mercury injection for capillary pressure

[vibhore]

I have a SCAL report for capillary pressure data in which the mercury injection experiment has been performed for injection pressure of 60,000 psia. the reservoir pressure is only 4500 psia. Can anyone explain the necessity of performing this experiment for such high pressures?

Thanks,
Vibhore

[DAH7542]

Mercury Injection Capillary Pressure Tests (MICP) are always performed to very high capillary pressures (Pc) when compared to Porous Plate and Centrifuge methods.
Furthermore, Pc is not related to reservoir pressure, so the maximum Pc in your test has nothing to do with the reservoir pressure in your case. Capillary pressure is function of the interfacial tension, pore throat size and distribution, contact angle, and interfacial tension between the fluids involved.
The reason why the MICP tests reach greater capillary pressures is due to the fact that the mercury is used in the tests, this fluid has an interfacial tension with air 10 or more times greater than that between the oil and wáter (or brine).
In addition I suppose that the rock tested in your case has very low permeability.

[DAH7542]

Mercury Injection Capillary Pressure Tests (MICP) are always performed to very high capillary pressures (Pc) when compared to Porous Plate and Centrifuge methods.
Furthermore, Pc is not related to reservoir pressure, so the maximum Pc in your test has nothing to do with the reservoir pressure in your case. Capillary pressure is function of the density difference between the fluids, pore throat size and distribution, contact angle, and interfacial tension between the fluids involved.
The reason why the MICP tests reach greater capillary pressures is due to the fact that the mercury is used in the tests, this fluid has an interfacial tension with air 10 or more times greater than that between the oil and water (or brine).
In addition I suppose that the rock tested in your case has very low permeability.

[for_lon]

Hi vibhore!

I also have some doubts with core analysis, like capillary pressure by mercury injection. I think, there is a good book that could help both of us: R.P. Monicard, Properties of Reservoir Rocks: Core analysis. It's supposed to describe all core analysis methods, including mercury injection, which is an old method.

Take a look to my thread: "Book required: R.P. Monicard,Properties of Reservoir Rocks" in order to see if some one can share this book, and maybe we can learn about this topic.

Regards,

[vibhore]

Thanks,
It's evident that Pc doesn't depends on Pres. But my reservoir is around 200 m thick. So assuming oil gradient as 0.24 psi/ft and water gradient as 0.43 psi/ft. max Pc considering the whole thickness would be around 1000 psi. but the experiment was conducted upto 60,000 psi. And the permeability for the reservoir is around 700 md.

Another question is that I've MICP data and Porous-plate data for some cores. So while calculating a J-function does both data should be considered? And as we convert MICP Pc data to reservoir condition, does porous-plate data is also converted to reservoir condition? In-case of porous plate the Lab has only reported Kair (air permeability) but in case of MICP klinkenberg permeability is reported.

[DAH7542]

I now understand you better vibhore. For such reservoir permeability I also agree that the maximum Pc reached in the test is questionable. Ask the laboratory directly.

As for the other questions here are my comments:

Does porous-plate data is also converted to reservoir condition?
- Yes. Even though oil-water system is used in the test, interfacial tension changes from 48dynes/cm at lab conditions to aprox. 30 dynes/cm at average reservoir conditions. Take into account that air-water systems are also used to conduct this test (make proper corrections to reservoir conditions).

While calculating a J-function does both data (MICP and porous plate) should be considered?
- Yes, although in my opinion (shared by other colleagues of mine), the porous plate test yields results that are more representative of the reservoir physics, then, if there are enough porous plate tests (or centrifuge tests) to characterize all the rock types (or flow units, or whatever is your method of rock characterization) the MICP test are conveniently disregarded when it comes to calculate the J-function. However, needless to say the importance of MICP test to estimate the pore size distribution, r35, etc.

In-case of porous plate the Lab has only reported Kair (air permeability) but in case of MICP klinkenberg permeability is reported.
- Make standard corrections to make both perm measurements comparable.

[itag]

Vibhore - this is a late reply to your question but there are 2 main reasons why Mecrury Injection pressures are much higher

a) the conversion from lab to reservoir will require a scaling factor of the inverse s.cost(lab)/s.cost(res) ... this relation is typically 450/70 dyne/cm or roughly a factor of 7. All things equal Hg pressures need to be a factor of 7 higher in the lab.

b) more importantly mercury cap pressure is used for pore throat analysis .... you can analyze the contributions of different pore throat sizes to the available porosity. As long as Pc keeps changing as P is increased then smaller and smaller pores are being accessed. Pore thoat distributions may or may not be of interest to you - but for systems with lots of micro-porosity ( pores less than 1-5 micron) then this can provide useful insights.

[itag]

Vibhore - this is a late reply to your question but there are 2 main reasons why Mecrury Injection pressures are much higher

a) the conversion from lab to reservoir will require a scaling factor of the inverse s.cost(lab)/s.cost(res) ... this relation is typically 450/70 dyne/cm or roughly a factor of 7. All things equal Hg pressures need to be a factor of 7 higher in the lab.

b) more importantly mercury cap pressure is used for pore throat analysis .... you can analyze the contributions of different pore throat sizes to the available porosity. As long as Pc keeps changing as the wetting saturation decreases then smaller and smaller pores are being accessed. Note that Pc increasing at constant (and unchanging) saturation means that no additional pore space is being "seen". Pore throat distributions may or may not be of interest to you - but for systems with lots of micro-porosity ( pores less than 1-5 micron) then this can provide useful insights.