Production forecasting glossary

This glossary was created through discussions among members of the SPE Production Forecasting Global Integrated Workshop Series. Some definitions were not contested at all, others generated fierce discussions. Sources include Guidelines for Application of the Petroleum Resources Management System, November 2011, sponsored by: o Society of Petroleum Engineers (SPE) o American Association of Petroleum Geologists (AAPG) o World Petroleum Council (WPC) o Society of Petroleum Evaluation Engineers (SPEE) o Society of Exploration Geophysicists (SEG)

A

ACQ

Annual Contractual Quantity. The contract quantity is the contractually agreed volumes and limits: predefined (annual) volume of natural gas on contract level.

Availability

A factor applied to forecasts to take into account the fact that a Production System will not always operate at 100% of its capacity.

See also: IPSC and ABNR

ABNR

Available But Not Required, that part of the IPSC that is available for production but not produced because of low off-take demand. ABNR typically occurs in Demand Driven Production Systems.

C

Choke Model

A model visualising and quantifying a series of restrictions or chokes that represent the areas of production loss, i.e. Reservoir potential (as measured by well tests), that is not, or cannot be, delivered at custody transfer point. These are simplified for management reporting as Reservoir, Wells, Plant, and Export chokes.

Constraint

A production or injection constraint is a factor limiting production or injection capacity. This can be a physical constraint induced by existing or planned equipment capacity (e.g. compressor capacity) or an operational constraint induced by commercial, political, social, economic, regulatory, permitting, government, or environmental guidelines (e.g. flare limits, max allowable reservoir voidage, contractual production limits, etc.).

Controllable variable

A variable that can be influenced by staff through improved working procedures, for example down-time. See also: non-controllable variable.

CTP

Custody Transfer Point, the point at which the forecast volumes are quantified. Note: this may be different from the volumes produced from the reservoir and wells, as it takes into account “own use”, flare/vent volumes and potential losses in the production system.

D

DCQ

Daily Contracted Quantity. Can be absolute or derived from the ACQ.

Decline Curve Analysis

A method of forecasting well or reservoir production by extrapolating past trends in well or reservoir behaviour.

Deferment, or Deferred Production/Injection

Deferment is the reduction in Production or Injection Availability caused by an activity, breakdown, trip, poor equipment performance, or sub-optimum operations, that results in a reduction in the volume sold or injected, delaying the production or injection until some later time.

See also: Scheduled/Unscheduled Deferments.

Demand Driven Production System

A Production System with Load Factor potentially < 1. Production from a Demand Driven System is determined by external product demand. This applies mainly to gas production systems where gas demand may fluctuate.

Demand Profile

A demand profile is a time series that describes the expected future demand over time for a given counterparty.

Deterministic Forecast

A deterministic forecast is combining a single set of discrete parameter estimates (gross rock volume, average porosity, development plan, equipment availability, etc.) that represent a physically realizable and realistic combination in order to derive a single, specific estimate of production per time step and/or recoverable quantities.

A deterministic forecast is based on a specific combination of parameters representing a specific scenario, but does not give quantitative information on the probability of a certain outcome, even if the probability of the individual input parameters is known.

Dynamic Reservoir Simulation Model

A dynamical system is a concept in mathematics where a fixed rule describes the time dependence of a point in a geometrical space. A dynamic reservoir simulation model is a computer model used to predict the flow of fluids in a reservoir.

E

EoFL

End of Field Life, a point in time when production from a field ended, for instance when abandonment conditions have been reached.

Expectation Forecast

See Mean Forecast

F

FDP

Field Development Plan

Forecast

In general: a forecast is a prediction based on study and/or observation. In the Oil & Gas Industry, a forecast is the projection in time of a quantity (production, injection, emissions, energy consumption, etc.); the projection is computed using a quantitative model that processes input data.

H

High Estimate (resources)

With respect to resource categorization, this is considered to be an optimistic estimate of the quantity that will actually be recovered from an accumulation by a project. If probabilistic methods are used, there should be at least a 10% probability (P10) that the quantities actually recovered will equal or exceed the high estimate.

History Matching

Modifying reservoir model to match the historical production and pressure data with simulated results as closely as possible. The history matching quality depends on the quality of the reservoir model and the quality and quantity of historical data. The history matched reservoir models are subsequently used to help predict future reservoir behaviour.

I

IAM

Integrated Asset Model

IPSC

Integrated Production System Capacity, the capacity the integrated production system is, or would be able to deliver at the Custody Transfer Point for the integrated production system at 100% availability. Note: This is not necessarily equal to the capacity that could be produced from wells at 100% availability as it is defined at delivery point and takes into account own use and vent/flare volumes.

IPSC = Production + Deferment (+ Losses) + ABNR

See also: Availability

IPSM

Integrated Production System Model, modelling the flow and changes in composition of hydrocarbons and other fluids through wells and facilities from the reservoir to delivery point, taking into account the effects of (re)injection, flare, vent, “own use”, surface treatments.

L

L - M - H

Low - Medium –High, three discrete values to describe the uncertainty range of forecast input parameters, whereby the medium value is the "best estimate".

L - M -H can also be used to describe the uncertainty range for deterministic forecasts, in which case no probability may be attached to the individual scenarios.

LNG

Liquified Natural Gas

Load Factor

The ratio of the average load to the peak load during any particular time period. The Load Factor is a measure of the continuity of the demand. A Load Factor less than 1 means that one will not be able to sell the total volume that the system could physically deliver at the custody transfer point.

Long Term

The period from now until end-of-field-life (EOFL). LT forecasts are generally prepared for resource volume estimates and expressed in annual volumes.

Losses

That part of the IPSC that could have been delivered to customers but is not, due to leaks, theft, etc.

Low Estimate (resources)

With respect to resource categorization, this is considered to be a conservative estimate of the quantity that will actually be recovered from the accumulation by a project. If probabilistic methods are used, there should be at least a 90% probability (P90) that the quantities actually recovered will equal or exceed the low estimate.

M

Mean Forecast

In probabilistic production forecasting: the concatenation in time of mean values of the forecast range as calculated per time-step. Not necessarily the forecast that results from using the mean values per uncertain input parameter!

Note: Expectation forecasts may be aggregated (Sum of the Mean is the Mean of the Sum)

Medium Term

The period starting now and ending one or two years beyond the start of the next budget year. This period is defined separately from ST (in-year) and LT (EoFL) because the quality of this forecast is much dependent on the contributions and ownership from various Disciplines (e.g. Development, Operations). The MT forecast is affected by Controllable Variables such as Opex/Capex investments and equipment performance/availability. The MT forecast may be expressed in terms of annual volumes or (average) daily rates.

Model

A (set of) mathematical equation(s) that converts (model) input parameters to (model) output parameters, given certain inner and outer boundary conditions.

N

NFA

No Further Activity: the forecast without new Capex invested.

Nomination

Nomination is a binding commitment or order to deliver, buy or transport gas.

Non-controllable Variable

A variable that cannot be influenced by staff through improved working procedures, for example permeability.

NTR

Non Technical Risk. These are risks directly affecting a specific project, caused by (non-contractor) external Stakeholders that trigger a deviation from the locally established and/or expected behaviours / practices / regulations. What sets NTR apart from technical risks within a project context is that there is a clear linkage to external stakeholders, i.e. parties in commercial, political, social, economic, regulatory, permitting, government, and environmental areas that have a real or perceived interest in the project.

O

Own Use

Produced hydrocarbons used to operate the system, such as: Continuous Flare pilot, (Continuous) Vent purge, Fuel (e.g. for power generation and compressors), Blanket Gas. Own Use gas is produced gas not available for sales.

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