Oxidized matters, produced in the laboratory reacting lignite with dil-HNO3, are discussed as thinners and emulsifiers for drilling fluids. Changes of reaction conditions, especially in concentration of HNO3, were examined on their effective behavior in drilling fluids. Some essential parts for adjusting drilling fluids are detected in our oxidized lignites. Those parts which can be extracted by alkalis from differently processed oxidized lignites give equal behaviors in drilling fluids.
It is well known that about half parts are remained as unrecovered in oil reservoirs, when oil fields haye been treated by so-called primary oil recovery methods or secondary ones. In Japan, some oil fields seem to have vast quantities of oil unrecovered as they are so viscous and so heavy. We have studied on recovering methods of this remained oil, resulting successfully by thermal methods. Some parts of residual oil are burned by injecting necessary air from a well. By those energies caused by the in-situ combustion, residual oil are to be moved to another wells from which we can get large quantities oil of which have not yet been recovered.
The application of hydraulic fracturing process in Japan was initiated at Omonogawa No. 2 Well. As the result, notable success was obtained and it has enlighted the further application of fracturing process in the Japanese oil industry.
There are many clues or methods to investigate reservoir character. Electrical logging and bottom hole pressure measurement are the most reliable. Analysis of data obtained by bottom hole pressure measurement is not so well developed as electrical logging analysis is. However more developement might be possible.