Some instructions are given to Japanese people who will be engaged in oil production buisiness in foreign countries and it is emphasized that the most important thing is to have the confidence of Host Gavernmetns and the local peoples.
Cuttings taken from wells being drilled were analysed to study sloughing of strata. Sand and clay content was determined and the clay was analysed by X-ray diffraction. Results obtained are as follows: (1) Contents of sand, clay and montmorillonite in mud-stone differ a great deal between each stratum. (2) There is a relationship between the content of sand or montmorillonite and the sloughing of stratum. (3) Although much sand in mud-stone usually prevents sloughing, sand with an extremely small amount of montmorillonite results in severe sloughing. Much montmorillonite without sand also results in sloughin. (4) The amount of montmorillonite in large sloughed samples is usually greater than that of cuttings. (5) There is no relationship between the chloride ion chloride ion content of the stratum and than the sloughing.