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Porosity Prediction in Quartz-Rich Sandstones: Middle Jurassic, Haltenbanken Area, Offshore Central Norway

S. Bloch, R. K. Suchecki, J. R. Duncan, K. Bjorlykke

Reduction of primary porosity by mechanical compaction and pressure solution is the main control of reservoir quality in the upper member of Middle Jurassic, quartz-rich (Q > 75%) sandstones in the Haltenbanken area. The extent of secondary porosity and permeability generation is limited to volumetrically minor alteration or dissolution of feldspars. The effects of pressure solution, exhibited by petrographic textures, vary widely. The extent of significant porosity reduction by pressure solution was determined to be a function of the residence time of the sandstones within the "pressure-solution domain," a region roughly below 1,500-m burial depth in the Haltenbanken area. Porosity prediction curves were developed from plots of measured porosity and an integration of he burial history within the pressure-solution domain (i.e., the product of burial time and depth between 1,500 m and present-day depth). The curves, both for compacted and decompacted profiles, were constructed using data from six wells in the Haltenbanken area. Porosities of three wells drilled after the porosity prediction approach was developed, closely correspond to the predicted porosity values.

Average permeability also can be predicted relatively accurately because of the good correlation between porosity and permeability in these quartz-rich sandstones. The porosity-burial history relationship can be applied to porosity predictions prior to drilling in the Haltenbanken and related areas using burial histories interpreted from seismic-stratigraphic analysis.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.