Iraqi Journal of Chemical and Petroleum Engineering Vol.15 No.1 (March 2014) 51- 57 ISSN: 1997-4884 Apparent Viscosity Direct from Marsh Funnel Test Faleh H. M. Almahdawi, Ahmed Zarzor Al-Yaseri and Nagham Jasim Petroleum Engineering Department – College of Engineering- University of Baghdad-Iraq Abstract Accurate and simple techniques for measurement of fluid rheological properties are important for field operations in the oil industry. Marsh Funnels are popular quality- control tools used in the field for drilling fluids and they offer a simple, practical alternative to viscosity measurement. In the normal measurements, a single point (drainage time) is used to determine an average viscosity; little additional information is extracted regarding the non-Newtonian behavior of the fluid. Here, a new model is developed and used to determine the rheological properties of drilling muds and other non-Newtonian fluids using data of fluid density and drainage time collected from a Marsh Funnel as a function of viscosity. The funnel results for viscosity compare favorably to the values obtained from a commonly-used Fann 35 viscometer. Different quantities of bentonite, barite and other additives which have been used to prepare many samples. Empirical equations are obtained µapp. = ρ (t – 28) and µapp. = -0.0118t2 + 1.6175t - 32.168, where apparent viscosity (µapp.) in (cp), Marsh funnel time (t) in seconds and the density (ρ) in gm/cm3. Introduction Hydrocarbon production uses many fluids that are rheologically complex. Among these is cement, drilling muds, aqueous solutions of water-soluble polymer and of course crude oil itself. Drilling fluids can be air or water, but most commonly they are “muds” or suspensions of solids in an aqueous or oleic fluid. The solids are suspended with one or more surfactants. The solids are used to provide weight to the mud for pressure control, the main function of muds, but muds also lubricate the drill, carry drilling cuttings to the surface and cool the bit. Most muds are water-based as is the type used in this study. When fresh water is the liquid base, bentonite is the clay used for its superior properties necessary to achieve the goals stated for drilling mud [1]. Water-based fluids are suspensions of weight material in water, but also contain a number of additives to control fluid properties such as rheology, fluid loss, shale inhibition and lubricity. The standard weight material is API barite. There are also non-standard weight materials with considerably finer particle size, which generate low rheology and are used in some high- density and/or slim-hole applications. The liquid phase of drilling fluids generally contains a number of additives to control the various required properties of fluids, including one or more rheology additives to Iraqi Journal of Chemical and Petroleum Engineering University of Baghdad College of Engineering Apparent Viscosity Direct from Marsh Funnel Test 52 IJCPE Vol.15 No.1 (March 2014) -Available online at: www.iasj.net suspend the weight material. Thus, fluid rheology is generated partly by the suspended solids and partly by the rheology additives [2, 3]. Drilling mud exhibits several important rheological properties [4]. The viscosity or consistency index of a mud is a measure of flow resistance. Therefore viscosity should be as small as possible to limit friction pressure. However a certain amount of viscosity is required to improve the solids carrying capacity of the mud. If viscosity is too small, the mud may be unable to suspend drilled solids at the desired pump rate. This requires the pumps to be run faster to continue to circulate drilled solids out of the well. If viscosity is too high, an excessive pump pressure will be required to circulate the mud at the desired rate. Higher than necessary pump pressure is an added strain on the pumps and piping and an added pressure in the bore hole that can lead to well bore stability problems. Non- Newtonian fluids (drilling muds and polymers) may also exhibit a yield stress (or gel strength). For drilling operations, the higher the yield stress the more pump pressure will be required to initiate circulation. The yield stress can also be a desirable property because it will suspend the drilled solids and prevent or slow them from slipping back to the bottom of the hole during periods when there is no circulation. Fluid yield stress in fracturing fluids for example can help carry and suspend proppant, but can also make cleanup difficult [5]. Below the yield stress the material is solid- like and has an infinite viscosity. The solid-like behavior is typically a result of a three-dimensional microstructure at low stresses [6]. Above the yield stress the material deforms as a fluid and the viscosity is a function of shear rate. Many pastes, foodstuffs, gels, and drilling muds have a yield stress. The simplest yield-stress model is the Bingham model, in which the relationship between shear stress and shear rate is linear, with the yield stress defined as the extrapolated y-axis intercept [2]. Marsh Funnel The Marsh Funnel was invented by Hallan N. Marsh in 1931 [7]. It is used to measure the time in seconds required to fill a set volume of fluid. (In the United States the volume is one quart.) The flow through the small tip at the end of the funnel is related to the rheological properties of the fluid being measured. The Marsh Funnel “viscosity” is reported as seconds and used as an indicator of the relative consistency of fluids. The more viscous the fluid the longer the time to fill one quart. The calibration for Marsh Funnel time is 28 seconds per quart for fresh water. The standard Marsh Funnel is shown in Fig. 1 . The Marsh Funnel provides a simple and effective tool to determine the relative viscosity of drilling mud. Here, we also use the funnel for additional oilfield fluids. Fig. 1, Standard Marsh Funnel Figure 1 shows that the height of cone- portion of the funnel is 12 in. http://www.sciencedirect.com.tiger.sempertool.dk/science/article/pii/S092041051100088X#bb0060 http://www.sciencedirect.com.tiger.sempertool.dk/science/article/pii/S092041051100088X#bb0025 http://www.sciencedirect.com.tiger.sempertool.dk/science/article/pii/S092041051100088X#bb0055 http://www.sciencedirect.com.tiger.sempertool.dk/science/article/pii/S092041051100088X#f0005 Faleh H. M. Almahdawi, Ahmed Zarzor Al-Yaseri and Nagham Jasim -Available online at: www.iasj.net IJCPE Vol.15 No.1 (March 2014) 53 (30.5 cm) and the diameter is 6 in. (15.2 cm). The copper tubing is 2 in. (5.08 cm) in length and has a diameter of 3/ in. (0.48 cm). Although rheological properties of these fluids can be measured by conventional rheometers, a simple method is often needed. The goal of this work is to develop such a method for determining rheological properties of non-Newtonian fluids using a Marsh Funnel. An experiment consists of filling the funnel to a pre-specified height and measuring the rate at which the test fluid drains. The flow behaviour of a Marsh funnels is simulated numerically [8]. As a result, his simulation provides a general picture of the meaning of the Marsh funnel time and a correlation enabling this to be converted into a value for effective viscosity of non- Newtonian fluids. The final equation for M.J. Pitt is: µeff. = ρ (t – 25) …(1) Where: µeff. = effective viscosity (cp); ρ= density (gm/cc); t=time (sec.) The model presented in this work can estimate the apparent viscosity instead of effective viscosity depends on Pitt’s equation in this study we used experimental data instead of numerical simulation. Fluid Preparation Many of the fluids used in these experiments must be mixed before testing. The used fluids are water- based fluids. Before adding any solid particles or polymer to the water-based fluids used here, water was adjusted to approximately a pH of 9 by adding droplets of NaOH (sodium hydroxide). For all tests, the fluid was at room temperature (~ 30 °C), the density was measured using a density balance, and the rheology measured using a Fann V. G. 35 viscometer. Fluid was then poured in the Marsh Funnel for the tests. Different quantities of bentonite, barite and other additives which have been used to prepare samples and the measured values are listed in table 1. Marsh Funnel Test After the fluid rheology is measured, the fluid is placed in the Marsh Funnel as shown in table 1. The Marsh Funnel is designed so that 1500 mL of fluid can be poured into the funnel. A small stopper is placed in the orifice at the bottom to prevent flow out while the fluid is poured into the funnel. Once it reaches the bottom of the screen, this indicates that 1500 mL now rests in the funnel. The purpose of screening is to remove any unmixed solid particles from the rest fluid. Results and Discussion After measuring the fluid properties from Lab., an experimental correlation between the apparent viscosity and Marsh time is estimated as: µapp.=-0.0118t 2 +1.6175t -32.168 …(2) as shown in Fig. 2. Also, we investigated that the apparent viscosity is equal to µapp. = ρ (t – 28) …(3) Depend on Marsh time and density together as shown in Fig. 3. Table 2 shows the results of viscosity which show all calculations to determine the viscosity from observed equations. In addition, the accuracy of the present work compared to the true data. Apparent Viscosity Direct from Marsh Funnel Test 54 IJCPE Vol.15 No.1 (March 2014) -Available online at: www.iasj.net Table 1, Fluid properties from Lab No. Marsh time (second) Density (gm/cm 3 ) app viscosity from lab. (true value); cp 1 40.15 1.025 11.5 2 36.8 1.032 10 3 35.14 1.045 10 4 34.58 1.05 10.25 5 34 1.053 10.75 6 44.6 1.03 15 7 44.4 1.04 15 8 43.21 1.05 15 9 42.03 1.05 15.25 10 40.9 1.051 15.75 11 55 1.03 20.5 12 55.6 1.035 20 13 49.88 1.04 20.5 14 49.13 1.047 21 15 49 1.049 21 16 45 1.02 14.5 17 40 1.035 11.5 18 39 1.04 10.5 19 38 1.053 11 20 36.2 1.06 11 21 36 1.1 10 22 36.2 1.1 10.5 23 45 1.035 22.5 24 46.76 1.043 17.5 25 42.08 1.06 15 26 39.63 1.079 13 27 38.53 1.098 11.5 28 38 1.15 10.5 29 59.11 1.03 19.5 30 43.78 1.035 15.5 31 41.67 1.055 15 32 40.79 1.08 13.5 33 39.78 1.09 13.5 34 38 1.11 12.5 Fig. 2, The relationship between true app. viscosity (cp) Vs. Marsh funnel time(sec.) Faleh H. M. Almahdawi, Ahmed Zarzor Al-Yaseri and Nagham Jasim -Available online at: www.iasj.net IJCPE Vol.15 No.1 (March 2014) 55 Fig. 3, The relationship between true app. viscosity (cp) Vs.. µapp from equation (3) Table 2, Apparent Viscosity Calculations N Marsh time density app viscosity from lab Vis.= den. (t-28) app. Viscosity from time only Vis.= den. (t-25) 1 40.15 1.025 11.5 12.45375 12.96296666 15.52875 2 36.8 1.032 10 9.0816 11.20376633 12.1776 3 35.14 1.045 10 7.4613 10.37067288 10.5963 4 34.58 1.05 10.25 6.909 10.09549982 10.059 5 34 1.053 10.75 6.318 9.813648558 9.477 6 44.6 1.03 15 17.098 15.45686264 20.188 7 44.4 1.04 15 17.056 15.34100763 20.176 8 43.21 1.05 15 15.9705 14.65894974 19.1205 9 42.03 1.05 15.25 14.7315 13.99500999 17.8815 10 40.9 1.051 15.75 13.5579 13.37086832 16.7109 11 55 1.03 20.5 27.81 21.95340737 30.9 12 55.6 1.035 20 28.566 22.35578865 31.671 13 49.88 1.04 20.5 22.7552 18.64076205 25.8752 14 49.13 1.047 21 22.12311 18.17394784 25.26411 15 49 1.049 21 22.029 18.09351863 25.176 16 45 1.02 14.5 17.34 15.68962422 20.4 17 40 1.035 11.5 12.42 12.88199777 15.525 18 39 1.04 10.5 11.44 12.34744062 14.56 19 38 1.053 11 10.53 11.822043 13.689 20 36.2 1.06 11 8.692 10.89965975 11.872 21 36 1.1 10 8.8 10.79904076 12.1 22 36.2 1.1 10.5 9.02 10.89965975 12.32 23 45 1.035 22.5 17.595 15.68962422 20.7 24 46.76 1.043 17.5 19.56668 16.73033785 22.69568 25 42.08 1.06 15 14.9248 14.02289131 18.1048 26 39.63 1.079 13 12.54877 12.6831489 15.78577 27 38.53 1.098 11.5 11.56194 12.09935823 14.85594 28 38 1.15 10.5 11.5 11.822043 14.95 29 59.11 1.03 19.5 32.0433 24.76824529 35.1333 30 43.78 1.035 15.5 16.3323 14.98409134 19.4373 31 41.67 1.055 15 14.42185 13.79492469 17.58685 32 40.79 1.08 13.5 13.8132 13.31072456 17.0532 33 39.78 1.09 13.5 12.8402 12.76361318 16.1102 34 38 1.11 12.5 11.1 11.822043 14.43 Apparent Viscosity Direct from Marsh Funnel Test 56 IJCPE Vol.15 No.1 (March 2014) -Available online at: www.iasj.net Fig. 4, App. Viscosity from different methods Conclusions: A clear relationship between the Marsh Funnel viscosity (t) and the apparent viscosity was obtained through this study, as well as, an equation correlating the apparent viscosity to both density and Marsh Funnel viscosity (t) is presented. The comparison between the obtained equation 3 and the equation given by M. J. Pitt equation 1 show that constant (28) is more accurate and appropriate than constant (25) given by the same author. (see table 2) Figure 4 Shows that the relationship No. 2 is more accurate and it can be recommended for use as a relationship between the apparent viscosity measured from the device (multi- speed viscometer) and the viscosity values measured as time from Marsh Funnel. (see table 2) References 1- Matthew T. Balhoff and et. al. "Rheological and yield stress measurements of non- Newtonian fluids using a Marsh Funnel", Journal of Petroleum Science and Engineering,june, 2011 v.77 pp.393-402. 2- Ahmadi Tehrani, Behaviour of Suspensions and Emulsions in Drilling Fluids. annual transactions http://www.sciencedirect.com.tiger.sempertool.dk/science/article/pii/S092041051100088X http://www.sciencedirect.com.tiger.sempertool.dk/science/journal/09204105 http://www.sciencedirect.com.tiger.sempertool.dk/science/journal/09204105 Faleh H. M. Almahdawi, Ahmed Zarzor Al-Yaseri and Nagham Jasim -Available online at: www.iasj.net IJCPE Vol.15 No.1 (March 2014) 57 of the nordic rheology society, vol. 15, 2007. 3- Power, D. and Zamora, M. (2003), “Drilling Fluid Yield Stress: Measurement Techniques for Improved Understanding of Critical Drilling Fluid Parameters”, AADE- 03-NTCE-35, AADE Technical Conference, Houston, Apr. 1-3. 4- A.T. Bourgoyne Jr., M.E. Chenevert, K.K. Millheim, F.S. Young Jr. Applied Drilling Engineering, SPE Textbook Series, Vol. 2Society of Petroleum Engineers, Richardson, TX (1991). 5- E.A. May, L.K. Britt, K.G. Nolte,The Effect of Yield Stress on Fracture Fluid Cleanup SPE 38619, presented at the 1997 Society of Petroleum Engineers Annual Technical Conference and Exhibition in San Antonio, Texas (1997). 6- P.J. Carreau, D.C.R. De Kee, R.P. Chhabra,Rheology of polymeric systems Hanser/Gardner Publications, Inc., Cincinatti (1997). 7- H. Marsh, Properties and Treatment of Rotary Mud .Petroleum Development and Technology, Transactions of the AIME (1931), pp. 234–251. 8- M.J. Pitt,The Marsh Funnel and drilling fluid viscosity: a new equation for field use.Soc. Petroleum Eng., Drilling Completions, 15 (1) (2000), pp.3–6.