Experiments for fracturing hot dry rock by high speed water jet were carried out. In this study the effects of rock temperature and water jet speed were studied. Specimens were 75mm in diameter and 150mm in length and were made of castable fire-resistant material. Their minimum compressive and tensile strengths were shown in Table 1. Temperatures of the specimen tested were 15, 200, 400, 600, 800, 1, 000 and 1, 140°C. Water jet speeds used were 70, 84 and 98m/s at the nozzle exit. The nozzle diameter, Do=1.4mm I.D.. The distance between the nozzle exit and the test surface of the specimen was kept constant at 40mm. Jet operation time was fixed at 10s. The experimental results indicated that the fracturing pattern and effectiveness varied characteristically with the specimen temperature and the jet speed.
New blade-type bits with small cylindrical chips are tested to evaluate their drilling performance under laboratory conditions. Four types of chip are selected; No. 1-semi-circular tungsten carbide chip of 2.0mm diameter, No. 2-spindle-shape tungsten carbide chip of 2.3mm width, No. 3-circular tungsten carbide chip of 2.5mm diameter, and No. 4-circular polycrystalline diamond compact (PDC) covered with tungsten carbide sheath of 2.5mm diameter. These bits are tested in tuff and andesite of which compressive strength covers a wide range from 20MPa to 170MPa. Penetration rate, bit torque and bit wears are evaluated. A helical-type drilling model is proposed and equations of chip penetration and force acting on chip are derived from the model. Some of the major conclusions drawn from these tests are summarized as follows: 1. A bit with tungsten carbide chips is able to drill rocks of which compressive strength are up to 70MPa. 2. A bith with PDC chips has possibility of drilling of rocks of which compressive strength are about 170MPa. 3. These test bits are able to drill soft rocks stably at high rotary speed of about 7rev/s.
The present paper deals with the results of descriptive and experimental works on the socalled glauconites found in the Tertiary coal-bearing formations in Kyushu, Japan. Green colored materials in the examined specimens can be discriminated into chloritic mineral and glauconitic one, and the latter is classified further into four types based on their morphology and internal structure observed under a microscope. The results of the experimental studies indicate that the latter is a di-octahedral micaceous mineral involving the 10-30 percent expandable layers. Glauconite grains obtained from the separated districts occupy the peculiar area on a Fe2O3-K2O diagram. This chemical variation may reflect that of depositional environments among each district.
Present temperature gradients and some factors controlling the gradients in the Niigaga basin are discussed. Paleotemperature of sedimentary rocks in the Niigata basin is estimated from the present temperature gradients based on some assumptions. The distribution of temperature gradients in the Niigata basin shows that it is strongly affected by the depth of the "GREEN TUFF" formation (Oligocene-Early Miocene volcanic rocks). This is explained by a thermal model. After correction of the effects of the depth of the "GREEN TUFF" formation. The thermal potential values are expressed as in the values from zero to ten and both values are equivalent to the minimum and the maximum values of the initial temperature gradients in the Niigata basin. The values show thermal characteristics (thermal conductivity or heat flow) of the "GREEN TUFF" and underlying formations. Thermal potential values indicate that their distributive trend is perpendicular to basin trend. It presumably suggests that the differentiation of the thermal potential values has been made during and/or before the deposition of the "GREEN TUFF" formation. Thermal potential values accord with a distribution of oil and gas fields: Gas fields mainly locate in the high thermal potential (6-10) areas, oil fields mainly locate in the intermediate thermal potential (2-6) areas and no oil and gas fields locate in the low thermal potential (0-2) area. Paleotemperature is estimated from thermal potential values and the depth of the "GREEN TUFF" formation (burial history of the "GREEN TUFF" formation) on a assumption that thermal potential values have not been changed after deposition of the "GREEN TUFF" formation.
Routine analyses of natural gas-dissolved-in-brine have been performed on the assumption that (1) contents of minor components except CO2 and N2 are negligible, and (2) the gas has no O2. Detected O2 and corresponding N2 are subtracted from the resulting data of analyses, because they are regarded as contaminants from the air. Higher quality of present analytical equipments has made possible even trace components analyses, if necessary, and the other hand, air correction has been considered as not always applicable. So, to determine whether the assumptions were appropriate or not, we conducted precise analyses of the gases from Narutoh field adopting gas-chromatografic methods. Following experimental results were obtained. As to the minor components tested, C2H6 and A were found in all of the samples, C3H8 from 2/3 of the wells, but H2 and He were actually not. And even the detected gases, the amounts were very small. About O22, it was found that O2 had entered into samples through displacing water, so the ratio of O2/N2 which usually adopted for air correction was not that of the air (1/3.55), but that of dissolved air (about 1/2). Therefore, the result of usual air correction had been over-subtraction of N2. However, concerning to calorific values of the gases, existence of the higher calorific C2H6 and the increase of non-calorific N2 offset each other. In conclusion, routine analyses may be performed as before for little influences on calorific values, but it should be noted that the procedure is only for conveniences.