Petroleum engineering, the branch of engineering that involves the development and exploitation of crude oil and natural gas fields as well as the technical analysis and forecasting of their future performance.

Reservoir engineers are concerned with the physics of oil and gas distribution and their flow through porous rocks—the various hydrodynamic, thermodynamic, gravitational, and other forces involved in the rock–fluid system. They are responsible for analyzing the rock–fluid system, establishing efficient well-drainage patterns, forecasting the performance of the oil or gas reservoir, and introducing methods for maximum efficient production.

The production engineer’s work begins upon completion of the well—directing the selection of producing intervals and making arrangements for various accessories, controls, and equipment. Later his work involves controlling and measuring the produced fluids (oil, gas, and water), designing and installing gathering and storage systems, and delivering the raw products (gas and oil) to pipelinecompanies and other transportation agents. He is also involved in such matters as corrosion prevention, well performance, and formation treatments to stimulate production. As in all branches of petroleum engineering, the production engineer cannot view the in-hole or surface processing problems in isolation but must fit solutions into the complete reservoir, well, and surface system.

Drilling engineering was among the first applications of technology to oil-field practices. The drilling engineer is responsible for the design of the earth-penetration techniques, the selection of casing and safety equipment, and, often, the direction of the operations. These functions involve understanding the nature of the rocks to be penetrated, the stresses in these rocks, and the techniques available to drill into and control the underground reservoirs. Because modern drilling involves organizing a vast array of machinery and materials, investing huge funds, and acknowledging the safety and welfare of the general public, the engineer must develop the skills of supervision, management, and negotiation.