Welcome to the February 2011 edition of Quintessa Update, the electronic newsletter of Quintessa Limited.
This edition covers Quintessa's scientifically-based consultancy, contract research and software for supporting decisions related to the geological storage of CO₂, natural gas and acid gas.

Scenario Modelling to Support Monitoring Plans for CO₂ Storage Sites

Quintessa contributed to a recent review of technologies and approaches for measurement, monitoring and verification (MMV) of possible future offshore CO₂ storage sites adjacent to the UK. The project was led by the British Geological Survey (BGS) for the Energy Technologies Institute (ETI). Quintessa simulated the movement of CO₂ in different kinds of CO₂ storage sites as a basis for judging which MMV technologies and approaches would be appropriate in each case. Four hypothetical sites were specified to represent the range of storage options in the northern and central UK North Sea. Hypothetical, unexpected leakage scenarios involving flow through wells, faults and enhanced permeability zones were modelled using Quintessa's QPAC software. For more information, please contact Richard Metcalfe.

Modelling Long-term Cement Well Seal Stability in the Presence of CO₂

In a paper presented at the GHGT10 conference, Quintessa investigated well seal stability in the presence of CO₂ using fully-coupled geochemical transport models of cement degradation developed with Quintessa's QPAC software. Simulations explored the significance of formation water salinity and investigated approaches to simulating cement degradation in the presence of brines. Both the 'ion pairing and complexing' and 'specific ion interaction' ('Pitzer') approaches were used. Each one successfully reproduced the results of a cement carbonation experiment (covering 9 days) and field observations of cement degradation from the 'SACROC' site (covering 30 years), but gave increasingly differing results over progressively longer timescales. It is suggested that simulations of long-term seal performance in boreholes in contact with highly saline formation waters should adopt the Pitzer approach. The results illustrate that, on its own, matching simulation results and observed well seal behaviour over the short period for which data are available (a few tens of years) is an unreasonable basis on which to build confidence in long-term (>10² years) modelled seal performance. For more information, please contact James Wilson.

Guideline for Selection and Qualification of Sites and Projects for CO₂ Geological Storage (CO2QUALSTORE)

The recently published CO2QUALSTORE guideline serves as a reference for how to qualify, manage and approve CO₂ geological storage sites and projects. The guideline was developed by the CO2QUALSTORE joint industry project (JIP) led by DNV. The JIP included the following partners from a number of sectors; oil and gas companies (BP, BG Group, Petrobras, Shell and Statoil); energy companies (DONG Energy, RWE Dea and Vattenfall); technical consultancy and service providers (Schlumberger and Arup); the IEA Greenhouse Gas R&D Programme; and two Norwegian public enterprises (Gassnova/Climit and Gassco). A workbook accompanying the CO2QUALSTORE Guideline gives practical examples of how to follow the risk-based guidance and its various steps. One of these examples is an advanced evidence based logic (ESL) approach developed with Quintessa's TESLA decision support software. For more information, please contact Richard Metcalfe.

RISCS: Potential Impacts of CO₂ Storage on Receptor Environments

RISCS (Research into Impacts and Safety in CO₂ Storage) is a 4-year EC and industry project, led by the British Geological Survey (BGS) that aims to improve understanding of the potential environmental impacts of geological storage of CO₂, in the unlikely event that leakage occurs. Such understanding is required for developing regulations and guidance, even though facilities for the geological storage of CO₂ will be designed to prevent leakage. Under Task 1 of RISCS, Quintessa led the development of some reference European receptor environments, together with associated high-level impact scenario descriptions. These scenarios provide the basis for mathematical modelling studies that will be undertaken later in the project, and input to experimental studies in both terrestrial and marine environments. For each receptor environment a baseline 'most likely' scenario has been defined in which the storage system evolves as designed, with no leaks occurring. For comparison, unexpected 'alternative evolution' scenarios have also been identified. For example, for terrestrial systems unexpected 'alternative evolution' scenarios include potential impacts on animals and plants caused by direct releases to the atmosphere following well seal failure, and localised releases of CO₂ to aquifers and the near-surface environment. For more information, please contact Alan Paulley.

CO₂ FEP Database Experience

Quintessa's on-line database of generic features, events and processes (FEPs) relating to systems analysis for geological storage of CO₂ was established in 2004 and currently has over 1000 registered users. A review of its use, which was presented at the GHGT10 conference, revealed the database to be a proven valuable tool for 'top-down' auditing and 'bottom-up' conceptual model building and has thereby helped to build confidence in wide-ranging long-term geological storage assessments. The database continues to be developed (e.g. for the marine environment) and suggestions for further improvements are always welcome. For more information, please contact Russell Walke.