This paper presents a numerical model to predict the proceeding of the reinjection water front within the Ordinary-type water-dissolved natural gas reservior. The model decribes two dimensional flow of gas and water through the reservior. Dilution of dissolved gas by the mixing of water poor in gas has been taken into account, and the decreasing gas concentration can be esimated by considering the process as a variable bubble-point problem. Numerical dispersion caused by solving the flow equation with finite difference method is discussed. A calculation example shows the difference between the results by this model and the traditional one phase model for the production gas water ratio and the bottom-hole pressure.
Simulation study was carried out to investigate the behavior of fireflooding and to obtain basic information for designing and/or screening fireflood projects. The simulator used has been reported elsewhere (JJAPT 52, 5, 1987). Parameters investigated were (1) residual oil saturation, (2) oil density, and (3) air injection rate, which was the only one parameter that could be controlled directly. Results are summerized as follows; (1) In general oil production methods other than fireflooding, oil recovery is low as residual oil saturation is high. Because the amount of oil used as fuel is little in fireflooding, the oil recovery is less affected by residual oil saturation, though the combustion reaction zone w ould be extinguished if the residual oil saturation is too small to leave sufficient amount of oil being supplied as fuel. (2) In fireflooding, the cork formed by the thermal decomposition of heavy components would be the fuel, so that the fireflooding would be impossible unless the oil density is high enough. However, the recovery and the prodution rate are higher as the oil is lighter in the range of operating condition. (3) Production rate would vary with air injection rate. But the optimum air injection rate may exist from the economical point of view.
Lost circulation is one of the most severe problems encountered in drilling and completing geothermal wells. New Energy and Industrial Technology Development Organization (NEDO) is conducting an active research and development aimed at solving lost circulation problems. The objective of the R & D is to develop systematic procedures for field use in combating lost circulation, and the program consists of loss zone detection/analysis techniques and meterials/placement techiques. In this program, the application of expert system to fluid loss control is devised. An expert system is a computer program which simulates a decision process of human expert in a given field. In a preliminary system, the existing body of knowledge on lost circulation methods and materials has been assembled in such a manner as to provide a computerized tool for use in the field. Based on known drilling parameters and available information, the system wold suggest courses of action to be taken which would reduce uncertainity and mistake in the decision process of field personnel.
It is about thirty years since computer application started in the industrial fields such as steel plant, power plant, and refinery plant. Today computers have prevailed in all kinds of industial fields and we cannot think of their operation without using computers. On the other hand, in the field of oil drilling, there exist many problems against computer applications, such as geogruphical distribution of rigs, difficulty of mechanical automation, instrumentations and estimation of underground gelogical conditions, and so computer application cannot be said to be more advanced than that in the other industries. This paper outlines today's feature of computer application in industrial fields, especially concerning seeds technology such as distributed and totalized system configuration technology, man machine interface, artificial intelligence, simulation, process control and database and how these technologies can be applied to the drilling field.