Rhelogy of non-aqueous mud

The three popular rheological models to describe the flow pattern of fluid in annulus have a fundamental feature incorporated, on the basis of which the values of rotational viscometer are used to calculate PV, Yp, AV and gel strength of the fluid, be it water based or oil based. That fundamental feature is thixotropy. The development of gel strength is believed to be a result of aggregation of clay layers, where electrostatic forces of attraction also play an important role! Oil based muds have non-polar continuous phase which leads to absence of electrostatic forces and hence the rheological values measured with the help of by rotational viscometer readings cannot truly represent the flow pattern of oil base mud inside the annulus. In addition to it, the expansion feature of oil base mud with increase in temperature is distinctly of higher degree when compared with water base mud. This will increase cuttings slip velocity and such cuttings will not suspend in oil base mud as effectively as in water base mud. Therefore, the values of PV, Yp and Gel strength measured in oil base mud in the way we calculate for WBM, shall mislead in terms of rheological values, because expansion feature leadig to decrease in rheology values of Oil base mud does not find adequate representation due to absence of adequate electrostaatic forces of attraction, leading to formation of gel structure! In simple words - if the Yp value of 20 lbs/100ft2 is adequate to lift the cuttings in WBM, the same value need not necessarily represent the same level of hole cleaning in oil base mud and probably to get comparable representation the actual Yp for Oil base mud has to be > 20 lbs/100 ft2. This brings up a very basic question in focus, should we have a different rheological model for Oil base mud? I believe yes. This different model should incorporate increased cuttings slip velocity as a deterrent and account for appropriate correction factor. In real field we do not encounter hole cleaning related issues with Oil base mud simply because this is more than compensated by higher flow rate we can maintain in oil base mud without excessive increase in annular pressure losses and ECD. Since it isn't having a visible impact does not mean that it doesn't exist! Lets wear our thinking caps and have a healthy discussion please.