[2]P11 North Sea Studies: A Natural Laboratory for Technical Developments

[2]P11 North Sea Studies: A Natural Laboratory for Technical Developments

Multi-disciplinary teams of geoscientists and engineers have been deployed on a series of studies in the North Sea. The purpose of these teams is to employ comprehensive data sets on projects aimed at improving our subsurface predictive capability.The results are predictive techniques which address and mitigate exploration and exploitation risks. In production, for example, a high resolution sequence stratigraphic framework has been modelled for the Cormorant Field using 2D fluid flow simulation and these have then been compared with traditional lithostratigraphic correlations. Predictive benefits are quantifiable and substantiated by reservoir experience.In the Viking Graben most remaining exploration potential is within deep (>3500 m) high pressure, high temperature Jurassic traps. By isolating the main controls on reservoir quality, namely: facies, pore fluid type, pressure history and sedimentary provenance, the areas of highest remaining deep potential may be identified.The work has provided a hierarchy of the controls on reservoir quality in the North Sea.In the Central North Sea, an area underlain by mobile salt, defective top seal and fault seal limit Jurassic entrapment. An important pre-requisite to understanding fault and bed seal properties is accurate definition of the hydrocarbon system using pressure and geochemical data, together with regional carrier bed maps. Mechanical trap failure via hydraulic fracturing occurs at high pore pressures where the effective stress approaches zero. It is at this time, additional stresses due to buoyant salt forces affect the seal, the entire hydrocarbon charge may be lost. Predicting such sites requires accurate pressure prediction and stratigraphic forecast together with a measure of late strain across the closure.By combining specialist skills with local basin expertise and building an accurate quality-controlled database, the processes governing hydrocarbon movement, trapping and producibility can be recognized and quantified.The anticipated result is improved drilling success.APPROACH A series of detailed field studies were completed, analysing and integrating 3D seismic with densely spaced well log, core and engineering data. A better understanding of the controls on reservoir productivity and how faults control fluid movement is gained. This field information has been combined with the regional petrographic, facies, stratigraphic and rock/fluid physics records and populates a basinwide, relational data base. Analysis of these data has led to the establishment of highly constrained empirical relationships. The incorporation of a number of specialists working with explorationists has resulted in: Predictive technologies linked to an understanding of the causal

1994-05-29

Cayley, G. T.

conferencePaper

9C9XBPVX