Abstract A Middle to Late Miocene compression phase has been documented along the Norwegian margin from 62°N to 68°N. Reverse faults and inversion domes are numerous on the 300 to 450 km wide central mid-Norwegian margin, but are only locally observed on the Møre and Lofoten margins. A major regression forced the coastline of the syn-tectonic Kai Formation 50–150 km west of the present coastline and a genetic link between the regression and the smaller-scale contraction structures is observed. Long wavelength (200–300 km) lithospheric bulging is suggested to explain the coastline regression at the onset of the compression phase. The position of the regressed coastline suggests that the continent -shelf transition guides the lithospheric buckling such that the thicker crust segment is uplifted. Long wavelength folding may account for additional crustal shortening along the sharp crustal transitions on the Lofoten and Møre margins. It is suggested that the Norwegian onshore domes were formed during at least two independent stages – a Middle to late Miocene compression-related uplift and later regional glacial isostatic uplift. The syn-tectonic Kai Formation fills in the depressions around the contraction-related structures and is dated as late Middle to Late Miocene. It is suggested that both the Utsira Formation and the assumed northern equivalent, the Molo Formation, were deposited after the compression event and, thus, are mainly early Pliocene in age. The Middle to Late Miocene compression phase is observed throughout the North Atlantic and the sea-level fall at the initiation and rise at the termination corresponds with significant shifts in climate.

ABSTRACT Acomputer simulation model, Facies-3D, designed to model the sedimentary processes for carbonates and siliciclastics, has been developed. The Facies-3D carbonate model simulates three-dimensional carbonate facies based on water depth and current velocity in conjunction with estimated paleotopography. It also simulates porosity changes in meteoric diagenetic settings. Input data to the simulations include parameters that define sedimentary facies, basement topography, sea level change, and original current velocity and direction. Output data include sedimentary facies, thickness, and porosity for each grid. Two simulation case studies were conducted using a depositional and diagenetic model for the Pleistocene Ryukyu Group in Irabu Island of the southern Ryukyus, southwest Japan, and another model of carbonate reservoirs of the upper Miocene Kais Formation in the Walio oil field of Irian Jaya, Indonesia. The Ryukyu Group in Irabu Island consists of two major lithofacies: (1) the coral limestone facies of a shallow shelf setting, predominant in the eastern part of the island, and (2) the rhodolith limestone facies of a deeper shelf setting, predominant in the western part. Enhancement of porosity was observed beneath subaerial exposure surfaces. The Kais reefal carbonate reservoirs in the eastern Walio field were divided into seven shallowing-upward cycles, which were correlated with sequence boundaries of a third-order or a higher order cycle. The cycles consist of the fore-reef facies in the eastern edge of the area and the back-reef facies in the central and western parts. The Kais reservoirs were affected by meteoric diagenesis. In the simulation case studies of these two depositional models, the Facies-3D carbonate model provided a close approximation to the distribution of the sediments in relation to water depth, current velocity in conjunction with paleotopography, and degree of meteoric diagenesis in relation to paleotopography and sea level change. The Facies-3D carbonate model demonstrates the potential for application as a test tool of a geologic model in a reservoir characterization in oil and gas fields.

Abstract: Luminescence microscopy is used to identify stages of cementation in petroleum reservoirs and classify the physical and chemical properties of oils and oil inclusions. The lifetime of fluorescence induced by a pulsed laser is related to the API gravity of oil and can be used to determine API gravity on microliter samples of oil or oil in inclusions. Luminescence microscopy data are combined with geological (burial history, stratigraphy, tectonics, environment of deposition) and geochemical (fluid inclusion P-T-X values, stable isotopes, trace elements, petroleum geochemistry) data to determine the timing of geological events and constrain models of diagenesis, oil migration, and reservoir prediction. This method is applied to studies of reservoir diagenesis and petroleum maturation, migration, and correlation for the Mishrif Formation, Dubai, the Kais Formation, Indonesia, the Ellenburger Dolomite, Texas, and the Great Oolite Limestone, England. In the Great Oolite Limestone, cathodoluminescence of cements shows that occurrence of zoned cements correlates with high reservoir porosity consistent with a model of porosity perservation resulting from diagenesis in a mixing zone between freshwater and marine phreatic environments. Photoluminescence of oil inclusions in cements of the Great Oolite shows that inclusions are more mature near the basin depocenter. In the Ellenburger Dolomite, Texas, several episodes of fracture development and sealing are shown by cathodoluminescence enabling a relative timing to be determined. Temperature and composition data from fluid inclusions are collected with respect to the cathodoluminescence and used to quantify the environment of cementation.

Abstract 2D and 3D seismic data from the mid-Norwegian margin show that polygonal fault systems are widespread within the fine-grained, Miocene sediments of the Kai Formation that overlie the Mesozoic/Early Cenozoic rift basins. Outcropping polygonal faults show that de-watering and development of polygonal faults commenced shortly after burial. On the other hand, the polygonal fault system's stratigraphic setting, upward decreasing fault throw and the association with fluid flow features that are attributed to de-watering of the polygonal fault systems shows that polygonal faulting and fluid expulsion is an ongoing process since Miocene times.

Abstract Along continental margins with rapid sedimentation, overpressure may build up in porous and compressible sediments. Large-scale release of such overpressure has major implications for fluid migration and slope stability. Here, we study if the widespread crater-mound-shaped structures in the subsurface along the mid-Norwegian continental margin are caused by overpressure that accumulated within high-compressibility oozes sealed by low-permeability glacial muds. We interpret 56 000 km 2 of 3D and 150 000 km 2 of 2D-cubed seismic data in the Norwegian Sea, combining horizon picking, well ties and seismic geomorphological analyses of the crater-mound landforms. Along the mid-Norwegian margin, the base of the glacially influenced sediments abruptly deepens to form 28 craters with typical depths of c. 100 m, areal extents of up to 5130 km 2 and volumes of up to 820 km 3 . Mounds are observed in the vicinity of the craters at several stratigraphic levels above the craters. We present a new model for the formation of the craters and mounds where the mounds consist of remobilized oozes evacuated from the craters. In our model, repeated and overpressure-driven sediment failure is interpreted to cause the crater-mound structures, as opposed to erosive megaslides. Seismic geomorphological analyses suggest that ooze remobilization occurred as an abrupt energetic and extrusive process. The results also suggest that rapidly deposited, low-permeability and low-porosity glacial sediments seal overpressure that originated from fluids being expelled from the underlying high-permeability and high-compressibility biosiliceous oozes.