Reservoir diagenesis and hydrocarbon migration under hydrostatic palaeopressure conditions

Fluid inclusion studies from two contrasting fields in the Northern North Sea reveal hydrostatic pressure conditions during the formation of secondary quartz overgrowths which trapped both brine and petroleum inclusions. In these fields, dating of authigenic illite, part of the diagenetic sequence and broadly coeval with quartz cementation, permits comparison with modelled pressure conditions. Pressure modelling indicates the likelihood of several periods of overpressure in the past, interspersed with normal pressure. The timing of diagenesis coincides with one of these periods of hydrostatic pressure. Furthermore, as both fields are now highly overpressured, the cause and timing of overpressure generation post-date the diagenesis. A model is proposed to link the pressure history and diagenesis.

[1]  Craig M. Bethke,et al.  A Numerical Model of Compaction-Driven Groundwater Flow and Heat Transfer and Its Application to the Paleohydrology of Intracratonic Sedimentary Basins , 1985 .

[2]  A. Robinson,et al.  Duration of quartz cementation in sandstones, North Sea and Haltenbanken Basins , 1992 .

[3]  L. D. Harris,et al.  Conodont color alteration; an index to organic metamorphism , 1975 .

[4]  E. R. Verbeek,et al.  Structural Evolution of Gilsonite Dikes, Eastern Uinta Basin, Utah , 1992 .

[5]  D. M. Mann,et al.  Prediction of pore fluid pressures in sedimentary basins , 1990 .

[6]  J. Goff.  Hydrocarbon generation and migration from Jurassic source rocks in the E Shetland Basin and Viking Graben of the northern North Sea , 1983, Journal of the Geological Society.

[7]  R. Burruss.  Paleotemperatures from Fluid Inclusions: Advances in Theory and Technique , 1989 .

[8]  J. Hanor.  Dissolved methane in sedimentary brines; potential effect on the PVT properties of fluid inclusions , 1980 .

[9]  R. Haszeldine,et al.  Open and restricted hydrologies in Brent Group diagenesis: North Sea , 1992, Geological Society, London, Special Publications.

[10]  J. Marshall.  Isotopic composition of displacive fibrous calcite veins; reversals in pore-water composition trends during burial diagenesis , 1982 .

[11]  J. Thorne,et al.  Quantitative Analysis of North Sea Subsidence , 1989 .

[12]  John G. Sclater,et al.  Continental stretching: An explanation of the Post-Mid-Cretaceous subsidence of the central North Sea Basin , 1980 .

[13]  N. White,et al.  Subsidence analyses from the North Sea ‘triple-junction’ , 1993, Journal of the Geological Society.

[14]  S. Larter,et al.  The Effects of Oil Emplacement on Diagenetic Processes: Examples from the Fulmar Reservoir Sandstones, Central North Sea: Geologic Note (1) , 1992 .

[15]  I. Barnes,et al.  Precipitation of Laumontite with Quartz, Thenardite, and Gypsum at Sespe Hot Springs, Western Transverse Ranges, California , 1981 .

[16]  W. Narr,et al.  Origin of Reservoir Fractures in Little Knife Field, North Dakota , 1984 .

[17]  P. Ungerer,et al.  Are numerical models useful in reconstructing the migration of hydrocarbons? A discussion based on the Northern Viking Graben , 1991, Geological Society, London, Special Publications.

[18]  M. Giles,et al.  K-Ar dating of illites in Brent Group reservoirs: a regional perspective , 1992, Geological Society, London, Special Publications.

[19]  O. Walderhaug.  A Fluid Inclusion Study of Quartz-Cemented Sandstones from Offshore Mid-Norway--Possible Evidence for Continued Quartz Cementation During Oil Emplacement , 1990 .

[20]  S. Burley,et al.  Timing diagenesis in the Tartan Reservoir (UK North Sea): constraints from combined cathodoluminescence microscopy and fluid inclusion studies , 1989 .