In this paper equations of oil recovery and water-oil interface are derived for a water drive in a horizontal, cylindrical homogeneous oil reservoir by an extension of the Daalen and Domselaar's theory developed for a rectangular model. The influence of capillary forces are not taken into account. A necessary condition for the validity of the equations is that the water should underrun the oil.
Results of the cylindrical model are compared with those of the rectangular model. It is found that oil production curves of both models agree precisely when an angle between initial water-oil interface and cap rock is only 90 degrees, and that the interfaces of both models after water invasion become different shapes, respectively.

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It is an important problem to determine the pore size distribution in porous material in order to understand the mechanism of fluid flow in enhanced recovery of oil.
For the purpose, we had developed a simple apparatus to be able to measure the distribution of macro-pore radii by means of volumetric mercury displacement.
The apparatus is mainly consisted of a sample holder, a micro-burette, a monometer and a mercury reserved bulb.
Prior to the measurement, the holder with a sample and the burette were evacuated, and then the sample was immersed into mercury under the balance of zero pressure between internal and external of pore. The displacement volumes of mercury were measured by the micro-burette when the mercury was gradually subjected to varying external pressure from 0.06 atm (6×10³ Pa) to 1.6 atm (1.6×10⁵ Pa).
From the experiment of the Berea sandstones, the following results were obtained:
(1) This apparatus can be used for the measurement of pore size distribution of a rock which will be considered having a bundle of macro-pore capillary tubes larger than 47×10^-5cm in radius.
(2)The permeabilities calculated from the Burdine's equation by using the distribution function are directly proportional to the air permeabilities measured by a fundamental core analysis.

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Chemical Oxygen Demand (COD) of subsurface brine of water-soluble natural gas is higher than that of sea water. We investigated why the brine has higher value than sea water.
We adopted as samples both Narutoh gas field water and artificial brines. The latter samples contained inorganic ions such as NH₄⁺, HCO₃^-, Br^-, I^- etc. These ions are more concentrated in those samples both in Narutoh field water and in the artificial brines than in sea water.
COD of these samples were determined adopting acidic KMnO₄ method at 100°C.
As most ions tested, except halides, hardly misled the determination, they could not virtually influence on COD value.
3 halide ions interfered COD determination, leading to higher value than usual. As bromide ion as well as chloride ion could be masked with silver salt in JIS method, COD value could not be misdetermined by both ions.
To get net COD value, it was necessary to exclude iodide ion as silver iodide from the reaction system, because iodide ion was unmasked with silver salt.
Some of organic compound dissolved in the brine was considered to be another oxygen scavenger.

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The cathodoluminescence microscope, model TCL-1, equiped with a monochrometer and a highly sensitive photon-counter for spectral analysis, is devised and described. Both normal optical image and cathodoluminescence image on the same polished thin section are able to be observed alternately with the microscope. On the preliminary study, we observed the cathodoluminescence of quartz and carbonates of variable occurrences and measured the spectra. The cathodoluminescence microscope is very useful for sedimentary petrological studies, e. g., provenance of sandstone, cementation and pore structure of reservoir rocks, etc.

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