The purposes of the study are (1) to make clear the history of the proceeding water front under the conditions shown in Fig. 2, (2) to calculate the sweep efficiency of the system, and (3) to inspect the effects of the edge water line on the sweep efficiency. In Fig. 3 the results of calculation are shown. A relaxation method is used in the study. The sweep efficiency of 37.1% was obtained. It is assumed that the four edge water lines are between the rows of input-wells and outputs-wells. Each line is 5 meters, 10 meters, 15 meters and 20 meters apart from water injection wells. The behavior of the edge water was determined (see Fig. 6, Fig. 7, Fig. 8 and Fig. 9). The sweep efficiencies under such conditione were 49.3%, 48.8%, 49.2% and 46.6%. The ratios of the area invaded by edge water to the area EBCF are each 75.5%, 76.3%, 79.2% and 77.5%. Accordingly, we must carry out any other plan within the area AEFD for increasing efficiency in this system.
It is characteristic of the oil fields in Japan that strata are steep and reservoirs are limited. Therefore, the study of water flooding at limited and steep oil reservoirs is very significant, especially in our country. The writer tried to analyse the up-dip flooding where producers are directly opposite to injection wells (cf. Fig. 1.) from the viewpoint of solving the boun-dary-value problem for the 2-dimensional, steady flow of single and incompressible fluid through porous media. Thus the derived results for the pressure distribution; the relation between well pressures, injection (or production) rate and dip of strata; the loss of flow capacity against the gravity; and the sweep efficiency are (6) or (7); (10), (15) or (16); (17) or (18); and (24) or (25), respectively.
Recently exploratory works for methane gas associated with brine in the upper Pliocene formations were successfully completed at the southern end of the Kujukuri gas field. The stratigraphy, micro-biofacies, and chemofacies are described in this paper. The main reservoir of the field is thick coarse sand of deep-water deposits in the Otadai formation.