The hydraulic fracturing has been promoted in its engineering year after year since its introduction into the oil industry in 1948, and today it is the most popular stimulation method which is extensively and intensively applied in the oil fields all over the world. Therefore, many studies have been directed to improve the engineering of fracturing. Most of them are made by practical and experimental developments, but not much on theoretical matter.
Here, the study was made to consider and find the theoretical pressure conditions of fracturing, using the various data of fracturing practices at the wells of Yabase deep zones. The pressures, which are factors of fracturing, are the injection pressure, the pressure of resistance loss through the pipe line, and the perforated holes, the pressure emerging of fluid column, the pressure of breakdown which practically works on the formation, and others. The author tried to develop study on these pressures theoretically, and further obtained the magnitudes of fracturing pressures, which are required to make fractures in the formation, for each part of Yabase oil field. According to these results, the highest injection pressure is expected in Sotoasahigawa district, and the lowest in Omonogawa and Araya districts. The good coincidence was found between the theoretically obtained pressure figures and the practically observed pressures of many fracturing practices in the oil field.

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Radioactive piston-ring Plated with ⁵⁹Fe was used to study the abrasion of ring for the purpose of comparing the qualities of lubricating oils.
Piston-rings plated with ⁵⁹Fe, having specific activity of 20-30μc/g were prepared from FeCl₂ solution, containing 10g/l of ⁵⁹Fe as FeCl₃. The specific activities of these rings increased at the initial stage, and then decreased gradually. The abrasions of these rings were measured with a small gasoline combustion engine.
The running conditions of engine were as follows;
outside cylinder temp. 85-90°C
lubricating oil temp. 53-2°C
engine revolution 3, 000rpm
engine load 0 and 250 watt
Under the unloaded condition, the same rate of abrasion (except initial wear) was observed as the previous running when one radioactive ring was used for 1st ring; however, the rate increased twice as much as the previous when two radioactive rings were used for 1st and 2nd rings.
Under the loaded condition using two radioactive rings, the rate of abrasion increased as compared with unloaded condition and changed with lubricating oils used.
Accordingly, radioactive plated piston-ring shall be used to determine the abrasion of ring for the purpose of comparing the qualities of lubricating oils.

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The investigations have been made on the effects exerted upon the operating conditions and yield of product by changing the properties and components of cracker feed stock, and the following results are obtained:
(i) It is most desirable for the cracker feed to contain the oils of small contents of heavy metals dissolved, such as nickel, vanadium, iron, and copper.
These desirable feed stocks are the vacuum distillates and the slack wax obtained from the solvent dewaxer. In general, the allowable limits of these metals dissolved in feed stock can not be determined clearly, because the contamination of catalyst by these metals is closely connected with its stack loss.
(ii) The dissolved metals in feed stock are proportional to its carbon residue. It is possible to presume the metals contents in the stock by measuring its carbon residue.
(iii) The yield of cracked gasoline is proportional to the aniline point of its feed stock. Therefore, the feed stock having high aniline points is recommended for the production of the gasoline with high yield.
(iv) As the deasphalted oil contains more metals than the other distillates, it is desirable to use the feed stock containing less deasphalted oil or to use the highly refined deasphalted oil.
(v) There is a linear relation between the contamination index and the nickel content in the stationary operation; therefore, it should be possible to indicate the contamination degree of the catalyst by nickel content in place of the contamination index.

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The properties of catalyst in the stationary operation, in particular, its activity and selectivity were investigated from the stand-point of operation; then, the most economical rate of catalyst supply and the method of replacement of contaminated catalyst were examined.
(i) By the analysis of operating conditions in several years it was shown that the most economical supplying rate of new catalyst was 0.2lbs/bbl fresh feed to maintain the constant activity of catalyst.
By the analysis of catalyst contamination, it was found that the rate of 0.2-0.3lbs/bbl fresh feed was applicable. When it was less than 0.2lbs/bbl metals were accumulated on the catalyst and when it was more than 0.3lbs/bbl the content of metals in catalyst tended to decrease.
(ii) The contaminated catalyst was separated into three groups (particle range of 0-40μ, 40-80μ, and over 80μ) by roller method and the contents of metals in each group were measured. The highest content was found in the group of over 80μ. This result suggests that the most economical method is to separate away coarse particles of catalyst from the unit by classifier or elutriator and to supply fresh one into the unit in order to maintain the lower content of the metals.

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The kinetics of the isomerization of xylene mixture, which was accompanied by the disproportionation of xylene and the cracking of ethyl benzene, and the effect of ethyl benzene concentration in xylene mixture on the side reaction products have been studied with silica-alumina catalyst in the presence of steam at the temperatures of 500-530°C.
The results obtained were summarized as follows:
i) As far as the change of relative ratio of xylene isomers in the feed stock was in such a range as p:m:o=6-10:60-70:20-30 (mole %), the xylene fraction of the isomerized oil had the composition almost equal to the thermodynamical isomerization equilibrium, independent of the concentration of ethyl benzene both in the feed stock and the isomerized oil.
ii) The rates of decompositions (side-reactions) of xylene and ethyl benzene were dependent of the reaction temperature and their concentrations in the feed stock.
500°C X_D=0.0338X_F²/(1+0.0338X_F), E_D=0.0772E_F
515°C X_D=0.0431X_F²/(1+0.0431X_F), E_D=0.1106E_F
530°C X_D=0.0548X_F²/(1+0.0548X_F), E_D=0.1333E_F
where
X_D: the rate of decomposition of xylene.
X_F: the concentration of xylene in the feed stock.
E_D: the rate of decomposition of ethyl benzene.
E_F: the concentration of ethyl benzene in the feed stock.
iii) Presences of H₂, CO₂ and CO were always observed in traces, accompanied by a few percents of C₃+C₃' and C₄+C₄' hydrocarbons in the produced gas. The presences of paraffins and olefins of low b. p. were confirmed in the produced oil, and substances of high b. p. were also suggested to be present in the product.

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