This paper summarizes the important trends and developments in production engineering, particularly for the period since 1941. This period has had an important influence upon the trend of engineering development because of the fact that the high wartime rates of oil production afforded an opportunity for quantitative observation and evaluation of petroleum reservoir characteristics under controlled conditions.

It is the writer's opinion that the most important development in petroleum engineering within recent years has been the inauguration of the transition from the qualitative to the quantitative stage. This transition is not complete but is in fact just sufficiently developed to be reaching the period of vigorous further growth and advancement. The groundwork for this quantitative stage has been built and the future should bring a degree of quantitative engineering control far surpassing expectations of a few years ago. This trend is illustrated with examples of technically controlled development and operation of selected oil reservoirs and the basic and applied research which forms the basis for the trend is briefly reviewed.

The suggestion is made that to keep pace with progress in the industry the technical man, engineer or geologist, must recognize the necessity of abandoning qualitative thinking and must adapt himself to the more difficult task of quantitative study. Those unable to accommodate themselves to this progressive change will lose ground in the same manner as has occurred in many a manufacturing industry when the processes have advanced from art to science.