The paper describes methods of solving several reservoir engineering and data processing problems using slow to medium speed computing machines. The problems handled are:Solution of the Hurst-van Everdingen material balance equation for which at first only water influx terms and y curves for PVT samples were calculated with the IBM 602A and 604 computers, while later the complete solution of the equation was programmed on the IBM 607 computer. The application of this equation requires computing cumulative water influx volumes at successive dates and matching these figures with the difference between the corresponding cumulative reservoir volumes withdrawn, and the corresponding cumulative expansions of the initial volume of reservoir oil and gas.Vapor-liquid equilibrium flash calculations which are solved rapidly with the IBM 602A or 604. Auxiliary calculations were made to convert the results into usable engineering quantities.Statistical analyses, performed on core data for several fields, providing a better understanding of the reservoir characteristics.Preparation of the annual (statistical) reserve report. This report starts with the previous year's figures for the gross and net reserves, cumulative and ultimate production, separated into oil, condensate and total liquid figures by leases. Revisions to reserves, classified according to 10 categories such as discoveries, new zones, extensions, etc. are added to the opening reserves and ultimate production figures, while the yearly production figures are subtracted from the revised figures and added to the cumulative figure. Statistical data concerning leasehold titles and ownership fractions, well counts, etc. are recorded. All figures are summarized according to zones, fields, leases, divisions and areas.Miscellaneous uses of analytical procedures for production accounting figures, such as oil pipe line runs, etc. provided better control of production operations. Introduction The annual reserve report is a statistical statement of gross and net reserves, including revisions of reserve estimates and production during the year. The responsibility for preparing this report was assigned to reservoir engineers and by 1952 the report required considerable engineering, clerical and stenographic time.