Effect of a Naturally Derived Deflocculant (Black Myrobalan) on Rheological Behavior of Heavy Drilling Fluids

Transcription

1 American Journal of Oil and Chemical Technologies: Volume 3. Issue 4. October 2015 Petrotex Library Archive American Journal of Oil and Chemical Technologies Journal Website: Effect of a Naturally Derived Deflocculant (Black Myrobalan) on Rheological Behavior of Heavy Drilling Fluids Jalal Neshat 1, Erfan Hosseini 2, Bahram Habibnia 3 1 Department of Petroleum Engineering, Ahwaz Faculty of Petroleum Engineering, Petroleum University of Technology, Ahwaz, Iran. 2 Department of Petroleum Engineering, Abadan Faculty of Petroleum Engineering, Petroleum University of Technology, Abadan, Iran. 3 Department of Petroleum Engineering, Ahwaz Faculty of Petroleum Engineering, Petroleum University of Technology, Ahwaz, Iran. Abstract: Drilling process is the most important part of exploitation of hydrocarbon reservoirs and accomplishment of drilling a well is determined by proper choice of the drilling fluid. The drilling fluid is related either directly or indirectly to almost every drilling problem. Improvement of drilling fluid properties therefore would have direct impact on drilling process. Replacing common additives by more efficient additives is an alternative to reach this goal. Plant based additives are suitable materials which have been studying by researchers in recent years with aim of improving drilling fluid properties. In this study effect of Black Myrobalan (also called Terminalia Chebula) extract on rheological behavior of a heavy weight mud were investigated experimentally. To do this different concentrations of a Black Myrobalan solution (0.2, 0.6, 1.2, and 3 Vol %) were added to salt saturated mud and its rheological properties, filtration volume along with density and ph were measured. Furthermore effect of time aging and hot rolling at 200 F was assessed. It was observed that Black Myrobalan decreases rheology of mud and increases filtration volume without affecting mud weight at both after and before hot rolling. Among rheological parameters yield point decreased more than other parameters. Moreover, hot rolling decreased the rheological parameters of mud while time aging increased them contrarily. The optimum concentration of Black Myrobalan in order to decrease rheology of mud was 1.2 Vol %. It was also observed that ph of mud decreased by increasing Black Myrobalan concentration. summarily Black Myrobalan acted as a deflocculant at concentrations up to 1.2 Vol %. Keyword: Deflocculant, Black Myrobalan, Rheology, Aging, Hot rolling. 1. Introduction Drilling operation is the most important phase in the exploitation of hydrocarbon deposits. The success of drilling a well depends crucially on the proper choice of the drilling fluid used (Benyounes et al. 2010).The drilling fluid is related either directly or indirectly to almost every drilling problem. A properly designed drilling fluid should be able to perform some major functions to meet up with design objectives and prevent drilling problems (Annis and Smith, 1996). Functions of drilling fluid are: controlling formation pressure and maintaining wellbore stability, suspending cuttings and transporting them to surface, cooling and lubricating drill string, Transmission of hydraulic energy to tools and bit, formation evaluation, control corrosion, facilitate cementing and completion [Annis and Smith, 1996; Amoco Production Company, 1994). Drilling fluids are separated into three major classifications: pneumatic, oil based, and water based. Water based fluids are the most extensively used drilling fluids. They are generally easy to build, inexpensive to maintain, and can be formulated to overcome most drilling problems (Amoco Production Industrial And Mining Research Center Cycle Science & Industry Comopany, Tehran, Iran

2 Company, 1994). They are also believed to be more environmentally friendly than other types of drilling fluids like oil based muds. There are some reasons to improve water based muds performance, which are: Due to the detrimental effect of some mud additives such as potassium chloride, potassium sulphate, polyamine and etc. in water based mud composition, drilling and operating companies were forced to review their mud additives selection guidelines to exclude or control the use of non-environment friendly and toxic mud additives in the formulation of water-based muds, so the industry is dedicated to replace some of the low toxic, less harmful and less pure mud additives that are acceptable according to currents environmental norms (Amanullah, 2007). Another major challenge of the indigenous petroleum companies is the importation of mud additives; this has not allowed them to compete favorably with foreign counterparts (Nmegbu and Bekee, 2014). Other reasons for improving drilling performance and management is cost. Contribution of drilling mud in terms of overall cost of drilling may be between 5 % and 15% but may cost 100% of drilling problems (Amanullah, 2007). Generally, a good drilling fluid should be simple and contain a minimum number of additives which allows easier maintenance and control of properties even at elevated temperature and pressure (Nmegbu and Bekee, 2014). Yousif et al. (2011) studied the characteristic properties of lignite from Lakhra (place in Pakistan) for use as drilling mud additive. The results showed that Lakhra lignite possess characteristics to be used as mud additive. It has capability to improve plastic viscosity in all mud samples and reduced yield point and gel strength. Also Lakhra was an effective mud thinner with satisfactory mud weight tolerance. Meng et al. (2012) investigated the effect of carbon ash on the rheological properties of bentonite dispersion. They observed that rheological properties of bentonite dispersion improved markedly in YP and especially for low solid content of bentonite dispersion. Riyapan and Wannakomol (2012) studied the filtration and rheological properties of water-based mud using natural rubber latex additive which was derived from the Hevea brasiliensis tree. They found that mud containing natural rubber latex had better static filtration properties compared to base bentonite mud. Narayana (2013) investigated the use of Myrobalan in reducing viscosity of drilling mud. He realized that of all the tannin-bearing materials, Myrobolan powder brings about the greatest reduction in viscosity, the lowest value being only 6% of the original, which remained constant with larger additions of Myrobolan. He also showed that the initial effect of adding small quantities of Myrobalan was equivalent to the tannic and ellagitannic content of the Myrobalan. The major purpose of this research is to investigate effect of hydroalcoholic extract of Black Myrobalan on heavy water based drilling fluid properties and finding the role of Black Myrobalan in mud. 2. Material and Experimental methods 2.1. Materials All of additives used for preparation of mud were provided by drilling fluids laboratory of National Iranian Drilling Company (NIDC). The hydroalcoholic extract of Black Myrobalan was purchased from Adonis Gol Daru pharmacy company (Tehran, Iran) Experimental Procedures Preparation of mud system To make a heavy drilling fluid these steps are followed: a. First of all 87.5 gr salt were added to 245 cc of distilled water and dissolved in water by stirring for 5 minutes. b. Soda ash is then added to extent of 1 gr. c. 14 gr green starch (potato starch) was added to mixture and stirred for 10 minutes. d. 332 gr standard barite was added to mixture (it was added slowly to prevent flocculation). e. 0.2 gr lime was added to adjust ph of mud. f. 1.5 gr xanthan gum was added to increase mud viscosity and thixotropy of mud and mixed 5 minutes. 2

3 Authors /American Journal of Oil and Chemical Technologies 3 (2015) g. Precalculated content of Black Myrobalan solution of 33 Vol % was added and mixed for 10 minutes Theory According to Bingham-Plastic model, the rheological parameters of mud such as AV, PV, YP (yield point) and RYP are calculated by equations 1-4: (1) (2) ( ) (3) ) (4) In which θ600 and θ300 are dial readings at 600 rpm and 300 rpm respectively (Meng et al., 2012). Figure 1. Preparation of heavy mud Measurement of Rheology and API Filtration Volume of Mud The testing of rheological properties was performed by a Fann-35A type rotating V-G meter (Figure 2a). In order to evaluate the thermal stability, the mud incorporating additives was rolled at 200 F for 4 hours using a hot rolling furnace, and then the rheological properties are also measured by a rotating V-G meter after cooling mud to 140 F. Filtration loss of mud sample was measured by using API filter press (Figure 2b) under a pressure of 100 psi for 30 min. The density of bentonite dispersion was determined by mud balancer at the room temperature. 3

4 Figure 2. (a): Fann V-G meter model 35A (b): Baroid API filter press 3. Results and discussion General properties of blank mud after preparation are given in Table 1. These properties are benchmark for evaluation of properties of mud containing Black Myrobalan. Table 1. Blank heavy mud properties Property Value Property Value Density (pcf) 115 ph 11 Plastic Viscosity (cp) 93 Water content (Vol %) 70 Yield Point (lb f /100 ft 2 ) 89 g.s 10 /10 (lb f /100 ft 2 ) 14/23.5 Chlorides (ppm) Filtrate (ml/30 min) 0.4 Mud cake thickness (1/32 nd in) A review on Black Myrobalan (Terminalia Chebula) Properties By analyzing Gas chromatography-mass spectrometry of Black Myrobalan in Figure 3 three major components: 1, 2, 3 benzentriol, Levenoglucosenone, and n-hexadecanoic acid were identified. These three components are responsible for special behavior of Black Myrobalan. 4

5 Figure 3. Gas chromatography-mass spectrometry of Black Myrobalan representing frequent components. Physical properties of Black Myrobalan are plotted against its concentration and shown in Figure 4. In this figure could be observed that critical micelle concentration for this material is obviously would be about 1.1 Vol % (1.2 Wt %). Figure 4. Physical properties of Black Myrobalan 5

6 Formulation of mud used in this paper is given in Table 2. Table 2. Composition of water based mud under study (NIDC formulation) Mud Composition Concentration (lb/bbl) Function Distilled Water 245 cc Base fluid NaCl 87.5 ( ppm) Contaminant Soda Ash 1 Water hardness control Green Starch 14 Viscosifier Barite 332 Weighting agent Lime 0.2 Alkalinity control XC polymer 1.5 Rheology control Mud Composition Concentration (lb/bbl) Function Distilled Water 245 cc Base fluid NaCl 87.5 ( ppm) Contaminant Soda Ash 1 Water hardness control Green Starch 14 Viscosifier 3.2. Effect of Black Myrobalan on Rheological behavior of Mud Flow Curve Figure 5-7 show the rheological behavior of mud incorporating various concentrations of Black Myrobalan after and before hot rolling and also after 24 hours aging. As can be observed in Figure 5, addition of Black Myrobalan to mud results in much smaller shear stresses compared to blank mud, at all shear rates. Figure 6 represents that hot rolling causes shear stress decrement to decrease by increasing Black Myrobalan concentration. As demonstrated in Figure 7 aging effect is contrary to hot rolling effect and recovers the shear stress decreased due to hot rolling. 6

7 Shear Streass (lbf/100 ft 2 ) Shear Streass (lbf/100 ft 2 ) Authors /American Journal of Oil and Chemical Technologies 3 (2015) % 0.60% 1.20% 3% Shear rate (1/s) Figure 5. Rheogram of mud for different concentrations of Black Myrobalan BHR % 0.60% 1.20% 3% Shear rate (1/s) Figure 6. Rheological behavior of mud containing various concentrations of Black Myrobalan AHR. 7

8 Shear Streass (lbf/100 ft 2 ) Authors /American Journal of Oil and Chemical Technologies 3 (2015) Shear rate (1/s) 0% 0.60 % 1.20 % Figure 7. Effect of aging on rheological behavior of mud incorporating different concentrations of Black Myrobalan Average Viscosity Variation of rheological parameters of mud versus Black Myrobalan concentration after and before hot rolling and also after 24 hrs aging is demonstrated in Figures Figure 8 indicates that increasing Black Myrobalan concentration decreases average viscosity continuously, until 1.2 Vol% and becomes steady. However hot rolling makes average viscosity curve more flat. By aging mud samples for 24 hours average viscosity values are recovered fully to their original value. Figure 8. Effect of aging and hot rolling on average viscosity of mud comprising different concentrations of Black Myrobalan. 8

9 Plastic Viscosity Effect of Black Myrobalan concentration on plastic viscosity of mud after and before hot rolling, and aging is illustrated in Figure 9. It is obvious that plastic viscosity lowers slightly at low concentrations and becomes nearly constant at higher concentrations. Hot rolling decreases plastic viscosity value while aging increases it. Plastic viscosity after aging is lowe r than before hot rolling which could be due to adhesion of Black Myrobalan to suspended particles and decreasing friction between them. Figure 9. Effect of aging and hot rolling on average viscosity of mud comprising different concentrations of Black Myrobalan Yield Point Yield point is indication of attraction force between particles in mud composition. According to Figure 10, as Black Myrobalan concentration increases, yield point decreases continuously. It could be also realized that yield point of hot rolled mud sample containing low concentrations of Black Myrobalan is lower than yield point of mud at room temperature and reversely at higher concentrations. It could be found that by increasing Black Myrobalan concentration difference between yield point before and after hot rolling decreases, which is indication of increased thermal stability of mud. 9

10 Figure 10. Effect of aging and hot rolling on low shear rate yield point of mud comprising different concentrations of Black Myrobalan Low Shear Rate Yield Point Figure 11 represents variation of low shear rate yield point versus Black Myrobalan concentration. As observed in this figure, by increasing Black Myrobalan concentration to 1 vol % LSRYP initially increases then starts to decrease at higher concentrations. Hot rolling the mud at 200 F decreases LSRYP and alters the trend of LSRYP curve such that it firstly decreases at low concentrations and becomes constant at higher concentrations. Figure 11. Effect of aging and hot rolling on low shear rate low shear yiel point of mud comprising various concentrations of Black Myrobalan. 10

11 Ratio of g.s 10 /g.s 10 Ratio of 10 sec gel strength to 10 min gel strength is an indication of how fast gel structure progresses passing time. Figur e 12 shows the variation of ratio of g.s 10 /g.s 10 of mud versus Black Myrobalan concentration. According to this figure, this ratio is nearly constant at low concentrations of Black Myrobalan, however by increasing concentration it increases continuously. Hot rolling decreases the mentioned ratio at a given concentration of Black Myrobalan while aging has adverse effect. Summary of rheological parameters for mud samples along with effect of hot rolling and aging is given in Table 2. Figure 12. Effect of aging and hot rolling on ratio of gel strength gel strength of mud comprising different concentrations of Black Myrobalan API Filtration of Heavy Mud According to Figure 13 API filtration Volume of mud increases as Black Myrobalan concentration increases until 1.2 Vol % and becomes nearly constant up to 3 Vol %. Another observation is that filtration volume of mud rolled at 200 F is higher than filtration volume of mud at ambient temperature. It should be mentioned that different between filtration volume in two cases decreases to minimum value at 1.2 Vol % ph Due to existence of acid groups in its composition, Black Myrobalan addition decreases ph of mud (Figure 14), this disturbs the equilibrium of carbonate, bicarbonate ions and carbon dioxide in mud Mud Weight According to Figure 15 it could be observed that effect of Black Myrobalan on mud density is insignificant. 11

12 Table 3. Rheological parameters of mud for different concentrations of Black Myrobalan. Rheological parameter B.M Conc. (Vol %) BHR AHR AA AV (cp) PV (cp) YP (lb f /100 ft 2 ) g.s 10 /g.s 10 (lb f /100 ft 2 ) 0 14/ /15 11/ /19.5 8/12 10/ /17 7/10 8/13 3 7/14 5/10 7/12 12

13 Figure 13. API filtration volume of mud after and before hot rolling. Figure 14. Effect of Black Myrobalan on ph of mud. 13

14 Figure 15. Effect of Black Myrobalan on mud weight. 4. Conclusions and recommendations 1. Black Myrobalan deflocculated heavy mud at low concentrations up to 1.2 Vol % while increases its filtration volume. In the other hand optimum concentration of Black Myrobalan to deflocculate the mud is about 1Vol % (0.6 Wt %). 2. Because of existence of acid groups in composition of Black Myrobalan, it decreases ph of mud. 3. Hot rolling decreases rheological parameters and filtration volume of mud while aging has adverse effect on these parameters. Black Myrobalan decreases variation of rheogram of mud at high temperature which is results in increasing thermal stability of mud. 4. Addition of Black Myrobalan has insignificant effect on density of mud. Acknowledgement The author would like to thank drilling fluids lab crew of National Iranian Drilling Company for their guidance and scientific supporting. 14

15 5. References [1] Benyounes, K., Mellak, A., Benchabane, A. (2010). The Effect of Carboxymethyl cellulose and Xanthan on the Rheology of Bentonite Suspension. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects. Vol. 32. No [2] Annis, M. R., Smith, V. (1996). Drilling Fluids Technology. Exxon Company. U.S.A. [3] Amoco Production Company. (1994). Drilling Fluids Manual. [4] Amanullah, M. (2007). Screening and Evaluation of Some Environment-Friendly Mud Additives to Use in Water-Based Drilling Muds. SPE paper No , presented at SPE E&P Environmental and safety Conference. Texas. U.S.A March. [5] Nmegbu, C.G.J., Bekee, B.A. (2014). Evaluation of Corn Cob Cellulose and its Suitability for Drilling Mud Formulation. [6] International Journal of Engineering Research and Applications. Vol. 4. No [7] Narayana, P.Y. (2013). Rotary Drilling Mud. Part I. The Effect of Tannin on the Viscosity. Journal of Indian Institute of Science. Vol. 21. No [8] Yusif, M., Khan, I.A., Khan, A.M. (2011). Characteristic Properties of Lakhra Lignite to be used as Drilling Mud Additive. [9] SPE paper No presented at SPE/PAPG Annual Technical Conference. Islamabad. Pakistan November. [10] Meng, X., Zhang, Y., Zhou, F., Chu, P.K. (2012). Effects of carbon ash on rheological properties of water-based drilling fluids. [1] Journal of Petroleum Science and Engineering. Vol [11] Riyapan, T., Wannakomol, A. (2012). Filtration and Rheological Properties of Natural Rubber Latex Added Drilling Fluid. [12] Suranaree Journal of Science and Technology. Vol. 18. No