Methods to Calculate Fluid in Place

8/11/2019 Methods to Calculate Fluid in Place

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Methods For Calculating

Oil or Gas In Place


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Natasha Asif

Misha Qazi

Faiza Siddique


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Volumetric Method

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MBE Method

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Decline Curve Analysis

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MBAL Software &Conclusion

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Methods For In Place Calculations

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There are commonly four methods to calculate in places for gasand oil:

Volumetric Method

Material Balance Method

Decline Curve Analysis

Reservoir Simulation


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Volumetric Method

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The volumetric equation is useful in reserve work for estimating fluid inplace at any stage of depletion.

Fluid in place using size of reservoir.

It consists of determining the total pore volume available to the fluid and,from a knowledge of fluid composition and the reservoir pressure andtemperature, calculating the amount of fluid.

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Procedure

Estimate the volume of subsurface rock that contains hydrocarbons. Thevolume is calculated from the thickness of the rock containing oil or gas andthe areal extent of the accumulation.

Determine a weighted average effective porosity.

Obtain a reasonable water resistivity value and calculate water saturation.

Finally calculate the original gas-in-place .

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Volumetric Equation

The equation for calculating gas in place is

WhereG = gas in place, scf

A = area of reservoir, acres

h = average reservoir thickness, ft = porosity Swi = water saturation, andBgi = gas formation volume factor, ft3/scf

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Volumetric Uncertainty

A volumetric estimate provides a static measure of oil or gas in place.

The accuracy of the estimate depends on the amount of data available,

which is very limited in the early stages of exploration.

The data increases as wells are drilled and the pool is developed .

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P/Z Method

For a volumetric reservoir and assuming no water production.

Equation of a straight line when (p/z) is plotted versus the cumulative gasproduction Gp.

Slope of the straight line is equal to

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Effect Of Water Drive P/Z Vs. GpRelationship

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Material Balance Equation(MBE)

Conservation of Mass

Defines producing mechanisms

Relates the reservoir fluid and rock expansion to thesubsequent fluid withdrawal.

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Basic Assumptions In MBE

Constant Temperature

Pressure Equilibrium

Constant Reservoir Volume

Reliable Production Data

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MBE Mathematical Form

The simplest form of MBE is

Initial volume = volume remaining + volume removed

By considering all the parameters involved

The above relationship is referred to as the material balance equation(MBE).

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Cont.

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Assuming no pressure maintenance by gas or water injection isbeing considered, MBE can be simplified as

In case when reservoir has no initial gas cap or water influx then,


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A plot of the parameter F as a function of the oil expansion parameter Eo wouldyield a straight line with a slope N and intercept equal to zero

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Gas Drive Reservoirs

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Introduction To Decline Curve Analysis

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Production decline analysis is a traditional means of identifying well production problems and predicting well performance and life basedon real production data

Conventional Analysis Techniques

Exponential decline (constant percentage decline) Harmonic decline, and Hyperbolic decline

Decline Type Curve

Fetkovich decline type curve


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Conventional Analysis Techniques

Di=initial decline rate, years-1 b=constant Qi=initial flow rate MSTB/day

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It is also known as arps techniques. Written below is generalizedequation:


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Cont..

VALUE OF b DECLINE METHOD

b=0 Exponential Decline

b=1 Harmonic Decline

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Cont.

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Cont.

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Cumulative Production Calculation

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Fetkovich Type Curve

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Grid Geometry

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MBAL Software

MBAL is a main tool for future performance prediction it is widely used inindustry for forecasting.We have different options in it like

Reservoir Analysis Tool

Material BalanceIt enables the user to perform historyMatching to find OOIP & water influx model.Decline Curve AnalysisUsed for history matching to predict

future performanceImporting DataExporting DataPlotting Schemes

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Plotting Schemes Of MBAL

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Conclusion

To calculate fluid in place there are different methods dependingupon the data availability. Volumetric method is the most uncertainmethod because of having just static data. MBAL is the most using

performance prediction tool.

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Methods to Calculate Fluid in Place