Print this pageIntegrated Characterization of Intra-Slope Reservoirs: Transferring Facies and Log Imaging Data to Seismic Inversion Constrained by Outcrop Analogues (Marulk Field, Offshore Norway)
Ormoy, Jorun 1; Rossi, Massimo 2; Pirera,
Francesca 2; Berto, Roberto 2; Tosoratti, Filippo 2;
Bersezio, Riccardo 3; Felletti, Fabrizio 3; Scaglioni,
Paolo 2
(1)Eni Norge AS, Stavanger, Norway. (2) Eni E&P, San
Donato, Italy. (3) Department of Earth Sciences, University of Milano, Milano,
Italy.
The Marulk Field in Block 6507/2 (PL122) is located on the Dønna Terrace, Norwegian Sea. A Cretaceous dome structure above a Jurassic horst block defines the trap The main reservoir (Lysing Fm.,Turonian-Coniacian) consists of a confined turbidite system fed from East and North-East; sandstone lobes onlap the crest of the tilted block.
The base of Lysing Fm. represents a discontinuity generated by the reactivation of the Marulk synsedimentary high; it also corresponds to a sequence boundary related to a regional basin-modification phase responsible for the increase of sand flux toward the basin.
The integration of facies, stratigraphic, high-resolution image logs and seismic inversion analyses permitted to identify the external shape of the system, the component depositional elements and their relationships with the syndepositional high. Elastic seismic attributes proved reliable in lithology and fluids definition and permitted to visualize the 3-D distribution of depositional elements. Paleocurrents from ripple cross laminations were measured using the image logs.
Along the eastern flank of the structure, two types of marine onlap are recognized: frontal onlap and lateral onlap. The high-angle (frontal) and the low-angle (lateral) oblique onlaps of turbidite lobes in an Oligocene confined slope-basin (Cengio Turbidite System - CTS, Tertiary Piedmont Basin, Italy) provide good outcrop analogues. The Marulk frontal onlap area is recognized in the North-East sector of the structural high, located in front of the main channel feeding the system, basinward of a flow-expansion zone. The major distinctive features of the frontal onlap deposits are: abrupt base, very high sand/shale ratio, quick seismic termination. The high-angle CTS onlaps show similar features: sharp-base, rapid pinch-out of sandstone bodies, pronounced increase of net-to-gross ratio and bed amalgamation towards the slope and decrease of sandstone beds thickness away from the slope. The Marulk lateral onlap area occurs in a more downcurrent sector along the South-Eastern flank of the syndepositional high. Distinctive features are chiefly: transitional base with the underlying mudstones, thickening-upward basal portion, gradual seismic termination. Comparable features characterize the low-angle onlaps above the gentle lateral slopes of the CTS analogue: gradual pinch-out, increase of net-to-gross and amalgamation ratios and moderate thickening of some sandstone beds away from the slope.
AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.