Oil and Gas Terms Beginning with “I” — Page 2

In-situ combustion (ISC) is a thermal enhanced oil recovery method in which air or oxygen-enriched air is injected into a heavy oil or bitumen reservoir and ignited, generating a high-temperature combustion front that… Read more →

In-situ fluid analysis (often shortened to IFA or DFA, downhole fluid analysis) is the suite of measurements performed by wireline formation-tester tools while held stationary at depth in an openhole logging string,… Read more →

In-situ viscosity evaluation is the downhole measurement or estimation of reservoir fluid viscosity under native pressure and temperature conditions, performed with logging tools rather than relying on surface samples… Read more →

What Is Inclination? Inclination (also called wellbore inclination or hole angle) is the angle in degrees between the wellbore axis and the vertical, measured during directional surveys at regular intervals along the… Read more →

An instrument used to measure the dip of the Earth's magnetic field. Read more →

In structural geology, an incompetent bed is a rock unit that is relatively weak and ductile, so under tectonic stress it tends to flow, thin, and thicken rather than break by brittle faulting or fracturing. Its… Read more →

Indicator methods are a way to model what is happening in a rock formation between the wells where we have data. Instead of trying to guess the exact value of a property like porosity at every point, indicator methods… Read more →

Models of reservoirs built using indicator (nonparametric) methods. Read more →

Induced gamma ray spectroscopy in well logging is a nuclear measurement technique in which a neutron source in the logging tool irradiates the formation and borehole with fast neutrons, causing neutron-capture and… Read more →

Induced particle plugging (IPP) in drilling engineering and wellbore stability is the deliberate addition of fine particles to drilling fluid that invade and seal the near-wellbore formation matrix by plugging pore… Read more →

What Is Induced Polarization? Induced polarization (IP) is a geophysical exploration technique that measures the capacitive electrical response of subsurface rocks by applying a time-varying current to the ground and… Read more →

An induction log is a wireline measurement of formation resistivity that uses electromagnetic induction rather than direct electrical contact to measure how well the formation conducts electricity. An alternating… Read more →

An induction electrical survey (IES) is a wireline logging measurement of formation resistivity using electromagnetic induction rather than direct electrical contact between the tool and the borehole fluid, making it… Read more →

Inelastic neutron scattering (INS) is a nuclear interaction in which a fast neutron collides with an atomic nucleus and excites it to a higher energy state, with the neutron losing kinetic energy to the nucleus and the… Read more →

Inertial resistance (also called non-Darcy flow resistance, turbulent resistance, or inertial pressure drop) in petroleum reservoir engineering refers to the additional pressure drop beyond Darcy's law that occurs in… Read more →

What Is Infill Drilling? Infill drilling is the addition of new wells between existing producers and injectors in a developed field to reduce average well spacing, improve sweep efficiency, and accelerate or increase… Read more →

What Is an Infinite-Acting Reservoir? Infinite-acting reservoir (also called the transient flow period or infinite-acting radial flow) is a reservoir flow condition during the early-time period of a pressure test or… Read more →

An infinite-conductivity fracture is an idealized hydraulic or natural fracture that conducts fluid to the wellbore with effectively zero pressure drop along its length during production. In reality no fracture is truly… Read more →

An inflatable packer in petroleum well completions and drilling is a downhole isolation tool that uses an inflatable rubber or elastomeric element — expanded by injecting fluid (typically drilling mud, brine, or cement)… Read more →

What Is the Inflow Performance Relationship? The inflow performance relationship (IPR) is the mathematical relationship between the sandface flow rate (q) of a well and the bottomhole flowing pressure (BHFP or p_wf) at… Read more →

Information theory is the mathematical study of the quantification, storage, transmission, and management of information, founded by Claude Shannon in his 1948 paper A Mathematical Theory of Communication and now… Read more →

In petroleum drilling engineering, to inhibit a drilling fluid means to add chemical additives that suppress the hydration, swelling, and dispersion of water-sensitive clay minerals (principally… Read more →

What Is Inhibited Acid? Inhibited acid (also called corrosion-inhibited acid or treated acid) is a hydrochloric acid solution formulated with a package of chemical additives designed to suppress the attack of the acid… Read more →

An inhibitive mud is a drilling fluid system specifically designed to slow or stop the hydration, swelling, and disintegration of shale formations during drilling operations — providing the operational chemistry needed… Read more →

In oilfield operations, an inhibitor is a chemical additive injected into or applied to production systems, pipelines, wellbores, and processing facilities to prevent or slow undesirable chemical or physical processes… Read more →

An initial flow period is the brief flow phase at the beginning of a drillstem test (DST) sequence — providing the initial flow event that creates the pressure disturbance which is then allowed to recover during the… Read more →

What Is Initial Reservoir Pressure? Initial reservoir pressure (also written as P i or original reservoir pressure) is the pore pressure measured in a virgin hydrocarbon accumulation before any production has begun,… Read more →

The initial shut-in period (ISIP) is the comparatively short pressure-buildup phase that follows the initial flow period of a drillstem test (DST) — a temporary suspension of flow during which the downhole gauges record… Read more →

Injection gas is natural gas deliberately pumped back into a subsurface formation to serve a reservoir-management or production objective rather than being sold or flared. It is the working fluid behind four distinct… Read more →

An injection line in oil and gas production and completion operations is a small-diameter high-pressure conduit (typically 1/4 to 1 inch nominal size, made from carbon steel, stainless steel, or corrosion-resistant… Read more →