Review of the Findings of the Iġnik Sikumi Co2-ch4 Gas Hydrate Exchange Field Trial

The Iġnik Sikumi Gas Hydrate Exchange Field Trial was conducted by ConocoPhillips in partnership with the U.S. Department of Energy, the Japan Oil, Gas, and Metals National Corporation, and the U.S. Geological Survey within the Prudhoe Bay Unit on the Alaska North Slope (ANS) during 2011 and 2012. The 2011 field program included drilling the vertical test well and performing extensive wireline logging through a thick section of gas-hydrate-bearing sand reservoirs that provided substantial new insight into the nature of ANS gas hydrate occurrences. The 2012 field program involved an extended, scientific field trial conducted within a single vertical well (“huff-and-puff” design) through three primary operational phases: 1) injection of a gaseous phase mixture of CO2, N2, and chemical tracers; 2) flowback conducted at down-hole pressures above the stability threshold for native CH4-hydrate, and 3) extended (30-days) flowback at pressures below the stability threshold of native CH4-hydrate. Iġnik Sikumi represents the first field investigation of gas hydrate response to chemical injection, and the longest-duration field reservoir response experiment yet conducted. Full descriptions of the operations and data collected have been fully reported by ConocoPhillips and are available to the science community. The 2011 field program indicated the presence of free water within the gas hydrate reservoir, a finding with significant implications to the design of the exchange trial – most notably the requirement to use a mixed gas injectant. While the use of mixed gas, as opposed to pure CO2, resulted in a complex chemical environment within the reservoir that greatly tests current experimental and modeling capabilities – without such a mixture, it is apparent that injection could not have been achieved. Although interpretation of the field data is continuing, the primary scientific findings and implications recognized to date are: 1) gas hydrate destabilization is self-limiting, dispelling any notion of the potential for uncontrolled destabilization; 2) wells must be ∗ Corresponding author: Phone: 304-293-9334 Fax 304-293-4139 E-mail: [email protected] Proceedings of the 8th International Conference on Gas Hydrates (ICGH8-2014), Beijing, China, 28 July 1 August, 2014