From the comparatively simple field mapping of 15 or 20 years ago, petroleum geology has become a highly complex science, with several specialized branches, such as micropaleontology and geophysics. Through persistent research, it has shown the way to the modern technique of oil and gas exploitation. Although it reduces the risk in wildcat drilling, and although a majority of pools discovered in the last 20 years have been found on geological evidence, nevertheless the percentage of producers to dry holes among wildcats is exceedingly low--for example, about 2 per cent in 21 counties in northeastern Texas. Because of the vast sums of money spent in wildcat-drilling, every effort should be made to secure all possible information from such holes while in process of drilling In the development of oil pools, the geologists should seek data on structure, stratigraphy, lithology, fluid conditions, and especially on characteristics of the reservoir rock and its fluid contents, and he should furnish these data to enable the petroleum engineer to formulate his program for development and production. The geologist works with earth conditions as nearly as possible in their original environment, whereas the petroleum engineer is primarily concerned with the artificial system for extracting the oil and gas.

The most significant contribution made by petroleum geology to science and the industry is the concept which includes the isolation of the pool, the physical environment of the fluids within it, and its original relations to ownership rights vested in the surface. Acceptance of this concept by all, with its logical consequences, is vital to further progress in the industry.