First EAGE/SBGf Workshop on Reservoir Monitoring and its Role in the Energy Transition

Geophysical reservoir monitoring (GRM) is in many cases a powerful tool and a very important part of the complex multi-disciplinary work to obtain a safe and optimized production management of our fields in a cost-efficient manner. The information from GRM data is used to understand what is going on in the reservoir and/or overburden. It can provide useful input for reservoir management and decisions regarding drilling of infill wells, optimization of production, interventions etc. Equinor has utilized 4D seismic and gravimetry data for overburden and reservoir monitoring for more than three decades and almost 70–80% of the Equinor operated fields are using GRM actively. All our assets are recommended to establish a GRM strategy.

When evaluating GRM strategies, the key is to assess the link between the expected and unexpected drainage strategy and model different production scenarios to see whether seismic/gravity will be able to discriminate between these. Modelling should also give insights into timing and frequency of surveys. Existing seismic data need to be evaluated and proper survey design for monitor survey is crucial to achieve good data quality. A business case is required as a part of the decision-making process and a decision tree methodology is used.

This presentation will showcase a practical workflow to estimate reservoir pressure and saturation changes from 4D seismic monitoring data. The workflow gradually evolves from a qualitative fast-track estimation to more robust quantitative estimations that utilize machine learning models, Bayesian statistics and stochastic sampling. The final solution integrates data from repeated well logs, reservoir simulations and 4D seismic data to provide a most likely estimation to the changes in dynamic reservoir properties and their associated uncertainties. This probabilistic solution can then provide multiple realizations of pressure and saturation distributions that match the 4D seismic data equally well. It can also provide conditional probability ranges that can be used to aid in decision making for reservoir management. The workflow is showcased with two real case applications from sandstone reservoirs in the North Sea.

An important difference between monitoring for hydrocarbon production and gas storage operations is the concern of leakage and its detection. The primary leakage pathways are legacy wells and damage zones around faults whose locations and existence are not necessarily known a priori. Further these leakage pathways are not static risks but can be activated during operations. When leakage occurs the quantities are (hopefully) small and detection is at or below of monitoring techniques. Uncertainties can be reduced or at least quantified with the help simulation and with their help optimal monitoring strategies can be devised. The larger the uncertainty the more simulations are required. Hence there is a need for efficient models representing the dominant features and processes. In this presentation I will cover three approaches: Multi-physics coupled flow diagnostics, multi-scale multi-physics modelling of leakage processes in the damage zone of faults and leakage modelling in vertically integrated modelling for CO2 storage.

The safety of CO2 storage operations will be ensured by appropriate monitoring techniques which will be deployed to assess both conformance and containment of the storage. Among the different techniques used to monitor CO2 storages as of today, geophysical methods (4D seismic and microseismic) are frequently used to follow the spatio-temporal evolution of the CO2 plume and / or to ensure that no CO2 is leaking from the reservoir to shallower formations.

In this presentation, capabilities of fiber optic cables to monitor future CO2 storages are investigated. As fiber optic cables are more mature technology to acquire both active and passive seismic data when deployed at borehole, the work presented in this talk is focusing on their use when deployed at seabed. Indeed, there are still some uncertainties whether this technology is sensitive and repeatable enough when deployed at seabed to monitor subsurface changes induced by CO2 injection. Two seismic case studies are presented (one active and one passive). In both cases, the results are very encouraging and are pushing fiber optic cables to be more and more used for reservoir monitoring in general, and CO2 storage in particular.

• Advantaged oil barrels—those with strong economics and low carbon emissions (A. Latham, 2020, Wood Mackenzie)—are likely to play a ballasting role as an economic energy supply during many energy transition scenarios.
• Maintaining advantage through the field life is a known challenge, but early effective reservoir management including seismic monitoring may help extend advantage longer, increasing a field’s robustness and relevance in transition scenarios.
• I share how ExxonMobil has taken a “Life Cycle Geophysics” perspective to the early development of long-term seismic monitoring programs.
• I highlight examples of the relevant challenges and opportunities posed by the fast pace and large scale of modern development projects.
• These conditions appear common across the South American Atlantic coast, making it one of the most exciting places in industry, and expanding these challenges and opportunities to a regional scale.

This talk will describe modern methods to answer specific questions about the subsurface of the Earth. Practical questions might be of the form: How large is this basin? Is this structure a potential CO2 storage reservoir? To what depth does this fault extend? The answers lie within the family of subsurface models that fit observed data. The talk will explain how we can find that family using methods from machine learning, and how to interrogate the family to obtain answers robustly.