| 講演要旨(和文) | | CO2の地中貯留やEORなどを行う際のTime Lapse(時間変化モニタリング)手法として地震波アクロスを用いる方法が検討されている。しかし地表震源の場合地表付近の水分変化、降雨や日変化、年周変化などの影響をうけることが確認されており、その影響を評価するために坑井内に地震計を用いることを検討している。本研究では震動実験のシミュレーションとして、地下に空洞などがある媒質を想定し、また地表付近に堆積層を持つ地震波速度構造モデルを用い地震波の伝搬を評価した。震源はアクロスの様な人工震源を想定した地表震源と、自然地震を想定した深部震源の2種類とした。観測点は地表および坑内地震計とした。その結果、空洞による地震波の散乱を含む観測波形を評価することができた。 |
|
|
| | 講演要旨(英文) | | For the time-lapse study in CCS and EOR, we have proposed the method using the seismic ACROSS (Accurately Controlled and Routinely Operated Signal System) and geophone array. However, it is considered that the near surface effects and their temporal changes caused by water content changes, temperature and surface wave generation, are very large for time-lapse estimation, in particular in time-lapse studies, and we would like to evaluate and reduce the near surface effects by the comparison of surface and borehole geophone records. We have carried out field experiment in Japan using a seismic source and simulation studies to evaluate the effects of near surface and heterogeneities such as having holes in the ground. We also evaluate the near surface effects by changing geophone depths. The result shows that if a seismic source is at the surface, the scattered wave caused by each hole is very large. Near surface source also generates very large surface waves. We will evaluate the sediment thickness by change of geophone depths. |
|
|
|
| |
|