Castor, What’s next?

June 2014

Some historic seismic event evidence shows that a well-planned monitoring system may have saved money and shutdown time, therefore limiting the economic impact, such as at the Castor Project in Valencia (Spain).
Almost one year after the beginning of the gas injection and after the seismic crisis, Castor gas reservoir has been brought again to the public forefront, this time due to the Instituto Geográfico Nacional’s report being made public. However contrary to what journalists claim, no conclusion on what should be done has emerged from the scientific studies. According to ESCAl UGS, project owner and operational company, scientific reports have still to emerge, however they may not provide any further light on the subject.
To summarise and move on to actual discussion and future possibilities, we can say that the Castor Project wanted to use an offshore old oilfield for a geological underground gas reservoir in front of the Valencia coastline, Spain, for national energetic and economical strategy. The Project as we know it nowadays is composed of 8 injection/extraction wells at around 1,800 m depth, a gas pipeline of 22 km and a treatment distribution plant inland. Three control wells are instrumented (P-T) for monitoring the reservoir.
On the 5th of September the seismological networks of the area detected an increase in seismic activity. These micro earthquakes where low magnitude and were associated with the gas injection. The micro earthquakes were higher than the natural seismicity earthquakes recorded in the zone, and were not felt by the population. However, around the end of the month, one week after the injection stopped (according to ESCAL), seismic activity returned and with an increased magnitude. The seismic crisis that alerted the civilian population was felt to be more than 400 seisms up to a magnitude 4.5. No damage or injuries were derived from the crisis.
ESCAL UGS, nowadays in an attempt to appear transparent, claim that they have been following all required regulations and scientific advice. However it is clear that some hypotheses were not totally correct, in particular regarding risk quantification. Within their actual strategy, an important point is based on presenting the scientific results of a diverse research project, done by the most outstanding worldwide authorities in the field of induced seismicity. They will attempt to find out what the problem was, so that the Spanish government can make the decision – to close or to continue operating. The hot potato will soon be in the government’s hands. However the political parties are not known for making brave or difficult decisions quickly, unpopular decisions, nor those with implied risk, although this topic is another non-politically correct discussion…
The scientific arguments that they present try to make different concepts understandable with regards to induced seismicity or triggered seismicity. The former corresponds to non-previous active tectonic activity so that faults are created (induced) by the injection, such as in fracking. The later corresponds to the advance of a natural seismicity where a critical stress system is triggered by some disturbance, in this case injection, so a pre-existing fault is remobilised. In any case it is clear that the seismicity crisis is related to the injection procedure.
Other arguments on the topic claim that during injection, the maximum pressure stress point fixed on the reservoir simulation has not yet been reached, and is not even close. And again trying to agree with the critical stress system hypothesis, it seems that the energy released by the seismicity crisis is much higher than the energy released by the injection process.
Returning to the lack of a well-suited monitoring system, important in terms of future decisions, the study recalls where all those earthquake were located and their focal mechanism, so that where, how and which faults have been involved in the crisis. All the published reports conclude that the most probable scenario is the mobilisation of one unique minor fault.
There is a key difference to the mobilisation of the Amposta fault, a major long fault that can produce earthquakes of up to M7, bigger than a minor fault in terms of hazards and risk assessment.
To try to accurately define localisation and focal mechanism of the earth motions, especially in these facilities where the control of the micro earthquakes is a must, it is important to have a dense seismological network. For this reason high signal to noise ratio (to decrease uncertainty) and closeness to the source would have improved the reservoir monitoring.
The Spidernano seismic recording unit uses a high signal to noise ratio; it is portable, light, robust and ideally suited for busy environments (like offshore platforms) and may have played an important role in making the studies easier which are currently taking months. Conclusion reports come from highly reprocessed data based on probabilistic and stochastic methods to refine the available information.
High amounts of forums and discussions have risen on the net. The scientific community is in favour of continuing with the study in order to obtain detailed information of stress system and particularly the active role of the fearsome fault. So what are the next steps? Many scientists are in favour of opening it again claiming that this reservoir facilities will take 4 years to equilibrate, many are against for its risk implication. Anyhow if they decide to start a new period of injection test active studies, they would be better off trying to refine the offshore monitoring systems, as well as the onshore ones.

About Worldsensing

Worldsensing is a global IoT pioneer. Founded in 2008, the industrial monitoring expert works with over 270 engineering partners in more than 60 countries to deploy critical infrastructure monitoring solutions in mining, construction, rail and structural health.

Worldsensing has more than 80 employees and offices in Barcelona, London, Los Angeles and Singapore and investors include Cisco Systems, Mitsui & Co, McRock Capital and ETF Partners, among others.

Press contact:
Jennifer Harth
press@worldsensing.com

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