Frédéric Huguet

Reservoir monitoring using permanent sources and vertical receiver antennae The Céré-la-Ronde case study

Arguably, the cheapest and safest place to store gas is inside a reservoir. Over the years, Gaz de France has developed a unique expertise in this field. A brine-filled reservoir is used to store imported gas during summer and pump it out in winter according to market demand. Monitoring bubble expansion, field pressure, and gas saturation is critical to optimize field management and gas recovery. Several seismic monitoring experiments have been carried out over Cere-la-Ronde test site, with varying degrees of success.

Characterizing reservoir parameters by integrating seismic monitoring and geomechanics

The Cere-la-Ronde underground gas storage reservoir in the Paris Basin, a test site to study and enhance reservoir seismic monitoring, is a water-bearing sandstone reservoir in a faulted anticline structure. Seismic data acquired so far have generated a qualitative interpretation of the location of the gas bubble by studying fluid saturation (Meunier, 1998). However, between 1994 and 1997, two sonic logs showed subtle differences in VP not explained solely by saturation variations. Changes in pore pressure and stresses also influence reservoir elastic properties. Hence, we used geomechanical modeling to evaluate quantitatively how exploiting the gas reservoir impacts seismic measurements.

Underground gas storage: estimating gas column height and saturation with time lapse seismic

Seismic monitoring is often used to check hydrocarbon movements during production. On the site of Céré-la-Ronde, an underground water-bearing gas storage facility developed by Gaz de France, a methodology has been implemented for estimating gas column height and saturation with time lapse seismic. The methodology is based on the Gassmann model, on the measurement of time-shifts and on the computation of a specific seismic function. The time-shifts obtained by cross-correlation techniques are used to derive the residual time-shift Δt induced by the presence of gas within the reservoir. A specific function is used to estimate both the gas bubble extension and the gas time thickness Ht. It is shown that knowledge of Ht and Δt and the use of a Gassmann model can lead to an estimation of the gas saturation. The methodology has been applied successfully on conventional seismic profiles as well as on vertical seismic profiles (VSP). The results obtained with seismic data are in good agreement with those obtained by logging (sonic and neutron logs) but with a lateral investigation, which is much larger than the one given by logging techniques. In our field example, the gas anomaly has been checked over a distance of 300 m with VSP data and over 2 km with surface seismic data.

Acquisition And Processing Challenges In Continuous Active Reservoir Monitoring

CGG, GDF and IFP have developed a comprehensive seismic monitoring system based on low-energy stationary seismic sources operating continuously and simultaneously in conjunction with vertical multi-component receiver antennae. This system, called SeisMovie, is fully automated and remotely controlled (1). Reservoir production induces changes in saturation, pore pressure and stresses, which may influence the process of wave propagation in rocks. This high-resolution seismic monitoring has the potential to optimize exploitation scenarios: tiny changes in the seismic response (a few microseconds and a quarter of a decibel) can be measured and calibrated to direct reservoir measurements.

Feasibility study of time‐lapse parameters estimate for mean effective stress and saturation changes in gas storage

Seismic measurements acquired at different stages in the life of an underground gas storage can help monitoring the fluid distribution over production time. The production from the reservoir induces changes in saturation, pore pressure and stresses, which may influence the process of wave propagation in rocks. These changes could be simulated through geomechanical and rock physics modeling. The stresses resulted from the geomechanical modeling and saturation variations can be used to generate synthetic logs and seismic traces. The sensitivity of the computed elastic and AVO parameters to the different reservoir properties was analyzed. The role of incidence angle and shear wave to measure reliable time-lapse parameters like time-shift delay attribute and amplitude variations was demonstrated.