Clay diapir

The identified characteristics of secondary hydrocarbon migration can be verified with e.g. the location and physico-chemical characteristics of known hydrocarbon accumulations (e.g. England and Mackenzie, 1989) direct and indirect observations of oil and gas seeps (direct visual observations indirect observations, such as hydrocarbon-charged sediments, pock marks, clay diapirs) and gas leakages indicated by seismic chimneys. 

Bouriak, S., Vanneste, M., and Saoutkine, A., 2000. Inferred gas hydrate and clay diapirs near the Storegga Slide on the southern edge of the Voring Plateau, offshore Norway. Marine Geology, 163 125-... 

There are maity different types of petroleum traps. They are commonly classified into five main categories and associated subcategories as shown in Table II. These will now be defined and then described in turn Stractural traps are those caused by tectonic forces in the earth s crast. They thus include anticlines and fault traps. Diapiric traps are due to density contrasts in sedimentary rocks, normaUy evaporites and overpressured clays. Stratigraphic traps are due to depositional, erosional, or diagenetic processes. 

The two rocks that can generate diapirs are the evap-orites and overpressnred clay. The evaporites commonly have a density of abont 2.03 g/cm. This is greater than that of freshly deposited sand and clay. Bnt as normal sediments compact, their density exceeds that of evaporites at about 800 m of burial. Below this depth, therefore, di-apiric deformation may be expected to commence. Movement may be initiated by stractnral forces, but can also apparently occur spontaneously. 

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