ABSTRACT

In the context of CCS, we aim at simulating the migration of the CO2 for performance assessment purpose and risk management. In the case of the Krechba reservoir aquifer (In Salah - Algeria), we focus at modeling the reservoir pressure field and the induced ground surface displacement associated with CO2 reinjection. While coupling 3D fluid-flow and geomechanical modelings, we benefit from InSAR satellite surface displacement data in addition to conventional ones. Preliminary results show that adjustment over time of the reservoir mechanical properties is required to match observed displacement data and suggest considering rock properties evolution of media within an explicit coupling modeling approach.

1. INTRODUCTION

CO2 storage in geological formations such as deep saline aquifers or depleted oil and gas reservoirs constitutes the Carbon Capture and Storage (CCS) option to fight against global warming. In this context, BP, STATOIL and SONATRACH started the In Salah Joint Venture to manage on a series of fields the CO2 produced by re-injecting it in the northern part of the aquifer of the Krechba gas field. The injection started in August 2004 and to date up to 3 million tons of produced CO2 have been re-injected, while 17 million tons being scheduled at least. In the frame of the CO2ReMoVe European project, IFP Energies nouvelles and his partners work at developing tools and methodologies to simulate the CO2 migration within the reservoir and the resulting site behavior of a series of pilot sites (including Krechba). The final objective of this project is to be able to model the short term behavior of the site and to predict its long term at the scale of the storage complex in order to assess the storage integrity and its long term performance. When considering modeling different kinds of data are available: some as input data, others as the targeted ones by the simulation; in this work, our objective is to reproduce the ground deformation data that have been measured by satellite.

2. THE IN SALAH PROJECT

The In Salah project concerns a series of gas fields located in central South Algeria (Fig. 1) that contain almost 1 to 10 % of CO2. To export the natural gas, it is necessary for operators to reduce the CO2 concentration to the sales gas export concentration threshold (0.3%). Hence, it was decided, in the In Salah project, to re-inject the captured CO2 into the Krechba reservoir aquifer: this will avoid the emission of approximately 17 millions tons of CO2 and in the same time this will help to study the CCS concept at an industrial scale. To have the most reliable fluid flow modeling representation of our problem, we start with an history matching approach in order to determine the best permeability distribution inside the reservoir that insures matching between the modeling results and the measured data. Preliminary works [5] show that a dual medium representation of the reservoir [6] is necessary to correctly mimic the field data, typical of fractured reservoir.

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