Integrated Usage of Surveillance Data for Estimating Cap Rock Integrity and Heat Distribution during Steam Injection in a Fractured Carbonate Reservoir

Abstract

Abstract EOR operations involving steam injection lead to heat being transferred to the reservoir, which expands, and the expansion is transferred to the overburden. This can induce a cap rock breach and steam/gas seep, leading to inefficient development and higher recovery costs. Thermal expansion could also re-activate faults, potentially affecting surface facilities. In a forward-modeling study of the cap rock integrity during steam injection in a giant fractured carbonate oil field in Oman the possible failure mechanisms of the cap rock were illustrated. Further, opportunities for cap rock and reservoir surveillance were identified. During a first phase steam development of the field a variety of well and reservoir surveillance data are being gathered, including (GPS and InSAR) surface deformation measurements, micro-seismic activity, and (distributed) temperature and saturation logs. Integrated usage of the surveillance data allows for calibration of and comparison between two geomechanical models. The geomechanical models are employed to monitor the cap rock integrity during the steam operation on a regular basis, and to derive the heat distribution (evolution) within the reservoir. To this end, both forward and inverse modeling workflows have been developed. The results of this study may trigger the development and evaluation of alternative steam injection schemes (well spacing, injection rates).