Closed-loop Reservoir Management

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Active reservoir management starts with the observation of the dynamic state of reservoirs (including the produc-tion infrastructure) and subsequent implementation of an optimal control strategy based on that state. To this end, ever more fields are equipped with down hole gauges, inflow control valves and other smart or intelligent comple-tions: so-called smart fields, intelligent fields or e-fields. Currently, the extent to which the capabilities of these smart fields are used is quite limited. On the short term, typically only those observations are used that directly translate into an appropriate response and lead to “actionable events” (e.g. water breakthrough, start-up failure). On the longer term, the period between updating of reservoir models (and subsequently the control strategy) is often several years even though new observations become available continuously. Additionally, from the large amounts of information that these fields produce, only a limited part is used, either because the datasets are too large to be handled manually, or because the translation of measured data into reservoir states is complex (or even ambiguous).

Reservoir Management Toolbox

Solving the problems of frequently updating

of reservoir models and of optimization

separately can add value in reservoir

management. However, the ultimate goal is

to get an integrated solution in what is often

called ‘closed-loop reservoir management’ or

‘real-time reservoir management’.

To provide this integrated solution, TNO has

developed a “Reservoir Management

Toolbox” that includes state-of-the-art

assimilation and optimization modules.

These modules may be either used as stand-

alone history-matching or field development

planning tools, or can be combined into a

closed-loop reservoir management workflow.

The toolbox also includes advanced up- and

down-scaling methods that help convert

detailed geological models into manageable

reservoir models.

System (reservoir,

wells, facilities)

Direct

Optimization

Control Monitoring

Figure 1. The main elements of classical (“direct”) control

System (reservoir,

wells, facilities)

System models

Control Monitoring

Model based

optimization

Data

assimilation

Initial modeling,

model reduction

Figure 2. The main elements of closed-loop reservoir management

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The Brugge field benchmark study

To gain experience with implementing

closed-loop reservoir management tools on a

realistic field and test different workflows,

TNO organized a unique benchmark study for

the SPE ATW on Closed-Loop Reservoir

Management held in Brugge on 23-26 June

2008. In total nine groups from both

universities and industry participated in this

benchmark. The goal set for the participants

was to 1) optimize a reservoir model using

the data provided over a period of 10 years

of production, and 2) come up with an

optimal waterflooding strategy for the next

10 years. This production strategy was tested

on the truth model and the resulting

production data were sent back to the

participant. With this additional data the

participants could update their models and

determine a strategy for the remaining

lifetime of the reservoir.

A highly detailed geological truth model was

constructed from scratch. From this model

synthetic well log data, as well as

information on top structure and base

structure were provided to the participants.

The geological model was upscaled to a

reservoir model with approximately 330 000

active gridblocks to serve as the truth

reservoir on which all the different water

flooding strategies provided by the

participants could be tested. Consistent with

well log data and top structure and base

structure data an additional 100 realizations

of the reservoir were constructed.

Participants were free to either build their

own reservoir models or start from these 100

realizations.

Figure 3. The Brugge Field showing the depth above and below the oil-water contact (in m) and the

30 wells

Figure 4. Six examples of the well logs generated using the detailed geological model

The results from the workshop showed a

spread of the Net Present value (NPV)

obtained by the different participants in

the order of 10%. The highest result that

has been obtained is only 3% below the

optimized case determined for the known

truth field. Although not an objective of

this exercise, it was shown that the

increase in NPV as a result of having three

control intervals per well instead of one

Figure 5. Development of realized NPV for

closed loop control with one year intervals.

Indicated with red triangles are the results

achieved with a ten year interval

Figure 6. Example of the interface for entering the production scenario

was significant (around 20%). The results

also showed that the NPV achieved when

additional production data became available

was consistently higher than before the data

became available.

With the participant from the University of

Oklahoma, a closed-loop exercise was done

with a feedback loop with a higher update

frequency, namely 1 year instead of 10 years.

The results showed a 1% gain in NPV for a

one-year interval compared to a 10-year

interval at year 20.

Brugge benchmark study follow-up

The Brugge field is currently still held by

TNO and is not available for third parties.

However, to make the Brugge field more

accessible and allow closed-loop studies with

a higher level of interaction, we are currently

working on making the model available for

running via web-services. Initially only for

our partners NTNU and Stanford University,

but in a later stage probably also for a wider

public.

For support on integrated closed loop solu-tions or more details of the Brugge benchmark study, please contact TNO. A description of the benchmark study and its results can also be found in SPE119094-MS.

TNO Built Environment and GeosciencesGeological Survey of the Netherlands is the central geoscience centre in the Netherlands for information and research to promote the sustainable management and use of the sub-surface and its natural resources.

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Princetonlaan 6PO Box 800153508 TA UtrechtThe Netherlands

T +31 30 256 46 00F +31 30 256 46 05E info-geoenergy@tno.nl

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