HPHT reservoir evolution: a case study from Jade and Judy fields, Central Graben, UK North Sea

Abstract

Abstract3D basin modelling of a study area in Quadrant 30, UK North Sea was performed in order to elucidate the burial, thermal, pressure and hydrocarbon generation, migration and accumulation history in the Jurassic and Triassic high-pressure high-temperature sequences.Calibration data, including reservoir temperatures, pressures, petroleum compositional data, vitrinite reflectance profiles and published fluid inclusion data were used to constrain model predictions. The comparison of different pressure generating processes indicated that only when gas generation is taken into account as a pressure generating mechanism, both the predicted present day as well as palaeo-pressure evolution matches the available calibration data. Compositional modelling of hydrocarbon generation, migration and accumulation also reproduced present and palaeo bulk fluid properties such as the reservoir fluid gas to oil ratios. The reconstruction of the filling histories of both reservoirs indicates that both were first charged around 100 Ma ago and contained initially a two phase system in which gas dominated volumetrically. Upon burial reservoir fluid composition evolved to higher GORs and became undersaturated as a function of increasing pore pressure up to the present day situation. Our results indicate that gas compositions must be taken into account when calculating the volumetric effect of gas generation on overpressure.2

Exceptional reservoir quality in HPHT reservoir settings: Examples from the Skagerrak Formation of the Heron Cluster, North Sea, UK

“…obtained from fluid inclusions in mineral cements were used to help calibrate the model (Swarbrick et al, 2000;di Primio and Neumann, 2008). We also conducted new fluid inclusion analysis in quartz cements to further constrain palaeotemperatures.…”

Enhanced porosity preservation by pore fluid overpressure and chlorite grain coatings in the Triassic Skagerrak, Central Graben, North Sea, UK

“…Schneider & Wolf 2000) and thermal upwelling models (e.g. Swarbrick et al 2000;Carr 2003;di Primio & Neumann 2008). In this study we used the palaeo-basement heat flow and palaeo-surface temperature history published by Swarbrick et al (2000).…”

“…Pore pressures can exceed 80 MPa in the upper part of the Skagerrak Formation at depths of 4000-5000 mbsf where temperatures are in the range 166-2008C di Primio & Neumann 2008;Nguyen et al 2013). Overpressures are widespread in the Mesozoic reservoirs in the Central North Sea, a region that since the early Cretaceous has experienced almost continuous sedimentation of dominantly fine-grained lithologies (Osborne & Swarbrick 1999;Swarbrick et al 2000;Yardley & Swarbrick 2000).…”

The role of salt tectonics and overburden in the generation of overpressure in the Dutch North Sea area

“…The observed overpressures in the Jurassic reservoirs in Holm's study reach almost lithostatic pressure conditions. DiPrimio & Neumann (2008) state that the observed overpressures in the Jurassic and Triassic reservoirs in the UK sector of the North Sea cannot be calibrated by using basin modelling if only one pressure generating method (generation of HC or disequilibrium compaction) is used. Moss et al (2003) believe that stress-related mechanisms, such as sedimentary loading, and gas generation are the two dominant causes contributing to overpressures in Central North Sea basins.…”