U.S. patent application number 12/439553 was filed with the patent office on 2010-03-18 for method in an oil and/or a gas production system.
Invention is credited to Hans Petter Bieker, Olav Slupphaug.
Application Number | 20100070182 12/439553 |
Document ID | / |
Family ID | 39276291 |
Filed Date | 2010-03-18 |
United States Patent
Application |
20100070182 |
Kind Code |
A1 |
Bieker; Hans Petter ; et
al. |
March 18, 2010 |
METHOD IN AN OIL AND/OR A GAS PRODUCTION SYSTEM
Abstract
A method in an oil and/or a gas production system including a
plurality of oil and/or gas wells and parameter testers adapted for
oil and/or gas production parameter testing. The method is adapted
to compare a plurality of options related to the oil and/or gas
throughput in the oil and/or gas production system. A plurality of
parameter samples are drawn from a parameter distribution. A
performance measure is generated for each parameter sample by using
the parameter sample and a characterizer for each of the options.
An aggregated performance measure is generated for each of the
options by using the performance measures.
Inventors: |
Bieker; Hans Petter; (Oslo,
NO) ; Slupphaug; Olav; (Osol, NO) |
Correspondence
Address: |
VENABLE LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Family ID: |
39276291 |
Appl. No.: |
12/439553 |
Filed: |
August 28, 2007 |
PCT Filed: |
August 28, 2007 |
PCT NO: |
PCT/IB07/02460 |
371 Date: |
October 15, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60840705 |
Aug 29, 2006 |
|
|
|
Current U.S.
Class: |
702/12 ;
73/152.23 |
Current CPC
Class: |
G06Q 50/06 20130101;
E21B 49/00 20130101; G06Q 10/04 20130101; E21B 43/00 20130101 |
Class at
Publication: |
702/12 ;
73/152.23 |
International
Class: |
E21B 49/08 20060101
E21B049/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2006 |
NO |
20063837 |
Claims
1. A method in an oil and/or a gas production system comprising a
plurality of oil and/or gas wells and parameter testers adapted for
oil and/or gas production parameter testing, wherein said method is
adapted to compare a plurality of options related to the oil and/or
gas throughput in the oil and/or gas production system, said method
comprising: drawing a plurality of parameter samples from a
parameter distribution; generating, for each parameter sample, a
performance measure by using said parameter sample and a
characterizer for each of said options, and generating an
aggregated performance measure for each of said options by using
said performance measure, said parameter distribution is generated
by using historical and/or online measured and/or estimated data
obtained from the oil and/or gas production system.
2. The method according to claim 1, wherein said parameter
distribution and the generation of the performance measure are
obtained by a statistical analysis.
3. The method according to claim 1, wherein said aggregate
performance measure for each of said options are used to select an
optimal option.
4. The method according to claim 1, further comprising: generating
at least one aggregation of said at least one aggregated
performance measure.
5. The method according to claim 4, wherein said aggregation
comprises a reference to at least one option or characterizer.
6. The method according to claim 5, wherein a routing valve is
manipulated using said reference to at least one option or
characterizer.
7. The method according to claim 1, wherein said parameter testers
adapted for oil and/or gas parameter testing comprise a test
separator.
8. The method according to claim 1, wherein at least one
characterizer of said options comprises information that a specific
well should be tested.
9. The method according to claim 1, wherein at least one
characterizer of said options comprises information on the
availability of a flow measurement device.
10. The method according to claim 1, wherein at least one
characterizer of said options comprises information on using of a
test separator, or measurement of flow rate, pressure, temperature,
fluid composition, gas-oil ratio, or water-oil ratio.
11. The method according to claim 1, wherein said performance
measure reflects the value associated with the oil production rate,
oil production volume, profit rate, profit or expenses, or any
combination thereof.
12. The method according to claim 1, wherein said aggregated
performance measure is generated using the average value of a
plurality of performance measures for said option or
characterizer.
13. The method according to claim 1, wherein said aggregated
performance measure is generated using the average value or sum
value of said performance measures.
14. The method according to claim 1, wherein a testing of a well
obtains information of the content of water, oil and/or gas.
15. The method according to claim 1, wherein a reference to at
least one option or characterizer is presented to the user.
16. The method according to claim 1, wherein said parameter testers
adapted for oil and/or gas parameter testing comprise a multiphase
flow measurement device.
17. A computer program product, comprising: a computer readable
medium; and computer program instructions recorded on the computer
readable medium and executable by a processing unit in a computer
based system, for carrying out a method in an oil and/or a gas
production system comprising a plurality of oil and/or gas wells
and parameter testers adapted for oil and/or gas production
parameter testing, wherein said method is adapted to compare a
plurality of options related to the oil and/or gas throughput in
the oil and/or gas production system, said method comprising:
drawing a plurality of parameter samples from a parameter
distribution; generating, for each parameter sample, a performance
measure by using said parameter sample and a characterizer for each
of said options, and generating an aggregated performance measure
for each of said options by using said performance measure, said
parameter distribution is generated by using historical and/or
online measured and/or estimated data obtained from the oil and/or
gas production system.
18. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method according to the
preamble of the independent claim.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a method for decision-making for
oil and/or gas production systems. Specifically, the invention
relates to production optimization of such systems.
[0003] Oil/gas well testing may be performed to support many
decisions including ones related to production optimization. In
production optimization information such as gas-oil ratio and
water-oil ratio are used to decide on, for example, which wells to
prioritize for choking back/opening so as to avoid
over/underutilization of the production capacity. Since the
reservoir properties change with time, uncertainties of estimates
increase with time, and eventually a new well test will be
required. As the uncertainty in an estimate grows, so does the risk
for prioritizing the wrong well(s) giving lower oil production than
necessary.
[0004] Production throughput is an important performance indicator
in an oil and/or gas production system. Herein, production
throughput is intended to mean the oil and/or gas production per
time interval. The throughput depends on many different factors;
some may be specific to each production system, others are more
general. One important general factor is how the limited processing
capacity of the production system is utilized.
[0005] By using a computer simulation or a mathematical
optimization method, good operational strategies may be found. The
accuracy of the computer simulations and mathematical optimization
methods depend on the accuracy of the parameters used in their
mathematical model. To ensure good accuracy of the simulation,
parameters are measured by installing measurement devices, and
experiments are performed to obtain values that may not easily be
measured during normal operation.
[0006] The testing of wells is generally performed by routing an
individual well to a dedicated test separator. The oil, water, and
gas rates at the outlet of the separator are then measured. Thus,
important properties including the gas-oil ratio and the water-oil
ratio can then be calculated. A test may take several hours, thus
constraining the frequency at which the wells can be tested. A
policy is therefore required to decide the frequency to test each
individual well. One simple strategy would be to test all wells at
the same frequency. Another strategy may be to test some wells more
than other wells. This may be due to higher uncertainty in some
wells, or that some wells are more important than others (e.g.
higher potential). Independent of the strategy used, the goal of
the well test is usually to give information that will enhance oil
production.
[0007] For an oil and/or gas production system, a well test is
typically performed by routing the production from a single well
(one of several wells in the system) 105, 106 or 127 (see FIG. 1)
to a dedicated test separator 107. This allows for measuring of
parameters from this single (specific) well. The values measured
are typically the flow rates of oil, water, and gas, as well as
test separator pressure and/or temperature, up- and downstream
wellhead pressure and temperature, and choke opening. From these
tests, values such as the gas-oil ratio and the water-oil ratio are
derived. These values are critical for the optimization of such
production systems.
[0008] There is typically only one or a few such test separators
107 in each production system. Therefore, all wells in the system
cannot continuously be monitored. The operation of an oil and/or
gas production system therefore requires a way of choosing which
well to test. Even if the test separator 107 may test all wells at
a satisfactory frequency, there may be other uses for the test
separator 107.
[0009] For production systems where the production separator 108
capacity is limiting the total oil production, the test separator
107 is often used in the same way as a production separator 108
when it is not used for testing wells 105, 106 or 127. Then, the
oil/gas flow from the multiple wells in the system may be routed to
the test separator 107 to fully utilize its processing capacity.
However, the measured values are then for a mixture from the
production of the wells, and not for each well. Thus, the measured
values can then not be used as a well test for a specific well.
[0010] The currently used method for deciding which well to test is
based on a schedule, where all wells are tested at the same
frequency. When suspecting changes in one well, e.g. based on
changes in measured values such as pressure or temperature, the
test schedule is then typically modified in order to investigate
this.
[0011] U.S. Pat. No. 6,978,210 discloses a method for automatically
scheduling tests of automated measurements and control devices.
According to the method, measurement data is automatically
collected from automated measurement and control devices that are
located in a hydrocarbon production system. The data that is
collected is compared with data stored in a database. The
comparison of data is used to automatically schedule test of the
plurality of automated measurement and control devices.
[0012] In Cramer, Moncur, and Berendschot, "Well-Test Optimization
and Automation", presentation at 2006 SPE Intelligent Energy
Conference and Exhibition in Amsterdam, The Netherlands, 11-13 Apr.
2006, a method for scheduling of well tests is proposed. However,
the proposed method uses a predetermined test schedule and the
system does not calculate which well should be tested by
itself.
[0013] A drawback of the known methods of scheduling the testing is
that they do not use numerical optimization to find a test
schedule. Another drawback is that the known methods do not use
uncertainty distributions to find a test schedule.
[0014] The general object of the present invention is to optimize
well testing in order to achieve the highest expected oil/gas
production.
[0015] More specifically, it is an object of the present invention
to provide an improved method for decision-making for oil and/or
gas production systems, or a part thereof, in order to maximize
production throughput.
SUMMARY OF THE INVENTION
[0016] According to the present invention, this above-identified
object is achieved by a method having the features defined in the
independent claim.
[0017] Preferred embodiments are set forth in the dependent claims
2-18.
[0018] According to the invention statistical analysis is
preferably used of the possible outcomes of the well test, herein
referred to as "options", in order to calculate the value of
getting more accurate information about a well. In particular, the
method according to the present invention is adapted to calculate
how more accurate information will change or increase the oil
and/or gas production rate because of better decisions.
[0019] The optimization is then achieved by choosing the option
that preferably gives the most valuable information. Examples of
options to choose from include "testing of a first well", "testing
of a second well", or "installing a flow measurement device in an
oil and/or gas production system".
[0020] According to the present invention a method is developed to
decide which well to test based on old test data and/or online
measured and/or estimated data. The method is preferably
implemented by a computer program that uses a Monte Carlo approach
for identifying which well test is likely to result in the highest
oil production rate after the well test information is utilized to
optimize the production.
[0021] The method according to the present invention is preferably
used to identify the next well to test in order to achieve the
highest expected oil production. The method preferably assumes that
the production from each well are independent and that the capacity
constraint in the production can be described as single flow rate
constraints in water, liquid, or gas. It is assumed that an
estimate of the gas-oil ratio and/or water-oil ratio is available
for each well.
SHORT DESCRIPTION OF THE APPENDED DRAWINGS
[0022] The accompanying drawings illustrate the present invention
by way of examples and, together with the description, further
serve to explain the principles of the invention and to enable a
person skilled in the pertinent art to use the invention.
[0023] FIG. 1 is a schematic drawing of an oil and/or gas
production system where an embodiment of the present invention is
applied.
[0024] FIG. 2 is a schematic drawing of an oil and/or gas
production system where an alternative embodiment of the present
invention is applied.
[0025] FIG. 3 shows a flow diagram illustrating a method according
to the present invention.
[0026] FIG. 4 shows an additional flow diagram illustrating a
method according to the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0027] In FIG. 1 is shown a schematic drawing of an oil and/or a
gas production system where the present invention may be
applied.
[0028] The system comprises three wells 105, 106 and 127, a
production separator 108 and a test separator 107. The invention
may naturally be used in systems comprising two wells, or more than
three wells.
[0029] 123 designates an upstream valve pressure of a valve 119 of
well 105; 124 designates an upstream valve pressure of a valve 120
of well 106, and 125 designates an upstream valve pressure of a
valve 126 for well 127. The term valve should herein be understood
in a broad sense, i.e. to include a choke, a gate valve, a routing
valve or a control valve.
[0030] 101, 102 and 128 designate routing valves for production
separator 108 for the wells 105, 106 and 127, respectively.
[0031] 103, 104 and 129 designate routing valves for test separator
107 for the wells 105, 106 and 127, respectively.
[0032] 109 designates a flow rate measurement device for gas of
production separator 108; 110 designates a flow rate measurement
device for oil of production separator 108; and
[0033] 111 designates a flow rate measurement device for water of
production separator 108. 115 designates a water level measurement
device for production separator 108;
[0034] 117 designates an oil level measurement device for
production separator 108; and
[0035] 121 designates a gas pressure measurement device for
production separator 108.
[0036] 112 designates a flow rate measurement device for gas of
test separator 107;
[0037] 113 designates a flow rate measurement device for oil of
test separator 107; and
[0038] 114 designates a flow rate measurement device for water of
test separator 107.
[0039] 116 designates a water level measurement device for test
separator 107;
[0040] 118 designates an oil level measurement device for test
separator 107; and
[0041] 122 designates a gas pressure measurement device for test
separator 107.
[0042] The water-oil ratio for the well being tested is calculated
by using flow measurement devices 113 and 114. The gas-oil ratio
for the well being tested is calculated by using flow measurement
devices 112 and 113.
[0043] The upstream valve pressures 123, and 124 and the valve
positions 119 and 120 may be recorded in a data storage for later
use
[0044] This later use includes the generation of the parameter
distributions, which is further discussed below.
[0045] An alternative method for measuring the water-oil ratio
and/or gas-oil ratio may be to close the level valves 135 and/or
134 of the test separator 107. The gas-oil ratio and the water-oil
ratio may then be calculated using the level measurement devices
116 and 118 for at least two instances of time.
[0046] FIG. 2 is a schematic drawing of an oil and/or gas
production system where an alternative embodiment of the present
invention is applied.
[0047] According to this alternative implementation, the test
separator 107 is replaced by a multiphase flow measurement device
130. After the stream has been measured, it is routed to the
production separator 108.
[0048] In FIG. 2, 130 designates a multiphase flow-rate measurement
device. 131, 132 and 133 designate routing valves for the
multiphase flow measuring device for wells 105, 106 and 127,
respectively.
[0049] All other items in FIG. 2 are described above in connection
with FIG. 1.
[0050] The inventive method in an oil and/or a gas production
system comprises a plurality of oil and/or gas wells and means
adapted for oil and/or gas parameter testing. The method is adapted
to compare a plurality of options related to the oil and/or gas
throughput in the oil and/or gas production system, and includes
the steps of:
[0051] a) drawing a plurality of parameter samples from a parameter
distribution;
[0052] b) generating, for each parameter sample, a performance
measure by using said parameter sample and a characterizer for each
of said options, and
[0053] c) generating an aggregated performance measure for each of
said options by using said performance measures.
[0054] The parameter distribution is generated by using historical
and/or online measured and/or estimated data obtained from the oil
and/or gas production system.
[0055] Said data preferably includes at least oil flow rate, gas
flow rate, water flow rate, liquid flow rate, gas-oil ratio,
water-oil ratio, pressure, temperature, or fluid composition, or
any combination thereof.
[0056] The method preferably includes the further step of:
[0057] d) generating at least one aggregation of said at least one
aggregated performance measure.
[0058] The aggregation then comprises a reference to at least one
option or characterizer.
[0059] The parameter distribution in step a) and b) is preferably
obtained by a statistical analysis, preferably by a Monto Carlo
simulation.
[0060] The aggregate performance measures determined for each of
the options are used to select the optimal option which may be
which well to test next or to install a multiphase flow meter.
[0061] According to a preferred embodiment the means adapted for
oil and/or gas parameter testing is performed by using a test
separator 107.
[0062] Alternatively, the testing may be performed by using a
multiphase flow measurement device 130.
[0063] In the inventive method, at least one characterizer of the
options comprises information that a specific well should be
tested, and/or comprises information regarding the availability of
a flow measurement device.
[0064] Furthermore, at least one characterizer of the options
comprises information regarding use of a test separator, or
measurement of flow rate, pressure, temperature, fluid composition,
gas-oil ratio, or water-oil ratio.
[0065] The performance measure reflects the value associated with
oil production rate, preferably the total oil production rate, oil
production volume, preferably the total oil production volume,
profit rate, profit or expenses (or any combination thereof) and
the aggregated performance measure is generated by using the
performance measures of each specific option characterizer. The
aggregated performance measure is preferably generated by using the
average value, or sum value, of said performance measures.
[0066] The present invention also relates to a computer program
product loadable into the internal memory of a processing unit in a
computer based system, such as an oil and/or gas production system
server, comprising the software code portions for performing one or
more of the method steps described above, when the computer program
product is run on said system.
[0067] In addition the invention relates to a computer program
product stored on a computer readable medium, comprising software
code portions or a computer program for causing a processing unit
in a computer based system, such as an oil and/or gas production
system server, to control an execution of one or more of the method
steps described above.
[0068] Thus, the method according to the present invention may be
implemented as software, hardware, or a combination thereof. A
computer program product implementing the method or a part thereof
comprises software or computer program, run on a general purpose or
specially adapted computer, processor or microprocessor. The
software includes computer program code elements or software code
portions that make the computer perform the method using at least
one of the steps according to the inventive method.
[0069] The program may be stored in whole or part, on, or in, one
or more suitable computer readable media or data storage means such
as a magnetic disk, CD-ROM or DVD disc, hard drive, magneto-optical
memory storage means, in RAM or volatile memory, in ROM or flash
memory, as firmware, or on a data server.
[0070] A data flow of the inventive method is illustrated in FIG.
3. The method preferably comprises the following types of
components: measured data 201, parameter distribution 211,
parameter sample 221/222/223/224, characterizer 231/233,
performance measure 241/242/243/244, aggregated performance measure
251/253, and aggregation 261. In addition, the term option 271/273
is used for grouping of a set of parameter samples; performance
measures 241/242/243/244; characterizer 231/233; and aggregated
performance measure 251/253.
[0071] As shown in FIG. 4, the first column of plots represents
measured data 201, which are obtained from well tests. The second
column of plots represents parameter distribution 211 and/or
parameter sample 221/222/223/224, which are obtained from said
measured data 201. The third column of plots represents performance
measure 241/242/243/244, which are obtained from said parameter
sample 221/222/223/224. In this figure the performance measure is
the total oil production rate for all wells in the oil and/or gas
production system. The fourth column of plots represents the
aggregation 261, which suggests which well should be tested. The
aggregated performance measure 251/253 is represented on the line
between the third and the forth column.
[0072] As mentioned above the parameter distribution and the
generation of the performance measure are preferably obtained by a
Monte Carlo simulation. Monte Carlo simulation is a powerful method
for obtaining an approximate distribution of any dependent value of
stochastic variables. The distributions of the stochastic variables
are assumed to be known. Using these distributions, a finite number
of samples of the stochastic variables are drawn. For each sample
the dependent value is calculated. Important properties such as the
standard deviation and average of the dependent variables
calculated using Monte Carlo simulation will converge to the
expected value. An illustrative data flow of the method used for
testing two wells is shown in FIG. 4. In the preferred embodiment
of the inventive method, the stochastic variable is the gas-oil
ratio and/or the water-oil ratio of each well. The dependent
variable is preferably the total oil production rate for the oil
and/or gas production system.
[0073] The production optimization is normally based on estimates
of parameters because the accurate value is not known, more
specifically it is normally based on estimated gas-oil ratio and/or
water-oil ratio . The estimate may be found using various
techniques, but the simplest is perhaps the last well test. This is
also the most commonly used technique. The uncertainty in the
gas-oil ratio and/or water-oil ratio r.sub.i for well i can be
described by the distribution D.sub.i. Methods for estimating the
distribution D.sub.i for each well will be discussed further below.
Given these distributions, m samples {r.sub.i, l, K, r.sub.i, m}
are drawn. Furthermore, if a test of well k is conducted, the
estimate is updated. It is assumed that the well test is accurate,
and thus,
? := { r i , j i = k ? else , ? indicates text missing or illegible
when filed ( 1 ) ##EQU00001##
where is the estimate of the gas-oil ratio and/or water-oil ratio
of well i after well k is tested using sample j.
[0074] For each such sample, the optimized oil production rate will
be calculated. Furthermore, the oil production rate is calculated
for each of the wells k .di-elect cons. I considered for testing.
Because r.sub.i, j is not known to the operator of the process, the
inaccurate estimate is used for well prioritization in the
optimization. Let
z.sub.k, j:=f((r.sub.l, j, K, r.sub.n, j), (, K, ), (
q.sub.l.sup.o, K, q.sub.n.sup.o), q) (2)
be the function returning the total oil production rate found in
the calculation using the sample j and testing well k, where
q.sub.i.sup.o is the oil production potential for well i. The
expected total oil production rate is
z k := 1 m j = 1 m z k , j , ( 3 ) ##EQU00002##
given that well k is tested. The well to test can then be
calculated by
k*:=arg max.sub.k.di-elect cons.l z.sub.k. (4)
[0075] The described method draws a finite number of samples from a
distribution, evaluates each of the samples using the same function
f(.cndot.). This means that n Monte Carlo simulations are
conducted, one for each well test candidate. Monte Carlo simulation
is a simple but powerful method. Most of the assumptions made here
can easily be relaxed allowing other strategies to be used. Usually
there is some inaccuracy in the well test performed, and this can
easily be included by adjusting (1) to adding uncertainty for the
case i=k. Furthermore, the goal can easily be changed to e.g.
maximize the profit instead of oil production rate by adjusting the
function f(.cndot.) accordingly. Risk may be accounted for by
adjusting (3) to penalize for variance.
[0076] A calculation is required to evaluate the optimized oil
production rate of the oil and/or gas production system for a given
set of physical parameters, e.g. gas-oil ratio and/or water-oil
ratio, and the corresponding estimates used for operation of the
oil and/or gas production system. One simple and commonly used
method is the swing producer based method, (Bieker, Slupphaug,
Johansen, "Real Time Production Optimization of Offshore Oil and
Gas Production Systems: A Technology Survey", paper SPE 99446
presented at the 2006 SPE Intelligent Energy Conference and
Exhibition, Amsterdam, The Netherlands, 2006). The method assumes
that at most a single processing constraint is active and that each
well has a maximal production rate. The goal is to maximize the oil
production rate. The wells are controlled under the rule that the
wells with the lowest (estimated) gas-oil ratio and/or water-oil
ratio are opened at the expense of choking back wells with the
highest gas-oil ratio and/or water-oil ratio. In the end, there
will be one well partly choked back. The rest will be fully closed
or opened.
[0077] In the following the steps according to the present
invention are described in detail with references to FIGS. 1-4.
Generating a Characterizer
[0078] The characterizers 231 and 233 are preferably predetermined.
They define the differences between the options 271 and 273 to be
evaluated.
[0079] In the preferred embodiment characterizers 231 and 233
determine which well 105, 106 or 127 is scheduled for testing. The
characterizers 231 and 233 may also include well test schedules,
predetermining the time of at least one well test to be
performed.
[0080] The characterizers 231 and 233 are also used to predetermine
if a multiphase flow measurement device 130 is available. They may
also contain more specific data such as the type, position and/or
accuracy of the flow measurement device 130.
Generating a Parameter Distribution
[0081] The parameter distribution 211 is preferably generated by
using the measured data 201 that may be both online and/or
historical data.
[0082] In another embodiment the parameter distribution 211 is
provided by the user, a computer program or similar.
[0083] For well test optimization, it is preferred that the
parameter distribution 211 comprises at least one gas-oil ratio or
water-oil ratio of each well 105, 106, or 127.
[0084] For well test optimization, it is preferred that the
parameter distribution 211 is generated by obtaining the times
since each well 105, 106 or 127 were tested, and for each well 105,
106 and 127 obtaining the distribution of the change in the gas-oil
ratio or water-oil ratio for each well 105, 106 or 127 for a
plurality of intervals of preferably the same length as the time
since each well 105, 106 or 127 were tested.
[0085] An interpolation method such as Spline in Matlab is
preferred for pre-processing of the well test data. It is preferred
to offset the parameter distribution 211 by the gas-oil ratio
and/or water-oil ratio of the last well test.
Generating Parameter Samples
[0086] By using the parameter distribution 211, a plurality of
parameter samples 221/222/223/224 are drawn for each of the options
271 and 273. Preferably, the same parameter sample 221/222/223/224
is drawn for all options 271 and 273. Preferably, the number of
parameter samples 221/222/223/224 is determined based on the
convergence of the calculation of aggregated performance measure
251 or 253, or alternatively by a predetermined integer.
Generating Performance Measure
[0087] For each of the parameter samples 221/222/223/224, a
performance measure 241/242/243/244 is calculated using the
parameter samples 221/222/223/224. Preferably, the performance
measure is calculated using said characterizer.
[0088] Preferably, said performance measure reflects the total oil
rate, the total gas rate, or profit rate. It is preferred that said
performance measure is calculated using a model of how the
production system is operated. This is preferably achieved by using
the processing capacity of the production system in the
calculation.
Generating Aggregated Performance Measure
[0089] The aggregated performance measure is calculated for each
option using the performance measures for that option. Preferably,
the aggregated performance measure is calculated for each option
using by the average of the performance measures for that option. A
preferred way is to return the average, with an optional
penalization of the variance of the oil and/or gas production.
[0090] The aggregated performance measure may be a visualization of
the distribution of at least one of the performance measures for
the option. An example of such visualization is a histogram where
the performance measure is on one of the axis, and the frequency is
on the other.
[0091] The aggregated performance measure may be at least one of
the performance measures themselves.
[0092] A person skilled in the art will understand that the
performance measures may be scaled or transformed.
Generating Aggregation
[0093] The aggregation is preferably generated by using the
aggregated performance measures for the different options. A
preferred way of generating the aggregation is to choose that
option resulting in the maximum, or minimum, aggregated performance
measure.
[0094] Alternatively, the aggregation may be an ordered list of
options or characterizers.
[0095] In an alternative embodiment, the aggregation is generated
as a visualization of the aggregated performance measures.
Preferably, the visualization is ordered such that the aggregated
performance measures are sorted in some way.
[0096] The method according to the present invention was
implemented for choosing which well to test based on real well test
data from an offshore oil production system in the North Sea. The
simulation included 21 wells, and the total liquid production was
restricted to 10000 Sm.sup.3/D in liquid production. The length of
the simulation was 180 days.
[0097] Each well was modelled in the simulation as a producer of
oil and water. The well model consisted of an oil production
potential and a water-oil ratio. The oil production potential for
each well was defined by an interpolation of the oil potential
found in the well test data, making it time variant. To ensure a
reasonable interpolation, it was restricted to zero from below. The
water-oil ratio was defined as an interpolation of the water-oil
ratios found in the well test data, but restricted to zero from
below.
[0098] The present invention is not limited to the above-described
preferred embodiments. Various alternatives, modifications and
equivalents may be used. Therefore, the above embodiments should
not be taken as limiting the scope of the invention, which is
defined by the appending claims.
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