Assessment of Field-Scale Geomechanical Risks Associated to Carbonate Reservoir Production in South Senoro Field

Abstract

Senoro is a carbonate gas field in Banggai basin in Eastern Indonesian, an area with active collision margin. A comprehensive field-scale study is carried out to investigate the potential geomechanical related risks associated to the field production for the entire life of the Southern part of Senoro field. Well-centric geomechanical models were built for the exploration and appraisal wells in the South Senoro field. A robust field-scale geomechanical model is built for the area of interest which covers the entire South Senoro field. This is done by propagating the well-centric geomechanical model properties and parameters in the field-scale model using geostatistical approach tied with seismic attributed. Using a finite element approach, the model is then coupled with the reservoir flow dynamic model and simulated for the entire life of the field. The simulation results were used to assess the field-scale geomechanical related risks associated to production. The changes in stresses, strains and displacement induced by the carbonate reservoir depletion are obtained over the entire model at the end of each geomechanical simulation step. These are used to conduct detailed geomechanical analyses over the life of the field. The results shows that a stress path of approximately 0.69 is expected in the carbonate reservoir. This is while the stress changes in the caprock layer is relatively lower, and as expected, with a reverse trend. This is mainly because the reservoir compaction is relatively low with a maximum of 0.13% after 2,500 psi reservoir depletion. Subsequently, the maximum surface subsidence is also insignificant with less than 0.12 meters. Since the stresses within the caprock tend to slightly increase by production, the risk of tensile failure reduces over time. The risk of shear failure in the caprock appears to be negligible. The fault tau-ratio seems to increase only in the carbonate reservoir. However, it does not exceed more than 0.60 which indicates a stable state for the fault surfaces. Overall, the results show that there is no risk associated to compaction, surface subsidence, stability of the faults and caprock layer for the entire life of South Senoro field. The comprehensive workflow used to carry out the study covers all the geomechanical aspect of the risks associated to producing from South Senoro field which is essential to optimize the development plan and design of the surface and subsurface facilities.