| 講演要旨(和文) | | 我々は米国SWP（南西部パートナーシップ）に参加してCO2地中貯留のテストサイトでの重力モニタリングを開始した．我々の研究目的の一つは４ｄ反射法を補完する比較的安価なモニタリング手法の開発である．精密重力計測はCO2地中貯留モニタリングの有望な手法の一つであるが，貯留層が薄い場合や深部にある場合は地表で観測される信号レベルは小さい．この難点の解決策として我々は高感度重力計による連続測定の導入を計画している．超伝導重力計の連続記録に適切な時系列解析を行うことでnGalレベルの信号を検出された実績に期待した．テストサイトに超伝導重力計と絶対重力計の並行観測用の基台を設置した．基台での最初の絶対重力計測をA10重力計で2011年12月に実施した．重力モニタリングの基点として良好なデータが得られた． |
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| | 講演要旨(英文) | | We have started gravity monitoring at a CO2 sequestration field in collaboration with Southwest Regional Partnership on Carbon Sequestration. One of the purposes of our study is development of monitoring methods which are cost-effective to apply and bring about additional and independent information to complement 4D seismic data. Microgravity monitoring is thought to be a promising technique for evaluating CO2 geological storage. Reservoirs, however, are relatively thin and deep, resulting in subtle time-lapse signals at the earth's surface that must be compete with the presence of noise. Recent advances in superconducting gravimeters (SG) are quite attractive. We can extract gravity changes with nGal accuracy by applying time series analysis to data from continuous SG measurements. As the first step of our monitoring, a couple of pillars were made at the test field for parallel measurements with an absolute gravimeter and a SG meter. The first absolute gravity measurements were made using an A10 absolute gravimeter at the site in December 2011. Variance of the data was smaller than usual so that the location was evaluated to be a good base station for microgravity monitoring. |
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