RESERVOIR SIMULATION

Assignment on

1. History matching and prediction

2. MBE with emphasis on Gas reservoir

BY

PARVEZ NOPHEL

B.TECH APE UP (2011 - 15)

R870211019

500017479

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CONTENTS

WHAT IS RESERVOIR SIMULATION?

SIMULATOR AND ITS TYPES

HISTORY MATCHING AND PREDICTION

CASE STUDY

MBE

MBE FOR GAS RESERVOIR

EXAMPLE NUMERICAL ON GAS MBE

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WHAT IS RESERVIR SIMULATION:

A digital description of reservoir together combined

with physical and mathematical equations along

with good reservoir engineering which is used to

predict the future performance of the reservoir and

hence managing the asset is called reservoir

simulation

Reservoir simulation deals with solving set of

equations, a representative of reservoir, using

computer programming called simulator.

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SIMULATOR AND ITS TYPES

Black-oil model (IMEX)

Compositional model (GEM)

Thermal model (STARS)

Chemical

Miscible

Dual Porosity

Dual permeability

Simulator is nothing but mathematical equations

solving by the execution of set of computer programs.

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HISTORY MATCHING AND PREDICTION

History matching is the process of building one or

more sets of numerical models (representing a

reservoir) which account for observed, measured

data.

It is a part of Uncertainty quantification.

It matches the developed model with geospatial,

geological and production data to create a perfect

reservoir model.

The matched model is used for future performance

of the reservoir.

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Figure 1.6

CASE STUDY

Organization: TNO - 1996

As the History matching is a process of selection of

appropriate model for the future prediction, it should

be more accurate.

Proper parameterization of the stochastic process

involved.

The model parameter is assigned as show in the

figure 1 which is an iterative process.

The data consistent with many models.

Subjective decision was made by the reservoir

engineer. 7

The uncertainty in any prediction cannot be

assessed from just one model.

One point selection / base case.

The study demonstrates how limited and biased

that practice is. Yet, most long-term forecasts are

still based on a single history-matched.

Sometimes the best matched results may be

improper due to the reason that the statistical

nature of history matching and the inherent bias in

the history-matching workflow are ignored.

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TNO’S NEW METHOD: AN AUTOMATIC

PROBABILISTIC HISTORY-MATCH PROCEDURE:

An automatic probabilistic history-match and

prediction procedure has been implemented by

TNO.

This procedure automatically generates many

realisations of the reservoir reproducing the history

data with satisfactory accuracy.

Using these realisations, predictions are derived

and processed into an expectation curve.

Most of the theory behind this methodology has

been developed and demonstrated on synthetic

cases within the Production forecasting with

Uncertainty Quantification project (PUNQ) 9

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Traditional history

matching, keeps

geological model

along with the

geological data out of

the loop.

Modern history

matching, keeps

geological model

along with the

geological data in

the loop.

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RESULTS OF TNO’S WORKS:

The geo- spatial data is correlated with the fluid

flow model with least uncertainty by using PUNQ.

25 values are optimized by using PUNQ for just one

parameter – Water production.

This produces accurate model for the future

prediction of the reservoir.

Thus a successful history matching is achieved.

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MBE:

The material balance equation and its many

different forms have many uses including:

Confirming the producing mechanism

Estimating the OOIP and OGIP

Estimating gas cap sizes

Estimating water influx volumes

Identifying water influx model parameters

Estimating producing indices.

o Law of conservation of mass forms the basis for

the MBE calculations for a reservoir estimation.

o Predict future reservoir performance under

various drive mechanism.

ADVANTAGES OF MBE:

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MBE FOR GAS RESERVOIR

([Solution gas present in

the

reservoir initially(st. vol.)

] +

[Free gas present in the

reservoir initially (st.

vol.)] - [Gas produced

(st. vol.) ] +

[Gas injected (st. vol.)] )

([Solution gas

present in the

reservoir finally (st.

vol.)] +

[Free gas present in

the reservoir finally

(st. vol.)] )

=

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CONCEPT

COMPRESSIBILITY OF GAS IS VERY

SIGNIFICANT DRIVE MECHNISM IN GAS

RESERVOIRS AS COMAPRED TO RESERVOIR

PORE VOLUME.

IF THERE IS NO WATER DRIVE IN THE

RESVOIR, THE CHANGE IN PORE VOLUME

WITH PRESSURE IS NEGLIGIBLE

EQUATION FOR THE VOLUME OF THE GAS IN

RESERVOIR IS A FUNCTION OF PRTESSURE.

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EQUATION FOR GAS MBE

In gas reservoir oil volume is zero, thus the following is derived from

Generalized MBE :

Water and Formation compressibility is negligible when compared to

gas compressibility

For volumetric reservoir, We and Wp will become zero.

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REFERENCES:

“Principles of Applied Reservoir Simulation”,

Second edition; Fanchi, R. John; Gulf Professional

publishing, Elsevier, USA; 2001.

http://www.streamsim.com/technlogy/history-

matching/

http://www.streamsim.com/technology/sentivity-

analysis-and-screening/

“Production forecasting with uncertainty

quantification” – TNO. –

http://www.tno.nl/downloads%5C309beno.pdf

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