Eor Calculator

Oil recovery happens in three stages, like squeezing water from a sponge with increasing force. Primary recovery uses the reservoir's natural pressure — oil flows out on its own, but pressure drops quickly, leaving 85-95% behind. This phase typically lasts 3-7 years and requires minimal infrastructure investment.

Secondary recovery maintains pressure by injecting water or gas, like adding new water to keep squeezing the sponge. Water flooding pushes oil toward production wells, while gas injection maintains reservoir pressure. This phase can last 15-30 years and typically doubles or triples total recovery compared to primary methods alone.

Enhanced oil recovery uses chemistry and physics to mobilize stubborn oil that water injection cannot reach. Chemical EOR reduces surface tension between oil and rock, thermal methods heat heavy oil to flow better, and CO2 injection dissolves in oil to reduce viscosity. EOR requires significant upfront investment but can recover oil for decades after conventional methods are exhausted.

Use this calculator during field development planning to estimate total recoverable reserves and compare development scenarios. Input geologic and engineering estimates for each recovery phase to determine field economics and optimal development strategy. Essential for reserve reporting, financing decisions, and regulatory approvals.

Apply the calculator when evaluating EOR project feasibility in mature fields. Compare incremental recovery from EOR against implementation costs to determine project viability. Particularly valuable for fields approaching primary or secondary depletion where EOR represents the only path to extended production.

Utilize during acquisition due diligence to validate seller recovery estimates and identify upside potential. Cross-check provided recovery factors against analogous fields with similar reservoir characteristics. Critical for determining fair asset value and negotiating purchase terms based on realistic production forecasts.

The most common error is adding recovery factors that exceed physical possibilities. Oil recovery cannot exceed 100% of original oil in place, yet many calculations assume optimistic recovery factors without considering reservoir constraints. Always verify that primary + secondary + EOR factors sum to less than 80% for realistic field conditions.

Another mistake is applying uniform recovery factors across different reservoir zones. Heterogeneous reservoirs may have high-permeability zones with 50% recovery and low-permeability zones with 10% recovery. Using average values can significantly overestimate total field recovery and lead to poor investment decisions.

Ignoring the time value of money represents a critical economic error. Primary recovery may occur over 5 years, secondary over 20 years, and EOR over 30+ years. A barrel recovered in year 30 is worth much less than a barrel recovered in year 5 when discounted to present value. Always consider recovery timing, not just total volumes, for economic evaluation.

The EOR calculator sums three sequential recovery factors: RF_total = RF_primary + RF_secondary + RF_EOR. Each factor represents the percentage of original oil in place (OOIP) recovered during that phase. For example, with OOIP of 100 million barrels, 10% primary recovery yields 10 million barrels, 15% secondary adds 15 million more, and 10% EOR adds another 10 million, totaling 35 million barrels (35% recovery).

Recovery factors vary significantly by reservoir type. Light oil reservoirs might achieve 15% primary recovery, while heavy oil reservoirs may only reach 5%. Sandstone reservoirs typically allow higher recovery than carbonate reservoirs due to better permeability. The calculation assumes each phase operates independently, though in practice they may overlap or interact.

Maximum theoretical recovery approaches but never reaches 100% due to physical limitations. Even under laboratory conditions, microscopic capillary forces trap 10-30% of oil in rock pores. Economic limits typically constrain field recovery to 40-70%, as marginal production costs eventually exceed oil prices. The calculator flags total recovery factors above 80% as potentially unrealistic for field validation.

Recovery factors are calibrated from analog field performance, but reservoir heterogeneity makes direct application problematic. The Dykstra-Parsons coefficient quantifies permeability variation — fields with coefficients above 0.8 show significantly lower recovery than homogeneous analogs. Professionals use probabilistic analysis with P10/P50/P90 recovery scenarios rather than deterministic single-point estimates.