Glossary

Oil & gas terms used across the pipeline — what each number means and how it's computed here.

Arps Decline EquationDecline

q(t) = qi / (1 + b·Di·t)^(1/b). Foundation of decline-curve analysis; b sets the curve shape (0 exponential, 0<b<1 hyperbolic, 1 harmonic).

b-factor (Decline Exponent)Decline

Exponent in the Arps equation controlling curvature. Unconventional wells often show b>1 in early time.

Modified Hyperbolic DeclineDecline

Hyperbolic decline that switches to exponential at a terminal-decline threshold, preventing unrealistic long-term forecasts. In EE Cloud this is the per-segment Final Decline of the 4-segment Aries shape.

Terminal DeclineDecline

The floor annual decline a hyperbolic segment switches to (exponential). Caps late-life EUR. Stored per segment as Final Decline.

EUR (Estimated Ultimate Recovery)Production

Total volume expected to be economically recovered over a well's life; computed by integrating the decline curve to the economic limit.

Economic LimitEconomics

Minimum rate at which a well is still profitable to operate; below it the well is shut in / abandoned.

NPV (Net Present Value)Economics

Sum of future cash flows discounted to present value. EE Cloud uses mid-month discounting: factor = (1+rate)^(-(MoY+0.5)/12).

IRR (Internal Rate of Return)Economics

Discount rate at which NPV = 0; the expected compound annual return.

Working Interest (WI)Economics

Ownership share of a lease carrying its proportionate share of costs.

Net Revenue Interest (NRI)Economics

Share of revenue after royalty burdens: NRI = WI × (1 − total royalty burden).

LOE (Lease Operating Expense)Economics

Recurring cost to operate a producing well (labor, power, chemicals, workovers, saltwater disposal).

Payout PeriodEconomics

Time for cumulative cash flow to recover the initial investment.

Type CurveDecline

Representative production profile from a population of wells, usually shown as P10/P50/P90.

GOR (Gas-Oil Ratio)Production

Gas produced per barrel of oil (scf/bbl); rises as reservoir pressure depletes.

Lateral LengthCompletion

Horizontal wellbore length through the target formation; longer laterals generally increase reservoir contact.

AFE (Authorization for Expenditure)Economics

The itemized capital estimate for a well or project (drilling, completion, facilities, land, etc.) used in deal evaluation and budgeting.