A custom-designed solution provided real-time monitoring of seismicity, enabling continuous operation of a gas storage site while protecting the local population and fulfilling government regulations. The system helped the operator correlate potential microseismic activity with gas storage operations and mitigate potential risk in a timely manner.
An independent operator in the field of gas storage services was operating a large underground storage facility in northern Italy and needed to monitor the site for induced seismicity potentially caused by injection and extraction activities. The gas was stored in a series of methane-depleted, anticlinal reservoirs of Pliocene sandstone with local caprock consisting of Lower Pleistocene claystone.
With such an operation, it becomes important to carefully monitor seismicity in the caprock and at lower depths to ensure reservoir integrity. High-resolution monitoring helps to precisely locate such events, especially on the depth scale.
The operator’s main objective was to protect the security of the gas supply and comply with all applicable government regulations. Continuous, focused monitoring and surveillance would affirm the company's commitment to protect the environment and the local population from any potential leak events.
SLB was chosen to provide a solution because of its long experience managing and processing data from various downhole and surface networks. After analyzing the regulatory requirements and technical challenges, SLB organized a multidisciplinary effort to provide a solution that would ensure continuous, long-term, automated, high-resolution microseismic monitoring of the gas storage activities for at least 5 years.
The solution was built around the Seismic Focal Point™ real-time induced seismicity monitoring service (SFP), an automated, cloud-based monitoring system that is fully customizable for client’s needs. Such a service was needed because classic seismological networks and sensors are not capable of detecting low-level microseismic events at reservoir or caprock depths and, therefore, cannot provide accurate seismic information for correlation with injection and extraction activities.
The SLB solution included two downhole, multilevel, multicomponent, digital seismic acquisition sensors deployed just above the caprock. At the surface, the digitally acquired data were transformed into a continuous stream and transmitted via cellular phone channels to the SFP cloud system.
The custom-designed solution now provides monitoring and continuous supervision for the company’s daily operations, enabling continued operation of the gas storage site while protecting the interests of the local community. For this project, SFP can detect in real time any local or regional seismic event.
When anomalous events are detected, email notifications are transmitted to SLB experts who analyze and verify the events, enabling the operator to correlate potential seismic activity at a microseismic level with the injection and extraction rates and mitigate potential risk in a timely manner. The implemented solution has been in continuous operation since November 2018.
