Main objective and subgoals
Frontiers of knowledge and technology
Research tasks, approach, methods and international co-operation
   Task A
   Task B
   Task C

A PETROMAKS KMB by the University of Tromsø (UiTø)


Main objective and sub-goals.
The main objective of the project is to develop depositional models for Cenozoic sandy systems in order to better identify and quantify factors critical to reservoir rock occurrence and distribution. The main objective will be achieved through: development of depositional models of Cenozoic sandy systems on the Barents Sea margin from the study of three selected areas (Fig. 1). The models will be based on interpretation of 3D and 2D seismic data. Results on the nature, origin and development of a modern sandy system in a nearby area, on the continental margin of northern Norway will be integrated.

Fig. 1

Figure 1: Bathymetric map of the Barents Sea including the outline of the three study areas; A (Task A, see below), B (Task B), and C (Task C). The location of the Andøya Canyon (Figure 5) is indicated.

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Frontiers of knowledge and technology.
Hydrocarbons of the glacigenic Late Cenozoic succession offshore Norway has so far been of interest in exploration mainly as a geo-hazard or as indication of deeper prospective reservoirs (e.g. Heggeland, 1998). A recent gas discovery in the North Sea is located at just 160 m sub-bottom depth. The reservoir consists of Pliocene glacial sandstone capped by glacial diamicton; it represents a milestone in exploration of the North Sea (Carstens, 2005), and highlights the potential for commercially recoverable hydrocarbons in the thick succession of glacigenic sediments offshore Norway.

Fig. 2 Fig. 3

Figure 2: A) Map showing location of 3D area in Sørvestsnaget Basin (red box) in the Barents Sea (the dense grid of 2D seismic lines in the western Barents Sea is not included). The orange line in the 3D box shows location of the geoseismic profile of Figure 2B, and the white circles indicate location of the wells. Black lines indicate structural elements. The bathymetry is from the International Bathymetric Chart of the Arctic Ocean (Jakobsson et al. 2000). B) Geoseismic interpretation of 3D-seismic inline NH9803-2936 in the Sørvestsnaget Basin (location indicated by white line in Figure 2A). The chronology of the pre-Pliocene succession is based on results from well 7216/11-1S (from Ryseth et al. 2003). Modified from Andreassen et al. 2007a.

The hydrocarbon potential of the Cenozoic of the Barents Sea Margin has so far hardly been explored. The existence of significant Middle Eocene reservoir sandstones is documented from wells 7216/11-1S and 7316/5-1 (Fig. 2; Ryseth et al. 2003; Knutsen et al. 2000). It was also recently documented that sandy sedimentary systems occur commonly within the Plio-Pleistocene successions (Andreassen et al. 2007a). This includes straight and meandering channels and attached depositional lobes. Seismic phase-reversed reflection segments of anomalously strong amplitude indicate that many of these systems are gas-bearing (Figs. 3 and 4).

 Fig. 3b

Fig. 3: (a) Detail of a seismic profile from the Sørvestsnaget Basin 3D data set. (B) Root-mean-square (RMS) amplitude of the volume indicated by the shaded zone of (a).  High-amplitude anomalies are associated with sandy, fan shaped debris flow deposits (for further details, see Fig. 4). Modified from Andreassen et al. 2007a.

Fig. 4

Fig. 4: (a) Left: vertical seismic section showing inferred gas anomalies (yellow). Right: map view of Root Mean Square seismic amplitude of the shaded zone of seismic profile. (b) Model sketches showing vertical seismic section (left) and plan-view images (right) of sandy fan-shaped debris-flow deposits. (c) Model sketches illustrating development of gas accumulations: 2) differential compaction causing apparent uplift of Marginal High and faulting 3) gas migration from deeper reservoirs (indicated by small red arrows). Blue lines indicate flat spots of gas reservoirs. The yellow lines on the map view images indicate locations of the vertical profiles to the left. Modified from Andreassen et al. 2007a.

The main focus of this study will be to develop depositional models for the sandy glacigenic systems of the Cenozoic sediment wedge of the Barents Sea Margin. The investigation will be based on a semi-regional industry 3D seismic data set, regional 2D seismics and well information, most of which is already in the data base at the University of Tromsø. With dense sampling and 3D migration techniques, 3D seismic data opens new avenues to seismic interpretation, with detailed plan-view images of depositional environments, structural features, distribution patterns of different lithologies, and their changes in space and time.

The seismic data sets provide information of part of these systems only, because of their limited areal extent. In order to obtain more details on the sand distribution and its controlling factors, the results from a modern system will be integrated. Studies of low-latitude systems have shown the advantages of using modern analogues for petroleum geology (Piper and Normark, 2001). Here we will focus on a nearby turbidite system in the Lofoten Basin, Norwegian Sea; the Andøya Canyon - Lofoten Basin Channel. This system can be followed from source to sink, the sediment source area is a prominent canyon on the continental slope (Laberg et al. 2007) (Figure 5). From its mouth at the base of the slope a channel continues for about 200 km into the deepest part of the Lofoten Basin where sandy turbidites have been found (Laberg et al. 2005).

Fig. 5

Figure 5: 3D-image of the Andøya Canyon (looking south) based on multibeam echo-sounder data. From Laberg et al. 2007. See Figure 1 for location of the canyon.

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Research tasks, approach, methods and international co-operation

Task A
The Cenozoic Barents Sea margin and the study aims
Thick successions of late Cenozoic sediments are present along the western Barents Sea
continental margin; and the Sørvestsnaget Basin study area (Fig. 1) contain a 3-4 km thick and relatively complete Cenozoic succession (Fig. 2). The existence of significant Middle Eocene reservoir sandstones was documented in wells 7216/11-1S and 7316/5-1 (Ryseth et al. 2003; Knutsen et al. 2000). New analyses of the 3D-seismic data from the Sørvest-snaget Basin reveal that gas accumulations occur commonly within the 2-3 km thick stratigraphic column of the Plio-Pleistocene glacigenic sediments. The association of inferred Plio-Pleistocene gas accumulations and migration pathways with underlying polygonal fault systems and deeper-seated faults indicates upward migration of a mixture of fluids from pore-fluid-dewatering and deeper thermogenic hydrocarbons from early Tertiary reservoirs or older (Andreassen et al. 2007a).

Research approach and methods
The objective is, based on 3D- and 2D seismics and well information, to study the Cenozoic paleoenvironment of the Sørvestsnaget Basin, with special focus on development of sandy systems. Issues that will be addressed are:

      1. where are the sandy deposits located,
      2. what is their geometry, architecture and volume,
      3. how and why was the sand transported into the basin,
      4. what characterise the Cenozoic depositional environment of the Barents Sea and how does it compare with the Norwegian and north-western UK margin


The Sørvestsnaget 3D data set is strategically located in an area with a thick succession of Cenozoic sediments (Figure 2), and will be the main database for the investigations. Earlier studies of the late Cenozoic sediments and environments of the Barents Sea margin were based on analysis of 2D reflection seismic profiles (e.g. Vorren et al. 1991). 3D seismic data open new approaches to geological interpretation, allowing amazingly detailed imaging of depositional environments and structural features (e.g. Figures 3 and 4; Andreassen et al. 2007b), and better and more precise understanding of lithologic distribution patterns and enhanced prediction of reservoir, source and seal facies (Posamentier, 2004). Volumetric attributes of seismic intervals will provide additional insights into the sedimentary environments and their changes in space and time. A new method integrating multiple attributes and neural networks (e.g. Rafaelsen et al. 2003; Ligtenberg 2005) will be used for automated recognition of 3D-seismic facies and fluid migration pathways. A dense grid of 2D seismic data will be used to obtain regional overview, and for correlation with other studies and wells.

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Task B
The Andøya-Lofoten system and the study aims
Located on the northern Norwegian continental slope the Andøya Canyon (Figures 5 and 5) represents a 30 km long, up to 20 km wide and 1100 m deep incision as shown from recent multibeam echo-sounder mapping. A deep-sea channel, the Lofoten Basin Channel, extends about 200 km beyond the Andøya Canyon from the base of the Norwegian continental slope to the abyssal plain of the Lofoten Basin (Figure 5). (Laberg et al. 2005).

Studies of selected parts of the modern system, the Andøya Canyon – Lofoten Basin Channel will focus on:

      1. Where are the turbidites deposited, and what is the composition and geometry of the deposits?
      2. What are the age, frequency and volume of the turbidites?
      3. How and why are sediments remobilized from the source area into the deep sea?
      4. How was the turbidite emplacement controlled by external factors as sea-level variations and paleo-climate?

Fig. 6

Figure 6: Part of side-scan profile MAKAT-85 (30 kHz) across the lower part of the Andøya Canyon (and corresponding sub-bottom profile) showing the coarse-grained sediment wave field occupying about 50 % of the canyon floor in this area. A well-developed right-hand levee is also seen. (From Laberg et al. 2005).

Research approach and methods
Based on newly acquired multibeam echo-sounder data (Figure 5) including backscatter data together with high-resolution seismic records, a morphologic and seismostratographic analysis of the Andøya Canyon will be undertaken. This in order to identify the turbidite source areas and how sediments are brought into the canyon. To study the sandy deposits in the deep sea a new survey will jointly be conducted with prof. Ivanov at Lomonosov Moscow State University. The Russian research vessel Professor Logachev will be used to collect new side-scan and high resolution seismic from selected parts of the system including the depositional lobe at the channel mouth, the channel, channel levee and the source area. These data will form the basis for the acquisition of gravity core samples for sedimentological and chronostratigraphical studies.

Core data (two long cores, one from the depositional lobe, and the other from the channel levee) will be collected using the new Calypso corer of the Institute of Marine Sciences/ University of Bergen research vessel G.O. Sars by prof. Haflidi Haflidason. An initial data set based on which the core sites can be identified already exists from the Lofoten Basin (Laberg et al. 2005; Haflidason et al. 2007).

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Task C
The northern Barents Sea margin and the study aims
On the northern Barents Sea continental margin, very little is known on the Cenozoic paleoenvironment including the occurrence of sandy systems. However, in a recent paper by Geissler and Jokat (2004) the sediment thickness on the outer shelf was for the first time estimated from multichannel seismic. The thickness is up to 3.5 km, comparable to the western Barents Sea (e.g. Vorren et al. 1991) and includes progradational systems in front of the shelf troughs as well as more irregular slope segments (Geissler and Jokat, 2004). To the west of our study area (see Figure 1, Area C), the continental slope was affected by a giant submarine landslide (Vanneste et al. 2007). Task C will be a pilot study of a selected part of the northern Barents Sea margin (see Fig. 1).

Data compilation.

      1. We will have access to unpublished multichannel seismic acquired by the Norwegian Petroleum Directorate (NPD) ( H. Brekke, NPD).
      2. We will compile and utilize available Russian seismic data.

Study aims.

      1. Establish a sequence stratigraphic framework,
      2. Describe and discuss the geometry, seismic facies and volume of the identified sequences,
      3. Elucidate on the Cenozoic paleoenvironment of the northern margin,
      4. From the seismic data available and by comparison with the western Barents Sea results, can we identify sandy systems and what are their characteristics?

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