Reef trap

Fig. I. Types of natural gas reservoirs and entrapments (a) anticlinal trap (b) coral reef trap (c) stratigraphic trap (d) fault trap and (e) unconformity...

Combination tra/ s—sedimentary trap features that result from both stratigraphic and structural mechanisms. There can be many combinations for stratigraphic and structural traps. An example of such a trap would be a reef feature overlaying a porous and permeable sandstone, but in which the sequence has been faulted (see Figure 2-54). Without the fault, which has provided an impregnable barrier, the hydrocarbons would have migrated further up dip within the sandstone. 

Lagoonal Of lagoons, which are semi-isolated bodies of seawater trapped between coral reefs and volcanic islands or between the mainland and barrier islands. Seawater in lagoons tends to be hypersaline. 

Reef-Type Traps. These have accounted for some of the most important production in recent years. The reef is generally considered a type of stratigraphic trap. The reef was formed under the right combination of conditions by the remains of millions of small underwater animals. Building their limestone residences on top of those built by their ancestors, the tiny... 

Wild, C., Huettel, M., Klueter, A., Kretnb, S. G., Rasheed, M. Y. M., andjorgensen, B. B. (2004a). Coral mucus functions as an energy carrier and particle trap in the reef ecosystem. Nature 428, 66-70. 

Wild, C., Huettel, M., et al. (2004). Coral mucus as an energy carrier and particle trap in the reef... 

The differences between these reefs probably reflect differences in their structural framework and variations in wave characteristics and tidal range in the two environments. Anaerobic reactions in reef interstitial waters may not progress far if reef structures are open and well flushed. If, however, the systems are nearly closed, little fresh reactant will enter via seawater exchange and mass transfer will be limited by the reactants trapped in the reef interstitial waters. An important conclusion of Sansone s studies was that thermodynamic disequilibrium among dissolved species such as CH4 and S04 implies microzonation of chemical reactions. Microzonation resulting in slight differences in reef interstitial water compositions may account for the coexistence of different cement mineralogies in reef structures. 

Traps associated with salt intrusions are of many types (example Fig. 1.2 -1.3) limestone reefs (Fig. 1.4) can also serve as reservoir rocks and give rise to overlying traps of anticlinal form as a result of different compaction. Examples are also known in which the reservoir rock extends to the surface of the earth but oil and gas are sealed in it by clogging of the pores by bitumen or by natural cements [3], Many reservoirs can display more than one of the factors that contribute to the entrapment of hydrocarbons. 

Unassociated with unconformities (channels, bars, and reefs) Diagenetic traps (due to solution or cementation)... 

FIGURE 8 Block diagram to illustrate the diflierent types of stratigraphic traps. (A) Fossil reef limestone. (B) Coastal barrier-bar sand. (C) Sandstone infilled channel. (D) Onlap of sand above unconformity. (E) Truncation of limestone beneath unconformity. 

Multifunctional multipolymeric surfactant mixtures which can be produced from the FRRPP process are capable of efficiently recovering trapped oil from subterranean sources. A typical oil reservoir, shown in Figure 5.1.1, is an anticline (inverted-dome) rock formation wherein the oil is trapped within the open-pore rock formation from sandstone or carbonate material bound by impermeable rock on top and brine in porous rock at the bottom. Immediately above the oil bank could be a layer of natural gas at high pressure, since this formation is originally underground where the pressures could at least be that of the ground overbearing material. Other oil bank formations cited in the literature include salt formations, reefs, etc. 

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