Sedimentology and sequence stratigraphy of the thistle field, northern north sea

Reynolds, Tony

doi:10.1016/s0928-8937(06)80071-8

Cited by 12 publications

(15 citation statements)

References 7 publications

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“…This interpretation is made on the basis of stacked fining-upwards units, some with erosive bases, of fine to rarely coarse-grained sandstones with various types of cross bedding and ripple laminations (Parry et al 1981;Brown & Richards 1989;Van Wagoner et al 1993). A similar origin has been suggested for the Thistle Field on the basis of poorly sorted, stacked fining-upward units with moderate or low-angle cross-stratification/plane parallel lamination, and the absence of marine trace fossils (Reynolds 1995). Importantly, Reynolds (1995) noted the presence of several marine trace fossils attesting a high-energy marine environment in the upper part of the Etive Formation and attributed this to an increasing marine influence in the fluvial channels.…”

Section: Fluvh~l-dominated Environmentssupporting

confidence: 54%

“…A similar origin has been suggested for the Thistle Field on the basis of poorly sorted, stacked fining-upward units with moderate or low-angle cross-stratification/plane parallel lamination, and the absence of marine trace fossils (Reynolds 1995). Importantly, Reynolds (1995) noted the presence of several marine trace fossils attesting a high-energy marine environment in the upper part of the Etive Formation and attributed this to an increasing marine influence in the fluvial channels. Elliott (1989) noted that channel sandstones are extremely common in the lower part of the Etive Formation, and interpreted these deposits in terms of a braid-plain system, noting that as being atypical of a wave-dominated system.…”

Section: Fluvh~l-dominated Environmentssupporting

confidence: 54%

“…However, literature review shows that the more detailed subenvironmental interpretations vary greatly depending on the areas studied; some of these are well-documented and backed up by core-descriptions, others are not. Some of the more detailed sedimentological analyses are given by Daws & Prosser (1992), Scott (1992), Johannessen et al (1995), Olsen & Steel (1995) and Reynolds (1995).…”

Section: Etive Depositional Environmentsmentioning

confidence: 99%

“…For example one of the most common facies of the Etive Formation, stacked fining-upward units with lowangle trough cross-stratification commonly associated with plane parallel laminated sandstones, has apparently been variably interpreted as (i) the product of storm-waves and fairweather currents on the upper shoreface (Olsen & Steel 1995), (ii) evidence of fluvially influenced channels (Reynolds 1995) or (iii) as tidal channel-fill sandstones (Daws & Prosser 1992). Consequently, the sharp-based nature of some of the fining-upward units within the Etive Formation (especially at its base) has variously been taken as proof of the importance of erosion by autocyclic processes related to longshore troughs, bars and rip channels on a normally prograding upper shoreface (Jennette & Riley 1996) as evidence of the importance of tidal channel incision (Scott 1992) or of distributary channel erosion (Livera & Caline 1990;Daws & Prosser 1992).…”

Section: Uncertainty In Facies and Surface Interpretationsmentioning

confidence: 99%

“…In terms of sequence stratigraphy, the origin of erosion surfaces, abrupt grain-size changes and unusual vertical facies changes, have been attributed to: (1) major basinward shifts of the system and the forced progradation of alluvial plain (Van Wagoner et al 1993;Reynolds 1995) or braidplain systems (Elliott 1989) across the area which previously had been the shoreline, (2) local development of incised valleys (Jennette & Riley 1996), (3) increased accommodation space to sediment supply ratio, during intervals of more rapid rise of relative sea level or when the system prograded into deeper water to the north (Olsen & Steel 1995) or (4) minor forced regression alternating with transgressive episodes (Olsen & Steel 1995).…”

mentioning

confidence: 99%

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The significance of the Etive Formation in the development of the Brent system: distinction of normal and forced regressions

Olsen

Steel

2000

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Recent sequence stratigraphic debate on the Brent system have focused on the interpreted nature of the progradational trajectory (horizontal, slightly upwards or downwards) of the shoreline (Rannoch/Etive Formations) through time, as this gives a direct measure of how late Aalenian-Bajocian relative sea level changed during regression. Early interpretations emphasized the unified shallowing-upward nature of the Rannoch-Etive-Ness depositional system, and implicitly accepted a uniform shoreline progradation, i.e. a shoreline trajectory that was horizontal or slightly rising, implying a stable or slightly rising relative sea level. No irregularities of the trajectory were noted, and unusual shifts in facies, grain size etc. were normally related to autocyclic processes.More recent work has suggested that in some instances there is evidence for more irregular shoreline progradation at certain times, and for fall(s) in relative sea level and forced regression. This evidence comes from incised valleys and deep erosion/subaerial exposure surfaces from the landward (Etive-Ness boundary) and basinward (Rannoch-Etive) reaches of the Brent system respectively. However, it is currently unclear if any of these downshift surfaces recognized in the strandplain/coastal plain and shoreface environments are in time-equivalent strata.Current debate is mostly handicapped by a lack of agreement on the origin and depositional facies of the Etive Formation. There is significant debate about the relative amounts of fluvial, tidal and wave influence detected in the strata of this formation, with some authors arguing for a dominance of fluvial distributaries and mouth-bar deposits, whereas others propose either tidal-channel and inlet deposits or wave-dominated shoreface and strandplain settings. The stratigraphy is impacted by this disagreement. The character and sharp base of the Etive Formation can be argued to be consistent with normal shoreline processes, where wave or tidal conditions can produce significant erosion in the shoreface, without the necessity of any forced regression. Other interpretations, particularly where the Etive Formation is seen in terms of fluvial facies and processes, require a significant basinward shift of the shoreline to explain the Rannoch-Etive superposition, and a fall of sea level to cause the erosive boundary between the two formations.However, there is now ample evidence, including new evidence presented here, that both of the end-member scenarios for the progradation of the Brent system are incorrect. The notion that the overall progradation was entirely a product of normal regression, during stable and/or slightly rising relative sea level, is negated by local evidence of incised valleys, of subaerial exposure and plant growth in lower shoreface strata in the Rannoch Formation, and of repeated erosion surfaces with coarse-grained lags at the base of the Etive Formation. On the other hand, the idea of continuous sea level fall or of a single, late-stage fall, such that there was regional valley inc...

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Section: Fluvh~l-dominated Environmentssupporting

confidence: 54%

Section: Fluvh~l-dominated Environmentssupporting

confidence: 54%

Section: Etive Depositional Environmentsmentioning

confidence: 99%

Section: Uncertainty In Facies and Surface Interpretationsmentioning

confidence: 99%

mentioning

confidence: 99%

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The significance of the Etive Formation in the development of the Brent system: distinction of normal and forced regressions

Olsen

Steel

2000

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Influence of reservoir oil charging on diagenesis and reservoir quality: An example from Dunlin Reservoir Sandstones, East Shetland Basin, North Sea, UK

Okunuwadje,

Ogbe,

Odokuma‐Alonge

2023

Geological Journal

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The sandstone facies from two reservoir blocks (extensional fault walls) of the Dunlin Field have been studied to evaluate the impact of the reservoir charge history on the diagenesis and reservoir quality of these sandstones. The study has identified seven main reservoir sandstone facies (D1–D7) from the reservoir crestal block (oil leg) to the flank block (water leg). These sandstone facies exhibited similar diagenetic patterns, controlled by their depositional parameters, hence having the same porosity and permeability values in both reservoir blocks (legs) until hydrocarbon charging in the Late Cretaceous‐Pliocene. The burial and thermal model indicates that these reservoirs were charged at a temperature of 60–75°C during the 80–50 Ma and 95–100°C during the 10 Ma to Present, and significantly controlled the mesodiagenetic output, notably illite, and quartz authigenesis. The reservoir oil leg recorded a higher amount of recovered bitumen (ca. 95%) than the water leg (ca. 5%), indicating that hydrocarbon charging of the sandstone reservoir was progressive rather than instantaneous, first filling the water leg (palaeo‐oil leg). Subsequent leak‐off depleted this reservoir block and remigrated to fill the reservoir leg (palaeo‐water). The fluctuating oil charging and leakage between these two reservoir fault blocks modulated diagenetic alteration of these reservoir sandstones; hence is the cause of the minor disparity in porosity values between these reservoir legs contrary to the wide variation between conventional reservoir oil‐ and water‐legs distinguished by hydrocarbon emplacement with no such complex history. This study, therefore, demonstrates the importance of evaluating the depositional and diagenetic controls on reservoir quality and charging of hydrocarbon‐bearing sandstones for optimum oil production and recovery in clastic depositional settings.

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Shoreface pinch-out style on the front of the brent delta in the easterly tampen spur area

Olsen

Steel

1995

Norwegian Petroleum Society Special Publications

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Sedimentology and sequence stratigraphy of the thistle field, northern north sea

Cited by 12 publications

References 7 publications

The significance of the Etive Formation in the development of the Brent system: distinction of normal and forced regressions

The significance of the Etive Formation in the development of the Brent system: distinction of normal and forced regressions

Influence of reservoir oil charging on diagenesis and reservoir quality: An example from Dunlin Reservoir Sandstones, East Shetland Basin, North Sea, UK

Shoreface pinch-out style on the front of the brent delta in the easterly tampen spur area

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