Estimate the OOIP and Reserves (Volumetric)

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Estimate the OOIP and Reserves (Volumetric)

Post by FANARCO »

This is a new thread on Calculating OOIP and Reserves by volumetric methods using different approaches.

Requirements:

Microsoft Excel 97 or later

CrystalBall Software. Download a free 30 days trial from here
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Post by FANARCO »

In order to calculate the OIP Volumetrically, you have to have the Area of the reservoir, Net Pay Thikness, Porosity, Oil Saturation and FVF.

The commmon area unit is Acre and thikness in ft (field unites), and the Gross Rock Volume GRV will be in Acre-ft.



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Post by FANARCO »

Oil in place by the volumetric method is given by the following formula:





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Post by FANARCO »

In Reserves Volumetric Calculations there are Two main Approaches (Deterministic and Probabilistic). And Mixed Approach.

In deterministic approach, all minimum values should be taken as Minimum (1P) Case and Vise versa for Most likely (2P) and Maximum (3P) Cases.

I.e. if we have the values of Area; 100, 150 and 250 Acre
And Porosity of 0.13, 0.15 and 0.19 fraction.
And So of 0.5, 0.7 and 0.9 fraction

So, the Low (Minimum or 1P) Case is to use the minimum values for each parameter 100 Acre in Area, 0.13 in porosity and 0.5 in Oil Saturation (So)
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Post by goode69bouy »

I see. thank you
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Re: Estimate the OOIP and Reserves (Volumetric)

Post by mero928 »

what is really mateers is to know exactly how to choose the distribution for each volumetric parameters in the equation
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Re: Estimate the OOIP and Reserves (Volumetric)

Post by FANARCO »

Dear Moslim,

Choosing each parameter for distribution is a matter or sensitivities and are different from one person to another.
For example, Porosity variation may be obtained from each well as an averaged you come up with average porosity value for each well, then you can distribute based on min, most likely and maximum.
In case you have one well may some other person choose the data obtained from this well in addition to some analogue wells data in the nearby fields.And vise versa
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Re: Estimate the OOIP and Reserves (Volumetric)

Post by mero928 »

I totally agree and support your post.

we need to know when I can choose normal distribution or Alpha distribution or triangle distribution and based on what we can defend our assumptions. these differences will not make great differences in the calculations but it can affect the numbers if you will use the different Possibilities to a certain project.

Thank you
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Re: Estimate the OOIP and Reserves (Volumetric)

Post by FANARCO »

Yes, generally the difference will be low for different distribution types.
But for highly effective parameters like Area of thickness for thick reservoirs may affect the results.

So, how to choose the best type of distribution matching your data. (You CAN)...

- Depends on the available data. For example if you have one well and a porosity curve obtained from OHL (lets say for each 0.5 ft and the thickness is 40 meters like Amal-9 well Kareem reservoir) :D
So take these 65 points and ask crystal ball to make regression on it and it will provide you with the best matched type.

- On the other side, if you have a set of data 0.1, 0.18, 0.12 . In this case you cannot follow the normal distribution curve, use any curve aligned to the right side because the majority of data supposed to align to 0.18 and 0.2 area.

- If you have WUT and ODT and you need to estimate the OWC but no MDT or any data proof that value of OWC. in this case you should choose homogeneous distribution (constant) meaning each point withing these values (ODT and WUT) are equal for probability.

In the future we can support by examples.
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