PNG 301
Introduction to Petroleum and Natural Gas Engineering

8.1.5: Decline Phase

Graph highlighting the Decline Phase of the life cycle of a hydrocarbon field, described below.
Figure 8.01e: Decline Phase of the Life-Cycle of a Hydrocarbon Field
Source: Greg King © Penn State, licensed CC BY-NC-SA 4.0

Later in the life of the field or reservoir, the drilling of additional new wells may be required after all phases of the original development plan have been completed and the reservoir management activities focus on arresting the reservoir decline. For example, in order to arrest the declining oil or gas production rates, Infill Drilling may be applied. Infill drilling is a method where the original drainage areas are reduced by drilling new wells between two or more existing wells. Also, in oil reservoirs, Pattern Realignment may be used in Secondary Recovery Operations (gas or water injection) to adjust the producer-injector patterns to recover any oil not recoverable from the original patterns.

As stated earlier, all oil and gas field activities that require a drilling rig are planned and supervised by drilling engineers. As such, the role of the drilling engineer spans the entire life span of the field or reservoir from exploration to decline and abandonment.