Hydrocarbon Reserve

Calculatation

Presented By :-Rishi Nandan Vashistha (44)

Robinu Rose Mathew (45)Sameer Sharma (46)

AgendaAgenda• To give a brief view of Hydrocarbon To give a brief view of Hydrocarbon

Reserve Estimation TechniquesReserve Estimation Techniques

• To give a brief view about the reserves To give a brief view about the reserves and their classifications.and their classifications.

• To give a brief view of reserve status To give a brief view of reserve status categoriescategories

IntroductionIntroduction• With this global expansion of the petroleum industry has With this global expansion of the petroleum industry has

come ongoing technological development that provides come ongoing technological development that provides better tools and techniques for analyzing reservoirs and better tools and techniques for analyzing reservoirs and reservoir fluids as well as greater understanding of how reservoir fluids as well as greater understanding of how reservoir geology affects reservoir performance.reservoir geology affects reservoir performance.

• The estimation of reserves is more than just a periodic, The estimation of reserves is more than just a periodic, statutory calculating and reporting of company assets. statutory calculating and reporting of company assets.

• It is an essential element of investment planning and It is an essential element of investment planning and resource management for every prudent operator. resource management for every prudent operator.

• Begins with identifying a drillable prospect, and it Begins with identifying a drillable prospect, and it continues while the prospect is developed and placed on continues while the prospect is developed and placed on productionproduction

Classification of ReservesClassification of Reserves

• In 1930s API made attempts to standardize In 1930s API made attempts to standardize classification.classification.

• • Since than evolution of technology has Since than evolution of technology has intensified the need for an improved intensified the need for an improved nomenclature to achieve consistency among nomenclature to achieve consistency among professionals working with reserve professionals working with reserve terminology. terminology.

• SPE and WPC drafted a strikingly similar sets SPE and WPC drafted a strikingly similar sets of reserve definitions and these were of reserve definitions and these were introduced in 1987.introduced in 1987.

• In 1993 the Petroleum Society of CIM In 1993 the Petroleum Society of CIM published a monograph containing a report published a monograph containing a report on reserve definitions.on reserve definitions.

• In 2000 SPE, WPC and AAPG jointly In 2000 SPE, WPC and AAPG jointly approved and published “Petroleum approved and published “Petroleum Resources Classification and Definitions”.Resources Classification and Definitions”.

• The Petroleum Society published The Petroleum Society published “Definitions and Guidelines for Estimating “Definitions and Guidelines for Estimating and Classifying Oil and Gas Reserve” in and Classifying Oil and Gas Reserve” in 2002.2002.

Reserves Definition According to Reserves Definition According to the Classificationthe Classification

• Total Petroleum–Initially–in–PlaceTotal Petroleum–Initially–in–Place: : It is the It is the quantity of petroleum which is estimated to exist quantity of petroleum which is estimated to exist originally in naturally occurring accumulations, plus originally in naturally occurring accumulations, plus those quantities in accumulations yet to be discovered those quantities in accumulations yet to be discovered on a given date. It may be subdivided into on a given date. It may be subdivided into

2.2. Discovered Petroleum-Initially-In-PlaceDiscovered Petroleum-Initially-In-Place

3.3. Undiscovered Petroleum-Initially-In-PlaceUndiscovered Petroleum-Initially-In-Place

Discovered-Petroleum-Initially –Discovered-Petroleum-Initially –In-PlaceIn-Place

• It is that quantity of petroleum which is estimated to be contained in known It is that quantity of petroleum which is estimated to be contained in known accumulation, plus those quantities already produced there.accumulation, plus those quantities already produced there.

• Discovered Petroleum initially-in-place may be subdivided into commercial and Discovered Petroleum initially-in-place may be subdivided into commercial and sub commercial categories, with the estimated potentially recoverable portion sub commercial categories, with the estimated potentially recoverable portion being classified as:being classified as:

c)c) Reserves (commercial)Reserves (commercial)

I. ProvedI. Proved

II. Proved plus probableII. Proved plus probable

III Proved plus probable plus possibleIII Proved plus probable plus possible

g)g) Contingent resources (Sub Commercial)Contingent resources (Sub Commercial)

I. Low EstimateI. Low Estimate

II. Best estimateII. Best estimate

III High Estimate III High Estimate

c) Unrecoverablec) Unrecoverable

a) Reservesa) Reserves• Those quantities of oil and gas anticipated to be economically Those quantities of oil and gas anticipated to be economically

recoverable from discovered resources from a given date forward recoverable from discovered resources from a given date forward are classified as reserves are classified as reserves (published in draft by the Society of (published in draft by the Society of Petroleum Engineers (SPE) and World Petroleum Congress Petroleum Engineers (SPE) and World Petroleum Congress (WPC))(WPC))..

• In general, quantities must not be classified as reserves unless there In general, quantities must not be classified as reserves unless there is an expectation that the accumulation will be developed and is an expectation that the accumulation will be developed and placed on production within a reasonable timeframe.placed on production within a reasonable timeframe.

I. Proved ReservesI. Proved Reserves• Proved reserves are those quantities of petroleum which, by Proved reserves are those quantities of petroleum which, by

analysis of geological and engineering data, can be estimated with analysis of geological and engineering data, can be estimated with reasonable certainty to be commercially recoverable, from a given reasonable certainty to be commercially recoverable, from a given date forward, from known reservoirs and under current economic date forward, from known reservoirs and under current economic conditions, operating methods, and government regulations. conditions, operating methods, and government regulations. Proved reserves can be categorized as developed or undeveloped.Proved reserves can be categorized as developed or undeveloped.

• If deterministic methods are used, the term reasonable certainty If deterministic methods are used, the term reasonable certainty is intended to express a high degree of confidence that the is intended to express a high degree of confidence that the quantities will be recovered. If probabilistic methods are used, quantities will be recovered. If probabilistic methods are used, there should be at least a 90% probability that the quantities there should be at least a 90% probability that the quantities actually recovered will equal or exceed the estimate.actually recovered will equal or exceed the estimate.

II. Proved Plus ProbableII. Proved Plus Probable

• Probable reserves are those Probable reserves are those Unproved Reserves* Unproved Reserves* which which analysis of geological and engineering data suggests are analysis of geological and engineering data suggests are more likely than not to be recoverable. In this context, when more likely than not to be recoverable. In this context, when probabilistic methods are used, there should be at least a probabilistic methods are used, there should be at least a 50% probability that the quantities actually recovered will 50% probability that the quantities actually recovered will equal or exceed the sum of estimated proved plus probable equal or exceed the sum of estimated proved plus probable reserves.reserves.

**Unproved reservesUnproved reserves may be estimated assuming future may be estimated assuming future economic conditions different from those prevailing at the economic conditions different from those prevailing at the time of the estimate.time of the estimate.

III. Proved Plus Probable Plus III. Proved Plus Probable Plus PossiblePossible

• Possible reserves are those unproved reserves Possible reserves are those unproved reserves which analysis of geological and engineering which analysis of geological and engineering data data suggests are less likely to be recoverable than suggests are less likely to be recoverable than probable reserves. In this context, when probable reserves. In this context, when probabilistic methods are used, there should be probabilistic methods are used, there should be at least a 10% probability that the quantities at least a 10% probability that the quantities actually recovered will equal or exceed the sum actually recovered will equal or exceed the sum of estimated proved plus probable plus possible of estimated proved plus probable plus possible reserves.reserves.

b) Contingent Resourcesb) Contingent Resources

• Contingent resources are defined as those quantities of oil Contingent resources are defined as those quantities of oil and gas estimated on a given date to be potentially and gas estimated on a given date to be potentially recoverable from known accumulations but are not currently recoverable from known accumulations but are not currently economic. Contingent resources include, for example, economic. Contingent resources include, for example, accumulations for which there is currently no viable market. accumulations for which there is currently no viable market. It can be categorize in three types :It can be categorize in three types :

III.III. Low EstimateLow Estimate

IV.IV. Best estimateBest estimate

V.V. High Estimate High Estimate

• Low Estimate:Low Estimate: This is considered to be a conservative estimate of This is considered to be a conservative estimate of the quantity that will actually be recovered from the accumulation. the quantity that will actually be recovered from the accumulation. If probabilistic methods are used, this term reflects a P90 If probabilistic methods are used, this term reflects a P90 confidence level.confidence level.

• Best Estimate:Best Estimate: This is considered to be the best estimate of the This is considered to be the best estimate of the quantity that will actually be recovered from the accumulation. If quantity that will actually be recovered from the accumulation. If probabilistic methods are used, this term is a measure of central probabilistic methods are used, this term is a measure of central tendency of the uncertainty distribution (most likely/mode, tendency of the uncertainty distribution (most likely/mode, P50/median, or arithmetic average/mean.)P50/median, or arithmetic average/mean.)

• High Estimate:High Estimate: This is considered to be an optimistic estimate of This is considered to be an optimistic estimate of the quantity that will actually be recovered from the accumulation. the quantity that will actually be recovered from the accumulation. If probabilistic methods are used, this term reflects a P10 If probabilistic methods are used, this term reflects a P10 confidence level.confidence level.

c). Unrecoverablec). Unrecoverable

• Unrecoverable resources, whether discovered or Unrecoverable resources, whether discovered or undiscovered, are neither technically possible nor undiscovered, are neither technically possible nor economic to produce. They represent quantities of economic to produce. They represent quantities of petroleum that are in the reservoir after commercial petroleum that are in the reservoir after commercial production has ceased, and in known and unknown production has ceased, and in known and unknown accumulations that are not deemed recoverable due accumulations that are not deemed recoverable due to lack of technical and economic recovery processes.to lack of technical and economic recovery processes.

2. Undiscovered Petroleum-Initially-2. Undiscovered Petroleum-Initially-In-PlaceIn-Place

• Undiscovered resources are defined as those quantities of Undiscovered resources are defined as those quantities of oil and gas estimated on a given date to be contained in oil and gas estimated on a given date to be contained in accumulations yet to be discovered. The estimated accumulations yet to be discovered. The estimated potentially recoverable portion of undiscovered resources is potentially recoverable portion of undiscovered resources is classified as prospective resources.classified as prospective resources.

a). Prospective resourcesa). Prospective resources

I. Low EstimateI. Low Estimate

II. Best estimateII. Best estimate

III High Estimate III High Estimate

b). Unrecoverableb). Unrecoverable

a). Prospective resourcesa). Prospective resources

• Prospective resources are defined as those quantities Prospective resources are defined as those quantities of oil and gas estimated on a given date to be of oil and gas estimated on a given date to be potentially recoverable from undiscovered potentially recoverable from undiscovered accumulations. They are technically viable and accumulations. They are technically viable and economic to recover.economic to recover.

• Low Estimate:Low Estimate: This is considered to be a conservative estimate of This is considered to be a conservative estimate of the quantity that will actually be recovered from the accumulation. the quantity that will actually be recovered from the accumulation. If probabilistic methods are used, this term reflects a P90 If probabilistic methods are used, this term reflects a P90 confidence level.confidence level.

• Best Estimate:Best Estimate: This is considered to be the best estimate of the This is considered to be the best estimate of the quantity that will actually be recovered from the accumulation. If quantity that will actually be recovered from the accumulation. If probabilistic methods are used, this term is a measure of central probabilistic methods are used, this term is a measure of central tendency of the uncertainty distribution (most likely/mode, tendency of the uncertainty distribution (most likely/mode, P50/median, or arithmetic average/mean.)P50/median, or arithmetic average/mean.)

• High Estimate:High Estimate: This is considered to be an optimistic estimate of This is considered to be an optimistic estimate of the quantity that will actually be recovered from the accumulation. the quantity that will actually be recovered from the accumulation. If probabilistic methods are used, this term reflects a P10 If probabilistic methods are used, this term reflects a P10 confidence level.confidence level.

b). Unrecoverableb). Unrecoverable• Unrecoverable resources, whether discovered or Unrecoverable resources, whether discovered or

undiscovered, are neither technically possible nor undiscovered, are neither technically possible nor economic to produce. They represent quantities of economic to produce. They represent quantities of petroleum that are in the reservoir after commercial petroleum that are in the reservoir after commercial production has ceased, and in known and unknown production has ceased, and in known and unknown accumulations that are not deemed recoverable due accumulations that are not deemed recoverable due to lack of technical and economic recovery processes.to lack of technical and economic recovery processes.

Reserves Status CategoriesReserves Status Categories

• Reserves status categories define the development and Reserves status categories define the development and producing status of wells and reservoirs.producing status of wells and reservoirs.

1. Developed Reserves: 1. Developed Reserves: Developed reserves are expected to Developed reserves are expected to be recovered from existing wells including reservesbe recovered from existing wells including reserves behind behind pipe. Improved recovery reserves are considered developed pipe. Improved recovery reserves are considered developed only after the necessary equipment has been installed, or only after the necessary equipment has been installed, or when the costs to do so are relatively minor. Developed when the costs to do so are relatively minor. Developed reserves may be subcategorized as producing or reserves may be subcategorized as producing or nonproducing.nonproducing.

a) a) Producing:Producing: Reserves subcategorized as producing are Reserves subcategorized as producing are expected to be recovered from completion intervals that are expected to be recovered from completion intervals that are open and producing at the time of the estimate. Improved open and producing at the time of the estimate. Improved recovery reserves are considered producing only after the recovery reserves are considered producing only after the improved recovery project is in operation.improved recovery project is in operation.

b) Nonproducing:b) Nonproducing: Reserves subcategorized as nonproducing Reserves subcategorized as nonproducing include shut-in and behind-pipe reserves. Shut-in reserves are include shut-in and behind-pipe reserves. Shut-in reserves are expected to be recovered from expected to be recovered from

(a) completion intervals that are open at the time of the (a) completion intervals that are open at the time of the estimate but that have not started producing, estimate but that have not started producing,

(b) wells which were shut in for market conditions or pipeline (b) wells which were shut in for market conditions or pipeline connections or connections or

(c) wells not capable of production for mechanical reasons. (c) wells not capable of production for mechanical reasons.

2. Undeveloped reserves2. Undeveloped reserves are expected to be recovered are expected to be recovered

(a) from new wells on undrilled acreage, (a) from new wells on undrilled acreage,

(b) from deepening existing wells to a different reservoir, (b) from deepening existing wells to a different reservoir,

(c) where a relatively large expenditures required to (c) where a relatively large expenditures required to

((II) recomplete an existing well or ) recomplete an existing well or

((IIII) install production or transportation facilities for ) install production or transportation facilities for primary or improved recovery projects. primary or improved recovery projects.

Classification of Reserves Classification of Reserves followed by ONGCfollowed by ONGC

• The professional expertise of The professional expertise of ONGC ONGC was imbibed from the was imbibed from the systems, approaches and regulations followed in erstwhile systems, approaches and regulations followed in erstwhile USSR. Therefore the classification of reserves followed in USSR. Therefore the classification of reserves followed in USSR was adopted with modifications suiting to Indian USSR was adopted with modifications suiting to Indian environment.environment.

• The reserves were classified as- The reserves were classified as- Geological Reserves Geological Reserves (In-(In-place volumes of hydrocarbons) and place volumes of hydrocarbons) and Recoverable reserves. Recoverable reserves. The reserves were divided into A, B, C1, C2 and Z -balance The reserves were divided into A, B, C1, C2 and Z -balance categories. categories.

• After global changes in petroleum industry, the ONGC After global changes in petroleum industry, the ONGC adopted a classification similar to that recommended by adopted a classification similar to that recommended by SPE, SPE, WPC and AAPG.WPC and AAPG.

Periodicity of the EstimatesPeriodicity of the Estimates

1.1. Prior to drilling of exploratory wellPrior to drilling of exploratory well

2.2. During and after appraisal and delineation During and after appraisal and delineation drillingdrilling

3.3. After trial production data becomes availableAfter trial production data becomes available

4.4. Prior to development strategy optimizationPrior to development strategy optimization

5.5. During productionDuring production

6.6. When the production is decliningWhen the production is declining

7.7. At depletionAt depletion

Range of Recovery Estimates Range of Recovery Estimates

• Estimated Ultimate Recovery: Estimated ultimate recovery (EUR) is an approximation of the quantity of oil or gas that is potentially recoverable or has already been recovered from a reserve or well.

• Cumulative production: The total amount of oil and gas recovered from a reservoir as of a particular time in the life of the field. Cumulative production can be referenced to a well, a field, or a basin.

Ranges in estimates of ultimate recovery during life of Ranges in estimates of ultimate recovery during life of reservoir reservoir

The Methods The Methods to followto follow

• Volumetric EstimatesVolumetric Estimates• Performance TechniquesPerformance Techniques

– Material balance approachMaterial balance approach

– Decline curve analysisDecline curve analysis

• Monte-Carlo Method Monte-Carlo Method

Volumetric EstimatesVolumetric Estimates

• Used early in the life of a reservoir, before Used early in the life of a reservoir, before sufficient production and/or pressure data sufficient production and/or pressure data to use the performance method,to use the performance method,

• Results from their use might be subject to Results from their use might be subject to considerable uncertainty,considerable uncertainty,

• Depends on the geologic setting and the Depends on the geologic setting and the amount and quality of geologic and amount and quality of geologic and engineering data.engineering data.

Estimation of Estimation of OILOIL Reserves Reserves

QQ0 0 = 7758 = 7758 xx ɸ ɸ x x SS00 xx h h xx A A

ββ00

where,where,• 7758 = bbl/acre feet (converts acre-feet into STB, Stock Tank bbl)7758 = bbl/acre feet (converts acre-feet into STB, Stock Tank bbl)

• QQ00 = Quantity of Oil in Barrels = Quantity of Oil in Barrels

• = Porosity of reserve in fraction ɸ = Porosity of reserve in fraction ɸ• SS00 = Saturation fraction = Saturation fraction

• h = Average effective thickness in feeth = Average effective thickness in feet• A = Area of pool AcresA = Area of pool Acres

• ββ00= Formation volume factor for Oil= Formation volume factor for Oil

Estimation of Estimation of GASGAS Reserves Reserves

QQgg = 43560 = 43560 xx ɸ ɸ xx S Sgg x x h h xx A A

ββgg

Where,Where,

• 43560 = ft43560 = ft33 / acre feet (1 acre = 43,560 sq. feet) / acre feet (1 acre = 43,560 sq. feet)

• QQgg = Quantity of gas in Standard Cubic Feet = Quantity of gas in Standard Cubic Feet

• = Porosity of the reservoir in fractionɸ = Porosity of the reservoir in fractionɸ• Sg = Gas saturation in fractionSg = Gas saturation in fraction• h = Average effective thickness in feeth = Average effective thickness in feet• A = Area of pool in acresA = Area of pool in acres

• ββgg = Formation volume factor for Gas = Formation volume factor for Gas

The Methods The Methods to followto follow

• Volumetric EstimatesVolumetric Estimates

• Performance TechniquesPerformance Techniques

– Material balance approachMaterial balance approach– Decline curve analysisDecline curve analysis

• Monte-Carlo Method Monte-Carlo Method

Performance Techniques Performance Techniques

• Material Balance ApproachMaterial Balance Approach– It is a computational procedure, treating the It is a computational procedure, treating the

reservoir as though it were a tank.reservoir as though it were a tank.– These methods can be used when there are These methods can be used when there are

sufficient historical reservoir pressure and sufficient historical reservoir pressure and production data to perform reliable calculations.production data to perform reliable calculations.

– The method is based on the premise that the Pore The method is based on the premise that the Pore Volume of a reservoir remains constant or changes Volume of a reservoir remains constant or changes in predictable manner with reservoir pressure in predictable manner with reservoir pressure drop.drop.

• The data used for this approach consist of the The data used for this approach consist of the following :following :– Production volumeProduction volume– Reservoir Pressure & Temperature Reservoir Pressure & Temperature – Fluid Analysis DataFluid Analysis Data– Log Data ,Core dataLog Data ,Core data– Drive mechanismDrive mechanism

The Equation• A general material balance equation that can be applied to all A general material balance equation that can be applied to all

reservoir types was first developed by Schilthuis in 1936.reservoir types was first developed by Schilthuis in 1936.

Expansion of oil in the oil zone +Expansion of oil in the oil zone +

Expansion of gas in the gas zone +Expansion of gas in the gas zone +

Expansion of connate water in the oil and gas zones +Expansion of connate water in the oil and gas zones +

Contraction of pore volume in the oil and gas zones +Contraction of pore volume in the oil and gas zones +

Water influx + Water injected + Gas injected Water influx + Water injected + Gas injected

==

Oil produced + Gas produced + Water producedOil produced + Gas produced + Water produced

Mathematically

where, where,

•Np = cumulative oil production, STBNp = cumulative oil production, STB•Bt = formation volume factor, total, RB/STBBt = formation volume factor, total, RB/STB•Bg = formation volume factor, gas, Rcf/scBg = formation volume factor, gas, Rcf/sc•Rp = cumulative (producing) gas/oil ratio, scf/STBRp = cumulative (producing) gas/oil ratio, scf/STB•Rsi = initial solution gas/oil ratio, scf/STBRsi = initial solution gas/oil ratio, scf/STB•Bw = formation volume factor, water, RB/STBBw = formation volume factor, water, RB/STB•Wp = cumulative water production, STWp = cumulative water production, ST•Ni = oil initially in place, STB or mNi = oil initially in place, STB or m•Bt = formation volume factor, total, RB/STBBt = formation volume factor, total, RB/STB•Bti = initial total formation volume factor, RB/STBBti = initial total formation volume factor, RB/STB•m = ratio of initial gas cap volume to initial oil column volume, dimensionlessm = ratio of initial gas cap volume to initial oil column volume, dimensionless•Bgi = initial formation volume factor, gas, Rcf/scf or RB/scfBgi = initial formation volume factor, gas, Rcf/scf or RB/scf•We = cumulative water influx, RBWe = cumulative water influx, RB

The Methods The Methods to followto follow

• Volumetric EstimatesVolumetric Estimates

• Performance TechniquesPerformance Techniques

– Material balance approachMaterial balance approach

– Decline curve analysisDecline curve analysis

• Monte-Carlo Method Monte-Carlo Method

Decline Curve AnalysisDecline Curve Analysis

• Analysis of Analysis of Production Decline CurveProduction Decline Curve can can provide estimation of three important provide estimation of three important items.items.

– Remaining Oil and gas reserves.Remaining Oil and gas reserves.– Future expected production rate.Future expected production rate.– Remaining productive life of well or reservoir.Remaining productive life of well or reservoir.

What it is……What it is……

• A A decline curve of a well is simply a plot of the well’s decline curve of a well is simply a plot of the well’s production rate on the y-axis production rate on the y-axis versus time on the x-versus time on the x-axis.axis.

• The plot is usually done on a semilog paper; i.e. the The plot is usually done on a semilog paper; i.e. the y-axis is logarithmic and the x-axis is linear.y-axis is logarithmic and the x-axis is linear.

• Three types of Decline CurvesThree types of Decline Curves– Exponential CurveExponential Curve

– Hyperbolic CurveHyperbolic Curve– Harmonic CurveHarmonic Curve

Exponential CurveExponential Curve

• When the data plots as a straight line, it is modeled with a When the data plots as a straight line, it is modeled with a constant percentage decline “constant percentage decline “exponential decline”.exponential decline”.

• The equation of the straight line on the semilog paper is given The equation of the straight line on the semilog paper is given by:by:

q= qq= qi i ee-Dt-Dt

• Where, Where, – q = well’s production rate at time t, STB/dayq = well’s production rate at time t, STB/day– qi = well’s production rate at time 0, STB/dayqi = well’s production rate at time 0, STB/day– D = nominal exponential decline rate, 1/dayD = nominal exponential decline rate, 1/day– t = time, dayt = time, day

Hyperbolic CurveHyperbolic Curve

• When the data plots concave upward, it is modeled with a When the data plots concave upward, it is modeled with a ““hyperbolic decline”hyperbolic decline”

• The equation of the hyperbolic decline is given by:The equation of the hyperbolic decline is given by:

q = qq = qii (1+bD (1+bDiit) t) -1/b-1/b

Where,Where,

• q = well’s production rate at time t, STB/dayq = well’s production rate at time t, STB/day

• qqii = well’s production rate at time 0, STB/day = well’s production rate at time 0, STB/day

• DDii = initial nominal exponential decline rate (t = 0), 1/day = initial nominal exponential decline rate (t = 0), 1/day

• b = hyperbolic exponentb = hyperbolic exponent• t = time, dayt = time, day

Harmonic CurveHarmonic Curve

• A special case of the hyperbolic decline is known as “harmonic decline”.

• The equation of the straight line on the The equation of the straight line on the semilog paper is given by:semilog paper is given by:

q = qq = qii

1+ bD1+ bDiitt

The Methods The Methods to followto follow

• Volumetric EstimatesVolumetric Estimates

• Performance TechniquesPerformance Techniques

– Material balance approachMaterial balance approach

– Decline curve analysisDecline curve analysis

• Monte-Carlo Method Monte-Carlo Method

Monte Carlo MethodMonte Carlo Method• A method of random sampling the Stochastic input A method of random sampling the Stochastic input

values to provide a picture of the output distribution values to provide a picture of the output distribution values and probabilitiesvalues and probabilities

• The model takes these inputs and calculates the The model takes these inputs and calculates the outputsoutputs

• These outputs are recordedThese outputs are recorded• The process is repeated x time until sufficient repeat The process is repeated x time until sufficient repeat

samples are collected to provide a probability samples are collected to provide a probability breakdown for a range of output valuesbreakdown for a range of output values

The EquationHydrocarbon in Place = GRV x N/G x Porosity x SHydrocarbon in Place = GRV x N/G x Porosity x Shh

FVFFVF• Gross Rock volume - amount of rock in the trap above the Gross Rock volume - amount of rock in the trap above the

hydrocarbon water contacthydrocarbon water contact• N/G - net/gross ratio - percentage of the GRV formed by the N/G - net/gross ratio - percentage of the GRV formed by the

reservoir rock ( range is 0 to 1)reservoir rock ( range is 0 to 1)• Porosity - (typically 5-35%)Porosity - (typically 5-35%)

• SShh - hydrocarbon saturation - hydrocarbon saturation

• FVF - formation volume factor - oil shrinks and gas expands FVF - formation volume factor - oil shrinks and gas expands when brought to the surface. The FVF converts volumes at when brought to the surface. The FVF converts volumes at reservoir conditions (high pressure and high temperature) to reservoir conditions (high pressure and high temperature) to storage and sale conditionsstorage and sale conditions

ReferencesReferences• Chapter 18, Estimation of Primary Reserves of Chapter 18, Estimation of Primary Reserves of

Crude Oil, Natural Gas, and Condensate. Ron Crude Oil, Natural Gas, and Condensate. Ron Harrell, SPE, Ryder Scott Co. and Chap Harrell, SPE, Ryder Scott Co. and Chap Cronquist, SPE, Consultant.Cronquist, SPE, Consultant.

• Chapter 11, Sec 11.4-11.7, Bassiouni, Z: Chapter 11, Sec 11.4-11.7, Bassiouni, Z: Theory, Measurement, and Interpretation Theory, Measurement, and Interpretation of Well Logs, SPE Textbook Series, Vol. 4, of Well Logs, SPE Textbook Series, Vol. 4, (1994) (1994)

• Corelab, Fundamentals of Core Analysis, Corelab, Fundamentals of Core Analysis, Houston, TX (1983), Chapter 7 Houston, TX (1983), Chapter 7

That’s all folks……!!!!!!!!That’s all folks……!!!!!!!!