Will there soon be more rumbling in the soil at Schoonebeek? According to the State Supervision of Mines (SodM), this cannot be completely ruled out. The SodM even expects that the risk of earthquakes may increase by injecting wastewater into empty gas wells near Schoonebeek.
Nevertheless, the regulator speaks of limited risks and is ‘cautiously positive’ about the wastewater plan of the Nederlandse Aardolie Maatschappij (NAM).
The NAM wants to restart oil extraction at Schoonebeek. Extraction has been halted since the end of 2021 because NAM did not meet certain conditions. For example, too high a level of the chemical toluene was found in the wastewater. The waste water is released when the viscous oil is extracted, which is, as it were, loosened with steam.
To restart the oil, NAM must come up with a good solution for the waste water. The oil giant thinks it can do this by pumping it into an empty gas field near the oil village in Drenthe.
The positive advice from SodM is an important step for NAM to restart oil extraction at Schoonebeek. It has been silent for more than two years. The issue of waste water played a major role in this.
Some local residents are following developments with suspicion. Fears of environmental damage, subsidence and earthquakes played a role in this. Both the SodM and TNO have examined the NAM extraction plan.
Both authorities have critical comments, but according to them there is no red flag. However, the SodM does propose conditions that NAM must take measures if earthquakes between 2 and 3 on the Richter scale occur. If the rumbling exceeds three, it will be over immediately for NAM: the gas field will be permanently closed.
The TNO also states that the relationship between earthquakes and wastewater injection cannot be completely ruled out. The fact that NAM places the wastewater wells at a distance from existing fault lines is a wise move, according to TNO. But existing fractures sometimes tend to shift, especially when they become wet. But if tremors occur, this will in the most unfavorable case lead to minimal, non-structural damage to buildings, according to TNO.
According to the SodM, soil subsidence due to extraction is also negligible. As a result, the ground has already dropped by 12 centimeters in the past. Looking ahead, the ground is expected to drop another 4 centimeters. But water injections probably dampen that effect by half.
Here too, TNO expects that the expected subsidence will not cause concrete damage to buildings. Subsidence of peat and clay soil poses a much greater risk. The research institute expects that this will lead to tens of centimeters locally in the next 25 years.
Finally, according to TNO, it is ‘very unlikely’ that wastewater injections dissolve salt formations in the soil layers. Opponents also made this argument as a risk of land subsidence.