Secondary Porosity Development in Incised Valley Sandstones from Two Wells from the Flemish Pass Area, Offshore Newfoundland

2021 ◽  
Author(s):  
John B. Gordon ◽  
Hamed Sanei ◽  
Per K. Pedersen
Keyword(s):  
Secondary Porosity ◽  
Incised Valley ◽  
Porosity Development

Diagenetic carbonate and evaporite minerals in Rotliegend aeolian sandstones of the Southern North Sea: their nature and relationship to secondary porosity development

Clay Minerals ◽  
1986 ◽  
Vol 21 (4) ◽  
pp. 443-457 ◽  
Author(s):  
K. Pye ◽  
D. H. Krinsley
Keyword(s):  
North Sea ◽  
Secondary Porosity ◽  
Southern North Sea ◽  
Carbonate Cements ◽  
Deep Burial ◽  
Reducing Conditions ◽  
Two Generations ◽  
Stage 1 ◽  
Evaporite Minerals ◽  
Porosity Development

AbstractDeeply buried (> 3·5 km) Rotliegend aeolian sandstones in the Southern North Sea Basin display a number of interesting diagenetic features including (i) zoned iron-rich carbonate cements, (ii) anhydrite, halite and baryte cements, (iii) at least two generations of authigenic illite, and (iv) significant secondary porosity created by cement and framework-grain dissolution. The creation and destruction of secondary porosity is the result of changes in porewater chemistry during burial and subsequent uplift. Three pore-fluid regimes can be identified: (1) alkaline, oxidizing conditions during shallow to intermediate burial; (2) acid, reducing conditions during intermediate to deep burial; (3) alkaline, reducing conditions during deep burial and uplift. The transition from stage 1 to stage 2 was probably caused by expulsion of waters from the underlying Carboniferous shales. The transition to stage 3 probably began when faulting associated with uplift allowed invasion by alkaline fluids derived from Zechstein sediments.

Quartz diagenesis and convective fluid movement: Beatrice Oilfield, UK North Sea

Clay Minerals ◽  
1984 ◽  
Vol 19 (3) ◽  
pp. 391-402 ◽  
Author(s):  
R. S. Haszeldine ◽  
I. M. Samson ◽  
C. Cornford
Keyword(s):  
Fluid Flows ◽  
Clay Content ◽  
Lower Jurassic ◽  
Burial History ◽  
High Permeability ◽  
Secondary Porosity ◽  
Fluid Velocities ◽  
Convective Cells ◽  
Convective Fluid ◽  
Porosity Development

AbstractThe extent of diagenesis in Lower Jurassic shoreline sandstones of the Beatrice oilfield was controlled primarily by their detrital clay content. Sandstones rich in detrital clay had low depositional permeabilities; these show preservation of detrital feldspars to the present day and have no extensive diagenetic quartz overgrowths. Sandstones poor in detrital clay had high permeabilities and show large quartz overgrowths as part of a normal sub-arkosic diagenetic sequence. Such quartz occurs preferentially below, but not above, impermeable mudstones. These low- and high-permeability features suggest that pore-fluid flow was important during diagenesis. Fluid inclusions trapped in diagenetic quartz overgrowths formed between 68° and 94°C. This silica was probably supplied in solution from the temperature-driven illitization of smectitic clays surrounding these sandstones deeper in the basin. Fluid volumes from clay dewatering, from mechanical compaction, or from influx of overlying seawater were too small to transport diagenetic silica volumes. Silica-rich fluids were probably transported up-dip by convective cells within the sandstones and authigenic quartz precipitated as these fluids cooled. This episode of quartz diagenesis could have been completed within 1·6 × 106 yr if fluid velocities were 3·1 m/yr. Similar convective fluid flows could have transported the fluids responsible for secondary porosity development and the hydrocarbons expelled from mudstones later in the basin burial history.

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