Oil and Gas Terms Beginning with “E”

Equivalent circulating density (ECD) is the effective density exerted by a circulating drilling fluid against the formation at a specific depth, taking into account both the static mud weight and the additional pressure… Read more →

EDA, extensive-dilatancy anisotropy, is a form of azimuthal seismic anisotropy that arises when a rock volume is pervaded by stress-aligned, fluid-filled microcracks and fractures that are not horizontal, so that the… Read more →

EDTA, ethylenediaminetetraacetic acid, is a hexadentate chelating agent whose molecule wraps around a metal cation through two amine nitrogen atoms and four carboxylate oxygen atoms to form an extremely stable,… Read more →

(noun) Abbreviation for Enhanced Oil Recovery. A collective term for tertiary recovery techniques used to extract crude oil from a reservoir beyond what is achievable through primary depletion and secondary… Read more →

The EPA, or Environmental Protection Agency, is the United States federal agency charged with administering the environmental laws passed by Congress, and for the oil and gas industry it is the single most consequential… Read more →

What Is the ES Test? The ES test is a standardised electrical measurement that evaluates the emulsion stability and oil-wetting quality of an invert emulsion (oil-based or synthetic-base) drilling mud by applying a… Read more →

What Is an ESP in Oil and Gas? An ESP (Electric Submersible Pump) is a downhole artificial lift system that uses a multi-stage centrifugal pump driven by a submersible electric motor to lift fluids from a wellbore to… Read more →

Hinged steel heavy duty clamps with manual operating handles that crew members latch onto a tool joint. Designed to grip a single size tubular and provide the means to hoist and lower the drill string. Read more →

The Epanechnikov kernel is a probability density function used in kernel density estimation (KDE), a non-parametric statistical method that estimates the probability density of a dataset without assuming a specific… Read more →

The Euclidian dimension is the count of mutually perpendicular, or orthogonal, directions needed to specify a position in ordinary geometric space, the familiar framework of a point on a line being one-dimensional, a… Read more →

Euclidian distance is the straight-line distance between two points in Euclidian space, where every dimension is orthogonal to the others, meaning all axes meet at right angles and represent independent directions in… Read more →

Early-time transient data in well testing and pressure transient analysis refers to the pressure and flow rate measurements recorded during the initial period of a well test — typically the first seconds to minutes of a… Read more →

Earthquake in the oil and gas context refers to seismic ground motion events — either naturally occurring tectonic earthquakes that affect the design and operation of upstream facilities, pipelines, and offshore… Read more →

Easy to disperse, almost always abbreviated ETD, describes a cement system whose rheology responds so steeply to dispersant concentration that very small dosing errors swing the slurry from too thick to fully… Read more →

Easy-to-disperse-in-salt (EDS) is a classification of Portland cement or specialty cement blend used in oil and gas well cementing operations that describes a cement formulation exhibiting high sensitivity to the… Read more →

An eccentralizer is a downhole casing or tubing accessory designed to deliberately hold the pipe off-center (eccentric) within the wellbore, the functional opposite of a centralizer which is designed to keep the pipe… Read more →

What Is Eccentricity in Well Logging? Eccentricity in well logging is the off-centre displacement of a logging tool from the borehole axis, quantified as the radial distance from the tool's geometric centre to the… Read more →

Echo spacing (TE, also called interecho time or echo time) in nuclear magnetic resonance (NMR) logging is the time interval between successive spin echoes in a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence,… Read more →

An eddy current is an alternating or transient electrical current induced within a conductive medium when that medium is exposed to a time-varying magnetic field, and the eddy current in turn generates its own opposing… Read more →

What Is Eddy-Current Measurement in Oil and Gas? Eddy-current measurement in oil and gas is an electromagnetic inspection technique that passes a high-frequency alternating current through a transmitter coil to induce… Read more →

An eel in marine seismic acquisition is a short hydrophone array section contained within a flexible, neutrally buoyant cable that can be attached to or inserted into a conventional seismic streamer system, suspended… Read more →

A technique for displacing drilling mud from the annulus using a laminar-flow regime. Read more →

Effective medium theory (EMT) is a rock physics framework that computes the bulk elastic, acoustic, and transport properties of a heterogeneous porous medium composed of minerals, pore space, and fluids by replacing the… Read more →

What Is Effective Permeability? Effective permeability (also called phase permeability) is the permeability of a porous rock to a specific fluid phase when two or more fluid phases are simultaneously present and flowing… Read more →

What Is Effective Porosity? Effective porosity (PHIE) measures the fraction of total rock volume occupied by interconnected pore space through which formation fluids can actually flow, explicitly excluding clay-bound… Read more →

Effective shot density in perforating refers to the number of perforations per foot that are actually contributing to production or injection flow — as distinguished from the nominal shot density (the total number of… Read more →

Effective velocity in seismic exploration is the single velocity value that, when used in the normal moveout (NMO) equation for a horizontally layered earth model, correctly predicts the travel time of a seismic… Read more →

(noun) The fraction of the effective (interconnected) pore volume in a reservoir rock that is occupied by water, calculated by excluding the clay-bound water volume. Effective water saturation is a key parameter in log… Read more →

What Is Effective Wellbore Radius? Effective wellbore radius (also called apparent wellbore radius or r we ) is the radius that a well appears to have based on its inflow performance, accounting for any near-wellbore… Read more →

An eigenvector is a non-zero vector that, when a linear transformation (represented by a square matrix) is applied to it, changes only in magnitude (scaled by a corresponding scalar called the eigenvalue) but does not… Read more →