ABSTRACT This chapter presents an overview of the geochemical composition of 15 heavy oils from producing and exploration wells onshore Suriname aiming to determine the organic facies generating them. The inferred facies are integrated with the geologic framework of the Guyana Basin in a two-dimensional basin model to further assess their thermal history in the shelfal area of the basin. Detailed biomarker and carbon isotope geochemistry indicates that two compositional groups occur onshore Suriname. Oils produced from Cenozoic reservoirs (Group A) possess compositional attributes characteristic of oils generated from a distal marine shale. Their composition suggests the Upper Cretaceous shales of the Canje Formation as their possible source. In contrast, oil shows in the Upper Cretaceous strata (Group B) have biomarker relationships diagnostic of oils derived from a proximal marine depositional system rich in terrestrial organic matter. Uncertainty exists as to the age and spatial distribution of this organic facies. A Late Jurassic–Early Cretaceous age is provisionally proposed. Oil-maturity estimates indicate generation from source rocks at the mid-oil window for all the sample set. Thermal maturity modeling suggests that generation from the Upper Cretaceous (Canje Formation) and Upper Jurassic–Lower Cretaceous source rock facies started in the early Oligocene. The Upper Cretaceous clay-rich facies has only transformed 30% of its potential in the shelf with expulsion starting in the middle Pliocene. Accordingly, entrapment of Canje-generated oils in the onshore Tambaredjo trapping structure is suggested to be younger than the middle Pliocene. The Upper Jurassic–Lower Cretaceous facies in most of the shelf area has nearly reached peak generation with expulsion commencing in the late Miocene given the input parameters. In the shelf area, updip migration of hydrocarbon expelled from these two organic facies is dominant and terminates around the onshore Tambaredjo area.

Abstract The northern Dutch offshore is an area that has seen less hydrocarbon exploration activity than other areas of The Netherlands. Acquisition of a new regional 3D seismic dataset allowed further testing and re-evaluation of established geological concepts in this area. It is recognized that the presence and movement of Upper Permian Zechstein evaporites had a major impact on depositional patterns in Mesozoic sediments, structural development and hydrocarbon migration. As such, this study looks specifically at the role of salt tectonics in tectonosedimentary development. To assess this salt tectonic evolution within its structural context, a restoration of the Step Graben and Dutch Central Graben was performed. It follows that depositional patterns are closely linked to the nature of salt structure movement and the timing of regional tectonism. For example, during Late Triassic rifting, salt pillows developed and sedimentation focused away from salt structures into depocentres along regional fault trends. Restoration results show that this interplay between salt movement and tectonism is needed to accommodate the sedimentation patterns associated with the formation of the Step Graben and Central Graben during the Triassic and Jurassic, and later during Late Cretaceous and Cenozoic inversion tectonics.

Abstract The reservoir rock of the Schoonebeek oil field is formed by the sandstones of the Bentheim Sandstone Member. The sedimentology and depositional environment of this sandstone have been extensively studied, but the relationship between the geometry of the sandstone and tectonic activity in the Schoonebeek area remains poorly understood. 355 boreholes and two three-dimensional (3D) seismic surveys were used to study this relationship. An eroded zone in the west of the field and an area where the original depositional thickness is still intact were identified. Using the ezValidator software package it can be seen that uplift of a local anticline played an important role in the erosion of the sandstone. Deposition of the sands of the Bentheim Sandstone Member and the overlying Vlieland Sandstone and Claystone formations occurred on an unstable changing palaeotopography, whereby the instability was probably driven by halokinetic movement of the underlying Late Permian Zechstein salt. Syndepositional tectonic movements affected local thickness variations in the Bentheim Sandstone Member in the west of the field, leading to westwards thinning.