Abstract

To achieve substantial national and global greenhouse gas abatement, carbon capture and sequestration (CCS) must be deployed at large scale in many locations. Individual large projects (5 million tons/y) will inject volumes on the order of 80,000–130,000 bbls/day equivalent continuously for 30 years or more. This requires explicit consideration of and management of growing reservoir pressure unlike CO2-EOR. Accurate reservoir descriptions of fault networks and the in-situ stress tensor are critical to successful management. Small uncertainties in the structural geometry or stress tensor azimuth can potentially produce very different results for fault activation and risk, which in turn affect the potential for induced seismicity in an active injection.

Although smaller than the injection pressure wave, the large injection footprint will make monitoring and verification challenging. Key challenges involve reduction of cost and improvement of accuracy using non-seismic methods. Careful integration of monitoring results and understanding of uncertainties are critical to avoid subsurface trespass and far-field migration. Demonstrations of InSAR, microseismic, and electrical survey methods have improved understanding of these technologies and may lead to improved monitoring suites. Seafloor monitoring has received little attention, but will be central to shelf deployments. Direct monitoring of groundwater systems may also be required by regulations, but have received little attention.

In order to avoid excessive local build-up of pressure and to maintain a small injection footprint, active management of the reservoir may be needed. Co-production and treatment of reservoir brines could provide a cost-effective means of reducing both operational risk and project costs. More aggressive reservoir management (interception wells and induced flow fields) may be needed to avoid trespass onto adjacent properties. Such measures are standard practice in many oilfield operations, suggesting that the incremental cost and risk posed by active management is likely to be small.

Introduction

Since first proposed (Marchetti, 1977), carbon capture and sequestration (CCS) through geological storage has gained in prominence as a greenhouse gas abatement strategy. This is reflected in part through the three commercial CCS projects (Weyburn, In Salah, and Snohvit) and the numerous field demonstrations (e.g., Frio, Otway, Nagaoka, CO2SINK) which have entered the field in the last 10 years (Michael et al., 2009). It is also reflected in conclusions by the IPCC, EIA, IEA, WEC, MIT, and others that CCS is a key component of any strategy for steep CO2 emissions reductions (REFS), as well as the creation of institutions like the DOE regional partnerships, the Carbon Sequestration Leadership Forum, and the Global CCS Institute. Finally, the large number of proposed large CCS projects has grown dramatically in the past 3 years, including ZeroGen, Gorgon, GreenGen, Schwartzepumpe, HECA, NowGen, and FutureGen.

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