Summary
The need for additional underground gas storage (UGS) in Europe and in France is increasing. TOTAL has therefore undertaken feasibility studies to convert the depleted Pécorade oil field, situated in South West France, into an UGS.
The Pécorade field offers a number of positive characteristics which make it a good candidate for UGS, but it is also deep at 2500 m and contains hydrogen sulphide.
This paper describes some of the challenges faced by the project, including:
The sizing of the working volume (volume of gas which can be stored and cycled each year), which required the acquisition and processing of a new 3D seismic program, and the construction of specific geological and reservoir models.
The safety and environmental issues related to caprock integrity and sour-gas production.
The conversion of existing oil and gas wells into gas injection and production wells.
The processing of cycled gas (including sour-gas treatment).
The cost of the project compared to more conventional UGSs. The main benefits expected from the project are:
The development of a sizeable working volume, in the order of one billion cubic meters, in an ideal location to serve the French and possibly Spanish market.
An improved oil recovery, as the annual cycling of the gas would induce production of an additional 20 to 30% over current projections.
These studies also confirmed that the development of a sizeable UGS is a lengthy, difficult, and complex project.
The decision to launch the project is mainly dependent on the results of the future preproject studies, regulations, and market conditions.
