Florida State University Libraries 2016 Dynamics of Natural Hydrocarbon Seeps in the Northern Gulf of Mexico Caroline Van Limbeek Johansen Follow this and additional works at the FSU Digital Library. For more information, please contact [email protected] FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES DYNAMICS OF NATURAL HYDROCARBON SEEPS IN THE NORTHERN GULF OF MEXICO By CAROLINE VAN LIMBEEK JOHANSEN A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2016 Caroline Johansen defended this dissertation on June 3, 2016. The members of the supervisory committee were: Ian R. MacDonald Professor Directing Dissertation Tarek Abichou University Representative Bill Dewar Committee Member Jeff Chanton Committee Member Michael Abrams Committee Member The Graduate School has verified and approved the above-named committee members, and certifies that the dissertation has been approved in accordance with university requirements. ii I dedicate this thesis to Mother Earth. Thank you for the nature and nurture you provide. My hope is that one day the human species will collectively recognize that we need you. In the meantime, I’ll do my best to learn from you and advocate for you. iii ACKNOWLEDGMENTS First and foremost, I thank my advisor, Dr. Ian MacDonald. Thank you for the all the opportunities, thank you for your patience, thank you for believing in me, and thank you for your friendship. My PhD has been a fruitful and meaningful experience that I am honored and proud to have completed under your guidance. I would also like to acknowledge my lab mates Samira Daneshgar Asl and Mauricio Silva Aguilera; for their support and becoming my lab family. Additionally I would like to thank my committee members for insightful discussion and guidance. Particularly Dr. Dewar, a mentor and listening ear both in my academic and personal life. Finally, thank you to all colleagues at FSU and other Universities and Institutions that have been supporters, collaborators, and become friends throughout my PhD. This research was made possible in part by a grant from The Gulf of Mexico Research Initiative, and in part by National Science Foundation Award (EF-0801741). Data are publicly available through the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) at https://data.gulfresearchinitiative.org (R1.x132.137:0011, R1.x132.137:0009, R1.x132.137:0028, R1.x132.137:0033, R1.x132.137:0010, R1.x132.137:0037, doi: 10.7266/N7M906N3). iv TABLE OF CONTENTS List of Tables ............................................................................................................................... viii List of Figures................................................................................................................................ ix Abstract........................................................................................................................................ xiv 1. INTRODUCTION.....................................................................................................................1 1.1 Introduction.........................................................................................................................1 1.2 Geological features in the Gulf of Mexico .........................................................................3 1.2.1 Formation of the Gulf of Mexico................................................................................3 1.2.2 Salt deposition and movement....................................................................................4 1.3 Oil production in the Gulf of Mexico basin........................................................................6 1.3.1 Source rocks................................................................................................................7 1.3.2 Migration and pathways to seeps................................................................................9 1.4 Natural seeps .....................................................................................................................10 1.4.1 Mud volcanoes..........................................................................................................11 1.4.2 Brine pools................................................................................................................11 1.4.3 Gas hydrates..............................................................................................................11 1.4.4 Carbonates.................................................................................................................12 1.4.5 Chronic natural and anthropogenic oil discharges....................................................12 1.5 Study location ...................................................................................................................12 1.6 Thesis objectives...............................................................................................................13 2. EQUIPMENT AND METHODS...........................................................................................15 2.1 Video Time Lapse Camera ...............................................................................................15 2.1.1 High Definition VTLC for deep sea time-lapse imaging..........................................16 2.1.2 Autonomous and triggered event settings.................................................................18 2.1.3 Deployment and retrieval..........................................................................................18 2.2 Semi-automatic bubble counting method .........................................................................19 2.2.1 Pre-program run........................................................................................................22 2.2.2 Automatic bubble counting program ........................................................................23 2.2.3 Bubble algorithm ......................................................................................................24 v 3. BUBBLE RELEASE PROCESSES AT NATURAL HYDROCARBON SEEPS IN THE GULF OF MEXICO ...............................................................................................................25 3.1 Introduction.......................................................................................................................25 3.2 Study Site..........................................................................................................................28 3.3 Methods ............................................................................................................................29 3.3.1 Camera properties .....................................................................................................29 3.3.2 Camera deployments.................................................................................................30 3.3.3 Measuring bubble size ..............................................................................................31 3.3.4 Overview of image processing..................................................................................33 3.3.5 Bubble counting algorithm .......................................................................................35 3.3.6 Extrapolation.............................................................................................................36 3.4 Results...............................................................................................................................36 3.4.1 Vent characteristics...................................................................................................36 3.4.2 Bubble measurements and rates................................................................................39 3.4.3 Pressure differential and bubble release ...................................................................40 3.5 Discussion.........................................................................................................................40 3.5.1 Considerations for long-term deployment ................................................................40 3.5.2 Temporal variation of bubble release .......................................................................43 3.5.3 Bubble flow rate comparisons ..................................................................................45 3.6 Conclusion ........................................................................................................................46 4. A HYDROCARBON BUDGET FOR A GULF OF MEXICO NATURAL SEEP SITE: GC600.......................................................................................................................................47 4.1 Introduction.......................................................................................................................47 4.1.1 Indications of fluid flow............................................................................................49 4.2 Site Description ................................................................................................................50 4.3 Methods ............................................................................................................................51 4.3.1 Faults and salt distribution........................................................................................52 4.3.2 Subbottom blanking zones........................................................................................52