Rheology of Oil-Base Muds

Abstract

INTRODUCTIONAlthough a great deal has been written about the pressure and temperature behaviour of the viscosity of simple non-ABSTRACT Newtonian fluids, and an understanding of this behaviour at The theological behaviour of invert emulsion muds has been the molecular level is emerging, no consensus exists on how studied at pressures up to 1000 bar and temperatures up to to deal with concentrated suspensions. This can easily be 240°C. Theological parameters were calculated for the Bingunderstood, considering the widely different nature of nonham, Herschel-Bulkley and Cssson theological models. The Newtonian fluids, Invert emulsion muds are suspensions of Iierachel-Bulkley and Cesson modeb both give good fits to the solids and emulsions at the same time, and as there is no experimental rheograms. The Cesson model is more reliable generally accepted theological model that can be applied to for extrapolation purposes than the Herschel-Bulkley model. emulsions and suspensions, the engineering aspects of invert A pair of two similar exponential expressions were found to emulsion muds are not always based on very sound scientific be able to model the pressure and temperature behaviour of principles, Thus, while it is known that at pressures and temthe two parameters of the Casson model. The expressions, peratures encountered in the wellbore the rheology of the mud which are baaed on the relation for pure liquids derived theoretically by Eyring, contain temperature dependent pressure will be different from that measured at the surface, lack of coefficients. The simplifications inherent in the temperature the ability to quantify the effects involved has perpetuated the and pressure model are dkcussed in the light of the tempera-field practice of using theological parameters measured at atture and pressure behaviour of the viscosity of common base mospheric pressure. Traditionally the mud industry has, with oils and their constituent hydrocarbons. Field application of a few exceptions, adhered to the uee of the Bingham and power the model requires measurement of the rheology of the mud at law theological models, which have the advantage that hytwo or more temperatures and knowledge of the pressure co-draulics calculations are available for fluids obeying these modefficients relating the behaviour of the plastic viscos~ty to that els. Hence, it is not surprising that the existing techniques for of the yield point, or the Casson high shear visccgity to that prediction of downhole rheology are based on these models. of the Casson yield stress. Pressure meaauremer !S or other A number of recent publications have dealt with the problem. information are then not required. Applications can be baaed Combs and Whitmire (1) showed that the change in the viscoson Caason or Bingham theological meesurements. The rela-ity of the continuous phase is the main factor in controlling the tionships between the parameters of the Casson and Bingham change in the viscosity of the mud with pressure. Both yield models are disussed. point and plas...

Combined Effect of Pressure and Temperature on the Viscous Behaviour of All-Oil Drilling Fluids

“…Likewise, the decrease observed in the piezo-viscous coefficient with temperature is progressively less marked as temperature increases (Tab. 6), as reported elsewhere (Chaudemanche et al, 2009) Hence, the influence of pressure is mainly dependent on base oil flow properties, as has been pointed out by different authors (Houwen and Geehan, 1986;Hermoso et al, 2014). It also interesting to notice that B34-based drilling fluid piezo-viscous coefficient presents a slightly higher temperature dependence than both B128-based one and SR10 oil, as can be seen in Table 6.…”

“…Changes in B34-based drilling fluid piezo-yield stress could be associated with the thermal weakening of interparticle interactions in the agglomerates and reduction in the effective agglomerate concentration, being the yielding behaviour less sensitive to pressure changes as temperature increases, even enhancing its compressibility with temperature (Paredes et al, 2012). In addition, this decrease in yield stress with an increase in temperature may be related to a decrease in oil viscosity (Houwen and Geehan, 1986).…”

Determination of drilling fluid rheology under downhole conditions by using real-time distributed pressure data

“…Over the past years, several studies were performed to find correlations between the rheological parameters of the drilling fluids and the effects of temperature and pressure. For instance, Annis (1967), Hiller (1963) and Alderman et al (1988) studied the rheology of water-based mud under HPHT conditions, while the rheology of invert drilling fluids (OBM/SBM) under HPHT conditions was investigated by McMordie et al (1975), Bailey et al (1986), Politte (1985), Houwen and Geehan (1986).…”

Advanced Cuttings Transport Study

“…Their research showed that, less toxic oils become more viscous as pressure is increased, but the viscosity differences among the oils tends to decrease with increasing temperature even if the pressure is increased. Moreover, temperature has the greatest effect on viscosity reduction below 200 o F. Houwen and Geehan (1986) [20] [11] show the effect of temperature and pressure on viscosity as follows: Equation (65) is valid until a thermal decomposition or transition of any component in the drilling fluid take place. At this point drilling fluids do not follow any mathematical model.…”