In this paper, the factors to form the zeolites in the oil-bearing Cretaceous and Tertiary systems of Hokkaido, Akita and Niigata are discussed. The following data are found at the top of each zeolite zone from the wells of the above areas. Top of the Maximum Geothermal Mudstone Cl- ion zeolite zone burial depth temperature porosity content (m) (°C) (%) (mg/l) Clinoptilolite 800-2, 150 57-69 31 4, 500-14, 000 Analcime 1, 450-3, 800 86-117 18 4, 000-13, 000 Albite 2, 000-5, 800 119-158 12 5, 300-5, 600 The reaction temperatures which begin to form zeolites in the areas are especially influenced by geothermal gradients and effective heating times (time within 15°C of maximum temperature) and/or times since sediments deposited. The relations of the reaction temperatures to geothermal gradients and effective heating times are tabulated below: Geothermal gradient Effective heating time 3°C/100m 5°C/100m 2 million 4 million years Clinoptilolite 67°C 59°C 65±3°C 60±3°C Analcime 116°C 89°C 111±8°C 95±8°C Albite 157°C 122°C 153±8°C 132±8°C Zeolites are controlled by geothermal temperatures, effective heating times and geothermal gradients, and have similar tendencies with the maturation of organic matters (e.g. vitrinite reflectance) in the sediments during diagenesis.
A multicell model was used to investigate phase behavior in the reservoir during CO2 injection. This numerical model computes the compositional changes that occur in the reservoir between the in-place oil and the injected fluid. The Peng-Robinson Equation of State was employed for these calculation. A mixture of methane, n-butane and n-decane was used as the in-place oil and CO2 was used as the injected fluid. Three injection pressures were considered, each of them correspondending to the first contact miscible, the multicontact miscible and the immiscible flooding respectively. The generation of the multicontact miscibility was discussed based on K value profiles, density profiles, composition profiles and composition histories. Distinct differences were observed among the immiscible flooding process and the multicontact miscible process.
In spite of the fact that 40% of "reservoir oils" in major oil fields of the world, or 50% of total oil of the "giant oil fields" (Moody, 1975) is in carbonate reservoirs, little worthwhile study has been published on organic matter in carbonates as effective petroleum and gas source rocks for a long time. Lately, however, its study is beginning to attract the attention of many petroleum geochemists. In this paper, the organic characteristics of carbonates as source rocks are reviewed on the basis of recent informations such as kerogen properties and its content. "hydrocarbon ratio", even predominance of n-alkane and pristane to phytane ratio in carbonates.