Application of X-ray Powder Diffraction and Rietveld Phase Analysis to Support Investigations of Failure for Submersible Pumps

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1 Application of X-ray Powder Diffraction and Rietveld Phase Analysis to Support Investigations of Failure for Submersible Pumps Dr. Husin Sitepu and Dr. Syed R. Zaidi ABSTRACT This article illustrates the applications of advanced X-ray powder diffraction (XRD and Rietveld phase analysis in the oil industry. XRD, which can be used to determine the polymorphs and crystalline phases of actual compounds present in the sample, is an excellent tool to identify the solids, sludge and deposits accumulated or formed at different locations within electrical submersible pumps (ESPs. Rietveld phase analysis has the advantage over conventional reference intensity ratio methods, given that no standards are required to achieve accurate results to within ±1%. The phase compositions obtained from Rietveld phase analysis of XRD data on local sludge and deposits can guide the engineers and scientists at the refinery and gas plant to overcome the deposition problems by drawing up the right procedures. For example, if calcium carbonate (CaCO 3 is present in the form of aragonite, the engineers know the sample is scale deposit, but if CaCO 3 is present as a calcite, the sample might be either scale materials or formation materials or both. In another example, the presence of either etteringite (Ca 6, which also occurs as a hydrous calcium aluminum sulfate mineral (Ca 6 26H 2 O, or portlandite (Ca(OH 2 shows the sample is coming from the cement. Scale and corrosion deposits frequently form inside the equipment used in the oil industry and can cause premature equipment failure. The main objective here was to study the deposits accumulated in ESPs, which are placed in boreholes and used for numerous applications. ESPs are frequently used in oil production to provide a relatively efficient form of artificial lift so as to enhance oil production. In the present study, 47 solid samples collected from ESPs at different wells were characterized by advanced XRD and Rietveld phase analysis to determine the phase composition accurately. The findings showed that different types of compounds were detected in these deposits, including corrosion products in the form of iron sulfides, iron oxides and iron carbonate, formation materials in the form of sand and dolomite, scale deposits such as CaCO 3 and calcium sulfate (CaSO 4, salts (sodium chloride (NaCl, and cementing materials such as Ca 6, brownmillerite (Ca 2 Fe Al Mg Si O 5 and calcium silicate (Ca(SiO 4 O. These deposits plugged the pump stages, causing motor overheating and pump failure. Knowing which compounds were involved can guide the engineers at the refinery and gas plants to overcome the problems by drawing up the right procedures and taking preventive action to stop the generation of those particular solids. INTRODUCTION Scale and corrosion deposits frequently form inside the equipment used in the oil industry. Failures of electrical submersible pumps (ESPs had been observed in refinery and gas plants for several years. The failures occurred mainly due to the deposition of corrosion products, formation materials, scale, salts and cementing materials. Due to the failure of the ESPs, the refinery and gas plants would have to be temporarily shut down. Therefore, the Research and Development Center (R&DC sought to provide support to the refinery and gas plant engineers by identifying and quantifying the nature and source of the compounds being accumulated e.g., corrosion products, formation materials, scale deposit, salts and cementing materials using advanced X-ray powder diffraction (XRD and Rietveld phase analysis. The findings can guide the engineers in taking proper action to prevent future occurrences and so avoid refinery and plant slowdowns that may result in loss of production. XRD is an excellent analytical technique 1 used for the phase identification of a crystalline material in catalysts, scale deposits, chemicals, cores, shells, clay minerals and cement. Importantly, it can be used to identify compounds, whereas other complementary techniques, such as X-ray fluorescence, inductively coupled plasma mass spectrometry and atomic absorption spectroscopy techniques, can only be used to identify elements and not compounds. An additional advantage of the XRD techniques 1-10 compared to the other analytical techniques is that XRD can be used to differentiate accurately between different forms of a compound with the same chemical formula. For example, calcite, aragonite and vaterite have the same chemical formula (CaCO 3, but they have different crystallographic structure. That means a sample that has the same chemical formula, calcium carbonate (CaCO 3, can be identified as scale formation materials, e.g., calcite or scale deposits (aragonite or vaterite. Moreover, the iron sulfides that are formed have a wide range of chemical compositions and different crys- 2 SPRING 2017 SAUDI ARAMCO JOURNAL OF TECHNOLOGY

2 talline structures: they can be identified as, for example, pyrite (FeS 2, marcasite (FeS 2, mackinawite (FeS 0.9, pyrrhotite (Fe 7 S 8 and greigite (Fe 3 S 4. It is very important to know the form of an iron sulfide because some of these iron sulfides are pyrophoric, presenting a risk of igniting. Furthermore, XRD can also differentiate among the hydration states of the compounds in the sample, e.g., distinguishing gypsum (CaSO 4.2H 2 O from bassanite (CaSO 4.0.5H 2 O, and both from anhydrite (CaSO 4. Rietveld phase analysis has successfully been used worldwide to determine the weight percentage (wt% for each of the above identified phases. The advantages of Rietveld phase analysis are that: It does not refine one peak only, but refines the whole patterns of the XRD data sets. It does not require measurement of calibration data. It does not use an internal standard for the crystalline materials, i.e., no amorphous content available. It needs only the approximate crystal structure of each of the identified phases to conduct the refinements. The use of an internal standard will allow the determination of total amorphous phase content in a mixture. Analysis of multiphases yields high-precision results, with errors generally less than 1.0% absolute. Since this technique fits the complete XRD pattern, Rietveld phase analysis is less susceptible to primary extinction effects and minor amounts of preferred orientation Additional benefits of this technique over traditional quantitative analysis methods 1-6 include the determination of precise cell parameters, approximate chemical compositions and the potential for the correction of preferred orientation effects The weight percentage, W, of each of these identified phases, p, is proportional to the product of the scale factor, s, as derived in the Rietveld phase analysis of the XRD pattern, with the mass and volume of the unit cell. It is given by: W p s p p n ( ZMV / s ( ZMV (1 i 1 where Z, M and V are the number of formula units per unit cell, the mass of the formula unit and the unit-cell volume (in i i Å 3, respectively. The basis of Rietveld phase analysis provides accurate phase analyses without the need for internal standards or for laborious experimental calibration procedures. It is noted that the Rietveld method for quantification of the 20 identified phases using software (X Pert HighScore Plus Version 2.2c PANalytical Inc. with a total of 6,000 reflections was 30,000 times more powerful than the reference intensity ratio method 1-6 for quantification of the two identified phases. The main objective of the present study was to examine the deposits (solids that accumulated in different ESP parts. These pumps are used in the boreholes of water wells and in oil wells for water abstraction, and they are frequently installed to enhance oil production by providing an efficient means of artificial lift. A compositional study was made of deposit samples that built up in the different ESP regions intake of pump, pump stage, etc. using advanced XRD and Rietveld phase analysis, which are well-known techniques, both for the identification of compounds and for the quantification of all the identified compounds 1-12 present in scale deposits, corrosion products and formation materials. EXPERIMENTAL PROCEDURE To fulfill the above objectives of the study, the authors conducted experimental work on the samples of water sludge, oil sludge or solid scale that were collected from various ESP parts from different wells in four different locations. The below shows the preparation procedure followed for each of the asreceived samples: 1. Solid samples were dried in a fume hood and/or vacuum oven. 2. Water sludge samples were separated in a filtration assembly. 3. Oil sludge samples were treated with dichloromethane to remove the hydrocarbon. 4. Separated solids were dried in a vacuum oven. Subsequently, the samples were manually ground by an agate mortar and a pestle for several minutes to achieve a fine particle size 8. Then the fine powders were mounted into the Name Instrument Radiation Optics Specimen Detector Acquisition Description Rigaku ULTIMA-IV XRD multipurpose X-ray powder diffractometer Copper-anode tube operated at 40 kv and 40 ma Wavelength: Cu Kα1 = Å Bragg Brentano, measuring circle diameter = 480 mm Divergence slit: 0.67, scattering slit: 0.67 and receiving slit: 0.3 mm Holder: rectangular format, dimension 22 mm x 22 mm Rotation on for all measurements Position sensitive detector Angular range in 2θ: 4 70 ; Step size: 0.02 ; Scan rate: 1 per minute Table 1. XRD pattern measurement conditions SAUDI ARAMCO JOURNAL OF TECHNOLOGY SPRING

3 sample holders of the Rigaku ULTIMA-IV XRD X-ray powder diffractometer by front pressing. High resolution XRD data of the samples were acquired using the diffractometer with a copper X-ray tube from 4 to 70 2θ-Bragg angles, with a step size of 0.02 and with a counting time of 1 per minute. Table 1 shows the XRD pattern measurement conditions. Fig. 1. Compounds present in the samples collected from Well 1 (S1, S2 and S3 and Well 2 (S4 and S5. Fig. 2. Compounds present in the samples collected from Well 3 (S6 and S7 and Well 4 (S8, S9, S10 and S11. The most widespread use of XRD is in the identification and quantification of crystalline materials. Both the 2θ-Bragg positions corresponding to d-spacings and the peak s intensity are indicative of a particular phase of the material. The first scientist who realized the analytical potential of creating a database of this identification was J.D. Hanawalt. A recent form of such a database is the Powder Diffraction File (PDF-4+ of the International Center for Diffraction Data (ICDD. This has been made searchable by computer through the work of XRD equipment manufacturers worldwide, and many databases are interfaced to a wide variety of diffraction analysis software. In the PDF-4+ published by the ICDD, there are now over 550,000 reference materials. The PDF-4+ contains many subfiles, such as minerals, corrosions, zeolites, metals and alloys, semiconductors, etc., and includes large collections of organic and inorganic reference material. In this article, the software package PANalytical High Score Plus (X Pert HighScore Plus Version 2.2c PANalytical Inc., combined with the ICDD of the PDF-4+ database of the standard reference materials, was used. When all the phases were identified using the High Score Plus software, the XRD data were refined using Rietveld phase analysis to determine the wt% for each of the identified phases semi-quantitatively. The parameters refined for the random orientation of crystallites were the same as those described by Sitepu et al. ( For all the identified phases as defined by the International Crystal Structure Database, there are phase-scale factors and the background component of the patterns as determined with a six-parameter Chebychev polynomial, lattice parameters, zero point 2θ offset in the 2θ scale of the goniometer the Lorentzian and Gaussian terms of the pseudo-voigt profile function and anisotropic strain parameters, and structural parameters and isotropic thermal parameters. RESULTS AND DISCUSSIONS Fig. 3. Compounds present in the samples collected from Well 5 (S12, Well 6 (S13, S14 and S15 and Well 7 (S16 and S17. A total of 47 deposit, sludge and solids samples collected from 14 wells were measured by a Rigaku ULTIMA-IV XRD multipurpose X-ray powder diffractometer. Then the High Score Plus software (X Pert HighScore Plus Version 2.2c PANalytical Inc. was used to identify the phases at all the XRD data 4 SPRING 2017 SAUDI ARAMCO JOURNAL OF TECHNOLOGY

4 sets. Finally, Rietveld phase analysis was used to determine the wt% for each of the identified phases. The identified compounds and quantification results are given in Figs. 1 through 8. It can be seen from these figures that the samples collected from the intakes of the pumps from different wells mostly consisted of CaCO 3 (calcite and aragonite with quartz (SiO 2 and dolomite (CaMg (CO 3 2. Iron sulfide (pyrite (FeS 2 and hydrated calcium sulfate (gypsum (CaSO 4.2H 2 O were also detected in most of the samples. These compounds plugged the pump stages, causing motor overheating and pump failure. The samples collected from the pump stage mostly consisted of corrosion products of iron oxide and/or iron sulfide. One pump stage sample showed high quantities of materials used in cement. They are: A few samples were collected from the ESP s protectors, which stop well fluids from entering the motor. The solids collected from the upper protectors mostly consisted of CaCO 3 scale, iron oxide and iron sulfide corrosion products, while the lower protector samples consisted of sodium chloride (NaCl and CaCO 3. The upper protector labyrinth solids consisted of iron oxide and iron chloride, and the upper protector labyrinth tube fluid solids were a mixture of CaSO 4, NaCl, CaCO 3 and iron oxide. The sample collected from outside of the Well 3 ESP stator hose showed dolomite as a major compound and iron sulfide, calcite and halite as minor compounds. The sample collected from the O-ring of the Well 3 ESP consisted of carbon, iron oxide and iron sulfide. Solids deposited around the O-ring of the Well 6 ESP showed iron carbonate as a major component. A sample collected from the top penetrator packer of the Well 4 ESP showed that halite was a major component and gypsum was a minor component. The sample collected from the pump shaft of the Well 4 ESP was mainly nickel sulfide. The pump shaft is connected to the gas separator or the protector by a mechanical coupling at the bottom of the pump. The ESP shaft is made up of nickel metal, and it may have reacted with hydrogen sulfide (H 2 S and formed nickel sulfide. The pump samples collected from Well 11 were mainly iron oxide (magnetite corrosion product and dolomite; samples Ca(SiO 4 O Etteringite [Ca 6 ] Calcium iron magnesium silicon oxide, with the mineral name of brownmillerite that has a chemical formula of Ca- Fe Al Mg Si O. The ICDD and PDF entry is Fig. 4. Compounds present in the samples collected from Well 8 (S18 and S19, Well 9 (S20 and Well 10 (S21 and S22. Fig. 5. Inorganic compounds present in the samples collected from Well 11. Fig. 6. Inorganic compounds present in the samples collected from Well 12. SAUDI ARAMCO JOURNAL OF TECHNOLOGY SPRING

5 Fig. 7. Inorganic compounds present in the samples collected from Well 13. Magnesium hydroxide in the form of brucite (Mg(OH 2 was present in samples collected from the intakes of the ESPs. Normally, Mg(OH 2 crystallizes in cement and concrete when it comes in contact with producing seawater. Copper sulfide, nickel sulfide, iron carbonate, iron chloride hydroxide and iron oxide are corrosion products. The ESP s connecting wire is made up of copper metal, and it may react with H 2 S to form copper sulfide. The ESP s shaft is made up of nickel metal, and it may react with H 2 S to form nickel sulfide. Fig. 8. Inorganic compounds present in the samples collected from Well 14. from Well 12 were CaCO 3 (aragonite and calcite scale; and samples from Well 13 were mainly iron oxide and iron oxide hydroxide corrosion products. Additionally, samples from Well 14 consisted of hydrated CaSO 4 (gypsum, CaCO 3 (calcite and dolomite. CaSO 4 scale, especially gypsum, has caused unpredictable problems in many oil fields, including severe plugging of the operating equipment. The nature of the compounds detected in the samples are: Calcite, aragonite and vaterite are polymorphs of CaCO 3. Calcite is the most stable form of CaCO 3. CaSO 4, including gypsum (CaSO 4.2H 2 O and anhydrite (CaSO 4, is normally a scale deposit. Anhydrite is also a formation material. Dolomite and quartz are formation materials, and they may come with water. Ca(SiO 4 O, Ca 6 and Ca 2 MgFeAlMgSi 2 O 5 are materials used in cement. H 2 S was found in the oil and gas. The oil and gas emerging from a geological formation always contains varying amounts of acid gas, carbon dioxide and H 2 S. Palygorskite, illite, kaolinite and chlorite are forms of hydrous aluminum phyllosilicate that occurs in a clay soil. NaCl (halite is a salt normally precipitated from water, especially seawater. CONCLUSIONS In the present study, the authors analyzed the depositions leading to the failures of ESPs in a number of wells. In identifying and quantifying 47 solid samples collected from ESPs in different wells using advanced XRD and Rietveld phase analysis, they detected corrosion products (iron sulfides, iron oxides and iron carbonate, formation materials (sand and dolomite, scale deposits (CaCO 3 and CaSO 4, salts (NaCl and cementing materials (Ca 6, Ca 2 MgFeAlMgSi 2 O 5 and Ca(SiO 4 O in these samples. The findings can be used to guide the engineers in taking proper action to prevent future occurrences in the ESPs so as to avoid refinery and plant slowdown that will result in loss of production. 6 SPRING 2017 SAUDI ARAMCO JOURNAL OF TECHNOLOGY

6 ACKNOWLEDGMENTS The authors would like to thank the management of Saudi Aramco for their permission to publish this article. Also, Yazeed A. Al-Dukhayyil and Mossaed A. Al-Fahad are acknowledged for his encouragement and support for this study. REFERENCES 1. Chung, F.H.: Quantitative Interpretation of X-ray Diffraction Patterns of Mixtures. I. Matrix-Flushing Method for Quantitative Multicomponent Analysis, Journal of Applied Crystallography, Vol. 7, Issue 6, December 1974, pp Chung, F.H.: Quantitative Interpretation of X-ray Diffraction Patterns of Mixtures. II. Adiabatic Principle of X-ray Diffraction Analysis of Mixtures, Journal of Applied Crystallography, Vol. 7, Issue 6, December 1974, pp Chung, F.H.: Quantitative Interpretation of X-ray Diffraction Patterns of Mixtures. III. Simultaneous Determination of a Set of Reference Intensities, Journal of Applied Crystallography, Vol. 8, Issue 1, February 1975, pp Klug, H.P. and Alexander, L.E.: X-Ray Diffraction Procedures: For Polycrystalline and Amorphous Materials, 2 nd ed., John Wiley, New York, 1974, 992 p. 5. Jenkins, R. and Snyder, R.L.: Introduction to X-ray Powder Diffractometry, John Wiley & Sons Inc., New York, 1996, 432 p. 6. Sitepu, H., Sherik, A.M., Zaidi, S.R. and Shen, S.: Comparative Evaluation of Cobalt and Copper Tubes Using X-ray Diffraction Data for Black Powder in Sales Gas Transport System, paper 10100, presented at the 13 th Middle East Corrosion Conference and Exhibition, Bahrain, February 12-15, O Connor, B.H., Li, D.Y. and Sitepu, H.: Strategies for Preferred Orientation Corrections in X-ray Powder Diffraction Using Line Intensity Ratios, Advances in X-ray Analysis, Vol. 34, 1991, pp Sitepu, H., O Connor, B.H. and Li, D.Y.: Comparative Evaluation of the March and Generalized Spherical Harmonic Preferred Orientation Models Using X-ray Diffraction Data for Molybdite and Calcite Powders, Journal of Applied Crystallography, Vol. 38, Issue 1, February 2005, pp Sitepu, H.: Texture and Structural Refinement Using Neutron Diffraction Data of Molybdite (MoO 3 and Calcite (CaCO 3 Powders and Ni 50.7 Ti Alloy, Powder Diffraction, Vol. 24, Issue 4, December 2009, pp Sitepu, H., Zaidi, S.R. and Shen, S.: Use of the Rietveld Method for Describing Structure and Texture in XRD Data of Scale Deposits Formed in Oil and Gas Pipelines: An Important Industrial Challenge, Advances in X-ray Analysis, Vol. 58, 2015, pp Hewat, A., David, W.I.F. and van Eijck, L.: Hugo Rietveld ( , Journal of Applied Crystallography, Vol. 49, Issue 4, August 2016, pp Shen, S., Mustafa, A.H., Zaidi, S., Sitepu, H., et al.: XRD Phase Identification and Residual Stress Analysis of the Turbine Blade Samples Before and After Heat Treatment, Advances in X-ray Analysis, Vol. 55, 2012, pp Bish, D.L. and Howard, S.A.: Quantitative Phase Analysis Using the Rietveld Method, Journal of Applied Crystallography, Vol. 21, Issue 2, April 1988, pp Madsen, I.C., Scarlett, N.V.Y., Cranswick, L.M.D. and Lwin, T.: Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: Samples 1a to 1h, Journal of Applied Crystallography, Vol. 34, Issue 4, August 2001, pp Scarlett, N.V.Y., Madsen, I.C., Cranswick, L.M.D., Lwin, T., et al.: Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: Samples 2, 3, 4, Synthetic Bauxite, Natural Granodiorite and Pharmaceuticals, Journal of Applied Crystallography, Vol. 35, Issue 4, August 2002, pp Hill, R.J. and Howard, C.J.: Quantitative Phase Analysis from Neutron Powder Diffraction Data Using the Rietveld Method, Journal of Applied Crystallography, Vol. 20, Issue 6, December 1987, pp O Connor, B.H. and Raven, M.D.: Application of the Rietveld Refinement Procedures in Assaying Powdered Mixtures, Powder Diffraction Journal, Vol. 3, Issue 1, March 1988, pp Leon-Reina, L., Garcia-Mate, M., Alvarez-Pinazo, G., Santacruz, I., et al.: Accuracy in Rietveld Quantitative Phase Analysis: A Comparative Study of Strictly Monochromatic Mo and Cu Radiations, Journal of Applied Crystallography, Vol. 49, Issue 3, June 2016, pp SAUDI ARAMCO JOURNAL OF TECHNOLOGY SPRING

7 BIOGRAPHIES Dr. Husin Sitepu joined Saudi Aramco s Research and Development Center (R&DC, Technical Services Division, in late December Since then, he has contributed to six ongoing research projects by providing crystallographic information file (CIF data on synthesized zeolite catalysts. Husin also conducted crystal structure and texture refinement of new materials by using the General Structure Analysis System (GSAS Rietveld software. Before joining Saudi Aramco, Husin worked at national and international research laboratories in the USA (National Institute of Standards and Technology and Virginia Tech, Germany (Ruhr-University Bochum, France (Institut Laue-Langevin, Canada (University of British Columbia and Australia (Curtin University of Technology. Since 1989, he has gained extensive experience in the Rietveld refinement of polycrystalline structures using powder X-ray, synchrotron and neutron diffraction data. Since 1989, Husin has published 40 papers in peerreviewed journals, including the International Union of Crystallography s Journal of Applied Crystallography, Powder Diffraction Journal and American Mineralogist. Also, he has presented 80 papers at various refereed conferences. Husin received his Postgraduate Diploma and his M.S. and Ph.D. degrees in Physics from the Curtin University, Perth, Western Australia, in 1989, 1991 and 1998, respectively. He is a member of the International Center for Diffraction Data (ICDD, the International Union of Crystallography (IUCr and the Neutron Scattering Society of America (NSSA. Dr. Syed R. Zaidi has been with Saudi Aramco since His specialized area of research is the mineralogical characterization of geological samples (clay and bulk rock by using the X-ray powder diffraction (XRD technique. Syed is also responsible for XRD method development and research work. He is familiar with other analytical techniques, such as X-ray fluorescence (XRF, scanning electron microscope (SEM, Fourier transform infrared spectroscopy (FTIR, thermogravimetric analysis (TGA, differential scanning calorimetry (DSC and inductively coupled plasma mass spectrometry (ICP-MS instruments. Syed received his B.S. degree (with honors and M.S. degree, both in Chemistry, from Aligarh Muslim University, Aligarh, India, in 1977 and 1980, respectively. In 1986, he received his Ph.D. degree in Inorganic Chemistry from Aligarh Muslim University, Aligarh, India. Syed has published more than 20 papers in peer-reviewed journals. He is a member of the American Chemical Society (ACS and the Society of Petroleum Engineers (SPE. 8 SPRING 2017 SAUDI ARAMCO JOURNAL OF TECHNOLOGY