Using Carbon Dioxide to Enhance Recovery of Methane from Gas Hydrate Reservoirs: Final Summary Report

Abstract

Executive SummaryAlthough recent estimates (MILKOV et al., 2003) put the global accumulations of natural gas hydrate at 3,000 to 5,000 trillion cubic meters (TCM), compared against 440 TCM estimated (COLLETT, 2004) for conventional natural gas accumulations, how much gas could be produced from these vast natural gas hydrate deposits remains speculative. What is needed to convert these gas-hydrate accumulations to recoverable reserves are technological innovations, sparked through sustained scientific research and development. As with other unconventional energy resources, the challenge is to first understand the resource, its coupled thermodynamic and transport properties, and then address production challenges.Carbon dioxide sequestration coupled with hydrocarbon resource recovery is often economically attractive. Use of CO 2 for enhanced recovery of oil, conventional natural gas, and coal-bed methane are in various stages of common practice. In this report, we discuss a new technique utilizing CO 2 for enhanced recovery of natural gas hydrate. We have focused our attention on the Alaska North Slope where approximately 640 Tcf of natural gas reserves in the form of gas hydrate have been identified. Alaska is also unique in that potential future CO 2 sources are nearby, and petroleum infrastructure exists or is being planned that could bring the produced gas to market or for use locally.The EGHR (Enhanced Gas Hydrate Recovery) concept discussed in this report takes advantage of the physical and thermodynamic properties of mixtures in the H 2 O-CO 2 system combined with controlled multiphase flow, heat, and mass transport processes in hydrate-bearing porous media. A chemical-free method is used to deliver a L CO2 -L w microemulsion into the gas hydrate bearing porous medium. The microemulsion is injected at a temperature higher than the stability point of methane hydrate, which upon contacting the methane hydrate decomposes its crystalline lattice and releases the enclathrated gas. Conversion of the microemulsion to CO 2 hydrate occurs over time as controlled by heat transfer, diffusion, and the intrinsic kinetics of CO 2 hydrate formation. Sensible heat of the emulsion and heat of formation of the CO 2 hydrate provide a low grade heat source for further dissociation of methane hydrate away from the injectate plume. Process control is afforded by variation in the temperature of the emulsion, ratio of CO 2 and water, and droplet size of the discrete CO 2 phase. Small scale column experiments show injection of the emulsion into a methane hydrate rich sand results in the release of CH 4 gas and the formation of CO 2 hydrate. The experimental results were verified with computer modeling using the STOMP-HYD simulator, which showed over 3X enhancement in production rate using the EGHR technique when compared with warm water injection alone.The gas exchange technology (including EHGR) releases methane by replacing it with a more thermodynamic molecule (e.g., carbon dioxide). This technology has four advantageous: 1) i...

Properties and phenomena relevant to CH4‐CO2 replacement in hydrate‐bearing sediments

“… a Numbers in parentheses are sources as follows: 1, Lu et al [2009]; 2, Waite et al [2009]; 3, McGrail et al [2007]; 4, this study, equation (7); 5, Kang et al [2005]; 6, Lenormand et al [1988]; 7, Donnelly and Katz [1954]; 8, Span and Wagner [1996] and Trusler and Zarari [1992]; 9, this study, section 4, Figure 4; 10, this study, equation (8); 11, Kleinberg et al [2003]; 12, Kneafsey and Pruess [2010]. …”

“…Methane can be recovered from hydrate‐bearing sediments by depressurization, heating or chemical injection. In particular, the injection of carbon dioxide, CO 2 , into hydrate‐bearing sediments can liberate methane, CH 4 , and sequester CO 2 in hydrate form [ McGrail et al , 2007; Ota et al , 2005a; Stevens et al , 2008; Svandal et al , 2006; Zhou et al , 2008a]. …”

P-wave monitoring of hydrate-bearing sand during CH4–CO2 replacement

“…Published theoretical studies and laboratory-scale experiments have shown the successful release of CH 4 as a result of the replacement reaction caused by CO 2 injection (Hirohama et al, 1996;Kvamme et al, 2007;Lee et al, 2003;McGrail et al, 2007;Tegze et al, 2007). Pore scale phenomena include heat release and diffusion controlled reactions, dissolution of fluid phases, gas production, and porefluid volume expansion (note: a comprehensive review of phenomena relevant to CH 4 -CO 2 replacement can be found in Jung et al (2010)).…”

CH4‐CO2 replacement in hydrate‐bearing sediments: A pore‐scale study

“…The injection of CO 2 into CH 4 hydrate-bearing sediments has the advantage of liberating CH 4 while simultaneously sequestering CO 2 leading to the more sustainable use of a fossil fuel [McGrail et al, 2007;Ota et al, 2005;Stevens et al, 2008;Svandal et al, 2006;Zhou et al, 2008].…”

“…Previous studies have observed no apparent dissociation during replacement [Stevens et al, 2008], and have monitored replacement ratios and rates which show that the CH 4 -CO 2 replacement rate increases near the CH 4 hydrate phase boundary and with increasing CO 2 gas pressure, reaching a constant value when the CO 2 liquefies [McGrail et al, 2007;Ota et al, 2005Ota et al, , 2007. The replacement ratio increases when a mixture of CO 2 and N 2 is used for replacement because the smaller N 2 molecule facilitates the replacement of CH 4 from the small cage in structure I hydrate [Park et al, 2006].…”