The objects of this investigation are the measurements of relative permeability of the sands in Mobara Gas Field and the improvements of the technique and apparatus used on the experiments. The results obtained from the experiments are given on Fig. 3 and Fig. 4. Fig. 3 shows warer permeabilities in thecase of very low value, but the writers have not enough data to explain on the factors affecting on the low values.
This report gives the progress of jet bit drilling and its theoritical foundation for penetration rate, and also shows that the jet bit drilling permits more rapid penetratin rates at R. 48 well and R. 53 well of Yabase oil field drilled by Teikoku Oil Co.
At Matsunoyama No 4 well, the first application of “mud acid” was made. At this well, the promising reservoir was found at the depth of 500 meter and 900 meter respectively, and the latter reservoir was treated with mud acid. At the result, gas and fluid have heen increased in quantity with no reservoir oil having heen found. The result was not a failure in respect to the phase of application, but no oil was found.
Recently in Japan the methane gas, of which geological occurence is free from petroleum, has been utilized. Except some cases, the gas is dissolved into formational water according to hydro-static pressure-temperature relation. The writer describes the result of the core analysis of exploration well for natural gas of this kind in this paper. The formational water dissolving natural gas under the reducing condition may be teken the place or degenerate by the invasion or diffusion of meteoric water along the permeable sediments, and consequently the gas potentiality may decline. The chemical analysis of the interstitial water of core may indicate the influence of the meteoric water and detect the vertical distribution of gas potentiality. In practice, this method is a application of usual methodology of “geochemical survey by underground water” to the interstitial water of muddy core. Chlorine may be a factor of chemical environment atf deposition and slso the measure of the destructive process by meteoric fresh water. Its concentration well shows the vertical change of the destructive process together with the values of long normal curve of electric logging. Ammonium and bicarbonate may be tne measure of potentiality as the products of the same phase of formation _??_ destruction equilibrium of gas. Furthermore, ammonium may be a measure of the destructive process by metheoric water as well as chlorine. The presence of nitrite and nitrate shows decidedly the characteristics of meteoric water of oxidative status. The consumption of potassium permanganate reaches the first peak at the contact zone of connate and meteoric water, where the intersticial water is dark brown-colored by humic matter, and again becomes larger downwards, where the interstitial water is colorless. The similar phenomenon is known horizontally within the Mobara gas field. But the absolute value is far higher in the core analysis. This may be caoused by the condition (especially pH) at the extraction of interstitial water. By the micropaleontological study of core, the gas bearing formations may be the Plio-Pleistocene sediment of lower neritic deposition. In the vicinity of the Mobara gas field, these formations are invaded by meteoric water, having no gas potentiality.