Characterization and Decomposition Kinetic Studies of Methane Hydrate in Host Sediments under Subsurface Mimic Conditions

EST-380-NEDA

Goal
The purpose of this study is to establish sediment lithology and quantification of methane in hydrates hosted in fine-grained sediments from the Gulf of Mexico (GoM), a marine site of methane hydrate occurrence. The results will help establish a correlation between laboratory data and hydrate accumulation field data on dispersed hydrates in natural environment.

Performer
Brookhaven National Laboratory (BNL), Upton, New York 11973

Background
Gas hydrates are located in permafrost and marine environments and show potential as a vast methane source worldwide. However, methane is about 17 times more potent greenhouse gas than CO2 and the inherent instability of hydrate deposits to temperature and pressure changes leading to uncontrolled methane release poses severe constraints on methane production methods under consideration. It is now documented from the accumulated well log data that hydrates show a wide variation in gas saturation, nature of accumulation, and heterogeneity of host sediments even within a specific hydrate site (Collect, 1998). A suite of new techniques and tools (Murray et al., 2006) such as interval velocity method are being deployed to characterize and quantify gas hydrate concentrations in hydrate reservoirs (Dai et al., The Leading Edge, 2004). Marine hydrates constitute much larger deposits than those found in permafrost with accumulations that are several meters thick below the seafloor though hydrate mounds are also found on the seafloor, likely formed through gas seepage.

The unconsolidated system is an excellent representation of hydrate mounds on the seafloor. Below the seafloor, the effect of overburden pressure is dominant as a function of depth and may affect methane saturation in a hydrate deposit. The accurate representation of such a natural system will be the application of overburden pressure on a sediment sample. The hydrate formation/dissociation kinetic data can yield hydrate saturation as a function of depth data though there is paucity of kinetics data in natural sediments as hosts. Recently, studies were reported by Winters et al (AAPG Hedberg Conference, 2004) and Kneafsey et al. (J. Pet. Sci. Eng., 2006) on hydrate formation in porous media, mostly with coarse sands as hosts.

Our present focus is on laboratory prepared consolidated cores of methane hydrates hosted in depleted fine sediments, recovered from the Gulf of Mexico (GoM), under subsurface-mimic conditions. We plan to quantify macro- and micro-level changes in lithology that accompany formation/decomposition of methane hydrates hosted in fine-grained sediments. Collectively, the BNL data would allow development of a correlation between measured laboratory data and hydrate reservoir field data on highly dispersed hydrates hosted in very fine silt (<2 µm) in the Gulf of Mexico (GoM). These data has relevance to the climate change aspect of methane hydrates within the DOE-led multi-agency Methane Hydrate (MH) program.

The BNL integrated approach combines elements of fundamental science, unique apparatus, instruments, education, results dissemination, and collaborations to understand the inherent instability of methane hydrate in porous media and its impact on climate change.

Laboratory Layout of the Flexible Integrated Study of Hydrates (FISH) Unit

Potential Impact
Characterization and study of host sediments from known methane hydrate sites will add to the understanding of factors that are crucial to kinetic stability of methane hydrate in sediments—information needed for reservoir models. Differences or similarities in the decomposition of hydrate from sediment samples with different characteristics will be observed. These differences or similarities may ultimately have a bearing on field assessments of hydrate occurrences and their potential for uncontrolled methane release under perturbation and consequent impact on climate change.

Accomplishments:

• Flexible Integration Study of Hydrate (FISH) unit modifications are almost complete. Completed modifications include: Labview (data collection program), Temco cell addition, precision on temperature controls, probes added for spatially-resolved data acquisition, capability to form both consolidated and unconsolidated hydrates, capability to form unconsolidated cores and membrane to eliminate hazardous hydrate formation.
• Three samples taken from varying depths (667 m, 50 m and 0.1 m) at the Blake Ridge Methane Hydrate site were analyzed using CMT and XRF techniques to characterize depleted sediments.
• Computed microtomography (CMT) images of hydrates formed from the THF/seawater in both Ottawa sand and glass beads have been completed and 2D and 3D images are being constructed.
• A comparison of static and dynamic mode of hydrate formation concluded that the static mode is more representative to seafloor conditions, dynamic modes disrupts sediments.
• Methane hydrate formation/dissociation runs were conducted with the sediment/hydrate system in the FISH unit using the deepest depleted sediment sample (667 m) from the Blake Ridge hydrate site. Further runs compared hydrate formation at three different pressures: 900, 1200, and 1500 psi. During each formation event a sharp temperature spike, indicative of hydrate formation, was observed. In each run, the step-down method was used during the decomposition event from which decomposition rate constants were extracted.
• A set of runs is completed with pure water replaced with mimic seawater to form unconsolidated cores. Kinetic rate constants have been extracted from the first-order plots.
• Researchers also completed a sensitivity study in which the effects of gas flow rate on hydrate formation in laboratory systems were assessed. The rate of gas flow into experimental apparatus is significantly higher than rates generally found in nature, resulting in documented differences between laboratory and natural hydrate-sediment samples. Results of this study helped corroborate and explain physical differences previously documented between laboratory and natural hydrate samples, and may eventually lead to recommendations on the most appropriate flow rate to use in order to ensure that laboratory samples are as similar as possible to those obtained from natural settings.
• A set of methane hydrate formation/decomposition runs using host sediments from the Gulf of Mexico (GoM) (re.: JIP/DOE cruise) has been completed and the data analyzed.

Current Status:
A new Field Work Plan (FWP) was established in May 2008 and new work under the plan will include:

• Finalizing modifications to the FISH unit will include adding: 1) a mass flow meter with LCD display to precisely (accuracy ±1 %) measure gas output during hydrate decomposition and 2) an Isco pump to deliver constant gas flow and overburden pressure on the core sample.
• Characterization of hydrate formation in sediments pre and post in situ hydrates formation/decomposition using a newly constructed cell and CMT images. Base runs use quartzite silt as a baseline standard and then repeat experiments with depleted sediment samples from the Gulf of Mexico.
• Develop a multi-step method that involves reproducible 3-D volume construction and rendering of the collected CMT data. The steps involved are: 1) Collection of 1200 views in an assembled file (.prj) in IPLab software, 2) Convert_x2b_netcdf_display.sav-routine for converting filename.prj to filename.volume, 3) Convert image sequence into raw data in ImageJ, 4) Raw data processing in Drishti, 5) Volume rendering and applying transfer function in Drishti.
• Microstructure from CMT data will be compared against six know hydrate-in-sediment models and natural hydrate sample.
• Runs will be designed, using Gulf of Mexico fine-grained sediments as hosts and pure methane gas with simulated seawater to mimic in situ hydrates formation in consolidated and unconsolidated sediment cores.
• Detailed characterization of pre-hydrate formation, GOM fine-grained sediments will include documenting microporosity, permeability and tortuosity. This will then be compared and contrasted to post-hydrate formation sediments including formation/decomposition kinetics, reservoir accumulation modes and methane saturation.
• Hydrate formation activity to include: unconsolidated samples formation using static mode operation of the FISH unit to mimic hydrate formation conditions that closely match the natural environment of surface hydrates, consolidated sample formation where efforts will focus on conditions to produce hydrate-bearing sediments that are fine grained.
• Performance of decomposition runs using a step-down pressure method to quantify released gas, a measure of pore saturation. The data should help define the effect of sediment nature on pore-filling processes.
• A comparison of the collected CMT and kinetic data of methane hydrate hosted in fine sediments to well log data.

Project Start: October 1, 2004
Project End: September 30, 2008

DOE Contribution: $500,000
Performer Contribution: $0

Contact Information
NETL – Traci Rodosta (Traci.Rodosta@netl.doe.gov or 412-285-1345)
Brookhaven National Laboratory – Devinder Mahanjan (dmahajan@bnl.gov or 631-344-4985)

Additional Information:
In addition to the information provided here, a full listing of project related publications and presentations as well as a listing of funded students can be found in the Methane Hydrate Program Bibliography [PDF].

2008 Hydrate Peer Review [PDF-5.00MB]

An article on this project is presented in the Fall 2005 edition of the hydrate newsletter,  "Fire in the Ice".

Pertinent Publications [Those marked with * are refereed]
M. Eaton, P. Kerkar, D. Mahajan, K. Jones, and R. Kleinberg. Methane Hydrate Formation in the Laboratory using Fine Depleted Natural Sediments as Hosts. Session: Gas Hydrates and Clathrates, Division of Fuel Chemistry, 236th ACS National Meeting & Exposition, Philadelphia, Pennsylvania, USA. August 17-21, 2008 (for presentation).

D. Mahajan, P. Kerkar, K.W. Jones, R.L. Kleinberg, W.B. Lindquist, S. Tomov, and H. Feng. Natural Gas Hydrate Mimics: Understanding Hydrate Growth Phenomenon in Host Systems. International Geological Congress OSLO 2008. Session: Exploration and Assessment of Gas Hydrates (GAH-03), Oslo, Norway, August 6-14, 2008 (for presentation).

M. Eaton, K.W. Jones and D. Mahajan. Methane hydrate formation/decomposition in depleted sediments. Proc. Geol. Soc. (London), In press (2007)*.

L. Zheng, H. Zhang, M. Zhang, P. Kerkar, and D. Mahajan. Modeling methane hydrate formation in marine sediments. AAPG Bullet, In press (2007)*.

K. W. Jones, D. Mahajan, W. B. Lindquist, P. Kerkar, M. A. Celia, C. A. Peters, W. Um, M. Rockhold, and H. Feng. Application of Synchrotron Computed Microtomography and Micro X-ray Fluorescence to Energy/Environmental Problems. Application of Synchrotron Computed Microtomography and Micro X-ray Fluorescence to Energy/Environmental Problems. International Symposium Breaking Frontiers: Submicron Structures in Physics and Biology, Zakopane, Poland. 19 - 24 May 2008.

D. Sloan, P. Brewer, R. Charter, N. Dutta, A. Johnson, E. Jones, K. Juenger, M. Kastner, D. Mahajan, S. Masutani, R. Swenson, J. Whelan, S. Wilson, R. Woolsey. “Four Critical Needs to Change the Hydrate Energy Paradigm from Assessment to Production”. The 2007 Report to Congress by The U.S. Federal Methane Hydrate Advisory Committee. Offshore Technology Conference 2008 (OTC08), Houston, Tx. May 5-8, 2008. OTC Paper Number: OTC-19519-PP.

K.W. Jones, P.B. Kerkar, D. Mahajan, W.B. Lindquist, and H. Feng. Microstructure of natural hydrate host sediments. Nuclear Instruments and Methods in Physics Research, B. 261, 504-507 (2007)*.

D. Mahajan and P. Somasundaran, eds. Final Report, March 2007. International Workshop on Science & Technology Issues in Methane Hydrates R&D. Sponsored by Engineering Conference International (ECI)- Cosponsors: US DOE, MMS-DOI, ConocoPhillips. JIP-Chevron. Kauai, Hawaii, March 5-9, 2006.

D. Mahajan, C.E. Taylor and G.A. Mansoori. An Introduction to Natural Gas Hydrate/Clathrate: The Major Organic Carbon Reserve on Earth. J. Pet. Sci. & Eng., 56(1-3) 1-8 (2007)*.

M. Eaton, D. Mahajan, and R. Flood. A Novel High-Pressure Apparatus to Study Hydrate-Sediment Interactions. J. Pet. Sci. & Eng. 56(1-3) 101-7 (2007)*.

K.W. Jones, H. Feng, S. Tomov, W.J. Winters, M. Prodanovic and D. Mahajan. Characterization of Methane Hydrate Host Sediments Using Synchrotron Computed Microtomography (CMT). J. Pet. Sci. & Eng., 56(1-3) 136-45 (2007)*.

M. Eaton, P. Kerkar, K. Jones, H. Feng, W. Winters, D. Mahajan. Mimicking Marine-based Natural Systems: A Study of Sediment-Hydrate Interactions Under In Situ Conditions. Inter-laboratory Hydrate Workshop, Colorado School of Mines, Golden, CO, September 19-20, 2006.

M. W. Eaton and D. Mahajan. Methane Hydrate Kinetics in Depleted Host Sediments using the FISH unit. Science & Technology Issues in Methane Hydrates R&D International Workshop, Kauai, Hawaii, March 5-9, 2006.

Prasad Kerkar, Keith Jones, Huan Feng, and Devinder Mahajan. Spectroscopic Characterization of Host Sediments. Science & Technology Issues in Methane Hydrates R&D International Workshop, Kauai, Hawaii, March 5-9, 2006.

P. Servio, M. Eaton, D. Mahajan, and W.J. Winters. Fundamental Challenges to Methane Recovery from Gas Hydrates. Topics In Catal. 32(3-4) 101-08 (2005)*.

M. Eaton, D. Mahajan, R. Flood, T. Koga, and M. Rafailovich. Hydrate-Sediment Interactions in Novel High- Pressure Apparatus. Symposium on Symposium on Gas Hydrates and Clathrates. Co-sponsored by the ACS Petroleum Chemistry and Fuel Divisions. 229th ACS National Meeting, San Diego, CA. March 13-17, 2005.

K.W. Jones, H. Feng, S. Tomov, W. J. Winters, Michael Eaton, and D. Mahajan. Morphology of methane hydrate host sediments. Symposium on Symposium on Gas Hydrates and Clathrates. Co-sponsored by the ACS Petroleum Chemistry and Fuel Divisions. 229th ACS National Meeting, San Diego, CA. March 13-17, 2005.

D. Mahajan, P. Servio, K.W. Jones, H. Feng, W.J. Winters. Methane hydrate studies: Delineating properties of host sediments to establish reproducible kinetics, Chapter 16 in Advances In the Studies of Gas Hydrates, C.E. Taylor and J.T. Kwan, eds., Kluwer Academic Publishers, Inc., New York, New York, pp. 239-50 (2005)*.

D. Mahajan, T.F. Kotzle, W.T. Klooster, L. Brammer, R.K. McMullan, and A. N. Goland. Crystal Growth, Structure Characterization, and Schemes for Economical Transport: An Integrated Approach to the Study of Natural Gas Hydrates. Ann. N.Y. Acad. Sci. 912 940 (2000)*.

D. Mahajan. “Technical Challenges to Mining Methane Hydrates: The next Energy Frontier”. Marine Sciences and Atmospheric Sciences Colloquium Series, Stony Brook University, New York. February 6, 2004.

D. Mahajan, K. W. Jones, H. Feng, and W. J. Winters. Methane Hydrate Studies: Delineating Properties of Sediments Using Synchrotron Computed Microtomography (CMT). Presented at the Symposium on Gas Hydrates, 2003 AICHE Spring National Meeting, New Orleans, LA March 30- April 3, 2003. Abstract # 78a.

P. Servio and D. Mahajan. Kinetic Reproducibility of Methane Production from Methane Hydrates. Symposium on Synthetic Clean Fuels from Natural Gas and Coal-bed Methane: 30 Years Since First Oil Crisis (Co-sponsored by the ACS Fuel and Petroleum Chemistry Divisions), 226th ACS National Meeting, New York, NY. September 7-11, 2003.

D. Mahajan, T. F. Koetzle, L. Brammer, W. T. Klooster, R. L. McGraw, R. K. McMullan, and G. Senum. Structure Characterization and Sono-Stimulated Kinetic Study with Tracers in Pressure Vessels: An Integrated Approach to the Study of Gas Hydrates. Symposium on the Fundamentals of Advanced Materials for Energy Conversion, Session on Gas Clathrate Hydrates. 2002 TMS Annual Meeting, Seattle, WA, February 17-21, 2002.

Relevant Awards and Other Professional Accomplishment
2008 - C.E. Taylor and D. Mahajan, Co-Organizers. Session on Gas Hydrates and Clathrates, Division of Fuel Chemistry, 236th ACS National Meeting & Exposition, Philadelphia, Pennsylvania, USA. August 17-21, 2008.

2008 - Editorial Board Member, The Open Petroleum Journal, BENTHAM Science Publishers, Ltd.

2007 - Outstanding Mentor Award, Office of Science, United States Department of Energy

2007 - Editorial Board Member, International Journal of Oil, Gas and Coal Technology.

2007 - J. Petroleum Science & Engineering. Special volume: “Gas Hydrates and Clathrates” 56(1-3), D. Mahajan and C.E. Taylor, eds.

2006 - Member, Technical Steering Committee, Inter-Laboratory Hydrate Workshop, Colorado School of Mines, Golden, CO, September 19-20

2006 - D. Mahajan and P. Somasundaran, Organizers. International Workshop on Science & Technology Issues in Methane Hydrates R&D. Sponsored by Engineering Conference International (ECI)- Cosponsors: US DOE, MMS-DOI, ConocoPhillips. JIP-Chevron. Kauai, Hawaii, March 5-9.

2005 - Session Organizer. Symposium on Gas Hydrates and Clathrates. Co-sponsored by the ACS Petroleum Chemistry and Fuel Divisions. 229th ACS National Meeting, San Diego, CA. March 13-17