Northeast Purdy Springer Unit

The North East Purdy Unit (NEPSU) and South East Battrum Unit (SEBAU) are CO₂-enhanced oil recovery projects located in Oklahoma within the Anadarko Basin region. The units are operated for tertiary oil recovery using miscible CO₂ flooding, with long-term geologic storage of retained CO₂ monitored under an EPA Subpart RR Monitoring, Reporting, and Verification (MRV) plan. The projects transitioned from primary production and waterflood operations to CO₂ injection to mobilize residual oil and extend field life. CO₂ supply is derived from multiple sources. Historically, anthropogenic CO₂ from a fertilizer plant has been delivered through pipeline infrastructure and distributed to injection wells via a field-wide manifold and distribution system. Produced gas streams containing CO₂ and hydrocarbons are transported to the Daylight Lindsay Gas Plant, where natural gas liquids (NGLs) are extracted and CO₂ is separated, recompressed, and recycled back to the field for reinjection. Injection volumes are tracked through multiple metering locations including pipeline receipt points, plant outlets, recycle streams, and individual wellhead meters. For any given injection well, CO₂ may originate from pipeline delivery, recycled production gas, or a mixture of both, with ratios varying over time. The reservoirs consist of mature conventional oil-bearing formations typical of the Anadarko Basin, characterized by heterogeneous sandstone intervals with structural and stratigraphic trapping. CO₂ flooding uses pattern-based injection strategies, commonly incorporating water-alternating-gas (WAG) cycles to control mobility and improve sweep efficiency. Long-term CO₂ retention occurs through structural trapping, residual trapping, and dissolution mechanisms within the reservoir.