öljykenttä

öljykenttä (oil field) is a geographical area containing a large, economically exploitable accumulation of crude oil within reservoir rocks. Most fields are located in sedimentary basins and can be onshore or offshore. They vary in size and in the number of reservoirs and wells. Oil fields are defined by the presence of an oil-water contact and trapping structures that retain hydrocarbons within permeable rocks.

Discovery and development: Oil fields are discovered through geological and geophysical methods, particularly seismic surveys, followed by exploratory drilling. If a discovery proves commercially viable, the field is appraised, development plans are made, and a production facility and wells are constructed. Infrastructure includes pipelines, processing facilities, and sometimes offshore platforms or onshore plants.

Production and recovery: Initial production relies on natural reservoir pressure; production optimization often uses artificial lift. Secondary recovery, such as water or gas injection, is common to maintain pressure and displace oil. Enhanced oil recovery methods, including CO2 flooding, steam injection, and chemical flooding, are used in suitable reservoirs to increase ultimate recovery. Oil fields may progress through phases from peak production to decline and abandonment, with ongoing monitoring and remediation.

Types and significance: Conventional oil fields contain liquid hydrocarbons in relatively permeable rocks; heavy oil and extra-heavy oil occur in more viscous formations; offshore fields present additional technical and safety challenges; tight oil and shale oil require advanced fracturing. The economics of a field depend on oil price, extraction costs, and regulatory conditions; fields contribute to energy supply, employment, and regional economies.

Environmental and regulatory aspects: Oil field operations involve management of produced water, emissions, land use, and potential spills. Decommissioning and site restoration are required at the end of a field's life, with reclamation of wells and facilities and monitoring for long-term environmental safety.