Introduction

The 12^th meeting of the IEAGHG’s Monitoring Network, hosted by Battelle and Core Energy, took place in Traverse City, Michigan between 13^th and 15^th June 2017.  The venue in northern Michigan is close to an area of interest to the Midwest Regional Carbon Sequestration Partnership.  Battelle, in partnership with Core Energy, are heavily engaged in research related to CO₂ storage and enhanced oil recovery in a series of pinnacle reef reservoirs that extend across the northern part of this state.  During the meeting the hosts organised a tour of technical facilities that included CO₂ injection, recovery and production facilities that helped delegates to appreciate the scale of CO₂ surface operations and the equipment requirements.

The theme for this meeting was ‘The Cost and Value-effectiveness of Monitoring: what key drivers are required to deliver an optimum outcome’.  Sessions included project updates, the application of oil and gas production experience, innovative monitoring techniques, offshore monitoring developments, overburden research including controlled release experiments, wellbore integrity and micro-seismicity.  Delegates also took part in a group exercise on how to respond to a hypothetical leak scenario. 

A topic of much discussion at previous meetings has been how to reduce the level and cost of monitoring for commercial-scale projects compared with the initial research-orientated projects.  The effectiveness of monitoring is now becoming evident at commercial-scale projects.  Experience gained from earlier demonstration projects has enabled more refined, optimised and reduced levels of monitoring at larger projects, that has resulted in more cost-effective monitoring overall.  This progression and technology-transfer was seen from the SECARB Cranfield project to Petra Nova, from IBDP to ICCS Project at Decatur, and at Quest which has learnt from experience gained across the USA’s RSCP projects.  

Advances in the use of autonomous underwater vehicles (AUVs), equipped with multiple sensors, was discussed at the meeting.  AUVs are now capable of large-scale offshore monitoring which enables surveillance to be conducted over wide areas.  Other topics included feedback from a US national wellbore integrity workshop following the Aliso Canyon disaster in October 2015.  Although this workshop relates to gas storage there are issues that are relevant to CO₂ storage notably risk management plans. 

Key Messages

• Commercial-scale projects are now able to evaluate and implement reductions in complexity of monitoring.

• The monitoring strategy applied at recent commercial scale projects (Petra Nova, IL-ICCS, Quest) has built on knowledge transfer and expertise gained from early projects (SECARB, IBDP) especially the selective deployment of different monitoring techniques.

• There is a trend towards right-sizing the number, type, and timing of technologies deployed at commercial-scale projects. 

• DAS technology and permanent seismic sources, plus other permanent receivers, have led to several beneficial advances including lower cost, decreased surface impact, and increased subsurface resolution. 

• There is clear progress towards the adoption of more derived, quantitative and targeted environmental monitoring both onshore and offshore.

• Environmental monitoring is useful for characterisation and to determine well defined performance metrics instead of simple baseline thresholds.

• There is a convergence towards more nuanced evaluation of methods, detection performance and probabilistic leakage detection plus the identification of false positives.

• The use of lower cost monitoring can be effective to define where and when more expensive monitoring is required to verify the presence of CO₂, for example conducting 2-D seismic before 3-D.

• The overall DAS technology is improving at a fast pace, for example, DAS – helical wound cable improvements are moving DAS into surface horizontal seismic configurations.

• A series of several simulations can be used to generate probability contours of a plume’s aerial extent and boundary.

• There has been substantial progress in monitoring technologies over the last decade.  For example advances in microseismic monitoring have provided greater insights into geomechanical processes during and post-injection.

• Data processing advancements (data hub, data pods, automated image filtering) can now be applied minimizing multiple image acquisition and enabling the selection of the most relevant observations.

• Cost-reduction can now be achieved using shore-to-shore AUVs without the need for ships.

• Experience from the Tomakomai project has demonstrated that care is needed when applied to thresholds derived from baseline data.
• Marine environmental transport mechanisms differ to onshore processes (diffusion is far faster in the atmosphere than in a water column).

• Some progress has been made with chimney characterisation with implications for fluid migration in the subsurface down to depths of 1-2km.

• Technology advancement in compact AUV design, and related mobile sensor systems, could lead to a global response system and portable laboratory facilities.

• Microseismic monitoring is important for regulatory requirements and for stakeholder assurance but it can increase characterisation costs.

• Well integrity continues to be very important with the potential for low level leakage.

• Monitoring at CO₂ storage sites has demonstrated that small amounts of CO₂ can be detected at depth with seismic, for example Otway, Aquistore, Frio.