Late Quaternary sedimentation on the Mid-Atlantic Reykjanes Ridge: clay mineral assemblages and depositional environment

1996 ◽  
Vol 85 (3) ◽  
pp. 525-535
Author(s):  
B. Gehrke ◽  
K. S. Lackschewitz ◽  
H.-J. Wallrabe-Adams
Keyword(s):  
Clay Mineral ◽  
Depositional Environment ◽  
Late Quaternary ◽  
Reykjanes Ridge ◽  
Mineral Assemblages

Clay mineralogy of onshore UK Carboniferous mudrocks

Clay Minerals ◽  
2006 ◽  
Vol 41 (1) ◽  
pp. 395-416 ◽  
Author(s):  
D. A. Spears
Keyword(s):  
Clay Mineral ◽  
Depositional Environment ◽  
Volcanic Ash ◽  
Clay Mineralogy ◽  
Source Rocks ◽  
Burial Diagenesis ◽  
Geographic Variations ◽  
Factors Affecting ◽  
Mineral Assemblages ◽  
Clay Rocks

AbstractThe Carboniferous in Britain is diverse and this is reflected in the clay mineral assemblages. Several factors affecting the assemblages are identified including climate, rates of weathering and erosion, source rocks in the hinterland, preservation of palaeosols, whether the source rocks are nearby or distant, sorting during transportation, the presence of altered volcanic ash-falls in the depositional environment and the extent of burial diagenesis. There are temporal and geographic variations in the clay mineral assemblages in the mudrocks as a result of these controls. There are also clay-rich rocks that differ from the normal mudrocks and a knowledge of the clay mineralogy of these is a necessary prerequisite to a full understanding of their origins. Mudrocks falling in this category, and described below, include bauxitic clays, flint clays, fragmental clay rocks, tonsteins and K-bentonites and various palaeosols.

Depositional Environment Drive as Overpressure Generation: Study Case in “Gap” Field, North West Java Basin

2020 ◽  
Author(s):  
A., C. Prasetyo
Keyword(s):  
Clay Mineral ◽  
Depositional Environment ◽  
Mineral Content ◽  
Hydrocarbon Generation ◽  
Well Test ◽  
Burial History ◽  
The South ◽  
North West ◽  
The North ◽  
Geological Processes

Overpressure existence represents a geological hazard; therefore, an accurate pore pressure prediction is critical for well planning and drilling procedures, etc. Overpressure is a geological phenomenon usually generated by two mechanisms, loading (disequilibrium compaction) and unloading mechanisms (diagenesis and hydrocarbon generation) and they are all geological processes. This research was conducted based on analytical and descriptive methods integrated with well data including wireline log, laboratory test and well test data. This research was conducted based on quantitative estimate of pore pressures using the Eaton Method. The stages are determining shale intervals with GR logs, calculating vertical stress/overburden stress values, determining normal compaction trends, making cross plots of sonic logs against density logs, calculating geothermal gradients, analyzing hydrocarbon maturity, and calculating sedimentation rates with burial history. The research conducted an analysis method on the distribution of clay mineral composition to determine depositional environment and its relationship to overpressure. The wells include GAP-01, GAP-02, GAP-03, and GAP-04 which has an overpressure zone range at depth 8501-10988 ft. The pressure value within the 4 wells has a range between 4358-7451 Psi. Overpressure mechanism in the GAP field is caused by non-loading mechanism (clay mineral diagenesis and hydrocarbon maturation). Overpressure distribution is controlled by its stratigraphy. Therefore, it is possible overpressure is spread quite broadly, especially in the low morphology of the “GAP” Field. This relates to the delta depositional environment with thick shale. Based on clay minerals distribution, the northern part (GAP 02 & 03) has more clay mineral content compared to the south and this can be interpreted increasingly towards sea (low energy regime) and facies turned into pro-delta. Overpressure might be found shallower in the north than the south due to higher clay mineral content present to the north.

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