The natural cases are occurred geologically in the following formations: 1) The Cretaceous formations. (Hokkaido) 2) The Tertiary formations. a. The oil fields. (Hokkaido, Akita, Yamagata, Niigata, Shizuoka and etc.) b. The gas fields. (Chiba, Miyazaki) 3) The Quarternary formations. (Hokkaido, Yamagata, Niigata, Suwa, and other basin plains.)
The gas reservoir has extremely high maximum efficient rate, and the characteristic feature is containing one phase of water nearly saturated with gas except small proportion of free gas bubbles. The sand of reservoir is very loose containing high percentage of fine grain sand and causes remarkable sand troubles. This is one of the most important technical problems to be solved. The better location of gas wells is on the structurally lower synclinal area, because the content of methane is also higher than those of structurally higher area.
Natural gas at the eastern districts, Chiba, occurrs in the tertiary sediments with salt water. Gas reserves in the sand beds with salt water. The geological structure of the gas-bearing beds are monoclinal dipping north-westward gently. The Otaki Natural Gas Co. Ltd. is exploiting the gas field to produce gas about 13000m3 per day, and it will be increased in the near future by the more active exploration.
Natural gas occurrs in the Tertiary marine sediments at the southern Miyazaki. Gas contains methane in high Percentages. However, the natural gas at Shikine and Kakuto, Kagoshima, occurrs in the Tertiay fresh water sediments, containing methane and carbon dioxide in high percentages. Carbon dioxide may be volcanic origin.
The following is the draft of an address to be given to the Japanese Natural Gas Technology Society at their meeting on 28 May 1948, by G.W. Underwood, NRS. GHQ. SCAP. In this paper I have attempted to point out the increasing emphasis and industrial development that has recently been activated in the natural gas industry in the United States. Rapidly advancing technology of gas processing, large and increasing proved reserves, accessibility of consumers by tremendous increase of pipe line systems and some concern over oil reserves have been instrumental in this development. The second part of the paper points out some of the more recent developments in production practice. The techniques mentioned have to do with control of unconsolidated sands, keeping in mind that control of wells sanding-up is of prime importance in the principal Japanese gas fields. It is hoped that by pointing out some of these recent developments employed in the U.S., with respect to similar prorlerns present in wells here in Japan, that some benefit may be realized by, at least, some experimentation along these lines.
By calculating the phenomena of the gas lift, the theoretical results are obtained as follows: (1) The characteristic curve of the gas lift indicates the most efficient method for the field work. (2) The maximum lifting capacity increases as the rate of submergence increases. (3) The minimum gas liquid ratio is on the point of 75 per cent of., the subme- rgence. (4) The tapered tubing method is not profitable because of the reduction of Reynolds number of the liquid.