Methane Injection Project, Example 1 of 8
In order to learn from past projects and to illustrate the negative and positive impacts of unexpected events caused by subsurface fluid injection, a series of eight examples is presented, beginning with this post. The examples include methane, water, and CO2 injection projects.
This first example focuses on the Castor Project in offshore eastern Spain. The project involved a depleted oil field (Amposta) selected for temporary natural gas storage. The reservoir consists of fractured and karstified dolomitic limestone. The plan was for the reservoir to store 1.3 billion cubic meters of natural gas, sufficient to meet 25% of Spain’s storage requirements.
Studies concluded that the reservoir characteristics, especially the distribution of porosity and the sealing capability of the caprock, were sufficient. However, this work did not consider the possibility of induced seismicity. Amposta Field had been produced under a natural water drive and there had been no previous injection in the field.
In 2013, just three days after gas injection began, a series of earthquakes occurred along a deeper, previously unidentified fault. This culminated in three earthquakes with a moment magnitude > 4. Injection was halted, and the site was permanently closed six years later at an estimated total cost to Spanish citizens of up to 4.7 billion Euros. A subsequent analysis showed that assessing fault stability prior to gas injection would have identified the risk of induced seismicity.
A cross-section (a) and map (b) depicting the location of injection is shown below. On the left, the yellow shading indicates the target reservoir. On the right, the black square is the injection well location, the circles are earthquake locations, and the black circles are the three largest earthquakes (from Foulger et al, 2018).
Reference: Foulger, G.R., Wilson, M.P., Gluyas, J.G., Julian, B.R. and Davies, R.J. 2018. Global review of humaninduced earthquakes. Earth-Science Reviews, 178, 438-514.