- Connate water saturation = swl = SWL
- Corporate Tax (Finance)
- Finance Rate = rf
- ICT Management
- Ideal Gas
- Ideal Gas EOS @model
- Igneous rock (Magmatic rock)
- ILS (In-line Spinner Logging Tool)
- Imbibition
- Imperial System of Unit
- Implicit correlation
- Implicit expression
- In-Casing Cross-Flow (ICX)
- INCL (Inclinometer Logging Tool)
- Inclinational Deviation (Trajectory)
- Income Tax (Finance)
- Income Tax Rate (Finance)
- Incompressible flow
- Incompressible fluid
- Incompressible matter
- Incremental Oil Recovery
- Indonesia Model (Poupon-Leveaux) @model
- Induced fracture
- Induced fracture collapse
- Induced fracture communication
- Induction Logging (IL)
- Infill drilling
- Infinite Acting Radial Flow = IARF
- Infinite acting reservoir flow boundary
- Infinite conductivity fracture
- Inflation
- Inflow Performance Relationship = IPR
- Initial Conditions
- Initial formation pressure = Pi
- Initial formation temperature = Ti
- Initial Formation Water Saturation
- Initial Investment (I0)
- Initial pore compressibility
- Initial Porosity
- Initial rate = q0
- Initial Recoverable Gas Reserves per well = VGui
- Initial Recoverable Oil Reserves per well = VOui
- Initial time = t0
- Initial Value Problem (IVP)
- Injecting well
- Injection (well flow status)
- Injection Intakes
- Injection Logging (ILT)
- Injection losses
- Injection Metering
- Injection rate
- Injection survey
- Injection water
- Injection well = Injector
- Injectivity Index (PI or J)
- Injector (well)
- Inlayer natural fracture communication
- Inner Diameter (IP)
- In-situ
- Instantaneous PIR
- Instantaneous Voidage Replacement Balance = IVRB
- Instantaneous Voidage Replacement Ratio = IVRR
- Intangible Asset (Finance)
- Integro-Differential Equation
- Intensive physical property
- Interest (Finance)
- Interest Rate = rf
- Internal energy (U)
- Internal Rate of Return = IRR
- International Financial Reporting Standards = IFRS (Finance)
- International Union of Pure and Applied Chemistry = IUPAC
- Inventory
- Inversion Temperature (Tinv)
- Investment
- Investment (Business)
- Investment Planning
- Inviscid flow
- Invoice (Finance)
- Ion
- Ionization
- Isentropic bulk modulus = KS
- Isentropic Compressibility
- Isentropic expansion factor = κ
- Isentropic exponent = κ
- Isentropic process (S = const)
- Isobaric Heat Capacity = Cp
- Isobaric molar heat capacity (cP)
- Isobaric process (P = const)
- Isochoric Heat Capacity = CV
- Isochoric molar heat capacity (cV)
- Isochoric process (V = const)
- Isothermal bulk modulus = KT
- Isothermal Compressibility = βT
- Isothermal process (T = const)
- Isoviscous process
- Real Gas
- Running Interest (Finance)