 core), thin bedded sandstones (facies 3), glauconitic sandstones (facies 4), bioturbated sandstones and mudstones (facies 5), dark argillaceous sandstones (facies 6) and pinstriped mudstones (facies 7). In terms of sedimentary processes, facies 1, 2 and 6 are interpreted as being deposited rapidly from turbidity currents. Somewhat controversial is the presence of glauconitic sandstones (facies 4) showing cross stratification e.g. 6506/12-5 (3160.76 m - 3165.31 m). Shanmugam et al. (1994) interpreted these units as a progradational delta front succession with tidal influence and therefore of shallow water affinity that may have "slid into deep water". However, the critical association of these glauconitic sandstones with hemipelagic pinstriped black mudstones and the lack of any basal slide plane led Walker (1998) to suggest that these cross stratified sandstones were emplaced by episodic bottom traction currents (oceanic contourites) in a deep, basin floor setting. These units yielded a microfauna dominated by deep water agglutinated foraminifera.

The Lysing Member is cored in the additional reference well 6506/3-1 located in the north-western part of the Dønna Terrace. In this core, the Lysing Member is represented by a heterolithic succession characterised by two facies: fine grained glauconite rich sandstones (equivalent to facies 4 of Walker) and pin-striped mudstones (facies 7 of Walker). The sandstones are typically thin (1-10 cm) beds with sharp bases, with massive to normal grading or ripple internal structures and Planolites dominating the moderate bioturbation (BI 3), whereas the pinstriped mudstones contain Zoophycos traces. The sandstones are interpreted as representing glauconite-rich, amalgamated low density turbidites. The lack of mudclasts and the sandstones association with pin-striped mudstones representing the background sedimentation suggest that these are the distal or lateral parts of a submarine fan lobe. The pin-striped mudstones may represent low density turbidity currents or reworking by weak ocean bottom currents in an outer shelf setting. The common glauconite is probably derived by re-deposition from a shallower marine setting. According to seismic interpretation, the Lysing sandstones in this well represent part of a lateral pinch-out of a large deep-marine system.

In terms of its biofacies character, the Lysing Member lies within the Marginotruncana zone of Gradstein et al. (1999) within an interval of sparse agglutinated foraminiferal assembages that generally lack calcareous taxa. They inferred a depositional setting of restricted bottom conditions in a bathyal setting. They suggested a degree of hydrodynamic sorting of test shapes during sediment transport into deeper water and some diagenetic loss of (calcareous) taxa due to dissolution. The common pyritised diatoms and radiolarians testify to normal marine salinity and bathyal conditions. These interpretations agree with the observations in the type and reference well cores and provide support to the sedimentological interpretation of a deep marine setting for the Lysing sandstones.

The sediment source direction of the Lysing sandstone is still controversial. It is likely that the sandstones were multi-sourced, being derived from easterly i.e. from the Trøndelags Platform, north-easterly and westerly directions i.e. east Greenland margin. This is the focus for current studies based on heavy mineral analysis and microfossil reworking ages. Swieckicki et al. (1998) included the Lysing sands as part of their (mega) Sequence K4 and attributed the source of the sands to a response to the rejuvenated uplift of the Nordland Ridge. They noted that the main depocentre was on the Dønna Terrace and that the seismic facies evidence suggested a westerly shale out of the interval away from the Nordland Ridge.

The Lysing Member is also tentatively assigned to Coniacian sandstones north of the Trøndelags Platform e.g. 6610/3-1 although these are probably locally sourced from either the Grønøy High or directly from Norwegian mainland via the Vestfjorden Basin. Vergara et al. (2001) suggested that in the area of the Helland Hansen Arch the sediment source was probably from the east in contrast to earlier studies by Sanchez- Ferrer et al. (1999). They also suggested the Lysing sandstones in the Vøring Basin well 6607/5-1 to be sourced from the north-east as a lobe of the Någrind Syncline Fan. Well 6707/11-1 probably has a similar source direction from the north-east). Lysing sandstones on the Vema Dome e.g. 6706/11-1 are probably sourced from the north-west from the area of the Vøring Marginal High.

References

Dalland, A., Worsley, D. and Ofstad, K. 1988. A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore Mid and Northern Norway. Bulletin of the Norwegian Petroleum Directorate 4:1-65.

Fugelli, E. and Olsen, T. 2005a. Screening for deep-marine reservoirs in frontier basins: Part 1 - Examples from offshore Mid-Norway. American Association of Petrolem Geologists Bulletin 89:853-882.

Fugelli, E. and Olsen, T. 2005b. Risk assesment and play fairway analysis in frontier basins: Part 2 - Examples from offshore Mid-Norway. American Association of Petrolem Geologists Bulletin 89:883-896.

Fugelli, E. and Olsen, T. 2007. Delineating confined slope turbidite systems offshore mid-Norway: the Cretaceous deep-marine Lysing Formation. American Association of Petrolem Geologists Bulletin 91:1577-1601.

Gradstein, F., Kaminski, M.A. and Agterberg, F.P. 1999. Biostratigraphy and paleoceanography of the Cretaceous seaway between Norway and Greenland. Earth-Science Reviews 46:27-98.

Hastings, S. 1986. Cretaceous stratigraphy and reservoir potential, mid Norway Continental shelf. In: Spencer, A.M. (ed.) Habitat of Hydrocarbons on the Norwegian Continental Shelf. Norwegian Petroleum Society/Graham & Trotman, London, 287-298.

Heskestad, B., Assereto, C and Stensland, D. 2009. The Gemini case history - seismic amplitudes versus well results. Abstract. Exploration Revived Conference Bergen, March 2009, abstract volume.

Lien, T. 2005. From Rifting to drifting: effects on the development of deep-water hydrocarbon reservoirs in a passive margin setting, Norwegian Sea. Norwegian Journal of Geology 85:319-332.

Sanchez-Ferrer, F., James, S.D., Lak, B. and Evans, A. M. 1999. Techniques used in the exploration of turbidite reservoir in frontier settings - Helland Hansen licence, Vøring Basin, offshore Mid-Norway. In: Fleet, A.J., & Boldy, S.A.R. (eds) Petroleum Geology of North West Europe. Proceedings of the 5th Conference. Geological Society of London, 281- 292.

Shanmugam, G., Lehtonen, L. R., Straume, T., Syvertsen, S. E., Hodgkinson, R. J. and Skibeli, M. 1994. Slump and debris flow dominated upper slope facies in the Cretaceous of the Norwegian and northern North Sea (61-67o N): implications for sand distribution. American Association of Petrolem Geologists Bulletin 78:910-937.

Swiecicki, T., Gibbs, P.B., Farrow, G.E. and Coward, M.P. 1998. A tectonostratigraphic framework for the Mid-Norway region. Marine and Petroleum Geology 15:245-276.

Vergara, L., Wreglesworth, I., Trayfoot, M., Richardsen, G. 2001. The distribution of Cretaceous and Paleocene deep-water reservoirs in the Norwegian Sea basins. Petroleum Geoscience 7:395-408.

Walker, R. 1998. Turbidite facies and reservoir architecture: examples from the Lysing formation, Smørbukk area, Mid Norway. Internal report Norsk Hydro Research Centre. 96 pages.

home	previous page