Capillary Pressure

[besucher]

Hey everyone,

Is there any possibility to correlate capillary pressures ? I didn't get the data from the lab, so I was wondering, if there is a reasonable correlation...
How big is the influence in my simulation, if I just assign zero capillary pressure in the Equilibration part... !? Are there any rules of thumb ?!

Any advice, idea, comment on this topic is apreciated !!

Regards.

[vinomarky]

Unless you have to characterize the transition zone (ie low relief reservoir, low perm) under your conditions I'd probably just go with log derived saturations cross plot against log perm and characterize the irreducible water saturations

If transition zone is important, again, you can perhaps go to your log derived saturations and log derived perm - taken in conjunction with the height above FWL you may be able to reverse out a generic relationship

There is no robust generic correlation that I am aware of.

[Shakespear]

Take a look at this

[link Point to another website Only the registered members can access]
The paper reviews a bit of what has been done in this direction and what they propose. Notice, without ANY DATA you are just GUESSING.

Can someone try to get a pdf file of this paper

Wettability and Its Effect on Oil Recovery
Authors

Norman R. Morrow, SPE, New Mexico Petroleum Recovery Research Center, New Mexico Inst. of Mining and Technology
Journal Journal of Petroleum Technology
Volume Volume 42, Number 12
Date December 1990
Pages 1476-1484
Copyright

1990. Society of Petroleum Engineers
Language English
Preview

Introduction

Reservoir wettability is determined by complex interface boundary conditions acting within the pore space of sedimentary rocks. These conditions have a dominant effect on interface movement and associated oil displacement. Wettability is a significant issue in multiphase flow problems ranging from oil migration from source rocks to such enhanced recovery processes as alkaline flooding or alternate injection of CO2 and water. In this paper, wettability will be discussed mainly in the context of recovery of light (low-viscosity) oils by waterflooding. Waterflooding has been widely applied for more than half a century; secondary recovery by waterflooding presently accounts for more than one-half of current U.S. oil production. Many research papers have addressed the effect of wettability on waterflood recovery during this period. For much of the past 50 years, however, a large body of reservoir period. For much of the past 50 years, however, a large body of reservoir engineering practice has been based on the assumption that most reservoirs are very strongly water-wet (VSWW); i.e., the reservoir-rock source always maintains a strong affinity for water in the presence of oil. The rationale for assuming VSWW conditions was that water originally occupied the reservoir trap; as oil accumulated, water was retained by capillary forces in the finer pore spaces and as films on pore surfaces overlain by oil. Wettability behavior other than VSWW was observed for reservoir core samples, but was often ascribed to artifacts related to core recovery and testing procedures. The majority of reservoir engineering measurements have been made on cleaned core with refined oil or air as the nonwetting phase to give results for, or equivalent to, VSWW conditions. Examples of such measurements are laboratory waterfloods, determination of electrical resistivity vs. water saturation relationships, and capillary pressure measurements for determination of reservoir connate water saturation. Mounting evidence on the effects of crude oil on wetting behavior has now led to wide acceptance of the conclusion that most reservoirs are at wettability conditions other than VSWW. This conclusion has led to a resurgence of interest in satisfactory procedures for measuring reservoir wettability and determining its effect procedures for measuring reservoir wettability and determining its effect on oil recovery, especially with respect to waterflooding. Determination of reservoir wettability and its effect on oil recovery by methods that involve core samples will be referred to as advanced core analysis for wettability (ACAW). Reservoir wettability is not a simply defined property. Classification of reservoirs as water-wet or oil-wet is a gross oversimplification. Various procedures for measuring wettability have been proposed. Two methods of quantifying wettability based on rock/brine/oil displacement behavior, the modified Amott test and the USBM test, are in common use. Each method depends on water saturation measurements and related capillary pressures or flow conditions to define a wettability scale. The tests show pressures or flow conditions to define a wettability scale. The tests show that reservoir wettability can cover a broad spectrum of wetting conditions that range from VSWW to very strongly oil-wet. Within this range, complex mixed-wettability conditions given by combinations of preferentially water-wet and oil-wet surfaces have been identified. In preferentially water-wet and oil-wet surfaces have been identified. In this paper, the adopted scales of reservoir wettability and their relationships to interface boundary conditions are considered together with the dramatic effects that wettability can have on oil recovery.

Contact Angles, Spreading and Adhesion

Contact Angle and Spreading. Contact angle is the most universal measure of the wettability of surfaces. Fig. 1 shows idealized examples of contact angles at smooth solid surfaces for oil and water of matched density. Early studies of wetting phenomena showed that the wetting properties of a solid are dominated by the outermost layer of molecules. (Films that result from spreading and other thin adsorbed films are not indicated in Fig. 1.) Large change in the wettability of a surface, such as quartz, can be achieved by adsorption of a monolayer of polar molecules so that the outermost part of the surface is composed of hydrocarbon chains. Extreme change in wettability (see Fig. 1), such as from a or b to e or f, or vice versa, is called wettability reversal. Adsorption of polar compounds from crude oil plays a critical role in determining the wetting properties of reservoir-rock surfaces. Many early studies of wetting behavior, even for comparatively simple systems, were plagued by problems of reproducibility. Aside from surface contamination, other forms of heterogeneity in chemical composition, surface roughness, and static and dynamic interface properties contribute to the complexity of observed wetting phenomena. Large differences in contact angles, depending on whether an interface was advanced or receded, called into question the validity of attempting to describe wettability by a single-valued equilibrium contact angle. Successful systematic studies of closely reproducible equilibrium-contact-angle measurements have been summarized by Zisman. By use of smooth (often polymeric), solid surfaces and pure liquids, contact-angle hysteresis was limited to within 1 or 20. In contrast, contact-angle hysteresis is observed almost invariably for crude-oil/brine systems. Fig. 2 shows examples of contact angles that exhibit small and large hysteresis. Receding angles are generally low (less than 30 degrees) and seldom exceed 60 degrees, whereas a wide range of advancing angles is observed. The shaded regions in Fig. 2 show the range of possible contact-angle values for a fixed position of the three-phase line of contact. Contact-angle measurements on reservoir-crude-oil/brine systems provide one approach to measuring reservoir wettability. For the most extensive set of data yet reported, contact angles for crude oil and simulated reservoir brine were measured at reservoir temperature and ambient pressure. Choice of mineral substrate, usually quartz or calcite, was pressure. Choice of mineral substrate, usually quartz or calcite, was based on what was judged from petrographic examination to be the predominant mineral at pore surfaces. (There are obvious limitations to predominant mineral at pore surfaces. (There are obvious limitations to representing the rock surface by a single mineral.)

JPT

P. 1476

I think everyone would benefit from reading it. I have seen it referenced quite a bit but do not have access to old JPT stuff. Heck, not even SPE

[sinodas]

Here is it

[link Point to another website Only the registered members can access]

[Shakespear]

Thank You very much "sinodas"

[besucher]

Thank you guys...

@vinomarky: I have rel perm curves and permeabilities (which are quiet high (800-3000mD)) from cores instead of logs (the logs are quiet old and almost useless...and just a few..).

I will go through the papers and lets see how i can create some reliable curves :>

[besucher]

Is there any case, where it makes sense (or at least is OK) to assign a capillary pressure value of zero in my simulation ?
Or will it falsen my results (too much) ?

[vinomarky]

Just using zero capillary pressure is entirely reasonable when the effect of your transition zone is negligible on the model outcome (ie high perm (low transition zone) or high relief (small fraction of HCIP in transition)). The net effect of using zero Pc is the model will initialize with saturations governed by rel perm endpoints

If all your pay is the high perm stuff you have SCAL for, then just use the rel perm curves as a starting point with zero Pc

[Shakespear]

Read on page 13

[link Point to another website Only the registered members can access]

and here

[link Point to another website Only the registered members can access]
and on page 17 here where nice pictures and very good explanation of concepts is provided

[link Point to another website Only the registered members can access]

That should explain it all. You will need to make the call based on situation you have.

Also some good discussion about using dimensionless number to evaluate reservoir processes, as in the end you will need to take your calculator and do some basic calculations to justify your assumptions.

[link Point to another website Only the registered members can access]
You will also find MANY good papers here on various subjects

[link Point to another website Only the registered members can access] look at "Research Publications by Subject "

[link Point to another website Only the registered members can access]

[besucher]

thanks a lot guys... I am not going to calculate thaaat exact my cap pressure curve, because it is not playing a major role in the reservoir! I rough estimate is enough!!

But again, thanks for the support and all the papers !

@shakespear: you are one of the reasons I am continue using this forum, because your advice and suggestion keeps this forum going on!
I hope, we can expand and structure this community a little bit more and get all even a bigger advance out of it !

regards.