#  > Petroleum Industry Zone >  > Reservoir >  >  >  Reservoir Simulation Fundamentals-IPIMS modules

## Alamen Gandela

hello guys ,I thought of sharing this nice basics of reservoir simulation,If you are interested please reply otherwise I will stop :EEK!: . 



Episode 1
What Goes Into Reservoir Simulation? 

The basic tool for conducting a reservoir simulation study is a simulator. The development of this tool requires a good understanding of the physical processes occurring in reservoirs and a high level of sophistication and maturity in advanced mathematics and computer programming. Although simulation engineers generally do not get involved in actual software development, the effective use of reservoir simulators requires that they at least appreciate what goes into this development. 

Like any tool, a reservoir simulator has its strength and limitations, and it is well to keep in mind the various assumptions that factor into its development. This is not to suggest that all simulation engineers must be expert programmers; rather, they must be intelligent users. Therefore, knowledge and understanding of the simulation process are necessary precursors to a reservoir simulation study. 

At first, a simulation study might look like a once-and-for-all exercise. In truth, however, it is an evolutionary process, throughout which we continually refine our conceptual understanding of the system. While we cannot overemphasize the importance of accurate reservoir description in a good reservoir simulation study, we must at the same time acknowledge that the data needed for an accurate description is seldom available; invariably, studies start out with less than complete data. However, by carefully analyzing and interpreting the voluminous information generated during the study, we should be able to refine and extend the input data base. Such refinement should lead to a better understanding of the system and, ultimately, to a better reservoir description. Of course, this requires some agility and creativity; there is no such thing as a casual simulation engineer. 

It is, therefore, apparent that there are three basic interwoven components that go into a simulation study. These are: 

 The tool: reservoir simulator 
 The intelligent user: simulation engineer 

 The pertinent information: reservoir description

Figure 1 depicts the necessary interactions among the simulation engineer, the simulator and the reservoir description. 


Figure 1 
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The engineer is clearly the prime mover in conducting the simulation study, and must be in control of other study components. 
This control involves: 

 being cognizant of the simulators limitations and the assumptions that go into its development 
 being able to adequately describe the reservoir 

 being fully conversant with the analytical techniques involved in interpreting the results.

Based on the initial results, it is not uncommon for the simulation engineer to revisit the appropriateness of the reservoir description through concept refinement. 
Why Do We Need Reservoir Simulation? 

The information we obtain from a newly discovered field is scanty at best. It is also disjointed to a certain extent, because bits and pieces of information are emanating from different parts of the field. Our first task is to integrate these pieces of information as accurately as possible in order to construct a global picture of the system. A reservoir simulation study is the most effective means of achieving this end. As field development progresses, more information becomes available, enabling us to continually refine the reservoir description. 

Once we establish a good level of confidence in our reservoir description, we can use the simulator to perform a variety of numerical exercises, with the goal of optimizing field development and operation strategies. We are often confronted with questions such as 

 what is the most efficient well spacing? 
 what are the optimum production strategies? 

 where are the external boundaries located? 

 what are the intrinsic reservoir properties? 

 what is the predominant recovery mechanism? 

 when and how should we employ infill drilling? 

 when and which improved recovery technique should we implement?

These are but a few of the critical questions we may need to answer. A reservoir simulation study is the only practical laboratory in which we can design and conduct tests to adequately address these questions. From this perspective, reservoir simulation is a powerful screening tool. 
What are the Simulation Approaches? 

The complexity of the problem at hand, the amount of data available, and the studys objectives invariably dictate the choice of reservoir simulation approach, granted that we have already taken into account the appropriate computational environment (both in terms of hardware and software). 

Broadly classified, there are two simulation approaches we can take: analytical and numerical. 

 The analytical approach, as is the case in classical well test analysis, involves a great deal of assumptionsin essence, it renders an exact solution to an approximate problem. 
 The numerical approach, on the other hand, attempts to solve the more realistic problem with less stringent assumptionsin other words, it provides an approximate solution to an exact problem.

From here on, we use the term simulation rather loosely to refer only to the numerical approach. 
The domain of interest can form another level of categorization for simulation approach and model selection. For instance, a study may focus on a single well and its interaction with the reservoir within its drainage area (i.e., single-well simulation in radial-cylindrical coordinate system). The other extreme case may be the study of an entire field (field-scale simulation in rectangular coordinate system) in which the overall performance analysis of the field is called for. In between these two extremes comes the case where only a section of the reservoir is targeted (window-study). 


Figure 2

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Figure 2 schematically represents these three simulation approaches. 

What are the Basic Steps of a Simulation Study? 

In general, a reservoir simulation study involves five steps: 

 Setting objectives 
 Selecting the model and approach 

 Gathering, collecting and preparing the input data 

 Planning the computer runs, in terms of history matching and/or performance prediction 

 Analyzing, interpreting and reporting the results

A critical step is selecting the model and the approach. We must decide at the outset how many dimensions will be adequate. Such decisions depend on the flow dynamics involved and the amount of detail required. There may be cases when a two-dimensional representation is sufficient to describe a thin reservoir, whereas a three-dimensional model is unavoidable in the case of a thick reservoir. The expected flow structure dictates the choice of the models coordinate system. For example, in most single well studies, we may use radial-cylindrical flow geometry. However, if a well is vertically fractured, we should assign an elliptical-cylindrical flow geometry. We also have to decide how best to represent physical phenomena. For instance, if compositional variation is important, we may have to employ a compositional simulator rather than the more commonly used "black oil" model. Similarly, if we intend to study a coalbed methane reservoir, we must use a specialized model that accounts for the desorption process. 
One of the most labor-intensive aspects of reservoir simulation study is data gathering, collection and preparation. Oftentimes, this requires collaboration among technical personnel with varying levels of expertise. For instance, geological and geophysical data are extremely crucial and need to be processed in the form that is useful for reservoir description. Data will be often be sparse or incomplete. In such situations, statistics or other tools can prove quite helpful. Because of the large volume of data being processed at this stage, and the likelihood of internal inconsistencies in the data, the engineer must have strong organizational skills and sound judgment. 

In simulation studies, time (both the engineers and the computers) is of the essence. A typical simulation study requires a large number of runs, which must be carefully orchestrated to yield the desired information. As we make each run, we must carefully analyze the results, and appropriately label them to avoid confusion and costly duplications. In addition, we must avoid runs that yield no new information. It is pertinent, therefore, to take into account the inferences from the previous runs in planning the next suite of runs. 

Perhaps the most important step in a simulation study is analyzing and interpreting the results. It is at this stage that our creative and discerning abilities are put to the test. As tempting as it may be to do so, we should not view every number that comes out of the computer as the absolute answer. Instead, we must always be asking questions such as, "what if? what then? why? so what?" In this way, we bring into play our experience, common sense, and perhaps sometimes extraneous knowledge. 

A simulation studys ultimate objective is to forecast reservoir performance. If we have selected the correct model, adequately prepared our data, conducted the appropriate computer runs, and made good, informed analyses, we should be confident of our ability to predict performance. Any mistakes we make in the previous steps will have a cumulative impact on performance prediction. 

We must communicate study results in an appropriate manner to other technical personnel and to management. This should be in the form of a comprehensive technical report with sufficient details for others to assess the studys quality. 

How are Reservoir Simulators Used? 

A reservoir simulator can be an effective tool for screening, analysis and design. The thought process that goes into appropriately using a simulator for these purposes, however, is quite involved. Figure 3 illustrates the interactions inherent in this thought process. 


Figure 3 
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The cornerstones of a reservoir simulator are the mathematical model, laboratory investigation (laboratory data), field observations and the computer code. In using reservoir simulators, these cornerstones generate signals, which propagate and interact with each other such that a continuous feedback takes place for the mutual benefit and enhancement of all the parts. For example, laboratory investigation, field observations and the computer code can highlight the need for improvement in the mathematical formulation. Similarly, a computer code originated from a robust formulation, together with pertinent field observations, may shed light on the validity of the experimental approach taken in the laboratory. This dynamic interaction illustrates the self-enhancing nature of reservoir simulators. 

What Does a Simulation Study Require? 

A simulation study is a challenging and demanding task, loaded with opportunities to learn more about the reservoir. To reap the full benefits of this powerful tool, it is imperative to recognize the proper roles of the engineer and of the reservoir simulator. In a successful study, neither of these can afford to dominate the other. The engineer should not demand from the simulator what it is not meant to do, but neither should he or she become overly dependent on the simulator. In a nutshell, the success of a simulation study hinges on a combination of a good engineer and the right simulator.


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cheersSee More: Reservoir Simulation Fundamentals-IPIMS modules

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## Alamen Gandela

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## tridays

thx a lot!

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## greges2009

This is very interesting and helpful. Please continue. Thank you.

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## dipak_m

Please carry on

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## tiger842002

Dear Alamen Gandela :

Really appreciating your great efforts , GO A HEAD

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## amahaminer

Me too ,,  Go ahead man  we are all ears

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## Alamen Gandela

Steps in a Simulation Study


There are five basic steps in conducting a reservoir simulation study:

 setting concrete objectives for the study
 selecting the proper simulation approach

 preparing the input data

planning the computer runs (including the order in which they occur)

 analyzing the results

Setting the Objectives
Setting objectives is the most important step in conducting a simulation study. Clearly defined objectives help us obtain the best information at the lowest cost and in the least amount of time. Improperly set objectives can take the study on a long, roundabout journey which leads to nowhere.

There are a number of factors that help us define appropriate objectives. The most important of these are data availability, the required level of detail, availability of technical support and available resources. In setting objectives , we use all of these factors to determine how to proceed. For example, it is unrealistic to attempt three-dimensional simulation when the available geological data gives no information about the presence and description of the various formation layers present in the reservoir.

In the broadest sense, when we consider all these factors, we will arrive at one of two types of objectives. These are sufficiently distinct that they affect the entire planning process of the simulation study. One type of objective is fact-finding, while the other is to establish an optimization strategy.

 Fact-finding involves answering questions about a system or process that is already in place. For example, a simulation study that matches well test data for the purpose of determining the damaged zone around a wellbore is a fact-finding mission.
 Optimization involves developing a number of plausible scenarios for a process (e.g., waterflooding) and studying the system response in an attempt to determine the optimum scenario. In this case,we must design a suite of numerical exercises, being careful to avoid waste on exercises that may not significantly contribute toward the goal.

Choosing the Simulation Approach
In choosing the simulation approach, we need to consider three basic factors:

 reservoir complexity
 fluid type

 scope of the study

While reservoir complexity and the scope of the study determine the simulators dimensions and coordinate geometry, the fluid type (together with the processes involved) dictate whether we should use a black-oil model or a more specialized model. For example, predicting well performance in a gas condensate reservoir will require a compositional rather than a black oil simulator. Furthermore, if the reservoir is thin and unlayered, it will be sufficient to use a one-dimensional radial flow geometry. Carrying out such a study with a three-dimensional compositional simulator will require additional computational resources whose added benefit cannot be justified. In any case, we must exercise our judgement and ingenuity in selecting the most appropriate simulation approach.
Preparing the Input Data

Because simulation studies usually require large volumes of information from a wide range of sources, preparing the input data can be a laborious task. However, the time spent in ensuring that data are properly prepared is worthwhile, in that it can prevent a great deal of headaches and waste later on in the study. Often, we discover data input errors only after a problem surfaces during the run, which wastes both time and computing resources.

It is our responsibility to ensure internal consistency in the data. Because data come from different sources, internal inconsistencies are not uncommon. We should resolve inconsistencies during the data input preparation. When data inconsistencies are present, they can lead to an ill-posed problem. Even worse, they could go undetected. With an ill-posed problem, we may be able to find the inconsistency by the failure of the simulator to run; but in the case of buried inconsistencies, the simulator may run and yield erroneous solutions.

Pre-processing capability, particularly for the commercial codes currently available, can facilitate data preparation. Sometimes these processors have internal checks to flag any detected inconsistencies in the data.

While data preparation is the simulation engineers job, input from other supporting personnel is extremely important. If inconsistencies appear in the data, or even if some data appear doubtful, it is imperative to resolve the problem with the help of the geologist, geophysicist and perhaps the production engineer. In summary, there is no overemphasizing the importance of adequate data preparation prior to making a simulation study. The payoff is exceptionally good.

Planning the Computer Runs

Planning computer runs is deceptively simple. To understand the necessity and the complexity of this planning, we only need to imagine a simulation study as a complex road map where the traveler knows the point of origin and the destination (these are clear enough from the objectives of the study). However, just as a traveler requires careful mapping out of the route that will get him or her to the destination in the best time possible, we must carefully map out the type and number of computer runs that will achieve the set objectives at a minimum cost. In so doing, we must account for several factors, which are usually problem dependent. We should consider the number of parameters to be examined, the duration of prediction, and the type of information needed to answer the pertinent questions.

Careful planning of computer runs includes not only determining their order, but also establishing a systematic labeling procedure for them. This is particularly important because of the large number of runs usually required and the voluminous amount of information invariably generated for analysis.

Analyzing the Results

When we have analyzed the results of the simulation study and made pertinent inferences from it, we can evaluate its success. This step caps all the efforts previously discussed. Considering the amount of effort that we expend on the simulation study up to this point, it is tempting to become a biased arbiter of the results. On the contrary, this is the time to ask critical questions and even ponder over the implications of the results. In other words, we must not become easy subscribers to our solutions.

The mode of analysis and the presentation of results will depend very largely on the audience for whom they are meant and the post-processing capability available. The graphics capabilities currently available on most computers makes this process easier and even more inviting. It is now not uncommon to display information using three-dimensional graphics. In addition, graphics features, such as image rotation and animation, enhance our interpretation and inferential ability.


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video for this episode

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enjoy it

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## doombuggy

please re-upload the videos..the 1st rapidshare link has expired

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## hichem

please upload again
on 4shared the rapid shre link was expired 
thanks a lot

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## emisosamassaro

great!! i appreciate it!! please continue!! do you have more videos?

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## sinodas

it will be very appreciated if anyone wil be able to reupload the videso

Thanks to the original upload

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## famousasif

Nice work brother. It is really helpfull.......


Plz Reupload the videos.....See More: Reservoir Simulation Fundamentals-IPIMS modules

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## pvthien

Link died. Please re-upload to 4shared.com
Many thanks

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## Alamen Gandela

Hi guys: 

sorry I was (still) a little bit busy !
so, I decided to upload the complete course in 4shared.com:


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videos:
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tested working fine

enjoy

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## emisosamassaro

Thanks you Very much dear Gandela!

What you have doing was incredible!! I will remenber that! Please If I can do something for you just tell me!

Yours Faithfully

Emilaino Sosa Massaro

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## sinodas

Thanks for upload !! MEga share

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## Alamen Gandela

I am here for help

I believe in knowledge share, so I will share whatever course materials I have,and I hope all people will have the same attitude :Big Grin: 

expect more surprises

cheers

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## emisosamassaro

JaJa!.. You are really kind! I agree with you.. Maybe soon I can share such a important material as you have been doing.

Thanks and regards!

Emiliano

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## reservoir_engineer

great work brother
thank you .
appreciated share
regards,
reservoir_engineer

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## Alamen Gandela

You are welcome reservoir_engineer
cheers

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## slcpetro

Hi Gandela,

Thank you for the work you did. I can't access the files. Can you please re-load the files. 

Thanks again.

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## nour_el_dien

good!!

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## slcpetro

Can someone post the material and videos. Interested to learn.

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## rhett21

Anybody know the data needed to simulate? On how to input the data in a simulator? Thank you

See More: Reservoir Simulation Fundamentals-IPIMS modules

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## adeeyo

Dear Alamen Gandela,
The videos have been deleted in 4shared. Can you or any other person upload it again or share with me using dropbox? 

Regards,
adeeyo

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## dauphin

Please
Can anyone share these video files ???

Thankx allot

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## kblacks

sgarThanks for sharing

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## dauphin

Please
Can anyone share these video files ???

Thankx allot

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## abdulx

Plese reupload Brother
Thanks

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## abdulx

Plese reupload Brother
Thanks

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## notachance

please could anyone re-upload the materials as i am in very need of these materials. thanks

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## brainzemy

Hiya,

Please we've had a lot of request about re-uploading the videos and materials on Resim in recent times.....Please can any one who has benefited from Gandela's good work do that?

Cheers.

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## brainzemy

Hiya,

Please we've had a lot of request about re-uploading the videos and materials on Resim in recent times.....Please can any one who has benefited from Gandela's good work do that?

Cheers.

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