MOLECULAR SIMULATION STUDY OF DIVERTING MATERIALS USED IN MATRIX ACIDIZING A Dissertation by ABDULLAH SULTAN Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2009 Major Subject: Petroleum Engineering MOLECULAR SIMULATION STUDY OF DIVERTING MATERIALS USED IN MATRIX ACIDIZING A Dissertation by ABDULLAH SULTAN Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, A. D. Hill Committee Members, P. B. Balbuena H. A. Nasr-El-Din J. M. Seminario B. T. Connell Head of Department, S. A. Holditch August 2009 Major Subject: Petroleum Engineering iii ABSTRACT Molecular Simulation Study of Diverting Materials Used in Matrix Acidizing. (August 2009) Abdullah Sultan, B.Sc.; M.Sc., King Fahd University of Petroleum & Minerals Chair of Advisory Committee: Dr. A. Daniel Hill Recently there has been a great deal of attention in the oilfield industry focused on the phenomenal properties of viscoelastic surfactants (VES). The interest is motivated by their applications as switchable smart fluids, their surface tension, and their thickening and rheology enhancement in aqueous solution. Surfactant molecules in solution are known for their ability to assemble spontaneously into complex structures. Under certain thermodynamic conditions, temperature and electrolyte concentrations, wormlike micelles are formed. These micelles share similar equilibrium and dynamic properties with polymer solutions, However, micellar chains can break and recombine spontaneously which make them part of the more general class of living polymers. It is vital to understand the properties of viscoelastic wormlike micelles with regard to their flow in porous media. The overall objective of this study is to establish a better understanding of counterion effect on behavior of VES. The dependence of macroscopic properties on intermolecular interactions of complex fluid systems such as VES is an enormous challenge. To achieve our objective, we use first-principle calculations and molecular dynamics (MD) simulations to resolve the full chemical details in order to study how the structure of the micellar and solution properties depends on the chemical structure of the surfactant head group (HG) and type of counterion. In particular, we run simulations for different structures in gas-phase and aqueous solutions together with their salt counterions at iv room temperature and atmospheric pressure. For this purpose, we consider four types of surfactant HG (anionic, cationic, betaine and amidoamine oxide) together with the most common ions present in the acidizing fluid of a carbonate reservoir such as Ca2+, Mg2+, 3+ 2+ 2+ - - - Fe2+, Fe , Mn and Zn , Cl , OH and HS . Hydration of ions as well as interactions with surfactant the HG are studied using density functional theory (DFT). The results give important insight into the links between molecular details of VES HG structure and observed solution properties. This study proposes for the first time the possible mechanisms that explain the exotic behavior of VES at high Fe(III) concentration. Also, our MD simulation suggests that distribution of chloride ion around surfactant molecules is responsible for their viscosity behavior in HCl solution. We believe that our results are an important step to develop more systematic procedures for the molecular design and formulation of more effective and efficient VES systems. v DEDICATION To my parents vi ACKNOWLEDGEMENTS All praises and thanks are for Allah (Subhanau-wa-Talla), the Lord of the entire creation that exists (in earth and in the Heavens). May his peace and blessings be upon all His messengers, prophets, and all humankind (alive or dead) Amen. I am extremely grateful to Almighty Allah who alone made this accomplishment possible. I am most thankful to my advisor, Dr. Dan Hill, for his invaluable support, guidance and, more importantly, for giving me the freedom to pursue my own ideas and think independently. He would always push me towards challenging tasks that could make a difference at the most fundamental level. He would continuously ask me questions which made me reflect on my course of thought and organize myself. Working with him has been a great learning experience, and I thank him for sharing his knowledge of engineering and other aspects of life, and for being a mentor as well as a good friend. With a deep sense of gratitude and appreciation, I would like to express my sincere thanks to Dr. Perla B. Balbuena for her inspiring guidance, help and excellent cooperation in co-supervising this research work. It was her keen interest which made this research work presentable in this format. I thoroughly enjoyed discussions with her new results in our bimonthly meetings which gave me a whole new perspective of my research and were most enlightening. She was very encouraging and inspiring, and I have been most fortunate to work with her. I’m very thankful to Dr. Hisham Nasr-El-Din, a committee member, who introduced me to the world of viscoelastic surfactant when I worked in his lab during my internship, summer 2006, and was always willing to provide insightful comments on my research before and after I joined Texas A&M University. I personally learned a lot of ethical and technical values by interacting with him. He is simply a model to be followed. Also, I would like to extend my thanks to Dr. J. M. Seminario, who helped me a lot before vii becoming a member of my committee as I learned the fundamentals of nanotechnology and computational chemistry in his classes. He always inspired my knowledge and reshaped my way of thinking with his frequent saying “we can do it.” Last but not least, I appreciate the time dedicated by Dr. B. T. Connell, a committee member, a great help all the times I dropped by his office to talk about molecular formulation or mechanisms. My PhD program would not have been possible without the generous support of my sponsor, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia, to which I owe much. I’m a proud graduate of this institution and will serve upon my return, with great honor, as a faculty member at KFUPM for many years to come. All thanks and gratitude are extended to the Saudi Arabian Cultural Mission in Washington D.C. and the sponsored students office at TAMU for their unlimited logistical support and help that made my time much easier. I’m very thankful to Dr. Lisa Peres of the molecular simulation lab in the Chemistry Department at Texas A&M University for her support while running my simulations. She was the first person to contact when unable to resolve a “termination error” in my simulation. With her excellent personality, strong knowledge of science and good experience, she easily manages to help a number of students at the same time. I would like to thank Dr. M. Hall, a professor of inorganic chemistry at TAMU for the many useful discussions we had. I would like to thank other research groups and professors from outside TAMU with whom I joined good discussions through e-mails and in particular, those who provided me with good hints on the first guess of moleculear structures. They include: Pamela Hill and Edwin Schauble of the Earth and Science Department at University of California, Los Angeles, C. W. Bock, and J. P. Glusker of the Institute for Cancer Research, Philadelphia University, Todor Dudev and Carmay Lim from the Institute of Biomedical Science at National Tsing Hua University, Taiwan. I also appreciate the many good discussions I had during the early stages of my research with E. S. Boek of Schlumberger Cambridge Research Center, J. T. Padding and W. J. viii Briels from the Computational Dispersion Rheology Group at the University of Twente, The Netherlands. I would like to thank all the Dr. Hills’ group members whom I had a chance to interact with over the years. This includes the ones who have left and the ones still here: Saleh, Wahby, Maysam, Manabu, Jassim, Omer, Mohammed, Mou, Jiayao, Nerwing, Jason, Ben, Rashad, Nimish, and Qi. They made it enjoyable and fun to be part of the group, especially those with whom I’m sharing the office. I thank Zhu’s group members for being our office mates and all the students, faculty and staff of the Petroleum Engineering Department who made my graduate life an enjoyable experience. I thank the Middle East Carbonate Research Consortium for providing the financial support required to carry out this research. I thank the Supercomputing facilities at Texas A&M University in College Station, and Doha, Qatar for providing the necessary supercomputing time and support. Finally, I thank all my innumerable friends in College Station, who made my stay here the most memorable experience. I thank my parents for their belief in me and for providing all the help and support throughout my life. I thank them for all the hardships they went through to make me reach this point of my career. I am forever indebted to them. I submit that all my successes and achievements drew that inspiration from their blessings, encouragement and support. Hence it is to them, to whom now and ever I owe my very self, that I dedicate this work of mine. ix NOMENCLATURE ab initio First principle quantum mechanical approach for obtaining the electronic properties of a molecule based on the approximate solution to the many-electron Schrodinger equation, using only fundamental concepts, the mass and charge of the nuclear particles; literally: “from the beginning”. Basis function function describing the atomic orbitals that when linearly combined make up the set of molecular orbitals in a quantum mechanics calculation, Gaussian basis sets and Slater type orbitals are example of basis functions.