Reservoir simulation

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
1

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
2

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.
3

SIMULATOR AND ITS TYPES
Simulator is nothing but mathematical equations
solving by the execution of set of computer programs.
 Black-oil model (IMEX)
 Compositional model (GEM)
 Thermal model (STARS)
 Chemical
 Miscible
 Dual Porosity
 Dual permeability
4

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.
5

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.
8

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

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.
11

RESULTS OF TNO’S WORKS:
 The geospatial 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.
12

MBE:
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:
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.
13

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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