Journal of Scientific Research & Reports 5(7): 591-597, 2015; Article no.JSRR.2015.125 ISSN: 2320-0227 SCIENCEDOMAIN international www.sciencedomain.org Temperature and Time-Dependent Behaviour of a Water Base Mud Treated with Maize (Zea mays) and Cassava (Manihot esculanta) Starches Akintola A. Sarah1* and S. O. Isehunwa1 1Department of Petroleum Engineering, University of Ibadan, Ibadan, Nigeria. Authors’ contributions This work was carried out in collaboration between both authors. Both authors read and approved the final manuscript. Article Information DOI: 10.9734/JSRR/2015/14870 Editor(s): (1) Masum A Patwary, Geography and Environmental Science, Begum Rokeya University, Bangladesh. Reviewers: (1) Anonymous, USA. (2) Anonymous, China. Complete Peer review History: http://www.sciencedomain.org/review-history.php?iid=753&id=22&aid=7964 th Received 27 October 2014 th Original Research Article Accepted 12 January 2015 th Published 30 January 2015 ABSTRACT Starch, one of the commonly used additives in drilling fluids, degenerates with time under cyclic temperature and pressure loads, causing changes in mud properties. This study was designed to establish the effect of temperature and aging on water base mud treated with starches prepared from maize (Zea mays) and cassava (Manihot esculanta) starches. The effect of potash and tannathin on the muds was also investigated. Plastic viscosity of treated samples at varying temperatures (24.4, 40.0, 60.0 and 80.0 O C) was determined using standard API practices over a period of 72 hours. At ambient conditions, the plastic viscosity of samples treated with maize and cassava varied between 5 and 7 cp and increased to between 6 and 12 cp when the samples were further treated with potash. Plastic viscosity for industrial starch varied from between 5 and 6 cp but increased to between 7 and 10 cp when further treated with potash. Predictive models for plastic viscosity and yield point gave coefficient of variance between 90 and 92% respectively. However, all the starches degenerated within 24 hours and would require further treatment to prevent biodegradation. Keywords: Starches; plastic viscosity; yield point; potash; tanna thin. _____________________________________________________________________________________________________ *Corresponding author: Email: sarah.akintola@mail1.ui.edu.ng; UNIVERSITY OF IBADAN LIBRARY Sarah and Isehunwa; JSRR, 5(7): 591-597, 2015; Article no.JSRR.2015.125 NOMENCLATURE PV = Plastic viscosity; YP =Yield point; AV = Apparent viscosity; Gel = Gel strength; 600 = rotational viscosity at 600 rpm; 300 = rotational viscosity at 300 rpm; X1,= Temperature (°C); X2 = Starch (g); X3 = Potash (g); βo , αo= Intercept coefficient; β1 , β2 and β3 ; = empirical constants for plastic viscosity; α α and = empirical constants for yield point; COV = Coefficient of Variance. 1, 2 α3 1. INTRODUCTION used factorial design to obtain a statistical model for predicting the rheological properties of water Drilling fluids are complex fluids consisting of base mud treated with starch and potash at high several additives, added to enhance / control the temperatures and pressures. Menezes et al [10] rheological properties. They perform a lot of evaluated the influence of carboxymethyl functions which ensure that a well is drilled cellulose on the rheological properties of successfully, safely, and economically. The bentonite dispersions in water-based drilling control of the flow properties of drilling fluids is fluids. Adebayo and Imokhe [11], compared the important as most of the drilling fluid functions use of barite and lignosulphate with some local are controlled by its rheological properties. additives. This present study was designed to Hence, there is a need to ensure that these evaluate the behavior of drilling muds treated properties are well monitored in the course of with selected local starches. drilling to ensure a successful drilling operation Starch, is an abundant biomass found in nature 2. MATERIAL AND METHODS [1], and was the first organic polymer used in substantial quantities in drilling mud. Its addition Cassava (Manihot esculenta) tubers and to bentonite dispersions as an additive is of great industrial starch were obtained from International industrial interest because the properties of Institute of Tropical Agriculture (IITA), Ibadan, drilling fluids are strongly modified by such while fresh maize (Zea mays) and potash were polymers [2,3]. There are two types of starch obtained from a local market in Ibadan. Fresh molecules; the linear or helical amylose and the tubers of cassava (500 g) were washed, peeled, branched amylopectin and always associated cut and soaked in water containing 100 ppm with them are minor constituents like proteins sodium metabisulphate. The tubers were wet (0.25%), lipids (0.1-0.3%) and compounds of milled at low speed using a blender with 1: 2 w/v phosphorus [4]. The performance of a given of tap water. The solution was filtered through a starch is governed by its physicochemical muslin cloth, and suspension was kept overnight properties which differ in their physical and for settling of starch. The supernatant was chemical properties and these properties are decanted, and the settled residue was further dependent upon the arrangement of the bonds purified with repeated suspension in tap water which link glucose units to one-another. Amylose (1:2 v/v) followed by the settling for 3 hours. The affects the gelling behavior in starch molecules purified starch was dried at 35°C, and sieved while the branched chain amylopectin reduces through a 200 m sieve. Maize starch was the mobility of the polymer and its orientation in extracted by steeping in hot water for 10 hrs and an aqueous environment. subsequent grinding. The resultant mash was centrifuged to allow the starch to settle down. Starches are inexpensive, abundance in supply, The starch was then washed several times using renewable, environmentally friendly and fully clean distilled water. Starch obtained was then biodegradable. Statistical and mathematical dried in an air forced oven at 40°C and then techniques have been used to study the stored at room temperature. Potassium influence of additives on the rheological Carbonate was grinded and sieved using a 200 properties of bentonite–water systems [5,6]. m sieve to obtain a fine powder. Isehunwa and Orji [7] had earlier employed factorial design to determine filtration properties The starches produced from maize and cassava of a drilling mud at high temperatures and were used as additives in drilling fluids with pressures and stressed that the method could composition as shown in Table 1. A control test reduce risk, time and money. Amanuallh et al [8] was carried out using industrial starch. Mud was developed corn-based starches using local allowed to hydrate for 24 hrs before treatment resources to study their suitability for use as with additives. Potash and tannathin were also drilling fluid additive. Okumo and Isehunwa [9] used as additives in concentrations as shown in 592 UNIVERSITY OF IBADAN LIBRARY Sarah and Isehunwa; JSRR, 5(7): 591-597, 2015; Article no.JSRR.2015.125 Table 2. A Hamilton beach mixer was used for starches was observed as temperature mixing, a Fann VG model at six different speed increased, this high temperature could have values (600, 300, 200, 100, 6 and 3 rpm), to contributed to the thinning effect due to partial obtain rheological properties, at incremental destruction of the hydration shell and temperatures of 24.4, 49, 60 and 80°C. Aging furthermore, cohesive forces within bentonite tests were conducted to determine how bottom- molecules could have contributed to the viscous hole conditions affect mud properties, shear stress leading to viscosity reduction and Experiments replication repeated for all mud this finding is in agreement with the report of Joel samples after 24 and 48 hrs. Plastic viscosity, and Nwokoye [12]. apparent viscosity, and yield point were determined from viscometer readings using, the Fig. 2 show results of PV of the mud sample equations (1), (2) and (3) respectively: Predictive treated with 5 g of starches at different models were obtained using response surface temperatures. The PV of the mud samples methodology and results were statistically increased to a peak for all samples treated with analyzed. starches, because as the temperature increased, the starch molecules are agitated leading to a    (1) break in intermolecular bonds thus allowing p 600 300 increased interaction with water molecules. At  high temperatures above 62°C, there was Av  600 (2) 2.0 complete loss of starch crystallinity and gelatinization occurred leading to a decrease in Yb 300   p (3) the PV. As additional 5 g of starch was added to the mud samples (Fig. 3) the viscosity increased 3. RESULTS AND DISCUSSION as a result of this additional solids. Increase in temperature, lower the viscosity; this is because The effects of maize and cassava starch on the higher temperature leads to a decrease the rheological properties of a water base mud were viscosity of the liquid phase in a drilling mud investigated. Results on plastic viscosity (PV) sample and also the breaking down of the bonds and yield point (YP) were obtained for mud within the polymer chains resulting in thermal samples treated with starch before and after degradation of starch. being subjected to increase in temperature over a period of 72 hrs. The behavior of cassava starch was closer to the control than that of maize starch and this could 3.1 Effect of Temperature be attributed to the variation of constituents in the starch molecule as variation in the amount of Fig. 1 shows the plastic viscosity of mud sample amylose and amylopectin in starch changes its without additives at different temperatures. A behavior of the starch, Amanuallh and Long [13]. decrease in the PV of the sample without Fig. 1. Plastic viscosity (cp) against Temperature (°C) of the drilling fluid without additives 593 UNIVERSITY OF IBADAN LIBRARY Sarah and Isehunwa; JSRR, 5(7): 591-597, 2015; Article no.JSRR.2015.125 Table 1. Composition for starch samples Mud Bentonite (g) Water (ml) Starch (g) Potash(g) Tannathin (g) Sample A 22.5 350.0 5.00 0.00 0.00 Sample B 22.5 350.0 10.0 0.00 0.00 Sample C 22.5 350.0 5.00 5.00 5.00 Sample D 22.5 350.0 5.00 10.0 10.0 Sample E 22.5 350.0 10.0 5.00 5.00 Fig. 2. Plastic viscosity (cp) against temp (°C) of drilling fluid treated with 5 g of starch Table 2. Order of Addition for mud samples The plastic viscosity of the mud samples treated with the different starches decreased as the time Order of addition (g) Mixing time (mins.) increased this can be as a result of the Hydrated sample 10 flocculation of the bentonite clay resulting from Starch 5 the loss of the continuous phase in the mud The plastic viscosity of starches treated with maize Potash 5 starch decreased more than that of cassava Tannathin 5 starch others, showed that aging enhance the hydration process for samples that have higher 3.2 Effect of Aging amylose content and higher water absorption capacity. An aged mud sample (before stirring) Fig. 1 also shows the plastic viscosity of determines gelling tendencies of fluid in the untreated drilling fluids over a period of 72 hrs borehole. Lyons and Plisga [17] observed setting showing decrease in PV of untreated mud of mud solid in an aged mud as an indication of showing agreement with Santoyo et al [14]. f o r m ation of a layer (hard/soft) of sediment in the Fig. 4 shows the apparent viscosity, yield point borehole. and gel strength for treated muds, this properties initially increased but eventually decreased 3.3 Effect of Potash and Tanna thin within 48 hour this is in agreement with the finding of Ali and Al-Marhoun [15] who observed The use of thinner in the drilling fluid system that effective viscosity, plastic viscosity, yield reduced the viscosity of the mud and therefore point and gel strengths (10 sec. and 10 min.) of reduced the amount of energy needed to rotate aged mud increase with aging time. Above 62°C the drill stem and the drill bit. The effects of a decrease in PV occurred as aging time potash on different mud treated with starches are increased and its effect on yield point diminished. shown in Fig. 5. As the amount of potash added This result agrees with that obtained by Shokoya increased, the viscosity of the samples et al [16] in their study of the rheology and decreases, this might be as a result of potash corrosivity of water-base drilling fluid under preventing attractive forces between the clay and simulated down hole conditions. the starch molecules which in turn will reduce the 594 UNIVERSITY OF IBADAN LIBRARY Sarah and Isehunwa; JSRR, 5(7): 591-597, 2015; Article no.JSRR.2015.125 amount of energy needed to rotate the drill stem properties of the muds. The response variables and the drill bit. were plastic viscosity (PV) and yield point (YP), while the independent variables were In order to ascertain the performance of potash, temperature (X1), starch (X2) and potash(X3). tanna thin was added into the same mud Equations (4) and (5) were obtained for PV and composition. The results of mud treated with YP respectively. Table 3 shows the empirical tanna thin are shown in Fig. 6. Tanna thin did not constants derived for plastic viscosity (PV) and show an instant increase in the plastic viscosity yield point (YP), while Table 4 gives the at low temperature but as temperature increased coefficient of variance for plastic viscosity. there were changes as an increase in plastic Equation (4) and Table (3) show that PV viscosity above 62°C after 23 hrs was observed. increases with increasing Temperature and Starch concentration but decrease with potash The addition of potash to the different starches concentration. A similar trend was observed in contained in the drilling fluid had varying effects the prediction of YP (equation 5 and Table 3). which were more pronounced in the industrial Furthermore, statistical analysis shows that there starch, followed by cassava starch than maize was a good correlation between the predicted PV starch. using the model with experimental values (Table 4). 3.4 Predictive Models for Rheological Properties PV   o   1 x1   2 x 2   3 x 3 ( 4 ) YP   o   1 x1   2 x 2   3 x 3 (5 ) Response surface methodology was used to develop predictive models for rheological Fig. 3. Pv (cp) against Temp (°C) a drilling fluid treated with 10 g Starch Fig. 4. Rheological properties against time for drilling fluid treated with starch 595 UNIVERSITY OF IBADAN LIBRARY Sarah and Isehunwa; JSRR, 5(7): 591-597, 2015; Article no.JSRR.2015.125 Table 3. Empirical constants for plastic viscosity and yield point predictive models Plastic viscosity Yield point Mud Sample β0 β1 β2 β3 α0 α1 α2 α3 Maize starch 5.95 1.06 0.81 -0.19 12.67 6.99 0.30 -5.13 Industrial starch 8.19 2.06 1.06 -0.56 13.77 7.63 0.38 -5.27 Cassava starch 7.76 1.94 0.94 -0.31 13.67 7.36 0.34 -5.23 Fig. 5. Plastic viscosity (cp) against Temp (°C) for drilling fluid treated with 10 g starch and 5g potash Fig. 6. Plastic viscosity (cp) against Temp (°C) of drilling fluid treated with 10g of starch and 5g tanna thin Table 4. Coefficient of Variance for Plastic fluids treated with maize and cassava starches Viscosity of Starches decrease with increase in temperature. This shows that these locally produced starches are Starch Variance CoV % useful in controlling the rheological properties of Maize 0.219 92.87 water base muds. Cassava starch provided Industrial 0.219 93.75 closer rheological profiles to that of industrial Cassava 0.219 93.25 starch. Empirical models have been developed to predict the rheological properties of treated water 4. CONCLUSION based drilling fluids. This method can help to Based on this study, it can be concluded that the achieve improved performance and significant rheological properties of water based drilling cost reduction. Furthermore, it was observed that 596 UNIVERSITY OF IBADAN LIBRARY Sarah and Isehunwa; JSRR, 5(7): 591-597, 2015; Article no.JSRR.2015.125 both maize and cassava starches degraded with 9. Okumo I, Isehunwa SO. Prediction of the time hence further research on their modification viscosity of a water-base mud treated with is required to reduce their biodegradation. cassava starch and potash at varying temperatures using factorial design. COMPETING INTERESTS Nigeria Annual International Conference and Exhibition. Abuja Nigeria; 2007. Authors have declared that no competing 10. Menezes RR, Marques LN, Campos LA, interests exist. Ferreira HS, Santana LNL, Neves GA. 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Petroleum Tech. 1997;36(3):45-50. _______________________________________________________________________________ © 2015 Sarah and Isehunwa; This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Peer-review history: The peer review history for this paper can be accessed here: http://www.sciencedomain.org/review-history.php?iid=753&id=22&aid=7964 597 UNIVERSITY OF IBADAN LIBRARY