All about Reserves Estimation
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Possible Reserves
Possible reserves are less certain than probable reserves and can be estimated with a low degree of certainty, insufficient to indicate whether they are more likely to be recovered than not.
In general, possible reserves may include (1) reserves suggested by structural and/or stratigraphic extrapolation beyond areas classified as probable, based on geologic and/or geophysical interpretation, (2) reserves in formations that appear to be hydrocarbon bearing based on logs or cores but that may not be productive at commercial rates, (3) incremental reserves attributable to infill drilling that are subject to technical uncertainty, (4) reserves attributable to an improved recovery method when a project or pilot is planned but not in operation, and rock, fluid, and reservoir characteristics are such that a reasonable doubt exists that the project will be commercial, (5) reserves in an area of a formation that has been proved productive in other areas of the field, but the subject area appears to be separated from the proved area by faulting and geologic interpretation indicates that the subject is structurally lower than the proved area.
Possible reserves are less certain than probable reserves and can be estimated with a low degree of certainty, insufficient to indicate whether they are more likely to be recovered than not.
In general, possible reserves may include (1) reserves suggested by structural and/or stratigraphic extrapolation beyond areas classified as probable, based on geologic and/or geophysical interpretation, (2) reserves in formations that appear to be hydrocarbon bearing based on logs or cores but that may not be productive at commercial rates, (3) incremental reserves attributable to infill drilling that are subject to technical uncertainty, (4) reserves attributable to an improved recovery method when a project or pilot is planned but not in operation, and rock, fluid, and reservoir characteristics are such that a reasonable doubt exists that the project will be commercial, (5) reserves in an area of a formation that has been proved productive in other areas of the field, but the subject area appears to be separated from the proved area by faulting and geologic interpretation indicates that the subject is structurally lower than the proved area.
Developed Reserves
Developed reserves are expected to be recovered from existing wells (including reserves behind pipe). Improved recovery reserves are considered developed only after the necessary equipment has been installed, or when the costs to do so are relatively minor. Developed reserves may be sub-categorized as producing or nonproducing.
Developed reserves are expected to be recovered from existing wells (including reserves behind pipe). Improved recovery reserves are considered developed only after the necessary equipment has been installed, or when the costs to do so are relatively minor. Developed reserves may be sub-categorized as producing or nonproducing.
Nonproducing
Nonproducing reserves include shut-in and behind-pipe reserves. Shut-in reserves are expected to be recovered from completion intervals open at the time of the estimate, but which had not started producing, or were shut in for market conditions or pipeline connection, or were not capable of production for mechanical reasons, and the time when sales will start is uncertain.
Behind-pipe reserves are expected to be recovered from zones behind casing in existing wells, which will require additional completion work or a future recompletion prior to the start of production.
Nonproducing reserves include shut-in and behind-pipe reserves. Shut-in reserves are expected to be recovered from completion intervals open at the time of the estimate, but which had not started producing, or were shut in for market conditions or pipeline connection, or were not capable of production for mechanical reasons, and the time when sales will start is uncertain.
Behind-pipe reserves are expected to be recovered from zones behind casing in existing wells, which will require additional completion work or a future recompletion prior to the start of production.
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Bilal Amjad
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Undeveloped
Undeveloped reserves are expected to be recovered (1) from new wells on undrilled acreage, (2) by deepening existing wells to a different reservoir, or (3) where a relatively large expenditure is required to (a) recomplete an existing well or (b) install production or transportation facilities for primary or improved recovery projects.
Undeveloped reserves are expected to be recovered (1) from new wells on undrilled acreage, (2) by deepening existing wells to a different reservoir, or (3) where a relatively large expenditure is required to (a) recomplete an existing well or (b) install production or transportation facilities for primary or improved recovery projects.
[align=center]Comparison of Definitions for Proved Reserves
Society of Petroleum Engineers (SPE, 1987)[/align]
"Reserves are estimated volumes of crude oil, natural gas, natural gas liquids, and as- sociated substances anticipated to be recoverable from known accumulations from a given date forward, under current economic conditions, by established operations and practices, and under current government regulations. Proved reserves can be estimated with reasonable certainty and are based on interpretation of geologic and/or engineering data available at the time of the estimate. Current economic conditions include prices and costs prevailing at the time of the estimate."
"Reservoirs are considered proved if commercial producibility is supported by actual production or formation tests."
"In certain instances, proved reserves may be assigned on the basis of electrical and other type logs and/or core analysis that indicate that the subject reservoir is hydrocarbon bearing and is analogous to reservoirs in the same area that are producing or have demonstrated the ability to produce on a formation test."
"The area of a reservoir considered proved includes (1) the area delineated by drilling and defined by fluid contacts, if any, and (2) the undrilled areas that can be reasonably judged as commercially productive on the basis on available geologic and engineering data. In the absence of data on fluid contacts, the lowest known structural occurrence of hydrocarbons controls the proved limit unless otherwise indicated by definitive engineering or performance data."
"Proved reserves must have facilities to process and transport those reserves to market time of the estimate, or there is a commitment or reasonable expectation to install such facilities in the future."
"Reserves that can be produced through the application of established improved recovery methods are included in the proved classification when (1) successful testing by a pilot or favorable production or pressure response of an installed program in that reservoir, or one in the immediate area with similar rock and fluid properties, provides support for the engineering analysis on which the project or program is based and (2) it is reasonably certain the project will proceed."
"Reserves to be recovered by improved recovery methods that have yet to be established through repeated commercially successful applications are included in the proved classification only (1) after a favorable production response from subject reservoir from either (a) a representative pilot or (b) an installed program where the response provides support for the engineering analysis on which the project is based, and (2) it is reasonably certain the project will proceed."
"Developed reserves are expected to be recovered from existing wells (including reserves behind pipe). Improved recovery reserves are considered developed only after the necessary equipment has been installed or the costs to do so are relatively minor."
"Undeveloped reserves are expected to be recovered (1) from new wells on undrilled acreage, (2) by deepening existing wells to a new reservoir, or (3) where a relatively large expenditure is required to (a) recomplete an existing well or (b) install production or transportation facilities for primary or improved recovery projects."
"... undeveloped reserves are assigned to undrilled locations that satisfy the following conditions: (1) the undrilled locations are direct offsets to wells that have indicated commercial productivity in the objective formation, (2) it is reasonably certain that the locations are within the known productive limits of the objective formation, (3) the locations conform to existing spacing regulations, if any, and (4) it is reasonably certain the locations will be developed. Reserves for other undrilled locations are classified as proved ... only where interpretation of data from wells indicates that the objective formation is laterally continuous and contains commercially recoverable hydrocarbons beyond direct offsets."
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Society of Petroleum Engineers (SPE, 1987)[/align]
"Reserves are estimated volumes of crude oil, natural gas, natural gas liquids, and as- sociated substances anticipated to be recoverable from known accumulations from a given date forward, under current economic conditions, by established operations and practices, and under current government regulations. Proved reserves can be estimated with reasonable certainty and are based on interpretation of geologic and/or engineering data available at the time of the estimate. Current economic conditions include prices and costs prevailing at the time of the estimate."
"Reservoirs are considered proved if commercial producibility is supported by actual production or formation tests."
"In certain instances, proved reserves may be assigned on the basis of electrical and other type logs and/or core analysis that indicate that the subject reservoir is hydrocarbon bearing and is analogous to reservoirs in the same area that are producing or have demonstrated the ability to produce on a formation test."
"The area of a reservoir considered proved includes (1) the area delineated by drilling and defined by fluid contacts, if any, and (2) the undrilled areas that can be reasonably judged as commercially productive on the basis on available geologic and engineering data. In the absence of data on fluid contacts, the lowest known structural occurrence of hydrocarbons controls the proved limit unless otherwise indicated by definitive engineering or performance data."
"Proved reserves must have facilities to process and transport those reserves to market time of the estimate, or there is a commitment or reasonable expectation to install such facilities in the future."
"Reserves that can be produced through the application of established improved recovery methods are included in the proved classification when (1) successful testing by a pilot or favorable production or pressure response of an installed program in that reservoir, or one in the immediate area with similar rock and fluid properties, provides support for the engineering analysis on which the project or program is based and (2) it is reasonably certain the project will proceed."
"Reserves to be recovered by improved recovery methods that have yet to be established through repeated commercially successful applications are included in the proved classification only (1) after a favorable production response from subject reservoir from either (a) a representative pilot or (b) an installed program where the response provides support for the engineering analysis on which the project is based, and (2) it is reasonably certain the project will proceed."
"Developed reserves are expected to be recovered from existing wells (including reserves behind pipe). Improved recovery reserves are considered developed only after the necessary equipment has been installed or the costs to do so are relatively minor."
"Undeveloped reserves are expected to be recovered (1) from new wells on undrilled acreage, (2) by deepening existing wells to a new reservoir, or (3) where a relatively large expenditure is required to (a) recomplete an existing well or (b) install production or transportation facilities for primary or improved recovery projects."
"... undeveloped reserves are assigned to undrilled locations that satisfy the following conditions: (1) the undrilled locations are direct offsets to wells that have indicated commercial productivity in the objective formation, (2) it is reasonably certain that the locations are within the known productive limits of the objective formation, (3) the locations conform to existing spacing regulations, if any, and (4) it is reasonably certain the locations will be developed. Reserves for other undrilled locations are classified as proved ... only where interpretation of data from wells indicates that the objective formation is laterally continuous and contains commercially recoverable hydrocarbons beyond direct offsets."
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Securities and Exchange Commission (1982)
"... estimated quantities of crude oil, natural gas, and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions, i.e., prices and costs as of the date the estimate is made. Prices in-dude consideration of changes in prices provided by contractual arrangements, but not on escalations based on future conditions."
"Reservoirs are considered proved if economic producibility is supported by either actual production or conclusive formation test."
"In certain instances, proved reserves may be assigned to reservoirs on the basis of a combination of electrical and other type logs and core analysis which indicate the reservoirs are analogous to similar reservoirs in the same field which are producing or have demonstrated the ability to produce on a formation test." (Interpretive response)
"The area of a reservoir considered proved includes (a) that portion delineated by drilling and defined by gas/ oil and/or oil-water contacts, if any, and (b) the immediately adjoining portions not yet drilled but which can be reasonably judged as economically productive on the basis of available geological and engineering data. In the absence of information on fluid contacts, the lowest known structural occurrence of hydrocarbons controls the lower proved limit of the reservoir."
"Reserves which can be produced economically through application of improved recovery techniques (such as fluid injection) are included in the proved
"... estimated quantities of crude oil, natural gas, and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions, i.e., prices and costs as of the date the estimate is made. Prices in-dude consideration of changes in prices provided by contractual arrangements, but not on escalations based on future conditions."
"Reservoirs are considered proved if economic producibility is supported by either actual production or conclusive formation test."
"In certain instances, proved reserves may be assigned to reservoirs on the basis of a combination of electrical and other type logs and core analysis which indicate the reservoirs are analogous to similar reservoirs in the same field which are producing or have demonstrated the ability to produce on a formation test." (Interpretive response)
"The area of a reservoir considered proved includes (a) that portion delineated by drilling and defined by gas/ oil and/or oil-water contacts, if any, and (b) the immediately adjoining portions not yet drilled but which can be reasonably judged as economically productive on the basis of available geological and engineering data. In the absence of information on fluid contacts, the lowest known structural occurrence of hydrocarbons controls the lower proved limit of the reservoir."
"Reserves which can be produced economically through application of improved recovery techniques (such as fluid injection) are included in the proved
Methods of Estimating Reserves
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Methods of estimating reserves may be classified as deterministic (i.e., calculating a single "best" estimate) or probabilistic (i.e., calculating a range of estimates reflecting the probability distributions of the basic data). While it has been recognized that there is always some degree of uncertainty in estimating reserves (see, for example, Walstrom et al. 1967) most of the published literature on reserve estimating has focused on deterministic methods. Probabalistic methods, however, have received continuing attention in the geologic literature on the evaluation of exploration "plays" (see, for example, Newendorp 1975).
With the advent of the North Sea discoveries in the late 1960
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[/align]Methods of estimating reserves may be classified as deterministic (i.e., calculating a single "best" estimate) or probabilistic (i.e., calculating a range of estimates reflecting the probability distributions of the basic data). While it has been recognized that there is always some degree of uncertainty in estimating reserves (see, for example, Walstrom et al. 1967) most of the published literature on reserve estimating has focused on deterministic methods. Probabalistic methods, however, have received continuing attention in the geologic literature on the evaluation of exploration "plays" (see, for example, Newendorp 1975).
With the advent of the North Sea discoveries in the late 1960
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driller4ever
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