Читать книгу Acoustic and Vibrational Enhanced Oil Recovery - George V. Chilingar - Страница 14

Under the influence of increasing overburden pressure and geothermal temperature, kerogen in argillaceous sediments will generate petroleum hydrocarbons by thermal decomposition. The chemical process of generation of oil has become well established (Welte, 1972 [37]). Many geologists believe that carrier water is necessary for the primary migration of oil (Hedberg, 1964 [16]). They consider that carrier water and oil migrate in the form of solution and/or emulsion. Interlayer water of montmorillonite released by transformation to illite during the late stage of diagenesis was considered to be essential for petroleum migration (Powers, 1967 [25]; Burst, 1969 [8]; Perry and Hower, 1972 [24]). On the other hand, Aoyagi and Asakawa (1980) [2] concluded that both the interlayer and interstitial water expelled during the middle stage of diagenesis were responsible for oil migration. On the other hand, McAuliffe (1966) [23] has objected to these opinions on the basis that oil is only very slightly soluble in water. Also, some geologists have favored the migration theories based on the movement of oil and gas due to the capillary phenomena, buoyancy effect, and gas expansion, which are generally independent of the movement of water (Dickey, 1975 [12]). Some migration of oil could also occur in a gaseous form (Chilingar and Adamson, 1964 [9]).

Based on extensive observations, shales composed of non-expandable clays such as kaolinite and illite did not act as source rocks, because of the absence of water necessary to push out the oil (Chilingar and Knight, 1960 [11]; Aoyagi et al., 1975 [4]). Also, many undercompacted (overpressed) shales did not act as source rocks, because compaction mechanisms were not operative to squeeze the oil into the reservoir rocks.

It is necessary to establish what conditions existed during the primary migration of oil (from the source rocks to reservoir rocks) compared to those during the secondary migration of oil (during production) to make the former so much more efficient. Several possible explanations are presented below. Among them are (1) seismic activity (earthquakes), (2) intense electrokinetics, (3) Earth tides, (4) compaction, and (5) migration in a gaseous form.